communications by blake solution manual
DESCRIPTION
Answers to Multiple Choice QuestionsTRANSCRIPT
Chapter 1: Introduction to Communication Systems
MULTIPLE CHOICE
1. The theory of radio waves was originated by:
a. Marconi c. Maxwell b. Bell d. Hertz
ANS: C
2. The person who sent the first radio signal across the Atlantic ocean was:
a. Marconi c. Maxwell b. Bell d. Hertz
ANS: A
3. The transmission of radio waves was first done by:
a. Marconi c. Maxwell b. Bell d. Hertz
ANS: D
4. A complete communication system must include:
a. a transmitter and receiver b. a transmitter, a receiver, and a channel c. a transmitter, a receiver, and a spectrum analyzer d. a multiplexer, a demultiplexer, and a channel
ANS: B
5. Radians per second is equal to:
a. 2π × f c. the phase angle b. f ÷ 2π d. none of the above
ANS: A
6. The bandwidth required for a modulated carrier depends on:
a. the carrier frequency c. the signal-plus-noise to noise ratio b. the signal-to-noise ratio d. the baseband frequency range
ANS: D
7. When two or more signals share a common channel, it is called:
a. sub-channeling c. SINAD b. signal switching d. multiplexing
ANS: D
8. TDM stands for:
a. Time-Division Multiplexing c. Time Domain Measurement b. Two-level Digital Modulation d. none of the above
ANS: A
9. FDM stands for:
a. Fast Digital Modulation c. Frequency-Division Multiplexing b. Frequency Domain Measurement d. none of the above
ANS: C
10. The wavelength of a radio signal is:
a. equal to f ÷ c b. equal to c ÷ λ c. the distance a wave travels in one period d. how far the signal can travel without distortion
ANS: C
11. Distortion is caused by:
a. creation of harmonics of baseband frequencies b. baseband frequencies "mixing" with each other c. shift in phase relationships between baseband frequencies d. all of the above
ANS: D
12. The collection of sinusoidal frequencies present in a modulated carrier is called its:
a. frequency-domain representation c. spectrum b. Fourier series d. all of the above
ANS: D
13. The baseband bandwidth for a voice-grade (telephone) signal is:
a. approximately 3 kHz c. at least 5 kHz b. 20 Hz to 15,000 Hz d. none of the above
ANS: A
14. Noise in a communication system originates in:
a. the sender c. the channel b. the receiver d. all of the above
ANS: D
15. "Man-made" noise can come from:
a. equipment that sparks c. static b. temperature d. all of the above
ANS: A
16. Thermal noise is generated in:
a. transistors and diodes c. copper wire b. resistors d. all of the above
ANS: D
17. Shot noise is generated in:
a. transistors and diodes c. copper wire b. resistors d. none of the above
ANS: A
18. The power density of "flicker" noise is:
a. the same at all frequencies c. greater at low frequencies b. greater at high frequencies d. the same as "white" noise
ANS: C
19. So called "1/f" noise is also called:
a. random noise c. white noise b. pink noise d. partition noise
ANS: B
20. "Pink" noise has:
a. equal power per Hertz c. constant power b. equal power per octave d. none of the above
ANS: B
21. When two noise voltages, V1 and V2, are combined, the total voltage VT is:
a. VT = sqrt(V1 × V1 + V2 × V2) c. VT = sqrt(V1 × V2) b. VT = (V1 + V2)/2 d. VT = V1 + V2
ANS: A
22. Signal-to-Noise ratio is calculated as:
a. signal voltage divided by noise voltage b. signal power divided by noise power c. first add the signal power to the noise power, then divide by noise power d. none of the above
ANS: B
23. SINAD is calculated as:
a. signal voltage divided by noise voltage b. signal power divided by noise power c. first add the signal power to the noise power, then divide by noise power d. none of the above
ANS: D
24. Noise Figure is a measure of:
a. how much noise is in a communications system b. how much noise is in the channel c. how much noise an amplifier adds to a signal d. signal-to-noise ratio in dB
ANS: C
25. The part, or parts, of a sinusoidal carrier that can be modulated are:
a. its amplitude c. its amplitude, frequency, and direction b. its amplitude and frequency d. its amplitude, frequency, and phase angle
ANS: D
COMPLETION
1. The telephone was invented in the year ____________________.
ANS: 1863
2. Radio signals first were sent across the Atlantic in the year ____________________.
ANS: 1901
3. The frequency band used to modulate the carrier is called the ____________________ band.
ANS: base
4. The job of the carrier is to get the information through the ____________________.
ANS: channel
5. The bandwidth of an unmodulated carrier is ____________________.
ANS: zero
6. The 'B' in Hartley's Law stands for ____________________.
ANS: bandwidth
7. The more information per second you send, the ____________________ the bandwidth required.
ANS: greater larger wider
8. In ____________________, you split the bandwidth of a channel into sub-channels to carry multiple
signals.
ANS: FDM
9. In ____________________, multiple signal streams take turns using the channel.
ANS: TDM
10. VHF stands for the ____________________ frequency band.
ANS: very high
11. The VHF band starts at ____________________ MHz.
ANS: 30
12. The UHF band starts at ____________________ MHz.
ANS: 300
13. A radio signal's ____________________ is the distance it travels in one cycle of the carrier.
ANS: wavelength
14. In free space, radio signals travel at approximately ____________________ meters per second.
ANS: 300 million
15. The equipment used to show signals in the frequency domain is the _________________________.
ANS: spectrum analyzer
16. Mathematically, a spectrum is represented by a ____________________ series.
ANS: Fourier
17. Disabling a receiver during a burst of atmospheric noise is called ____________________.
ANS: noise blanking blanking
18. For satellite communications, ____________________ noise can be a serious problem.
ANS: solar
19. Thermal noise is caused by the random motions of ____________________ in a conductor.
ANS: electrons
SHORT ANSWER
1. Name the five elements in a block diagram of a communications system.
ANS: Source, Transmitter, Channel, Receiver, Destination
2. Name five types of internal noise.
ANS: Thermal, Shot, Partition, 1/f, transit-time
3. Why is thermal noise called "white noise"?
ANS: White light is composed of equal amounts of light at all visible frequencies. Likewise, thermal noise has equal power density over a wide range of frequencies.
4. What is "pink noise"?
ANS: Light is pink when it contains more red than it does other colors, and red is at the low end of the visible spectrum. Likewise, pink noise has higher power density at lower frequencies.
5. Suppose there is 30 µV from one noise source that is combined with 40 µV from another noise source.
Calculate the total noise voltage.
ANS: 50 µV
6. If you have 100 mV of signal and 10 mV of noise, both across the same 100-ohm load, what is the signal-
to-noise ratio in dB?
ANS: 20 dB
7. The input to an amplifier has a signal-to-noise ratio of 100 dB and an output signal-to-noise ratio of 80
dB. Find NF, both in dB and as a ratio.
ANS: 20 dB, NF = 100
8. A microwave receiver has a noise temperature of 145 K. Find its noise figure.
ANS: 1.5
9. Two cascaded amplifiers each have a noise figure of 5 and a gain of 10. Find the total NF for the pair.
ANS: 5.4
10. Explain why you could use a diode as a noise source with a spectrum close to that of pure thermal noise.
How would you control the amount of noise generated?
ANS: When current flows through a diode, it generates shot noise that can be represented as a current source, the output of which is a noise current. The equation for the noise current is very similar to the equation for thermal noise voltage. Since the power in the shot noise is proportional to the diode current, controlling the diode current controls the noise power.
Chapter 2: Radio-Frequency Circuits
MULTIPLE CHOICE
1. The time it takes a charge carrier to cross from the emitter to the collector is called:
a. base time c. charge time b. transit time d. Miller time
ANS: B
2. A real capacitor actually contains:
a. capacitance and resistance only c. capacitance, inductance, and resistance b. capacitance and inductance only d. reactance only
ANS: C
3. Bypass capacitors are used to:
a. remove RF from non-RF circuits c. neutralize amplifiers b. couple RF around an amplifier d. reduce the Miller effect
ANS: A
4. A resonant circuit is:
a. a simple form of bandpass filter c. both a and b b. used in narrowband RF amplifiers d. none of the above
ANS: C
5. Loading down a tuned-circuit amplifier will:
a. raise the Q of the tuned circuit c. "multiply" the Q b. lower the Q of the tuned circuit d. have no effect on Q
ANS: B
6. The "Miller Effect" can:
a. cause an amplifier to oscillate c. reduce the bandwidth of an amplifier b. cause an amplifier to lose gain d. all of the above
ANS: D
7. The Miller Effect can be avoided by:
a. using a common-emitter amplifier c. increasing the Q of the tuned circuit b. using a common-base amplifier d. it cannot be avoided
ANS: B
8. In a BJT, the Miller Effect is due to:
a. inductance of collector lead c. base-to-emitter capacitance b. collector-to-emitter capacitance d. base-to-collector capacitance
ANS: D
9. In RF amplifiers, impedance matching is usually done with: a. RC coupling c. direct coupling b. transformer coupling d. lumped reactance
ANS: B
10. Neutralization cancels unwanted feedback by:
a. adding feedback out of phase with the unwanted feedback b. bypassing the feedback to the "neutral" or ground plane c. decoupling it d. none of the above
ANS: A
11. For a "frequency multiplier" to work, it requires:
a. a nonlinear circuit b. a linear amplifier c. a signal containing harmonics d. an input signal that is an integer multiple of the desired frequency
ANS: A
12. A sinusoidal oscillation from an amplifier requires:
a. loop gain equal to unity b. phase shift around loop equal to 0 degrees c. both a and b, but at just one frequency d. none of the above
ANS: C
13. The conditions for sinusoidal oscillation from an amplifier are called:
a. the loop-gain criteria c. the Bode criteria b. the Hartley criteria d. the Barkhausen criteria
ANS: D
14. The Hartley oscillator uses:
a. a tapped inductor c. an RC time constant b. a two-capacitor divider d. a piezoelectric crystal
ANS: A
15. The Colpitts VFO uses:
a. a tapped inductor c. an RC time constant b. a two-capacitor divider d. a piezoelectric crystal
ANS: B
16. The Clapp oscillator is:
a. a modified Hartley oscillator c. a type of crystal-controlled oscillator b. a modified Colpitts oscillator d. only built with FETs
ANS: B
17. A varactor is: a. a voltage-controlled capacitor c. used in tuner circuits b. a diode d. all of the above
ANS: D
18. Crystal-Controlled oscillators are:
a. used for a precise frequency b. used for very low frequency drift (parts per million) c. made by grinding quartz to exact dimensions d. all of the above
ANS: D
19. If two signals, Va = sin(ωat) and Vb = sin(ωbt), are fed to a mixer, the output:
a. will contain ω1 = ωa + ωb and ω2 = ωa – ωb b. will contain ω1 = ωa / ωb and ω2 = ωb / ωa c. will contain ω = (ωa + ωb ) / 2 d. none of the above
ANS: A
20. In a balanced mixer, the output:
a. contains equal (balanced) amounts of all input frequencies b. contains the input frequencies c. does not contain the input frequencies d. is a linear mixture of the input signals
ANS: C
21. "VFO" stands for:
a. Voltage-Fed Oscillator c. Varactor-Frequency Oscillator b. Variable-Frequency Oscillator d. Voltage-Feedback Oscillator
ANS: B
22. A "frequency synthesizer" is:
a. a VCO phase-locked to a reference frequency b. a VFO with selectable crystals to change frequency c. a fixed-frequency RF generator d. same as a mixer
ANS: A
COMPLETION
1. Generally, conductor lengths in RF circuits should be ____________________.
ANS: short
2. At UHF frequencies and above, elements must be considered as ____________________ instead of as
being "lumped".
ANS: distributed
3. When one side of a double-sided pc board is used for ground, it is called a ____________________.
ANS: ground-plane
4. Interactions between parts of an RF circuit can be reduced by using ____________________ between
them.
ANS: shielding
5. In high-frequency RF circuits, the placement of wires and ____________________ can be critical.
ANS: components
6. A ____________________ circuit is used to remove RF from the DC voltage bus.
ANS: decoupling
7. A ____________________ capacitor is used to short unwanted RF to ground.
ANS: bypass
8. The bandwidth of a tuned-circuit amplifier depends on the ____________________ of the tuned circuit.
ANS: Q
9. A value of ____________________ or more for Q is required for the approximate tuned circuit equations
to be valid.
ANS: 10
10. In a class C RF amplifier, the ____________________ extracts one frequency from all the harmonics
contained in the device current (e.g. collector current).
ANS: tuned circuit
11. Using additional feedback to compensate for "stray" feedback is called ____________________.
ANS: neutralization
12. A Colpitts oscillator uses a ____________________ voltage divider to provide feedback.
ANS: capacitive
13. Electrically, a piezoelectric crystal has both a ____________________ and a ____________________
resonant frequency.
ANS: series, parallel
14. To produce sum and difference frequencies, a mixer must be a non-____________________ circuit.
ANS: linear
15. At some bias point, a diode or a transistor can act as a ____________________-law mixer.
ANS: square
SHORT ANSWER
1. What inductance would you use with a 47-pF capacitor to make a tuned circuit for 10 MHz?
ANS: 5.4 µH
2. What value of Q is required for a 10-MHz tuned circuit to have a bandwidth of 100 kHz?
ANS: 100
3. A tuned-circuit amplifier with a gain of 10 is being used to make an oscillator. What should be the value
of the feedback ratio to satisfy the Barkhausen criteria?
ANS: 0.1
4. What is the advantage of a Clapp oscillator compared to a Colpitts oscillator?
ANS: It is more stable because it "swamps" the device capacitance with large value capacitors in the feedback divider.
5. If a varactor has a capacitance of 90 pF at zero volts, what will be the capacitance at 4 volts?
ANS: 30 pF
6. An oscillator has a frequency of 100 MHz at 20°C, and a tempco of +10 ppm per degree Celsius. What
will be the shift in frequency at 70°C? What percentage is that?
ANS: 50 kHz, 0.05%
7. Two sinusoidal signals, V1 and V2, are fed into an ideal balanced mixer. V1 is a 20-MHz signal; V2 is a 5-
MHz signal. What frequencies would you expect at the output of the mixer?
ANS: 15 MHz and 25 MHz
8. Suppose the phase-locked-loop frequency synthesizer of Figure 2.39 has a reference frequency of 1 MHz and a fixed-modulus divider of 10. What should be the value of the programmable divider to get an output frequency of 120 MHz?
ANS: 12
Chapter 3: Amplitude Modulation
MULTIPLE CHOICE
1. AM stands for:
a. Audio Modulation c. Angle Modulation b. Amplitude Modulation d. Antenna Modulation
ANS: B
2. The "envelope" of an AM signal is due to:
a. the baseband signal c. the amplitude signal b. the carrier signal d. none of the above
ANS: A
3. If the audio Va sin(ωat) modulates the carrier Vc sin(ωct), then the modulation index, m, is:
a. m = ωa / ωc c. m = (Va / Vc)2 b. m = Va / Vc d. m = Va / ωa
ANS: B
4. The equation for full-carrier AM is:
a. v(t) = (Ec + Em) × sin(ωct) c. v(t) = (Ec × Em) × sin(ωmt) × sin(ωct) b. v(t) = (Ec + Em) × sin(ωmt) + sin(ωct) d. v(t) = (Ec + Em sin(ωmt)) × sin(ωct)
ANS: D
5. Overmodulation causes:
a. distortion c. both a and b b. splatter d. none of the above
ANS: C
6. The peak voltage of an AM signal goes from Emax to Emin. The modulation index, m, is:
a. m = Emin / Emax c. m = (Emax – Emin) / (Emax + Emin) b. m = Emax / Emin d. m = (Emax + Emin) / (Emax – Emin)
ANS: C
7. If Va sin(ωat) amplitude modulates the carrier Vc sin(ωct), it will produce the frequencies:
a. ωc + ωa and ωc – ωa c. ωc + ωa and 2ωc + 2ωa b. (ωc + ωa)/2 and (ωc – ωa)/2 d. none of the above
ANS: A
8. At 100% modulation, the total sideband power is:
a. equal to the carrier power c. half the carrier power b. twice the carrier power d. 1.414 × carrier power
ANS: C
9. If a 5-kHz signal modulates a 1-MHz carrier, the bandwidth of the AM signal will be:
a. 5 kHz c. 1.005 MHz b. 10 kHz d. none of the above
ANS: B
10. If an AM radio station increases its modulation index, you would expect:
a. the audio to get louder at the receiver c. the signal-to-noise ratio to increase b. the received RF signal to increase d. all of the above
ANS: D
11. The modulation index can be derived from:
a. the time-domain signal c. both a and b b. the frequency-domain signal d. none of the above
ANS: C
12. The main problem in using quadrature AM would be:
a. requires too much bandwidth c. incompatibility with ordinary AM radios b. requires too much power d. all of the above
ANS: C
13. As compared to plain AM, SSB AM:
a. is more efficient b. requires a more complex demodulator circuit c. requires less bandwidth d. all of the above
ANS: D
14. The SC in SSB SC stands for:
a. single-carrier c. sideband-carrier b. suppressed-carrier d. none of the above
ANS: B
15. PEP stands for:
a. Peak Envelope Power c. Peak Envelope Product b. Peak Efficiency Power d. none of the above
ANS: A
16. If an SSB transmitter radiates 1000 watts at peak modulation, what will it radiate with no modulation?
a. 1000 watts c. 250 watts b. 500 watts d. 0 watts
ANS: D
17. Music on AM radio stations is "low-fidelity" because:
a. AM is susceptible to noise
b. commercial AM stations use low power c. commercial AM stations have a narrow bandwidth d. all of the above
ANS: C
18. The type of information that can be sent using AM is:
a. audio c. digital data b. video d. all of the above
ANS: D
19. Two tones modulate an AM carrier. One tone causes a modulation index of m1 and the other tone causes a
modulation index of m2. The total modulation index is: a. m1 + m2 c. sqrt(m1 × m2 + m2 × m1) b. (m1 + m2) / 2 d. sqrt(m1 × m1 + m2 × m2)
ANS: D
20. To demodulate a USB SSB signal, the receiver must:
a. be set to USB mode c. both a and b b. reinsert the carrier d. none of the above
ANS: C
COMPLETION
1. An advantage of AM is that the receiver can be very ____________________.
ANS: simple
2. A disadvantage of AM is its ____________________ use of power.
ANS: inefficient
3. The ____________________ of an AM signal resembles the shape of the baseband signal.
ANS: envelope
4. In AM, modulating with a single audio tone produces ____________________ sidebands.
ANS: two
5. Compared to the USB, the information in the LSB is ____________________.
ANS: the same
6. Compared to the USB, the power in the LSB is ____________________.
ANS: the same
7. In AM, total sideband power is always ____________________ than the carrier power.
ANS: less
8. In AM, as the modulation index increases, the carrier power _________________________.
ANS: remains constant
9. The power in an AM signal is maximum when the modulation index is ____________________.
ANS: one
10. In AM, a voice-band signal of 300 Hz to 3000 Hz will require a bandwidth of ____________________.
ANS: 6000 Hz
11. With a 1-MHz carrier, if the LSB extends down to 990 kHz, then the USB will extend up to
____________________.
ANS: 1010 kHz
12. If an AM transmitter puts out 100 watts with no modulation, it will put out ____________________ watts
with 100% modulation.
ANS: 150
SHORT ANSWER
1. An AM transmitter generates 100 watts with 0% modulation. How much power will it generate with 20%
modulation?
ANS: 102 watts
2. If the carrier power is 1000 watts, what is the power in the USB at 70.7% modulation?
ANS: 125 watts
3. A carrier is modulated by three audio tones. If the modulation indexes for the tones are 0.3, 0.4, and 0.5,
then what is the total modulation index?
ANS: 0.707
4. You look at an AM signal with an oscilloscope and see that the maximum Vpp is 100 volts and the
minimum Vpp is 25 volts. What is the modulation index?
ANS: 0.6
5. A SSB transmitter is connected to a 50-ohm antenna. If the peak output voltage of the transmitter is 20
volts, what is the PEP?
ANS: 4 watts
Chapter 4: Angle Modulation
MULTIPLE CHOICE
1. The FM modulation index:
a. increases with both deviation and modulation frequency b. increases with deviation and decreases with modulation frequency c. decreases with deviation and increases with modulation frequency d. is equal to twice the deviation
ANS: B
2. One way to derive FM from PM is:
a. integrate the modulating signal before applying to the PM oscillator b. integrate the signal out of the PM oscillator c. differentiate the modulating signal before applying to the PM oscillator d. differentiate the signal out of the PM oscillator
ANS: A
3. The bandwidth of an FM signal is considered to be limited because:
a. there can only be a finite number of sidebands b. it is equal to the frequency deviation c. it is band-limited at the receiver d. the power in the outer sidebands is negligible
ANS: D
4. Mathematically, the calculation of FM bandwidth requires the use of:
a. ordinary trigonometry and algebra c. Taylor series b. Bessel functions d. fractals
ANS: B
5. FM bandwidth can be approximated by:
a. Armstrong's Rule c. Carson's Rule b. Bessel's Rule d. none of the above
ANS: C
6. NBFM stands for:
a. National Broadcast FM c. Near Band FM b. Non-Broadcast FM d. Narrowband FM
ANS: D
7. When FM reception deteriorates abruptly due to noise, it is called:
a. the capture effect c. the noise effect b. the threshold effect d. the limit effect
ANS: B
8. An FM receiver switching suddenly between two stations on nearby frequencies is called: a. the capture effect c. the "two-station" effect b. the threshold effect d. none of the above
ANS: A
9. Pre-emphasis is used to:
a. increase the signal to noise ratio for higher audio frequencies b. increase the signal to noise ratio for lower audio frequencies c. increase the signal to noise ratio for all audio frequencies d. allow stereo audio to be carried by FM stations
ANS: A
10. A pre-emphasis of 75 µs refers to:
a. the time it takes for the circuit to work b. the "dead time" before de-emphasis occurs c. the time delay between the L and R channels d. the time-constant of the filter circuits used
ANS: D
11. FM stereo:
a. uses DSBSC AM modulation c. has a higher S/N than mono FM b. is implemented using an SCA signal d. is not compatible with mono FM
ANS: A
12. An SCA signal:
a. can use amplitude modulation c. is monaural b. can use FM modulation d. all of the above
ANS: D
13. The modulation index of an FM signal can be determined readily:
a. using measurements at points where J0 equals one b. using measurements at points where J0 equals zero c. using measurements at points where the deviation equals zero d. only by using Bessel functions
ANS: B
COMPLETION
1. FM and PM are two forms of ____________________ modulation.
ANS: angle
2. PM is extensively used in ____________________ communication.
ANS: data
3. Compared to AM, the signal-to-noise ratio of FM is usually ____________________.
ANS: better
4. Compared to AM, the bandwidth of FM is usually ____________________.
ANS: wider greater
5. FM transmitters can use Class ____________________ amplifiers since amplitude linearity is not
important.
ANS: C
6. Both the power and amplitude of an FM signal ____________________ as modulation is applied.
ANS: stay constant
7. In FM, the frequency deviation is proportional to the instantaneous ____________________ of the
modulating signal.
ANS: amplitude
8. The frequency deviation of an FM signal occurs at a rate equal to the ____________________ of the
modulating signal.
ANS: frequency
9. Mathematically, the number of sidebands in an FM signal is ____________________.
ANS: infinite
10. As FM sidebands get farther from the center frequency, their power ____________________.
ANS: decreases
11. Mathematically, the value of an FM modulation index can be as high as ____________________.
ANS: any number
12. In FM, as the modulating frequency decreases, the modulation index ____________________.
ANS: increases
13. In FM, as the frequency deviation decreases, the modulation index ____________________.
ANS: decreases
14. As the FM modulation index increases, the number of significant sidebands ____________________.
ANS: increases
15. For certain values of mf, such as 2.4, the amplitude of the carrier frequency ____________________.
ANS: disappears goes to zero
16. The bandwidth of an FM signal can be approximated using ____________________ rule.
ANS: Carson's
17. FM bandwidth can be calculated precisely using ____________________ functions.
ANS: Bessel
18. The ____________________ effect is characteristic of FM reception in a noisy environment.
ANS: threshold
19. The ____________________ effect is seen when an FM receiver is exposed to two FM signals that are
close to each other in frequency.
ANS: capture
20. Rest frequency is another name for an FM ____________________ frequency.
ANS: carrier
SHORT ANSWER
1. If a 2-volt instantaneous value of modulating signal amplitude causes a 10-kHz deviation in carrier
frequency, what is the deviation sensitivity of the modulator?
ANS: 5 kHz / volt
2. If a 2-kHz audio tone causes a frequency deviation of 4 kHz, what is the modulation index?
ANS: 2
3. What will be the deviation caused by a 3-kHz tone if the modulation index is 3?
ANS: 9 kHz
4. If the deviation sensitivity of an FM modulator is 2 kHz /V, what will be the modulation index caused by
a 1-volt, 1-kHz audio signal?
ANS: 2
5. At a modulation index of 2, how much power is in the carrier of a 1000-watt FM transmitter?
ANS: 48.4 watts
6. At a modulation index of 2, how much power is in the first pair of sidebands of a 1000-watt FM
transmitter?
ANS: 673 watts
7. At a modulation index of 2, how much power is in the fifth pair of sidebands of a 1000-watt FM
transmitter?
ANS: 200 mW (0.2 watt)
8. Using Carson's rule, what is the approximate bandwidth of an FM signal with a modulation index of 2
being modulated by a 5-kHz signal?
ANS: 30 kHz
9. Using the Bessel chart of Figure 4.1, what is the bandwidth of an FM signal with a modulation index of 2
being modulated by a 5-kHz signal if we ignore sidebands containing less than 1% of the total power?
ANS: 30 kHz
10. How would you use the fact that J0 is zero for certain known values of mf (2.4, 5.5, etc) to measure the
frequency deviation of an FM modulator?
ANS: Use an audio frequency generator to modulate the FM carrier. Using a spectrum analyzer, adjust the audio frequency until the carrier amplitude vanishes. Record the audio frequency. Then do the calculation: δ = fm × mf where mf will have one of the known values. For example, if fm is measured to be 2 kHz when mf is 5.5, then δ is 11 kHz.
Chapter 5: Transmitters
MULTIPLE CHOICE
1. The ability to change operating frequency rapidly without a lot of retuning is called:
a. agility c. VFO b. expansion d. spread-spectrum
ANS: A
2. The difference between the DC power into a transmitter and the RF power coming out:
a. is a measure of efficiency c. may require water cooling b. heats the transmitter d. all of the above
ANS: D
3. Baseband compression produces:
a. a smaller range of frequencies from low to high b. a smaller range of amplitude from soft to loud c. a smaller number of signals d. none of the above
ANS: B
4. ALC stands for:
a. Amplitude Level Control c. Accurate Level Control b. Automatic Level Control d. none of the above
ANS: B
5. In an AM transmitter, ALC is used to:
a. keep the modulation close to 100% c. maximize transmitted power b. keep the modulation below 100% d. all of the above
ANS: D
6. With high-level AM:
a. all RF amplifiers can be nonlinear c. minimum RF power is required b. minimum modulation power is required d. all of the above
ANS: A
7. With high-level AM:
a. the RF amplifiers are typically Class A c. the RF amplifiers are typically Class C b. the RF amplifiers are typically Class B d. the RF amplifiers are typically Class AB
ANS: C
8. With low-level AM:
a. the RF amplifiers must be Class A c. the RF amplifiers must be linear b. the RF amplifiers must be Class B d. the RF amplifiers must be low-power
ANS: C
9. Power amplifiers must be linear for any signal that:
a. is complex c. has variable frequency b. has variable amplitude d. all of the above
ANS: B
10. In high-level AM, "high-level" refers to:
a. the power level of the carrier c. the power level of the final RF amplifier b. the power level of the modulation d. none of the above
ANS: D
11. In high-level AM, the power in the sidebands comes from:
a. the modulating amplifier c. the driver stage b. the RF amplifier d. the carrier
ANS: A
12. In an AM transmitter with 100% modulation, the voltage of the final RF stage will be:
a. approximately half the DC supply voltage b. approximately twice the DC supply voltage c. approximately four times the DC supply voltage d. none of the above
ANS: C
13. Practical transmitters are usually designed to drive a load impedance of:
a. 50 ohms resistive c. 300 ohms resistive b. 75 ohms resistive d. 600 ohms resistive
ANS: A
14. Which of the following can be used for impedance matching?
a. pi network c. both a and b b. T network d. a bridge circuit
ANS: C
15. When a transmitter is connected to a resistor instead of an antenna, the resistor is called:
a. a heavy load c. a temporary load b. a dummy load d. a test load
ANS: B
16. When a transmitter is connected to a resistor instead of an antenna, the resistor must be:
a. wire-wound c. 1% tolerance or better b. noninductive d. all of the above
ANS: B
17. A Class D amplifier is:
a. very efficient c. essentially pulse-duration modulation
b. essentially pulse-width modulation d. all of the above
ANS: D
18. To generate a SSB signal:
a. start with full-carrier AM c. start with a quadrature signal b. start with DSBSC d. all of the above
ANS: B
19. The carrier is suppressed in:
a. a balanced modulator c. a frequency multiplier b. a mixer d. none of the above
ANS: A
20. To remove one AM sideband and leave the other you could use:
a. a mechanical filter c. both a and b b. a crystal filter d. none of the above
ANS: C
21. A direct FM modulator:
a. varies the frequency of the carrier oscillator b. integrates the modulating signal c. both a and b d. none of the above
ANS: A
22. An indirect FM modulator:
a. requires a varactor in the carrier oscillator b. varies the phase of the carrier oscillator c. both a and b d. none of the above
ANS: B
23. AFC stands for:
a. Amplitude to Frequency Conversion c. Automatic Frequency Control b. Automatic Frequency Centering d. Audio Frequency Control
ANS: C
24. Frequency multipliers are:
a. essentially balanced modulators c. essentially mixers b. essentially Class C amplifiers d. none of the above
ANS: B
25. With mixing:
a. the carrier frequency can be raised b. the carrier frequency can be lowered c. the carrier frequency can be changed to any required value
d. the deviation is altered
ANS: C
COMPLETION
1. The accuracy and stability of a transmitter frequency is fixed by the ____________________ oscillator.
ANS: carrier
2. In the USA, the ____________________ sets requirements for accuracy and stability of a transmitter's
frequency.
ANS: FCC
3. In Canada, _________________________ sets requirements for accuracy and stability of a transmitter's
frequency.
ANS: Industry Canada
4. Frequency ____________________ is the ability of a transmitter to change frequency without a lot of
retuning.
ANS: agility
5. Power output of SSB transmitters is rated by ____________________.
ANS: PEP
6. Reducing the dynamic range of a modulating signal is called ____________________.
ANS: compression
7. The opposite of compression is called ____________________.
ANS: expansion
8. ALC is a form of ____________________.
ANS: compression
9. High-level modulation allows the RF amplifiers to operate more ____________________.
ANS: efficiently
10. Low-level modulation requires the RF amplifiers to be ____________________.
ANS: linear
11. To isolate the oscillator from load changes, a ____________________ stage is used.
ANS: buffer
12. The peak collector voltage in a Class C RF amplifier is ____________________ than the DC supply
voltage.
ANS: higher
13. Most practical transmitters are designed to operate into a ____________________-ohm load.
ANS: 50
14. Transmitters built with transistor RF amplifiers often use a ____________________ network for
impedance matching.
ANS: T
15. Matching networks also act as filters to help reduce ____________________ levels.
ANS: harmonic
16. Severe impedance ____________________ can destroy a transmitter's output stage.
ANS: mismatch
17. Transceivers combine a transmitter and a ____________________ into one "box".
ANS: receiver
18. To allow a high modulation percentage, it is common to modulate the ____________________ as well as
the power amplifier in transistor modulators.
ANS: driver
19. Pulse-width modulation is the same as pulse-____________________ modulation.
ANS: duration
20. Switching amplifiers are sometimes called Class ____________________ amplifiers.
ANS: D
21. Because the sideband filter in a SSB transmitter is fixed, ____________________ is used to operate at
more than one frequency.
ANS: mixing
22. To generate a SSB signal, it is common to start with a ____________________ signal.
ANS: DSBSC
23. Indirect FM is derived from ____________________ modulation.
ANS: phase
24. Using a varactor to generate FM is an example of a ____________________ modulator.
ANS: reactance
25. The modern way to make a stable VFO is to make it part of a ____________________ loop.
ANS: phase-locked
SHORT ANSWER
1. If a 50-MHz oscillator is accurate to within 0.001%, what is the range of possible frequencies?
ANS: 50 MHz ± 500 hertz
2. What is the efficiency of a 100-watt mobile transmitter if it draws 11 amps from a 12-volt car battery?
ANS: 75.8%
3. The power amplifier of an AM transmitter draws 100 watts from the power supply with no modulation.
Assuming high-level modulation, how much power does the modulation amplifier deliver for 100% modulation?
ANS: 50 watts
4. If the final RF amplifier of an AM transmitter is powered by 100 volts DC, what is the maximum
collector voltage at 100% modulation?
ANS: 400 volts
5. Suppose the output of a balanced modulator has a center frequency of 10 MHz. The audio modulation
frequency range is 1 kHz to 10 kHz. To pass the USB, what should be the center frequency of an ideal crystal filter?
ANS: 10.005 MHz
6. Suppose you have generated a USB SSB signal with a nominal carrier frequency of 10 MHz. What is the
minimum frequency the SSB signal can be mixed with so that the output signal has a nominal carrier frequency of 50 MHz?
ANS: 40 MHz
7. Suppose you have an FM modulator that puts out 1 MHz carrier with a 100-hertz deviation. If frequency
multiplication is used to increase the deviation to 400 hertz, what will be the new carrier frequency?
ANS: 4 MHz
8. Suppose you had an FM signal with a carrier of 10 MHz and a deviation of 10 kHz. Explain how you
could use it to get an FM signal at 100 MHz with a deviation of 20 kHz.
ANS: First, put the signal through a frequency doubler to get a 20-MHz carrier with a 20-kHz deviation. Then mix that signal with an 80-MHz carrier to generate a 100-MHz carrier with 20-kHz deviation.
Chapter 6: Receivers
MULTIPLE CHOICE
1. The two basic specifications for a receiver are:
a. the sensitivity and the selectivity b. the number of converters and the number of IFs c. the spurious response and the tracking d. the signal and the noise
ANS: A
2. The superheterodyne receiver was invented by:
a. Foster c. Armstrong b. Seeley d. Hertz
ANS: C
3. Trimmers and padders are:
a. two types of adjusting tools c. small adjustable inductors b. small adjustable resistors d. small adjustable capacitors
ANS: D
4. "Skin effect" refers to:
a. the way radio signals travel across a flat surface b. the tissue-burning effect of a strong RF signal c. the increase of wire resistance with frequency d. none of the above
ANS: C
5. The "front end" of a receiver can include:
a. the tuner c. the mixer b. the RF amplifier d. all of the above
ANS: D
6. "IF" stands for:
a. intermediate frequency c. indeterminate frequency b. intermodulation frequency d. image frequency
ANS: A
7. AGC stands for:
a. Audio Gain Control c. Active Gain Control b. Automatic Gain Control d. Active Gain Conversion
ANS: B
8. The frequency of the local oscillator:
a. is above the RF frequency
b. is below the RF frequency c. can be either above of below the RF frequency d. is fixed, typically at 455 kHz.
ANS: C
9. The local oscillator and mixer are combined in one device because:
a. it gives a greater reduction of spurious responses b. it increases sensitivity c. it increases selectivity d. it is cheaper
ANS: D
10. Basically, sensitivity measures:
a. the weakest signal that can be usefully received b. the highest-frequency signal that can be usefully received c. the dynamic range of the audio amplifier d. none of the above
ANS: A
11. Basically, selectivity measures:
a. the range of frequencies that the receiver can select b. with two signals close in frequency, the ability to receive one and reject the other c. how well adjacent frequencies are separated by the demodulator d. how well the adjacent frequencies are separated in the mixer
ANS: B
12. When comparing values for shape factor:
a. a value of 1.414 dB is ideal c. a value of 1.0 is ideal b. a value of 0.707 is ideal d. there is no ideal value
ANS: C
13. When comparing values for shape factor:
a. a value of 2 is better than a value of 4 c. both values are basically equivalent b. a value of 4 is better than a value of 2 d. none of the above
ANS: A
14. Distortion in a receiver can occur in:
a. the mixer c. the IF amplifiers b. the detector d. all of the above
ANS: D
15. Phase distortion is important in:
a. voice communications systems c. monochrome video receivers b. color video receivers d. all of the above
ANS: B
16. The response of a receiver to weak signals is usually limited by: a. the AGC c. the dynamic range of the receiver b. noise generated in the receiver d. the type of detector circuit being used
ANS: B
17. Image frequencies occur when two signals:
a. are transmitted on the same frequency b. enter the mixer, with one being a reflected signal equal to the IF frequency c. enter the mixer, one below and one above the local oscillator by a difference equal to the
IF d. enter the mixer, and the difference between the two signals is equal to twice the IF
ANS: C
18. An image must be rejected:
a. prior to mixing c. prior to detection b. prior to IF amplification d. images cannot be rejected
ANS: A
19. Image frequency problems would be reduced by:
a. having an IF amplifier with the proper shape factor b. having a wideband RF amplifier after the mixer c. having a narrowband RF amplifier before the mixer d. none of the above
ANS: C
20. A common AM detector is the:
a. PLL c. ratio detector b. envelope detector d. all of the above
ANS: B
21. An FM detector is the:
a. PLL c. quadrature detector b. ratio detector d. all of the above
ANS: D
22. Germanium diodes are used in AM detectors because:
a. they are faster than silicon diodes b. they are cheaper than silicon diodes c. they minimize distortion from nonlinearity d. all of the above
ANS: C
23. A common SSB detector is:
a. a PLL c. a BFO b. a diode d. a product detector
ANS: D
24. BFO stands for:
a. Beat Frequency Oscillator c. Bipolar Frequency Oscillator b. Barrier Frequency Oscillator d. Bistable Frequency Oscillator
ANS: A
25. To demodulate both SSB and DSBSC, you need to:
a. use a Foster-Seeley discriminator b. reinject the carrier c. use double conversion d. use one diode for SSB and two diodes for DSBSC
ANS: B
26. Which would be best for DSBSC:
a. carrier detection c. envelope detection b. coherent detection d. ratio detection
ANS: B
27. An FM detector that is not sensitive to amplitude variations is:
a. Foster-Seeley detector c. a PLL detector b. a quadrature detector d. all of the above
ANS: C
28. The function of a limiter is:
a. to remove amplitude variations c. to limit dynamic range b. to limit spurious responses d. to limit noise response
ANS: A
29. Suppressing the audio when no signal is present is called:
a. AGC c. AFC b. squelch d. limiting
ANS: B
30. LNA stands for:
a. Limited-Noise Amplifier c. Low-Noise Audio b. Low-Noise Amplifier d. Logarithmic Noise Amplification
ANS: B
31. AFC stands for:
a. Audio Frequency Compensator c. Automatic Frequency Control b. Autodyne Frequency Compensation d. Autonomous Frequency Control
ANS: C
32. The function of AFC is:
a. maintain a constant IF frequency b. match the local oscillator to the received signal
c. lock the discriminator to the IF frequency d. none of the above
ANS: B
33. SAW stands for:
a. Symmetrical Audio Wave c. Silicon-Activated Wafer b. Surface Acoustic Wave d. Software-Activated Wave
ANS: B
34. The important property of a SAW is:
a. it stabilizes the audio in a receiver c. it is a stable bandpass filter b. it allows software radios to be built d. none of the above
ANS: C
35. The main function of the AGC is to:
a. keep the gain of the receiver constant b. keep the gain of the IF amplifiers constant c. keep the input to the detector at a constant amplitude d. all of the above
ANS: C
36. DSP stands for:
a. Dynamic Signal Properties c. Distorted Signal Packet b. Direct Signal Phase d. Digital Signal Processor
ANS: D
37. SINAD stands for:
a. Sinusoidal Amplitude Distortion b. Signal and Noise Amplitude Distortion c. Signal-plus-Noise-to-Noise Ratio d. Signal-plus-Noise and Distortion-to-Noise and Distortion Ratio
ANS: D
38. TRF stands for:
a. Tuned Radio Frequency c. Transmitted Radio Frequency b. Tracking Radio Frequency d. Tuned Receiver Function
ANS: A
COMPLETION
1. Almost all modern receivers use the _________________________ principle.
ANS: superheterodyne
2. The first radio receiver of any kind was built in the year ____________________.
ANS: 1887
3. When two tuned circuits ____________________ each other, it means that when the frequency of one is
adjusted, the other changes with it.
ANS: track
4. The ____________________ effect causes the resistance of wire to increase with frequency.
ANS: skin
5. The superhet was invented in the year ____________________.
ANS: 1918
6. In a receiver, the ____________________ refers to the input filter and RF stage.
ANS: front end
7. In a superhet, the output of the ____________________ goes to the IF amplifiers.
ANS: mixer
8. In a superhet, the ____________________ frequency is the difference between the local oscillator
frequency and the received signal frequency.
ANS: intermediate IF
9. The ____________________ circuit adjusts the gain of the IF amplifiers in response to signal strength.
ANS: AGC
10. An ____________________ converter uses the same transistor for both the local oscillator and the mixer.
ANS: autodyne
11. In low-side injection, the local oscillator is ____________________ than the received signal frequency.
ANS: lower
12. ____________________ is the ability of a receiver to separate two signals that are close to each other in
frequency.
ANS: Selectivity
13. ____________________ is the ability of a receiver to receive and successfully demodulate a very weak
signal.
ANS: Sensitivity
14. A receiver with two different IF frequencies is called a double-____________________ receiver.
ANS: conversion
15. A multiple-conversion receiver will have better rejection of ____________________ frequencies.
ANS: image
16. A demodulator is also called a ____________________.
ANS: detector
17. An ____________________ detector uses a diode to half-wave rectify an AM signal.
ANS: envelope
18. A ____________________ detector is used for SSB signals.
ANS: product
19. A BFO produces a locally generated ____________________.
ANS: carrier
20. A DSBSC signal requires a ____________________ detection circuit.
ANS: coherent
21. FM detectors have a characteristic ____________________-shaped curve.
ANS: S
22. While still commonly found, the Foster-Seeley and ratio detectors are ____________________.
ANS: obsolescent
23. Unlike the PLL detector, the quadrature detector is sensitive to changes in ____________________ of the
input signal.
ANS: amplitude
24. A dual-____________________ MOSFET is useful for AGC.
ANS: gate
25. Diode mixers are too ____________________ to be practical in most applications.
ANS: noisy
26. The IF amplifiers in an AM receiver must be Class ____________________.
ANS: A
27. A double-tuned IF transformer is usually ____________________ coupled for the response to have a flat
top and steep sides.
ANS: over
28. Multiple IF stages can be ____________________-tuned to increase the bandwidth.
ANS: stagger
29. Compared to tuned circuits, ceramic and crystal IF filters do not require ____________________.
ANS: adjustment
30. Up-conversion is when the output of the mixer is a ____________________ frequency than the incoming
signal.
ANS: higher
31. In a block converter, the frequency of the first local oscillator is ____________________.
ANS: fixed constant
32. Typically, AGC reduces the gain of the ____________________ amplifiers.
ANS: IF
33. An ____________________-meter is designed to indicate signal strength in many communications
receivers.
ANS: S
34. The effectiveness of FM ____________________ is measured by a receiver’s quieting sensitivity.
ANS: limiting
35. A ____________________ refers to any kind of FM or PM detector.
ANS: discriminator
SHORT ANSWER
1. Suppose the bandwidth of a tuned circuit is 10 kHz at 1 MHz. Approximately what bandwidth would you
expect it to have at 4 MHz?
ANS:
20 kHz
2. Using high-side injection for a 1-MHz IF, what is the frequency of the local oscillator when the receiver
is tuned to 5 MHz?
ANS: 6 MHz
3. An IF filter has a –60 dB bandwidth of 25 kHz and a –6 dB bandwidth of 20 kHz. What is the shape
factor value?
ANS: 1.25
4. Suppose a receiver uses a 5-MHz IF frequency. Assuming high-side injection, what would be the image
frequency if the receiver was tuned to 50 MHz?
ANS: 60 MHz
5. Suppose a SSB receiver requires an injected frequency of 1.5 MHz. What would be the acceptable
frequency range of the BFO if the maximum acceptable baseband shift is 100 hertz?
ANS: 1.5 MHz ± 100 hertz
6. The transformer of a double-tuned IF amplifier has a Q of 25 for both primary and secondary. What value
of kc do you need to achieve optimal coupling?
ANS: 0.06
7. What value of transformer coupling would a double-tuned 10-MHz IF amplifier with optimal coupling
need to get a bandwidth of 100 kHz?
ANS: 0.01
Chapter 7: Digital Communications
MULTIPLE CHOICE
1. The first digital code was the:
a. ASCII code c. Morse code b. Baudot code d. none of the above
ANS: C
2. In digital transmission, signal degradation can be removed using:
a. an amplifier c. a regenerative repeater b. a filter d. all of the above
ANS: C
3. TDM stands for:
a. Time-Division Multiplexing c. Ten-Digital Manchester b. Time-Domain Multiplexing d. Ten Dual-Manchester
ANS: A
4. Hartley's Law is:
a. I = ktB c. C = B log2(1 + S/N) b. C = 2B log2M d. SR = 2fmax
ANS: A
5. The Shannon-Hartley theorem is:
a. I = ktB c. C = B log2(1 + S/N) b. C = 2B log2M d. SR = 2fmax
ANS: B
6. The Shannon Limit is given by:
a. I = ktB c. C = B log2(1 + S/N) b. C = 2B log2M d. SR = 2fmax
ANS: C
7. The Nyquist Rate can be expressed as:
a. I = ktB c. C = B log2(1 + S/N) b. C = 2B log2M d. SR = 2fmax
ANS: D
8. Natural Sampling does not use:
a. a sample-and-hold circuit c. a fixed sample rate b. true binary numbers d. an analog-to-digital converter
ANS: A
9. Which is true about aliasing and foldover distortion? a. They are two types of sampling error. b. You can have one or the other, but not both. c. Aliasing is a technique to prevent foldover distortion. d. They are the same thing.
ANS: D
10. Foldover distortion is caused by:
a. noise c. too few samples per second b. too many samples per second d. all of the above
ANS: C
11. The immediate result of sampling is:
a. a sample alias c. PCM b. PAM d. PDM
ANS: B
12. Which of these is not a pulse-modulation technique:
a. PDM c. PPM b. PWM d. PPS
ANS: D
13. Quantizing noise (quantization noise):
a. decreases as the sample rate increases b. decreases as the sample rate decreases c. decreases as the bits per sample increases d. decreases as the bits per sample decreases
ANS: C
14. The dynamic range of a system is the ratio of:
a. the strongest transmittable signal to the weakest discernible signal b. the maximum rate of conversion to the minimum rate of conversion c. the maximum bits per sample to the minimum bits per sample d. none of the above
ANS: A
15. Companding is used to:
a. compress the range of base-band frequencies b. reduce dynamic range at higher bit-rates c. preserve dynamic range while keeping bit-rate low d. maximize the useable bandwidth in digital transmission
ANS: C
16. In North America, companding uses:
a. the Logarithmic Law c. the α Law (alpha law) b. the A Law d. the µ Law (mu law)
ANS: D
17. In Europe, companding uses:
a. the Logarithmic Law c. the α Law (alpha law) b. the A Law d. the µ Law (mu law)
ANS: B
18. Codec stands for:
a. Coder-Decoder c. Code-Compression b. Coded-Carrier d. none of the above
ANS: A
19. A typical codec in a telephone system sends and receives:
a. 4-bit numbers c. 12-bit numbers b. 8-bit numbers d. 16-bit numbers
ANS: B
20. Compared to PCM, delta modulation:
a. transmits fewer bits per sample c. can suffer slope overload b. requires a much higher sampling rate d. all of the above
ANS: D
21. In delta modulation, "granular noise" is produced when:
a. the signal changes too rapidly c. the bit rate is too high b. the signal does not change d. the sample is too large
ANS: B
22. Compared to PCM, adaptive delta modulation can transmit voice:
a. with a lower bit rate but reduced quality c. only over shorter distances b. with a lower bit rate but the same quality d. only if the voice is band-limited
ANS: B
23. Which coding scheme requires DC continuity:
a. AMI c. unipolar NRZ b. Manchester d. bipolar RZ
ANS: C
24. Manchester coding:
a. is a biphase code b. has a level transition in the middle of every bit period c. provides strong timing information d. all of the above
ANS: D
25. The number of framing bits in DS-1 is:
a. 1 c. 4 b. 2 d. 8
ANS: A
26. Framing bits in DS-1 are used to:
a. detect errors c. synchronize the transmitter and receiver b. carry signaling d. all of the above
ANS: C
27. So-called "stolen" bits in DS-1 are used to:
a. detect errors c. synchronize the transmitter and receiver b. carry signaling d. all of the above
ANS: B
28. The number of bits per sample in DS-1 is:
a. 1 c. 4 b. 2 d. 8
ANS: D
29. The number of samples per second in DS-1 is:
a. 8 k c. 64 k b. 56 k d. 1.544 × 106
ANS: A
30. The bit rate for each channel in DS-1 is:
a. 1.544 Mb/s c. 56 kb/s b. 64 kb/s d. 8 kb/s
ANS: B
31. In DS-1, bits are transmitted over a T-1 cable at:
a. 1.544 MB/s c. 56 kb/s b. 64 kb/s d. 8 kb/s
ANS: A
32. A T-1 cable uses:
a. Manchester coding c. NRZ coding b. bipolar RZ AMI coding d. pulse-width coding
ANS: B
33. The number of frames in a superframe is:
a. 6 c. 24 b. 12 d. 48
ANS: B
34. A typical T-1 line uses:
a. twisted-pair wire c. fiber-optic cable b. coaxial cable d. microwave
ANS: A
35. "Signaling" is used to indicate:
a. on-hook/off-hook condition c. ringing b. busy signal d. all of the above
ANS: D
36. A vocoder implements compression by:
a. constructing a model of the transmission medium b. constructing a model of the human vocal system c. finding redundancies in the digitized data d. using lossless techniques
ANS: B
37. Compared to standard PCM systems, the quality of the output of a vocoder is:
a. much better c. about the same b. somewhat better d. not as good
ANS: D
COMPLETION
1. Digitizing a signal often results in ____________________ transmission quality.
ANS: improved better
2. To send it over an analog channel, a digital signal must be ____________________ onto a carrier.
ANS: modulated
3. To send it over a digital channel, an analog signal must first be ____________________.
ANS: digitized
4. In analog channels, the signal-to-noise ratio of an analog signal gradually ____________________ as the
length of the channel increases.
ANS: decreases gets worse
5. The ____________________ value of a pulse is the only information it carries on a digital channel.
ANS: binary
6. A ____________________ repeater is used to restore the shape of pulses on a digital cable.
ANS: regenerative
7. There are techniques to detect and ____________________ some errors in digital transmission.
ANS: correct
8. Converting an analog signal to digital form is another source of ____________________ in digital
transmission systems.
ANS: error noise
9. ____________________-division multiplexing is easily done in digital transmission.
ANS: Time
10. All practical communications channels are band-____________________.
ANS: limited
11. ____________________ Law gives the relationship between time, information capacity, and bandwidth.
ANS: Hartley's
12. Ignoring noise, the _________________________ theorem gives the maximum rate of data transmission
for a given bandwidth.
ANS: Shannon-Hartley
13. The ____________________ limit gives the maximum rate of data transmission for a given bandwidth
and a given signal-to-noise ratio.
ANS: Shannon
14. ____________________ sampling is done without a sample-and-hold circuit.
ANS: Natural
15. The ____________________ Rate is the minimum sampling rate for converting analog signals to digital
format.
ANS: Nyquist
16. ____________________ distortion occurs when an analog signal is sampled at too slow a rate.
ANS: Foldover
17. ____________________ means that higher frequency baseband signals from the transmitter "assume the identity" of low-frequency baseband signals at the receiver when sent digitally.
ANS: Aliasing
18. The output of a sample-and-hold circuit is a pulse-____________________ modulated signal.
ANS: amplitude
19. ____________________ modulation is the most commonly used digital modulation scheme.
ANS: Pulse-code
20. ____________________ noise results from the process of converting an analog signal into digital format.
ANS: Quantizing
21. ____________________ is used to preserve dynamic range using a reasonable bandwidth.
ANS: Companding
22. In North America, compression is done using the ____________________-law equation.
ANS: µ mu
23. In Europe, compression is done using the ____________________-law equation.
ANS: A
24. A ____________________ is an IC that converts a voice signal to PCM and vice versa.
ANS: codec
25. In a PCM system, the samples of the analog signal are first converted to ____________________ bits
before being compressed to 8 bits.
ANS: 12
26. The number of bits per sample transmitted in delta modulation is ____________________.
ANS: 1 one
27. Delta modulation requires a ____________________ sampling rate than PCM for the same quality of
reproduction.
ANS: higher
28. ____________________ noise is produced by a delta modulator if the analog signal doesn't change.
ANS: Granular
29. In delta modulation, ____________________ overload can occur if the analog signal changes too fast.
ANS: slope
30. The ____________________ size varies in adaptive delta modulation.
ANS: step
31. Adaptive delta modulation can transmit PCM-quality voice at about ____________________ the bit rate
of PCM.
ANS: half
32. Unipolar NRZ is not practical because most channels do not have ____________________ continuity.
ANS: DC
33. In AMI, binary ones are represented by a voltage that alternates in ____________________.
ANS: polarity
34. Long strings of ____________________ should be avoided in AMI.
ANS: zeros
35. Manchester code has a level ____________________ in the center of each bit period.
ANS: transition
36. Manchester coding provides ____________________ information regardless of the pattern of ones and
zeros.
ANS: timing
37. There are ____________________ channels in a DS-1 frame.
ANS: 24
38. DS-1 uses a ____________________ bit to synchronize the transmitter and receiver.
ANS: framing
39. In DS-1, each channel is sampled ____________________ times per second.
ANS: 8000
40. Data is carried over a T-1 line at a rate of ____________________ bits per second.
ANS: 1.544 × 106
41. A group of 12 DS-1 frames is called a ____________________.
ANS: superframe
42. From a group of twelve frames, signaling bits are "stolen" from every ____________________ frame.
ANS: sixth
43. ____________________ compression transmits all the data in the original signal but uses fewer bits to do
it.
ANS: Lossless
SHORT ANSWER
1. Use Hartley's Law to find how much time it would take to send 100,000 bits over a channel with a
bandwidth of 2,000 hertz and a channel constant of k = 10.
ANS: 5 seconds
2. Use the Shannon-Hartley theorem to find the bandwidth required to send 12,000 bits per second if the
number of levels transmitted is 8.
ANS: 2000 hertz
3. What is the Shannon Limit of a channel that has a bandwidth of 4000 hertz and a signal-to-noise ratio of
15?
ANS: 16 kbps
4. What is the minimum required number of samples per second to digitize an analog signal with frequency
components ranging from 300 hertz to 3300 hertz?
ANS: 6600 samples/second
5. What is the approximate dynamic range, in dB, of a linear PCM system that uses 12 bits per sample?
ANS: 74 dB
6. What is the approximate data rate for a system using 8 bits per sample and running at 8000 samples per
second?
ANS: 64 kbps
7. If bits were "stolen" from every DS-1 frame, what would the useable data-rate be for each channel in the
frame?
ANS: 56 kbps
8. Assuming maximum input and output voltages of 1 volt, what is the output voltage of a µ-law compressor
if the input voltage is 0.388 volt?
ANS: 0.833 volt
Chapter 8: The Telephone System
MULTIPLE CHOICE
1. DTMF stands for:
a. Digital Telephony Multiple Frequency c. Dual-Tone Multifrequency b. Dial Tone Master Frequency d. Digital Trunk Master Frequency
ANS: C
2. PSTN stands for:
a. Public Switched Telephone Network c. Primary Service Telephone Network b. Private Switched Telephone Network d. Primary Service Telephone Numbers
ANS: A
3. POTS stands for:
a. Private Office Telephone System c. Primary Operational Test System b. Primary Office Telephone Service d. Plain Old Telephone Service
ANS: D
4. LATA stands for:
a. Local Access and Transport Area c. Local Area Telephone Access b. Local Access Telephone Area d. Local Area Transport Access
ANS: A
5. A LATA is a:
a. a local calling area c. a way of accessing a tandem office b. a type of digital local network d. a way of accessing a central office
ANS: A
6. Central offices are connected by:
a. local loops c. both a and b b. trunk lines d. none of the above
ANS: B
7. Local loops terminate at:
a. a tandem office c. a central office b. a toll station d. an interexchange office
ANS: C
8. Call blocking:
a. cannot occur in the public telephone network b. occurs on the local loop when there is an electrical power failure c. occurs only on long-distance cables d. occurs when the central office capacity is exceeded
ANS: D
9. In telephony, POP stands for:
a. Post Office Protocol c. Power-On Protocol b. Point Of Presence d. none of the above
ANS: B
10. The cable used for local loops is mainly:
a. twisted-pair copper wire c. coaxial cable b. shielded twisted-pair copper wire d. fiber-optic
ANS: A
11. FITL stands for:
a. Framing Information for Toll Loops c. Framing In The Loop b. Fiber In the Toll Loop d. Fiber-In-The-Loop
ANS: D
12. Loading coils were used to:
a. increase the speed of the local loop for digital data b. reduce the attenuation of voice signals c. reduce crosstalk d. provide C-type conditioning to a local loop
ANS: B
13. DC current flows through a telephone:
a. when it is on hook c. as long as it is attached to a local loop b. when it is off hook d. only when it is ringing
ANS: B
14. The range of DC current that flows through a telephone is:
a. 20 µA to 80 µA c. 2 mA to 8 mA b. 200 µA to 800 µA d. 20 mA to 80 mA
ANS: D
15. The separation of control functions from signal switching is known as:
a. step-by-step switching control c. common control b. crossbar control d. ESS
ANS: C
16. The typical voltage across a telephone when on-hook is:
a. 48 volts DC c. 90 volts DC b. 48 volts, 20 hertz AC d. 90 volts, 20 hertz AC
ANS: A
17. The typical voltage needed to "ring" a telephone is:
a. 48 volts DC c. 90 volts DC b. 48 volts, 20 hertz AC d. 90 volts, 20 hertz AC
ANS: D
18. The bandwidth of voice-grade signals on a telephone system is restricted in order to:
a. allow lines to be "conditioned" c. allow signals to be multiplexed b. prevent "singing" d. all of the above
ANS: C
19. VNL stands for:
a. voltage net loss c. via net loss b. volume net loss d. voice noise level
ANS: C
20. Signal loss is designed into a telephone system to:
a. eliminate reflections c. improve signal-to-noise ratio b. prevent oscillation d. reduce power consumption
ANS: B
21. The reference noise level for telephony is:
a. 1 mW c. 1 pW b. 0 dBm d. 0 dBr
ANS: C
22. The number of voice channels in a basic FDM group is:
a. 6 c. 24 b. 12 d. 60
ANS: B
23. Basic FDM groups can be combined into:
a. supergroups c. jumbogroups b. mastergroups d. all of the above
ANS: D
24. In telephone system FDM, voice is put on a carrier using:
a. SSB c. PDM b. DSBSC d. PCM
ANS: A
25. PABX stands for:
a. Power Amplification Before Transmission b. Private Automatic Branch Exchange c. Public Automated Branch Exchange d. Public Access Branch Exchange
ANS: B
26. SLIC stands for:
a. Single-Line Interface Circuit c. Subscriber Line Interface Card b. Standard Line Interface Card d. Standard Local Interface Circuit
ANS: C
27. In DS-1, bits are "robbed" in order to:
a. provide synchronization c. cancel echoes b. carry signaling d. check for errors
ANS: B
28. "Bit-stuffing" is more formally called:
a. compensation c. justification b. rectification d. frame alignment
ANS: C
29. ISDN stands for:
a. Integrated Services Digital Network c. Integrated Services Data Network b. Information Services Digital Network d. Information Systems Digital Network
ANS: A
30. Basic ISDN has not been widely adopted because:
a. it took to long to develop b. it is too slow c. it has been surpassed by newer technologies d. all of the above
ANS: D
31. ADSL stands for:
a. All-Digital Subscriber Line c. Allocated Digital Service Line b. Asymmetrical Digital Subscriber Line d. Access to Data Services Line
ANS: B
32. Compared to ISDN, internet access using ADSL is typically:
a. much faster c. much more expensive b. about the same speed d. none of the above
ANS: A
COMPLETION
1. A ____________________ is a local calling area.
ANS: LATA
2. Central offices are connected together by ____________________ lines.
ANS: trunk
3. One central office can be connected to another through a ____________________ office.
ANS: tandem
4. With 7-digit phone numbers, ____________________ thousand telephones can connect to a central
office.
ANS: ten
5. Call ____________________ is when it becomes impossible for a subscriber to place a call due to an
overload of lines being used.
ANS: blocking
6. New ____________________ switching equipment uses TDM to combine signals.
ANS: digital
7. Most local loops still use ____________________ copper wire.
ANS: twisted-pair
8. As compared to a hierarchical network, a ____________________ network never needs more than one
intermediate switch.
ANS: flat
9. ____________________ coils were used to reduce the attenuation of voice frequencies.
ANS: Loading
10. In a twisted-pair telephone cable, the red wire is called ____________________.
ANS: ring
11. In a twisted-pair telephone cable, the green wire is called ____________________.
ANS: tip
12. Of the red and green 'phone wires, the ____________________ wire is positive with respect to the other.
ANS: green
13. A telephone is said to have ____________________ the line when the central office sends it dial tone.
ANS: seized
14. The ____________________ functions are provided by a SLIC.
ANS: BORSCHT
15. A ____________________ coil prevents loss of signal energy within a telephone while allowing full-
duplex operation over a single pair of wires.
ANS: hybrid
16. In a crosspoint switch, not all ____________________ can be in use at the same time.
ANS: lines
17. The old carbon transmitters generated a relatively ____________________ signal voltage.
ANS: large
18. The generic term for Touch-Tone® signaling is ____________________.
ANS: DTMF
19. A ____________________ line provides more bandwidth than a standard line.
ANS: conditioned
20. In the telephone system, amplifiers are called ____________________.
ANS: repeaters
21. An echo ____________________ converts a long-distance line from full-duplex to half-duplex operation.
ANS: suppressor
22. ____________________ weighting is an attempt to adjust the noise or signal level to the response of a
typical telephone receiver.
ANS: C-message
23. In FDM telephony, the modulation is usually ____________________.
ANS: SSB SSBSC
24. In FDM telephony, ____________________ bands separate the channels in a group.
ANS: guard
25. Because of "bit robbing", a channel in a DS-1 frame allows only ____________________ kbps when
used to send digital data.
ANS: 56
26. A ____________________ is a group of 12 DS-1 frames with signaling information in the sixth and twelfth frames.
ANS: superframe
27. In DS-1C, ____________________ bits are used to compensate for differences between clock rates.
ANS: stuff
28. Busy and dial tone are referred to as ____________________ signals because they use the same pair of
wires as the voice signal.
ANS: in-channel
29. SS7 is the current version of _________________________ signaling.
ANS: common-channel
30. SS7 is a ____________________-switched data network.
ANS: packet
31. In ISDN, the ____________________ channel is used for common-channel signaling.
ANS: D
32. In ISDN, the ____________________ channels are used for voice or data.
ANS: B
33. Terminal equipment especially designed for ISDN is designated ____________________ equipment.
ANS: TE1
34. The A in ADSL stands for ____________________.
ANS: asymmetrical
35. In ADSL, the speed from the network to the subscriber is ____________________ than the speed in the
opposite direction.
ANS: greater faster
SHORT ANSWER
1. For a certain telephone, the DC loop voltage is 48 V on hook and 8 V off hook. If the loop current is 40
mA, what is the DC resistance of the local loop?
ANS: 1000 ohms
2. For a certain telephone, the DC loop voltage is 48 V on hook and 8 V off hook. If the loop current is 40
mA, what is the DC resistance of the telephone?
ANS: 200 ohms
3. Which two DTMF tones correspond to the digit "1"? (Use the table in the text.)
ANS: 697 Hz and 1209 Hz
4. Calculate the dB of VNL required for a channel with a 3 ms delay.
ANS: 1 dB
5. If a telephone voice signal has a level of 0 dBm, what is its level in dBrn?
ANS: 90 dBrn
6. A telephone test-tone has a level of 80 dBrn at a point where the level is +5dB TLP. If C-weighting
produces a 10-dB loss, what would the signal level be in dBrnc0?
ANS: 65 dBrnc TLP
Chapter 9: Data Transmission
MULTIPLE CHOICE
1. In practical terms, parallel data transmission is sent:
a. over short distances only c. over any distance b. usually over long distances d. usually over a coaxial cable
ANS: A
2. The five-level teletype code was invented by:
a. the Morkum Company c. Western Union b. the Teletype Company d. Emile Baudot
ANS: D
3. Data codes are also called:
a. character codes c. they do not have any other name b. character sets d. both a and b
ANS: C
4. Digital data that is not being used to carry characters is called:
a. FIGS data c. numerical data b. binary data d. all of the above
ANS: B
5. Character codes include:
a. alphanumeric characters c. graphic control characters b. data link control characters d. all of the above
ANS: D
6. ASCII stands for:
a. American Standard Character-set 2 b. American Standard Code for Information Interchange c. American Standard Code 2 d. Alphanumeric Standard Code for Information Interchange
ANS: B
7. BS, FF, and CR are examples of:
a. nonstandard character codes c. control characters b. escape characters d. none of the above
ANS: C
8. LF stands for:
a. Line Feed c. Line Forward
b. Link Feed d. Link Forward
ANS: A
9. UART stands for:
a. Universal Asynchronous Receiver-Transmitter b. Unidirectional Asynchronous Receiver-Transmitter c. Unaltered Received Text d. Universal Automatic Receiver for Text
ANS: A
10. In asynchronous transmission, the transmitter and receiver are:
a. frame-by-frame synchronized using the data bits b. frame-by-frame synchronized using a common clock c. frame-by-frame synchronized using the start and stop bits d. not synchronized at all, hence the name "asynchronous"
ANS: C
11. In asynchronous transmission, the time between consecutive frames is:
a. equal to zero c. equal to the start and stop bit-times b. equal to one bit-time d. not a set length
ANS: D
12. In synchronous transmission, the frames are:
a. about the same length as ten asynchronous frames b. much longer than asynchronous frames c. 128 bytes long d. 1024 bytes long
ANS: B
13. Synchronous transmission is used because:
a. no start and stop bits means higher efficiency b. it is cheaper than asynchronous since no UARTS are required c. it is easier to implement than asynchronous d. all of the above
ANS: A
14. In synchronous transmission, the receiver "syncs-up" with the transmitter by using:
a. the clock bits c. the CRC bits b. the data bits d. a separate clock line
ANS: B
15. To maintain synchronization in synchronous transmission:
a. long strings of 1s and 0s must not be allowed b. transmission must stop periodically for resynchronization c. the clock circuits must be precisely adjusted d. the channel must be noise-free
ANS: A
16. BISYNC:
a. is an IBM product c. requires the use of DLE b. is a character-oriented protocol d. all of the above
ANS: D
17. HDLC:
a. is an IBM product c. is identical to SDLC b. is a bit-oriented protocol d. all of the above
ANS: B
18. The use of flags in SDLC requires:
a. "bit-stuffing" c. FEC b. different flags at either end of a frame d. ARQ
ANS: A
19. The initials ARQ are used to designate:
a. automatic request for resynchronization c. automatic receiver queue b. automatic request for retransmission d. automatic request for queue
ANS: B
20. ARQ is used to:
a. correct bit errors c. put data into a temporary buffer b. correct synchronization problems d. none of the above
ANS: A
21. FEC stands for:
a. Fixed Error Control c. Forward Error Correction b. Forward Error Control d. False Error Condition
ANS: C
22. VRC is another name for:
a. FEC c. LRC b. ARQ d. parity
ANS: D
23. CRC stands for:
a. Control Receiver Code c. Cyclic Redundancy Check b. Correct Received Character d. Cycle Repeat Character
ANS: C
24. Huffman codes:
a. allow errors to be detected but not corrected b. allow errors to be detected and corrected c. allow alphanumeric data to be corrected
d. allow alphanumeric data to be compressed
ANS: D
25. Run-length encoding is used to:
a. encrypt data c. correct data b. compress data d. none of the above
ANS: B
26. Public-key encryption:
a. allows the use of digital signatures c. avoids the "password problem" b. is used to convey symmetric keys d. all of the above
ANS: D
27. SDLC stands for:
a. Synchronous Data Link Control c. Synchronous Data Link Character b. Synchronous Data Line Control d. Synchronous Data Line Character
ANS: A
28. HDLC is:
a. a bit-oriented protocol c. an ISO standard b. based on SDLC d. all of the above
ANS: D
COMPLETION
1. Parallel transmission can be used only for ____________________ distances.
ANS: short
2. The term "baud" was named after Emil ____________________.
ANS: Baudot
3. Data codes are also called ____________________ codes.
ANS: character
4. The ____________________ code is a 7-bit code commonly used in communication between personal
computers.
ANS: ASCII
5. The two letters ____________________ designate the code character used to advance a printer to the next
page.
ANS: FF
6. An asynchronous frame begins with the ____________________ bit.
ANS: start
7. An asynchronous frame ends with the ____________________ bit.
ANS: stop
8. At the end of an asynchronous frame, the line will be at the ____________________ level.
ANS: mark binary 1
9. An integrated circuit called a ____________________ is used in an asynchronous communication system
to convert between parallel and serial data.
ANS: UART
10. When receiving digital data, ____________________ are used to hold data until they can be read.
ANS: buffers
11. Synchronous communication is more ____________________ than asynchronous since there are fewer
"overhead" bits.
ANS: efficient
12. There must be sufficient 1-to-0 ____________________ to maintain synchronization in synchronous
transmission.
ANS: transitions
13. Clock sync is derived from the stream of ____________________ bits in synchronous transmission.
ANS: data
14. In the ____________________ protocol, each frame begins with at least two SYN characters.
ANS: BISYNC
15. In HDLC, each frame starts with an 8-bit ____________________.
ANS: flag
16. The first eight bits of an SDLC frame are ____________________.
ANS: 01111110
17. BCC stands for ____________________ check character.
ANS: block
18. DLE stands for data link ____________________.
ANS: escape
19. HDLC uses bit-____________________ to prevent accidental flags.
ANS: stuffing
20. ____________________ errors cause many consecutive bits to be bad.
ANS: Burst
21. FEC stands for ____________________ error correction.
ANS: forward
22. An ____________________ scheme corrects errors by requiring the retransmission of bad blocks.
ANS: ARQ
23. Parity fails when an ____________________ number of bits are in error.
ANS: even
24. CRC codes are particularly good at detecting ____________________ errors.
ANS: burst
25. Huffman coding and run-length encoding are examples of data ____________________.
ANS: compression
26. A ____________________ is an encoding scheme that is not public in order to protect data.
ANS: cipher
27. A ____________________ is often used to generate an encryption key because it is easier to remember.
ANS: password
28. If the key is ____________________ enough, private-key encryption can be quite secure.
ANS: long
29. Messages cannot be ____________________ using a public key.
ANS: decrypted
30. Because it is ____________________-intensive, public-key encryption can be slow.
ANS: computation
SHORT ANSWER
1. How many different characters could be encoded using a six-bit code?
ANS: 64
2. What is the numerical difference between ASCII 'a' and ASCII 'A' if you treat them as hexadecimal (hex)
numbers?
ANS: 20 hex (32 decimal)
3. The ASCII codes for the characters '0' through '9' are what hex numbers?
ANS: 30H to 39H
4. If an asynchronous frame is used to send ASCII characters in the form of bytes (8 bits), what is the
shortest time it could take to send 1000 characters if each bit in a frame is 1 msec long?
ANS: 10 seconds
5. Suppose an asynchronous frame holds 8 bits of data, a parity bit, and two stop bits (it could happen).
Calculate the efficiency of the communication system.
ANS: 66.7%
6. Suppose a synchronous frame has 16 bits of non-data in the front and a 16-bit BCC at the end. The frame
carries 1024 bytes of actual data. Calculate the efficiency of the communication system.
ANS: 97.0%
Chapter 10: Local Area Networks
MULTIPLE CHOICE
1. CSMA stands for:
a. Client-Server Multi-Access c. Carrier Server Master Application b. Carrier Sense Multiple Access d. none of the above
ANS: B
2. The CD in CSMA/CD stands for:
a. Carrier Detection c. Collision Detection b. Carrier Delay d. Collision Delay
ANS: C
3. The Internet is:
a. a network of networks c. a very large CSMA/CD network b. a very large client-server network d. not really a network at all
ANS: A
4. Most LANs:
a. are based on Ethernet c. use UTP cable b. use CSMA/CD d. all of the above
ANS: D
5. Dumb terminals are still used:
a. in token-passing networks b. in networks requiring central monitoring c. in networks that cannot provide central monitoring d. none of the above
ANS: B
6. In a circuit-switched network:
a. communication is half-duplex only b. each channel carries only one data stream c. connection is usually done using a bus topology d. all of the above
ANS: B
7. Each computer on a network is called a:
a. hub c. node b. token d. circuit
ANS: C
8. Compared to CSMA/CD systems, token-passing rings are:
a. slower c. not as widely used
b. more expensive d. all of the above
ANS: D
9. The key feature of a star network is that individual workstations are connected to:
a. a central ring c. a node b. a central bus d. none of the above
ANS: D
10. On networks, long messages are divided into "chunks" called:
a. packets c. carriers b. nodes d. tokens
ANS: A
11. When two or more PCs try to access a baseband network cable at the same time, it is called:
a. a collision c. excess traffic b. contention d. multiple access
ANS: B
12. When two PCs send data over a baseband network cable at the same time, it is called:
a. a collision c. excess traffic b. contention d. multiple access
ANS: A
13. One type of network that never has a collision is:
a. CSMA c. token-passing b. Ethernet d. all networks have collisions
ANS: C
14. In an Ethernet-based network, a switch can be used to reduce the number of:
a. nodes c. packets b. users d. collisions
ANS: D
15. The effect of too many collisions is:
a. the network goes down c. the cable overheats b. the network slows down d. data is lost
ANS: B
16. MAU stands for:
a. Multistation Access Unit c. Multiple Auxiliary Units b. Multiple Access Unit d. none of the above
ANS: A
17. The standard that describes Ethernet-type networks is:
a. EIA 232 c. IEEE 802.3
b. IEEE 488.1 d. CCITT ITU-E
ANS: C
18. Ethernet was invented by:
a. IBM c. Xerox b. INTEL d. Digital Equipment Corporation
ANS: C
19. An Ethernet running at 10 Mbits / second uses:
a. Manchester encoding c. NRZ encoding b. Three-Level encoding d. AMI encoding
ANS: A
20. A 100BaseT cable uses:
a. fiber-optic cable c. RG-58U coaxial cable b. twisted-pair copper wires d. 50-ohm coaxial cable
ANS: B
21. The word "Base" in 10BaseT means:
a. the cable carries baseband signals b. the cable has a base speed of 10 Mbps c. it can be used as the base for a backbone cable system d. none of the above
ANS: A
22. The reason a CSMA/CD network has a minimum length for packets is:
a. to increase the data rate b. to prevent packets from reaching all other nodes during transmission c. to make sure all other nodes hear a collision in progress d. all of the above
ANS: C
23. The reason a CSMA/CD network has a maximum length for cables is:
a. to increase the data rate b. to prevent packets from reaching all other nodes during transmission c. to make sure all other nodes hear a collision in progress d. all of the above
ANS: C
24. NIC stands for:
a. Network Interface Card c. Network Interface Code b. Network Interface Cable d. Network Internal Code
ANS: A
25. 10BaseT cable typically uses:
a. a BNC connector c. an RJ45 connector
b. a T connector d. an RS11 connector
ANS: C
26. UTP stands for:
a. Untwisted-Pair copper wire c. Uninterruptible Terminal Packet b. Unshielded Twisted-Pair copper wire d. Unicode Text Packet
ANS: B
27. Compared to twisted-pair telephone cables, CAT-5 cables:
a. are cheaper c. allow faster bit rates b. are easier to crimp connectors onto d. all of the above
ANS: C
28. A hub:
a. sends incoming packets out to all other terminals connected to it b. sends incoming packets out to specific ports c. cannot be used in an Ethernet-type network d. are more common in token-passing networks
ANS: A
29. A switch:
a. sends incoming packets out to all other terminals connected to it b. sends incoming packets out to specific ports c. cannot be used in an Ethernet-type network d. are more common in token-passing networks
ANS: B
30. An advantage of using a switch instead of a hub is:
a. it is cheaper when used in large networks b. it is faster when used in large networks c. it reduces the number of collisions in large networks d. all of the above
ANS: C
31. Broadband LANs:
a. modulate the data onto a carrier b. use coaxial cables c. are provided by cable TV companies for Internet access d. all of the above
ANS: D
32. Using one node in the network to hold all the application software is done in:
a. peer-to-peer networks c. both a and b b. client-server networks d. none of the above
ANS: B
33. Record locking is used to: a. store records securely on a server b. prevent multiple users from looking at a document simultaneously c. prevent one user from reading a record that another user is writing to d. none of the above
ANS: C
34. The software that runs a client-server network must be:
a. UNIX-based c. multitasking b. WINDOWS-based d. Novell certified
ANS: C
35. A "thin" client is:
a. basically, a PC with no disk drives c. same as a "dumb" terminal b. a node that rarely sends data d. all of the above
ANS: A
COMPLETION
1. A LAN is a ____________________ Area Network.
ANS: Local
2. The Internet is a network of ____________________.
ANS: networks
3. In a ____________________ network, all nodes are connected to a central computer.
ANS: star
4. In a ____________________-switched network, users have a dedicated channel for the duration of
communications.
ANS: circuit
5. The ____________________ of a network describes how it is physically connected together.
ANS: topology
6. Ring networks often use ____________________-passing.
ANS: token
7. A ____________________ is a short section of a message in digital form.
ANS: packet
8. ____________________ is when two nodes try to seize the same cable at the same time.
ANS: Contention
9. A ____________________ occurs when two nodes transmit simultaneously on the same baseband cable.
ANS: collision
10. In CSMA/CD networks, all collisions must be ____________________.
ANS: detected
11. Carrier-Sense means that a node "listens" for the cable to be ____________________ before using it.
ANS: quiet free unused available
12. A "____________________" cable links clusters of computers together.
ANS: backbone
13. 100BaseT cables can reliably carry up to ____________________ bits per second.
ANS: 100 mega
14. In CSMA/CD, packets must have a ____________________ length to ensure that collisions are detected.
ANS: minimum
15. In CSMA/CD, the ____________________ of a cable is limited to ensure that collisions are detected.
ANS: length
16. A unique numerical address is provided to a node by its ____________________.
ANS: NIC
17. A 100BaseTX cable is a ____________________ cable.
ANS: fiber-optic
18. Hubs can be ____________________ to form, in effect, one big hub.
ANS: stacked
19. A switch looks at the ____________________ of each incoming packet.
ANS: address
20. The effect of a switch is to greatly reduce ____________________.
ANS: contention
SHORT ANSWER
1. Explain how a network can be a physical bus but a logical ring.
ANS: A token-passing network sends the token from node to node in a prescribed order. So it doesn't matter how the physical connection is made. It still works like a token-passing ring.
2. What is the key difference between a hub and a switch?
ANS: A hub sends incoming packets out to all other ports on the hub. A switch sends a packet to a specific port based on the address in the packet.
3. What is the advantage of a CSMA/CD network over a basic star network?
ANS: If the central computer in a star network fails, the entire network is inoperative. If a node fails in a CSMA/CD network, it can be disconnected and the network still functions.
4. Why do CSMA/CD packets have a minimum size limit?
ANS: If a packet is too short, nodes at either end of a cable could get on, send a packet, and get off before the packets travel far enough to collide. The collision would not be detected.
5. What is a NIC address, and why is it unique?
ANS: The address is a long binary number "burned" into a NIC's memory chip at the factory. Each factory uses a different sequence of numbers, so the chances of two NICs on the same network having the same address is extremely small.
Chapter 11: Wide-Area Networks and the Internet
MULTIPLE CHOICE
1. MAN stands for:
a. Manchester Access Network c. Metropolitan-Area Network b. Multiple-Area Network d. Multiple Access Network
ANS: C
2. Packet switching is based on:
a. store-and-forward c. real-time delivery b. switched circuits d. all of the above
ANS: A
3. SNA stands for:
a. Standard Network Access c. Standard Network Architecture b. Small Network Access d. Systems Network Architecture
ANS: D
4. The number of layers in ISO OSI is:
a. 3 c. 7 b. 5 d. 8
ANS: C
5. The lowest-level layer in ISO OSI is called the:
a. physical layer c. cable layer b. link layer d. transport layer
ANS: A
6. Bad frames are usually detected by the:
a. frame layer c. error-check layer b. physical layer d. link layer
ANS: D
7. A virtual circuit is set up by the:
a. user c. network b. link layer d. frame
ANS: C
8. Frame Relay:
a. is faster than X.25 c. allows for variable length packets b. does less error checking than X.25 d. all of the above
ANS: D
9. ATM stands for: a. Asynchronous Transfer Mode c. Asynchronous Transmission Model b. Asynchronous Transmission Mode d. Automatic Test Mode
ANS: A
10. A bridge:
a. separates a network into "collision domains" b. looks at the address of each packet c. operate at the data-link level d. all of the above
ANS: D
11. IP stands for:
a. Internet Process c. Interconnect Protocol b. Internet Protocol d. Interconnect Procedure
ANS: B
12. TCP stands for:
a. Transmission Control Process c. Transfer Connection Protocol b. Transmission Control Protocol d. none of the above
ANS: B
13. Together, TCP/IP consists of:
a. 5 layers c. an application and a process b. 7 layers d. datagrams
ANS: A
14. IP is a:
a. connection-oriented protocol c. connectionless protocol b. virtual circuit d. non-robust protocol
ANS: C
15. The "lifetime" of a packet in an IP network:
a. is essentially forever b. depends on elapsed time since transmission c. depends on number of "hops" between nodes d. is approximately 200 milliseconds
ANS: C
16. UDP stands for:
a. User Datagram Protocol c. User Data Packet b. User Data Protocol d. Universal Data Packet
ANS: A
17. HTTP stands for:
a. High-speed Transmission Test Procedure
b. High-Level Transfer Test Procedure c. Hypertext Transmission and Transport Procedure d. Hypertext Transport Protocol
ANS: D
18. HTTP allows the use of:
a. dumb terminals c. browsers b. file transport d. none of the above
ANS: C
19. HTML stands for:
a. Hypertext Markup Language c. Hypertext Transfer-Mode Layer b. Hypertext Transfer-Mode Level d. High-speed Transfer-Mode Language
ANS: A
20. HTML allows:
a. telneting c. web page layout b. high-speed file transfer d. all of the above
ANS: C
21. FTP stands for:
a. File Transfer Protocol c. File Test Procedure b. File Transport Protocol d. Fast Transport Packet
ANS: A
22. FTP is used to:
a. transfer files between a server on the network and a user b. test files to see if their data has been "corrupted" c. transport packets at maximum speed through the network d. none of the above
ANS: A
23. SMTP stands for:
a. Short Message Transport Protocol c. Simple Mail Transport Protocol b. Simple Message Transport Protocol d. Secondary Mail Transfer Procedure
ANS: C
24. ISP stands for:
a. Internet Service Protocol c. Internet Service Procedure b. Internet Service Provider d. none of the above
ANS: B
25. The standard Internet address (or URL) is:
a. a 32-bit binary number c. running out of available values b. four groups of base-ten numbers d. all of the above
ANS: D
26. DNS stands for:
a. Domain Name Server c. Domain Numbering System b. Domain Name System d. Domain Naming System
ANS: A
27. A DNS:
a. has become obsolete on the Internet b. translates words to numbers c. stores all domain addresses d. describes the Internet address-naming procedure
ANS: B
28. An intranet connected to the Internet is often protected by:
a. a DNS c. a "firewall" b. a "brick wall" d. the use of "spoofing" protocols
ANS: C
29. OSI stands for:
a. Open Systems Interconnection c. Open Systems Internet b. Open Standard Interconnection d. none of the above
ANS: A
COMPLETION
1. A ____________________-Area Network would extend typically across a city.
ANS: Metropolitan
2. A ____________________-Area Network could extend across a nation.
ANS: Wide
3. A dedicated telephone line can be ____________________ on a monthly basis.
ANS: leased
4. The use of digital circuit-____________________ lines is cheaper than dedicated lines.
ANS: switched
5. Packet switching is done on a store-and-____________________ network.
ANS: forward
6. A ____________________ is a hierarchy of procedures for implementing digital communications.
ANS: protocol
7. Voltage levels on a cable are specified at the ____________________ layer.
ANS: physical
8. Bad frames are usually detected at the ____________________ layer.
ANS: data-link
9. Setting up a path through the network is done by the ____________________ layer.
ANS: network
10. The X.25 protocol was developed by the ____________________.
ANS: CCITT
11. In X.25, the data-link layer is called the ____________________ layer.
ANS: frame
12. In X.25, the network layer is called the ____________________ layer.
ANS: packet
13. The physical route of a ____________________ circuit changes each time it is used.
ANS: virtual
14. Frame Relay requires channels with low ____________________ rates.
ANS: bit-error
15. Compared to X.25, Frame Relay does ____________________ error checking.
ANS: less
16. All ATM frames contain just ____________________ bytes.
ANS: 53
17. Small frame size and a high-speed channel allow ____________________-time communications.
ANS: real
18. ____________________ simply regenerate and retransmit packets in a network.
ANS: Repeaters
19. ____________________ look at the address inside a packet to decide whether or not to retransmit it.
ANS: Bridges
20. ____________________ decide the best network path on which to forward a packet.
ANS: Routers
21. TCP/IP goes back to the ____________________ of the 1970s.
ANS: ARPANET DARPANET
22. Between ISO OSI and TCP/IP, ____________________ was used first.
ANS: TCP/IP
23. A ____________________ protocol does not track packets after they are sent.
ANS: connectionless
24. HTTP allows the use of ____________________ that jump to other pages on the web.
ANS: hyperlinks
25. The Internet "backbone" mostly uses high-speed ____________________ cables.
ANS: fiber-optic
26. A ____________________ translates words in an Internet address to numbers.
ANS: DNS
27. Intranets usually connect to the Internet through a ____________________ for security.
ANS: firewall
28. Voice over ____________________ is telephony done over the Internet.
ANS: IP
29. "____________________" is another term for real-time transmission over the Internet.
ANS: Streaming
30. Most people gain access to the Internet by subscribing to an ____________________.
ANS: ISP
SHORT ANSWER
1. Name the three parts of an IP address as used on the Internet.
ANS: Network number, Subnet number, Host number
2. Why is a logical channel called a "virtual" circuit?
ANS: A logical channel is a way of keeping track of which two nodes on the network have messages for each other. The actual physical path can change while packets are being sent. Virtual means it behaves like direct circuit between 'A' and 'B', but it is not a direct circuit.
3. Why is it faster to send packets of a fixed size compared to packets of variable size?
ANS: The processing required to store and forward packets of different lengths is greater than that required for packets of a fixed length. More processing implies more time per packet, which implies fewer packets per second through the network.
4. Why are the tasks involved in digital communications divided into layers in a protocol stack? Why not
just have one layer that does it all?
ANS: Divide and conquer: it reduces complexity to a manageable job. One big layer could not be adapted to newer media etc as easily as a system of independent layers. Think of subroutines in a computer program.
5. What is a "hop"?
ANS: Every time a packet is forwarded on to the next store-and-forward node in the network, it is considered to be one "hop".
6. What does it mean to say a packet has a lifetime measured in hops?
ANS: Each packet contains a number representing the maximum number of allowed hops. At each hop, this number is reduced by one. When it gets to zero, the packet is deleted from the network.
7. Why should packets have a lifetime?
ANS: If they didn't, then the number of "lost" packets traveling around the network would continuously increase. At some point, there would be no bandwidth left to carry real traffic.
Chapter 12: Digital Modulation and Modems
MULTIPLE CHOICE
1. FSK stands for:
a. Full-Shift Keying c. Full-Signal Keying b. Frequency-Shift Keying d. none of the above
ANS: B
2. PSK stands for:
a. Pulse-Signal Keying c. Phase-Signal Keying b. Pulse-Shift Keying d. Phase-Shift Keying
ANS: D
3. QAM stands for:
a. Quadrature Amplitude Modulation c. Quadrature Amplitude Marking b. Quadrature Amplitude Masking d. none of the above
ANS: A
4. In the equation I = ktB, I is measured in:
a. amperes c. bits b. amperes per second d. bits per second
ANS: C
5. In the equation C = 2Blog2M, M is the:
a. margin of noise c. number of possible states per symbol b. modulation index d. maximum number of symbols per second
ANS: C
6. An "eye pattern" shows a good channel when:
a. the eye is maximally open c. the eye is half open b. the eye is maximally closed d. the eye alternately opens and closes
ANS: A
7. What you see in an eye pattern is the effect of:
a. too many bits high c. intermodulation distortion b. too many bits low d. intersymbol interference
ANS: D
8. High-frequency radioteletype systems commonly use:
a. FSK c. PSK b. AFSK d. QAM
ANS: A
9. Instead of a single bit, a QPSK symbol contains: a. a byte c. a dibit b. 4 bits d. a Q-bit
ANS: C
10. To reduce the need for linearity, π/4 DQPSK uses:
a. angles of 0, 90, 180, and 270 degrees c. angles of π/4, 2π/4, 3π/4, and 4π/4 b. angles of 45, 135, 225, and 315 degrees d. double phase-shift angles
ANS: B
11. For QAM, a "constellation diagram" shows:
a. location of symbols in "symbol space" c. effects of noise on symbols b. separation of symbols in "symbol space" d. all of the above
ANS: D
12. For QAM, the two dimensions of its symbol space are:
a. amplitude and frequency c. frequency and phase angle b. amplitude and phase angle d. I-bits and Q-bits
ANS: B
13. The specs of the old Bell type 103 modem were:
a. 300 bps, full-duplex, FSK c. 1200 bps, full-duplex, FSK b. 600 bps, full-duplex, FSK d. 1200 bps, half-duplex, FSK
ANS: A
14. ITU is an abbreviation for:
a. International Telephony Unit c. International Telecommunications Union b. International Telephony Union d. International Telecommunications Units
ANS: C
15. The ITU is under the auspices of:
a. CCITT c. IEEE b. the U.N. d. ANSI
ANS: B
16. High-speed modems equalize the line to compensate for:
a. noise and interference b. uneven phase and frequency response c. low SNR d. inconsistent bit rates at either end of channel
ANS: B
17. The bits sent to allow equalization are called:
a. Gaussian bits c. a training sequence b. random bits d. a random sequence
ANS: C
18. The V.90 standard is issued by:
a. the EIA c. the ITU b. the TIA d. the ISO
ANS: C
19. MNP2, MNP3, MNP4, and MNP10 are all:
a. data-compression schemes c. both a and b b. error-correction protocols d. none of the above
ANS: B
20. MNP5 and V.42 bis are both:
a. data-compression schemes c. both a and b b. error-correction protocols d. none of the above
ANS: A
21. In RS-232, flow control is done using:
a. RTS/CTS handshake c. both a and b b. XON/XOFF characters d. none of the above
ANS: C
22. The official name for RS-232C is:
a. RS-232C c. ISO-232C/D b. EIA-232D d. ANSI-232C
ANS: B
23. In RS-232, a modem would be:
a. a DTR c. a DCE b. a DSR d. a DTE
ANS: C
24. In RS-232, a personal computer would be:
a. a DTR c. a DCE b. a DSR d. a DTE
ANS: D
25. On a DB-9 RS-232 connector, signal ground is pin:
a. 1 c. 5 b. 3 d. 7
ANS: C
26. On a DB-25 RS-232 connector, signal ground is pin:
a. 1 c. 5 b. 3 d. 7
ANS: D
27. The minimum lines required for RS-232 are:
a. TD and RD c. TD, RD, DSR, and signal ground b. TD, RD, and signal ground d. TD, RD, RTS, CTS, and signal ground
ANS: B
28. Hardware flow control uses:
a. XON and XOFF c. RTS and CTS b. TD and RD d. DSR and DCD
ANS: C
29. Software flow control uses:
a. XON and XOFF c. RTS and CTS b. TD and RD d. DSR and DCD
ANS: A
30. Which voltage represents a binary zero on an RS-232 data pin:
a. +15 volts c. +9 volts b. +12 volts d. all of the above
ANS: D
31. DSL stands for:
a. Data Signal Line c. Digital Subscriber Line b. Digital Signal Line d. Double-Speed Loop
ANS: C
32. ADSL stands for:
a. Asynchronous DSL c. Analog DSL b. Asymmetrical DSL d. All DSL
ANS: B
33. In a CATV system, HFC stands for:
a. Head Frequency Control c. Hybrid Fiber-Coax b. Hybrid Frequency Control d. Hybrid Fiber Control
ANS: C
34. In a CATV system, CMTS stands for:
a. Cable Modem Terminal Server c. Cable Modem Terminal System b. Cable Modem Transmission System d. Cable Modem Transmission Server
ANS: A
35. A "splitter" at the subscriber end is not required for:
a. Any DSL scheme c. ADSL Lite b. ADSL d. none of the above
ANS: C
COMPLETION
1. RTS means Request To ____________________.
ANS: Send
2. The response to RTS is ____________________.
ANS: CTS
3. FSK stands for Frequency-Shift ____________________.
ANS: Keying
4. DSR stands for ____________________ Set Ready.
ANS: Data
5. QAM stands for ____________________ Amplitude Modulation.
ANS: Quadrature
6. The number of symbols per second is called the ____________________ rate.
ANS: baud
7. The 2 bits of information in a QPSK symbol is called a ____________________.
ANS: dibit
8. QPSK uses ____________________ different phase angles.
ANS: four
9. DPSK stands for ____________________ PSK.
ANS: Delta
10. The QAM amplitude-phase combinations are shown with a ____________________ diagram.
ANS: constellation
11. ITU stands for International _________________________ Union.
ANS: Telecommunications
12. In QAM modems, ____________________ coding adds extra bits to improve performance on a noisy
line.
ANS: Trellis
13. ____________________ is used in a high-speed modem to compensate for uneven frequency and phase
response on a line.
ANS: Equalization
14. The maximum allowed speed for a modem on a dial-up line is about ____________________ bps.
ANS: 54k
15. The nominal maximum speed on an RS-232 cable is ____________________ bps.
ANS: 20k
16. In RS-232, the ____________________ line is asserted when the analog carrier from another modem is
being received.
ANS: CD DCD RLSD
17. Between hardware flow control and software flow control, ____________________ flow control is
preferred.
ANS: hardware
18. A voltage higher than ____________________ volts should be considered a high on an RS-232 receiver.
ANS: 3
19. A ____________________ modem cable is used to connect two DTEs via their serial ports.
ANS: null
20. ADSL stands for ____________________ DSL.
ANS: Asymmetrical
21. A typical CATV system is organized as a ____________________ network.
ANS: tree
22. In a CATV system using cable modems, a ____________________ is used to put several channels of data
onto a fiber-optic backbone.
ANS: CMTS
23. ____________________ is the process of synchronizing transmitted data from cable modems to a CMTS.
ANS: Ranging
24. ____________________ systems send high-speed data over a POTS line while sharing the line with dial-
up service.
ANS: ADSL
25. The ____________________ version of ADSL does not require a splitter at the subscriber end.
ANS: lite
26. ____________________ modulation divides the line bandwidth into many narrow bands called tones or
bins for ADSL.
ANS: DMT
27. A DSLAM is a DSL Access ____________________.
ANS: Multiplexer
SHORT ANSWER
1. Calculate the bits per second capacity of a system sending 1000 symbols per second with 16 possible
states per symbol.
ANS: 4000
2. How many points will be on the constellation diagram of a QAM system using 8 phase angles and 2
amplitude levels?
ANS: 16
3. A CATV system has 100 cable-modem customers sharing a single channel with a data rate of 36 Mbps. If
half the modems are active at any given time, what bit rate can a customer expect?
ANS: 720 kbps
4. A DMT system uses 4.3-kHz bins on a 1-MHz cable. Approximately how many bins are there?
ANS: 230
5. Assuming a maximum symbol rate of 400 per second, how many possible states must a symbol have to
achieve a data rate of 1200 bps?
ANS:
8
Chapter 13: Multiplexing and Multiple-Access Techniques
MULTIPLE CHOICE
1. TDMA stands for:
a. Time Domain Multiple Access c. Tone Division Multiple Access b. Time-Division Multiple Access d. none of the above
ANS: B
2. CDMA stands for:
a. Code-Division Multiple Access c. Compact Digital Multiplex Arrangement b. Carrier Division Multiple Access d. none of the above
ANS: A
3. TDMA is used instead of TDM when:
a. all the signals come from the same source b. the signals come from different sources c. TDM is used in RF communications d. they mean the same thing
ANS: B
4. When calculating the maximum number of users, a limiting factor in FDM is:
a. the type of media used c. the bandwidth of each signal b. the length of the channel d. all of the above
ANS: C
5. A DS-1 signal contains:
a. 12 channels c. 32 channels b. 24 channels d. 64 channels
ANS: B
6. The bit-rate of a DS-1 signal over a T-1 line is:
a. 64 kbps c. 1.536 Mbps b. 256 kbps d. 1.544 Mbps
ANS: D
7. Besides data bits, a DS-1 frame contains a:
a. timing bit c. signaling bit b. T-bit d. framing bit
ANS: D
8. In DS-1, a bit is "stolen" out of each channel:
a. every frame c. every sixth frame b. every other frame d. every twelfth frame
ANS: C
9. Moving signals from one line to another is called:
a. time switching c. line switching b. space switching d. cross-point switching
ANS: B
10. Moving PCM samples from one time-slot to another is called:
a. time switching c. signal switching b. space switching d. crosspoint switching
ANS: A
11. A digital space switch is a:
a. multiplexer c. computerized Strowger switch b. TDM switch d. crosspoint switch
ANS: D
12. Spread-spectrum can be done by using:
a. computer-controlled frequency reuse c. direct-sequence method b. frequency-hopping d. all of the above
ANS: D
13. The term "chip rate" is used in describing:
a. computer-controlled frequency reuse c. direct-sequence method b. frequency-hopping d. all of the above
ANS: C
14. For a given data rate, direct-sequence systems, compared to standard RF systems, use:
a. about the same bandwidth c. much less bandwidth b. much more bandwidth d. approximately double the bandwidth
ANS: B
15. "Processing gain" is another term for:
a. RF gain c. spreading gain b. computer speed d. improved signal-to-noise ratio
ANS: C
16. To calculate processing gain, divide the transmitted RF bandwidth by:
a. the digital data bit rate c. the S/N ratio b. bandwidth of original baseband d. the chip size
ANS: B
17. A receiver for frequency-hopping spread-spectrum would be:
a. a narrowband receiver c. a direct-conversion receiver b. a wideband receiver d. a CDMA receiver
ANS: A
18. A receiver for direct-sequence spread-spectrum would be:
a. a narrowband receiver c. a direct-conversion receiver b. a wideband receiver d. a "chip-rate" receiver
ANS: B
19. CDMA:
a. cannot be used with frequency-hopping spread-spectrum b. cannot be used with direct-sequence spread-spectrum c. cannot be used on an RF channel d. allows many transmitters to use a band simultaneously
ANS: D
20. For optimal performance, CDMA requires the use of:
a. orthogonal PN sequences c. true-random PN sequences b. non-orthogonal PN sequences d. none of the above
ANS: A
COMPLETION
1. Multiplexing allows many signals to ____________________ a channel.
ANS: share
2. Three methods of multiple access are FDMA, TDMA, and ____________________.
ANS: CDMA
3. In FDM, each signal uses part of the bandwidth ____________________ of the time.
ANS: all
4. In TDM, each signal uses all of the bandwidth ____________________ of the time.
ANS: part
5. Using CDMA on a radio channel, all signals can transmit ____________________ of the time.
ANS: all
6. DS-1 is an example of ____________________-division multiplexing.
ANS: time
7. The AM radio band is an example of ____________________-division multiplexing.
ANS: frequency
8. A DS-1 frame contains one sample from each of ____________________ channels.
ANS: 24
9. T1 uses the ____________________ line code.
ANS: AMI
10. Each DS-1 frame contains a total of ____________________ bits.
ANS: 193
11. A DS-1 frame is transmitted at a rate of ____________________ bits per second.
ANS: 1.544 Meg
12. Each sample in a DS-1 frame contains ____________________ bits.
ANS: 8
13. A group of twelve DS-1 frames is called a ____________________.
ANS: superframe
14. Switching signals from one line to another is called ____________________ switching.
ANS: space
15. Moving PCM samples from one time slot to another is called ____________________ switching.
ANS: time
16. The deep fades caused by signal-cancellation due to reflection are called ____________________ fading.
ANS: Rayleigh
17. A PN sequence is a ____________________-random noise sequence.
ANS: pseudo
18. One method of spread-spectrum is frequency ____________________.
ANS: hopping
19. It is ____________________ to jam a spread-spectrum signal.
ANS: difficult
20. It is ____________________ to eavesdrop on a spread-spectrum signal.
ANS: difficult
21. The extra bits added to the data in direct-sequence spread-spectrum are called ____________________.
ANS: chips
22. A chipping-rate of at least ____________________ times the bit rate of the data is common.
ANS: ten
23. The 'C' in CDMA stands for ____________________.
ANS: code
24. In a frequency-hopping CDMA system, when no two transmitters use the same frequency at the same
time the PN sequences are said to be ____________________.
ANS: orthogonal
SHORT ANSWER
1. What does Hartley's Law tell us about the relationship between time and bandwidth for digital
transmission?
ANS: The more bandwidth, the less time it takes to send a given amount of information. So the more bandwidth available, the higher the possible bit rate.
2. How many signals could fit into 1 MHz of bandwidth if each signal required 100 kHz of bandwidth and
the separation between adjacent channels was 10 kHz?
ANS: 9
3. Why is it difficult to jam a spread-spectrum signal?
ANS: Jamming requires an interference signal of sufficient power in the same part of the spectrum the information signal occupies. Because a spread-spectrum signal is, by definition, spread out over a very wide bandwidth, jamming can interfere with only a small fraction of the total signal.
4. Why is it difficult to eavesdrop on a spread-spectrum signal?
ANS: In a spread-spectrum transmission, the signal power at any given frequency in its band is so low that it is virtually indistinguishable from noise. An eavesdropper would not know a signal was being sent. And without knowing the exact sequence being used, it is virtually impossible to "de-spread" the signal.
5. Why is autocorrelation used to receive direct-sequence spread-spectrum signals?
ANS: Autocorrelation allows a signal to be "pulled out of" the noise even when the signal-to-noise ratio is less than one, as it is in spread-spectrum.
6. What is meant by "orthogonal sequences" in CDMA?
ANS: During transmission, the PN sequences determine which parts of the available bandwidth the spread-spectrum signal will occupy. Assume you have two PN sequences: PN1 and PN2. At some point in time, suppose PN1 would cause a transmission to occupy frequencies f11, f12, f13, and so forth. Now suppose PN2 would cause the transmission to occupy frequencies f21, f22, f23, and so forth. If the two sets of frequencies, (f11, f12, f13, ...) and (f21, f22, f23, ...), have no frequencies in common, then the two PN sequences are said to be orthogonal.
Chapter 14: Transmission Lines
MULTIPLE CHOICE
1. SWR stands for:
a. Shorted Wave Radiation c. Shorted Wire Region b. Sine Wave Response d. none of the above
ANS: D
2. TDR stands for:
a. Total Distance of Reflection c. Time-Domain Response b. Time-Domain Reflectometer d. Transmission Delay Ratio
ANS: B
3. An example of an unbalanced line is:
a. a coaxial cable c. an open-wire-line cable b. 300-ohm twin-lead TV cable d. all of the above
ANS: A
4. When analyzing a transmission line, its inductance and capacitance are considered to be:
a. lumped c. equal reactances b. distributed d. ideal elements
ANS: B
5. As frequency increases, the resistance of a wire:
a. increases c. stays the same b. decreases d. changes periodically
ANS: A
6. The effect of frequency on the resistance of a wire is called:
a. I2R loss c. the skin effect b. the Ohmic effect d. there is no such effect
ANS: C
7. As frequency increases, the loss in a cable's dielectric:
a. increases c. stays the same b. decreases d. there is no loss in a dielectric
ANS: A
8. The characteristic impedance of a cable depends on:
a. the resistance per foot of the wire used b. the resistance per foot and the inductance per foot c. the resistance per foot and the capacitance per foot d. the inductance per foot and the capacitance per foot
ANS: D
9. For best matching, the load on a cable should be:
a. lower than Z0 c. equal to Z0 b. higher than Z0 d. 50 ohms
ANS: C
10. The characteristic impedance of a cable:
a. increases with length c. increases with voltage b. increases with frequency d. none of the above
ANS: D
11. The velocity factor of a cable depends mostly on:
a. the wire resistance c. the inductance per foot b. the dielectric constant d. all of the above
ANS: B
12. A positive voltage pulse sent down a transmission line terminated in a short-circuit:
a. would reflect as a positive pulse b. would reflect as a negative pulse c. would reflect as a positive pulse followed by a negative pulse d. would not reflect at all
ANS: B
13. A positive voltage pulse sent down a transmission line terminated with its characteristic impedance:
a. would reflect as a positive pulse b. would reflect as a negative pulse c. would reflect as a positive pulse followed by a negative pulse d. would not reflect at all
ANS: D
14. A positive voltage-pulse sent down a transmission line terminated in an open-circuit:
a. would reflect as a positive pulse b. would reflect as a negative pulse c. would reflect as a positive pulse followed by a negative pulse d. would not reflect at all
ANS: A
15. The optimum value for SWR is:
a. zero c. as large as possible b. one d. there is no optimum value
ANS: B
16. A non-optimum value for SWR will cause:
a. standing waves c. higher voltage peaks on cable b. loss of power to load d. all of the above
ANS: D
17. VSWR stands for:
a. variable SWR c. voltage SWR b. vacuum SWR d. none of the above
ANS: C
18. The impedance "looking into" a matched line:
a. is infinite c. is the characteristic impedance b. is zero d. 50 ohms
ANS: C
19. A Smith Chart is used to calculate:
a. transmission line impedances c. optimum length of a transmission line b. propagation velocity d. transmission line losses
ANS: A
20. Compared to a 300-ohm line, the loss of a 50-ohm cable carrying the same power:
a. would be less c. would be the same b. would be more d. cannot be compared
ANS: B
21. A balanced load can be connected to an unbalanced cable:
a. directly c. by using a "balun" b. by using a filter d. cannot be connected
ANS: C
22. On a Smith Chart, you "normalize" the impedance by:
a. assuming it to be zero c. multiplying it by 2π b. dividing it by 2π d. dividing it by Z0
ANS: D
23. The radius of the circle you draw on a Smith Chart represents:
a. the voltage c. the impedance b. the current d. none of the above
ANS: D
24. The center of the Smith Chart always represents:
a. zero c. the characteristic impedance b. one d. none of the above
ANS: C
25. A TDR is commonly used to:
a. measure the characteristic impedance of a cable b. find the position of a defect in a cable
c. replace a slotted-line d. all of the above
ANS: B
COMPLETION
1. A cable that lacks symmetry with respect to ground is called ____________________.
ANS: unbalanced
2. Parallel lines are usually operated as ____________________ lines since both wires are symmetrical with
respect to ground.
ANS: balanced
3. Normally, a transmission line is terminated with a load equal to its ____________________ impedance.
ANS: characteristic
4. Twisted-pair cables are transmission lines for relatively ____________________ frequencies.
ANS: low
5. To analyze a transmission line, it is necessary to use ____________________ parameters instead of
lumped ones.
ANS: distributed
6. The increase of a wire's resistance with frequency is called the ____________________ effect.
ANS: skin
7. The increase of a wire's resistance with frequency is caused by the ____________________ field inside
the wire.
ANS: magnetic
8. Dielectrics become more ____________________ as the frequency increases.
ANS: lossy
9. The inductance and capacitance of a cable are given per unit ____________________.
ANS: length
10. Characteristic impedance is sometimes called ____________________ impedance.
ANS: surge
11. A cable that is terminated in its characteristic impedance is called a ____________________ line.
ANS: matched
12. A pulse sent down a cable terminated in a short-circuit will reflect with the ____________________
polarity.
ANS: opposite
13. The apparently stationary pattern of waves on a mismatched cable is called a ____________________
wave.
ANS: standing
14. SWR stands for ____________________-wave ratio.
ANS: standing
15. The ideal value for SWR is ____________________.
ANS: one
16. Transmission line impedances can be found using a ____________________ chart.
ANS: Smith
17. Short transmission-line sections called ____________________ can be used as capacitors or inductors.
ANS: stubs
18. Any cable that radiates energy can also ____________________ energy.
ANS: absorb
19. A ____________________-dB loss in a cable means only half the power sent reaches the load.
ANS: 3
20. It is often best to measure SWR at the ____________________ end of a cable.
ANS: load
21. Besides heat from I2R, the power a cable can carry is limited by the ____________________ voltage of
its dielectric.
ANS: breakdown
22. To normalize an impedance on a Smith Chart, you divide it by ____________________.
ANS: Z0
23. The ____________________ of a Smith Chart always represents the characteristic impedance.
ANS: center
24. A ____________________ wavelength transmission line can be used a transformer.
ANS: one-quarter
25. A slotted line is used to make measurements in the ____________________ domain.
ANS: frequency
SHORT ANSWER
1. A transmission line has 2.5 pF of capacitance per foot and 100 nH of inductance per foot. Calculate its
characteristic impedance.
ANS: Z0 = 200 ohms
2. Two wires with air as a dielectric are one inch apart. The diameter of the wire is .04 inch. Calculate,
approximately, its characteristic impedance.
ANS: 386 ohms
3. If a coaxial cable uses plastic insulation with a dielectric constant ∈r = 2.6 , what is the velocity factor for
the cable?
ANS: 0.62
4. If a cable has a velocity factor of 0.8, how long would it take a signal to travel 3000 kilometers along the
cable?
ANS: 12.5 ms
5. If a cable has a velocity factor of 0.8, what length of cable is required for a 90° phase shift at 100 MHz?
ANS: 0.6 meters
6. A cable has a VSWR of 10. If the minimum voltage along the cable is 20 volts, what is the maximum
voltage along the cable?
ANS: 200 volts
7. A lossless line has a characteristic impedance of 50 ohms, but is terminated with a 75-ohm resistive load. What SWR do you expect to measure?
ANS: 1.5
8. If a cable has an SWR of 1.5, what will be the absolute value of its voltage coefficient of reflection?
ANS: 0.2
9. A generator matched to a line with a voltage coefficient of reflection equal to 0.2 transmits 100 watts into
the line. How much power is actually absorbed by the load?
ANS: 96 watts
10. Using a Smith Chart to analyze a 50-ohm cable, what would be the normalized value of an impedance
equal to 200 + j50 ohms?
ANS: 4 + j1
Chapter 15: Radio-Wave Propagation
MULTIPLE CHOICE
1. Radio waves were first predicted mathematically by:
a. Armstrong c. Maxwell b. Hertz d. Marconi
ANS: C
2. Radio waves were first demonstrated experimentally by:
a. Armstrong c. Maxwell b. Hertz d. Marconi
ANS: B
3. The technology that made cell phones practical was:
a. the microprocessor chip c. high-power microwave transmitters b. the miniature cell-site d. all of the above
ANS: A
4. Cell phones reduce much of the problems of mobile communications with:
a. high power levels c. reuse of frequencies b. high antennas d. all of the above
ANS: C
5. Which of the following are electromagnetic:
a. radio waves c. gamma waves b. light d. all of the above
ANS: D
6. The electric and magnetic fields of a radio wave are:
a. perpendicular to each other c. both a and b b. perpendicular to the direction of travel d. none of the above
ANS: C
7. TEM stands for:
a. Transverse Electromagnetic c. True Electromagnetic b. Transmitted Electromagnetic d. none of the above
ANS: A
8. In free space, radio waves travel at a speed of:
a. 3 × 106 meters per second c. 3 × 106 miles per second b. 300 × 106 meters per second d. 300 × 106 miles per second
ANS: B
9. Which is a possible polarization for an electromagnetic wave: a. vertical c. circular b. horizontal d. all of the above
ANS: D
10. Which polarization can be reasonably well received by a circularly polarized antenna:
a. vertical c. circular b. horizontal d. all of the above
ANS: D
11. The number of circular polarization modes (directions) is:
a. 1 c. 3 b. 2 d. many
ANS: B
12. An antenna has "gain" as compared to:
a. an isotropic radiator c. a ground-wave antenna b. a vertically polarized radiator d. none of the above
ANS: A
13. EIRP stands for:
a. the E and I fields of the Radiated Power b. the Effective Isotropic Radiated Power c. the Effective Internal Reflected Power d. the Electric-field Intensity of the Radiated Power
ANS: B
14. The "attenuation of free space" is due to:
a. losses in the characteristic impedance of free space b. losses due to absorption in the upper atmosphere c. the decrease in energy per square meter due to expansion of the wavefront d. the decrease in energy per square meter due to absorption of the wavefront
ANS: C
15. Ground waves are most effective:
a. below about 2 MHz c. at microwave frequencies b. above about 20 MHz d. when using horizontally polarized waves
ANS: A
16. Radio waves would most strongly reflect off:
a. a flat insulating surface of the right size c. a flat metallic surface of the right size b. a flat dielectric surface of the right size d. a flat body of water
ANS: C
17. Radio waves sometimes "bend" around a corner because of:
a. reflection c. refraction
b. diffusion d. diffraction
ANS: D
18. Space waves are:
a. line-of-sight b. reflected off the ionosphere c. same as sky waves d. radio waves used for satellite communications
ANS: A
19. Sky waves:
a. are line-of-sight b. "bounce" off the ionosphere c. are same as space waves d. are radio waves used for satellite communications
ANS: B
20. Sky waves cannot be "heard":
a. close to the transmitter c. in the "silent" zone b. far from the transmitter d. in the "skip" zone
ANS: D
21. A 20-dB reduction in the strength of a radio wave due to reflection is called:
a. fading c. frequency diversity b. diffraction d. spatial diversity
ANS: A
22. "Ghosts" on a TV screen are an example of:
a. fading c. multipath distortion b. diffraction d. cancellation due to reflection
ANS: C
23. A "repeater" is used to:
a. send a message multiple times over a channel b. send a message over multiple channels at the same time c. extend the range of a radio communications system d. cancel the effects of fading
ANS: C
24. Cellular phone systems rely on:
a. high power c. the radio horizon b. repeaters d. the reuse of frequencies
ANS: D
25. If the number of cell-phone users within a cell increases above some limit:
a. the cell area is increased c. the power levels are increased
b. the cell area is split d. the number of channels is reduced
ANS: B
26. As a cell-phone user passes from one cell to another:
a. a "handoff" process occurs c. both cells will handle the call b. a "sectoring" process occurs d. nothing occurs
ANS: A
27. To receive several data streams at once, a CDMA spread-spectrum system uses:
a. a "funnel" receiver c. multiple receivers b. a "rake" receiver d. none of the above
ANS: B
28. The troposphere is the:
a. highest layer of the atmosphere c. lowest layer of the atmosphere b. middle layer of the atmosphere d. the most ionized layer of the atmosphere
ANS: C
29. Meteor-trail propagation is:
a. used for radio telephony c. also called "ducting" b. used to send data by radio d. not possible
ANS: B
COMPLETION
1. Radio waves were mathematically predicted by ____________________.
ANS: Maxwell
2. Radio waves were first demonstrated by ____________________.
ANS: Hertz
3. Radio waves are ____________________ electromagnetic waves.
ANS: transverse
4. The propagation speed of radio waves in free space is ____________________ m/sec.
ANS: 300 × 106
5. Electromagnetic radiation can be thought of as a stream of particles called ____________________.
ANS: photons
6. Unlike sound or water waves, radio waves do not need a ____________________ to travel through.
ANS: medium
7. The dielectric strength of clean dry air is about ____________________ volts per meter.
ANS: 3 × 106
8. Waves from an ____________________ source radiate equally in all directions.
ANS: isotropic
9. The wavefront of a point source would have the shape of a ____________________.
ANS: sphere
10. At a far distance from the source, a radio wavefront looks like a flat ____________________-wave.
ANS: plane
11. The polarization of a radio wave is the direction of its ____________________ field.
ANS: electric
12. The electric field of a radio wave is ____________________ to its magnetic field.
ANS: perpendicular
13. Both the electric and magnetic fields of a radio wave are ____________________ to its propagation
direction.
ANS: perpendicular
14. With ____________________ polarization, the direction of a radio wave's electric field rotates as it
travels through space.
ANS: circular
15. An antenna is said to have ____________________ in a certain direction if it radiates more power in that
direction than in other directions.
ANS: gain
16. The watts per square meter of a radio wave ____________________ as the wave-front moves through
space.
ANS: decrease
17. Reflection of plane-waves from a smooth surface is called ____________________ reflection.
ANS: specular
18. ____________________ is the "bending" of radio waves as they travel across the boundary between two different dielectrics.
ANS: Refraction
19. The process of ____________________ makes radio waves appear to "bend around a corner".
ANS: diffraction
20. ____________________ waves travel from transmitter to receiver in a "line-of-sight" fashion.
ANS: Space
21. ____________________ waves are vertically polarized radio waves that travel along the earth's surface.
ANS: Ground
22. ____________________ waves are radio waves that "bounce off" the ionosphere due to refraction.
ANS: Sky
23. The ____________________ zone is a region where sky waves cannot be received.
ANS: skip
24. "Ghosts" on a TV screen are an example of ____________________ distortion.
ANS: multipath
25. The "fast fading" seen in mobile communications is caused by ____________________ waves interfering
with direct waves.
ANS: reflected
26. Cell phones typically operate at a ____________________ power level.
ANS: low
27. The ____________________ of frequencies allows many cell-phone users to share a geographical area.
ANS: reuse
28. ____________________ is when a cell-site uses three directional antennas, each covering a third of the
cell area, to reduce interference.
ANS: Sectoring
29. The use of ____________________ chips makes cell phones a practical technology.
ANS: microprocessor
SHORT ANSWER
1. A certain dielectric has permittivity of 6.3 × 10–10 F/m and the same permeability as free space. What is
the characteristic impedance of that dielectric?
ANS: 45 ohms
2. If a point source of radio waves transmits 1 watt, what is the power density 10,000 meters from the
source?
ANS: 796 pW/m2
3. What power must a point-source of radio waves transmit so that the power density at 3000 meters from
the source is 1 µW/m2?
ANS: 113 watts
4. If a radio receiver needs 1 nW/m2 of power density to function, how far away from a 1-watt point source
will it continue to work?
ANS: 8.9 km
5. A line-of-sight radio link over flat terrain needs to use antenna towers 50 km apart. What, approximately,
is the minimum height for the towers assuming all the towers are the same?
ANS: 37 meters
6. A mobile radio is being used at 1 GHz in an urban environment with lots of reflecting structures. If the
car is traveling 36 km/hour, what is the expected time between fades?
ANS: 15 msec
Chapter 16: Antenna
MULTIPLE CHOICE
1. The real part of an antenna's input impedance is due to:
a. the radiated signal c. the SWR b. the reflected signal d. all of the above
ANS: A
2. A half-wave dipole is sometimes called:
a. a Marconi antenna c. a Yagi antenna b. a Hertz antenna d. none of the above
ANS: B
3. The end-to-end length of a half-wave dipole antenna is actually:
a. one wavelength c. slightly longer than a half-wavelength b. one half-wavelength d. slightly shorter than a half-wavelength
ANS: D
4. The radiation of energy from an antenna can be seen in the:
a. standing wave pattern around the antenna c. radiation resistance of the antenna b. SWR along the feed cable d. I2R loss of the antenna
ANS: C
5. Measured on the ground, the field strength of a horizontally polarized half-wave dipole antenna is
strongest: a. in one direction c. in all directions b. in two directions d. depends on the number of elements
ANS: B
6. The ability of an antenna to radiate more energy in one direction than in other directions is called:
a. directivity c. active antenna b. selectivity d. resonance
ANS: A
7. The front-to-back ratio of a half-wave dipole antenna is:
a. 0 dB c. 10 dB b. 3 dB d. infinite
ANS: A
8. An antenna's beamwidth is measured:
a. from +90° to –90° c. between half-power points b. from front to back d. between the minor side-lobes
ANS: C
9. ERP stands for:
a. Equivalent Radiation Pattern c. Equivalent Radiated Power b. Effective Radiation Pattern d. Effective Radiated Power
ANS: D
10. "Ground Effects" refers to the effects on an antenna's radiation pattern caused by:
a. radio signals reflecting off the ground b. buildings and other structures on the ground c. fading d. faulty connection of the feed cable ground
ANS: A
11. A 1-MHz monopole antenna must be:
a. mounted vertically c. at least one half-wavelength long b. mounted horizontally d. at least one wavelength long
ANS: A
12. The typical antenna in an AM radio is a:
a. dipole c. ferrite "loop-stick" b. folded dipole d. none of the above
ANS: C
13. The polarization of plane waves received from a satellite is changed by:
a. gamma rays c. helical rotation b. Faraday Rotation d. the distance traveled
ANS: B
14. A nonresonant antenna:
a. will not transmit c. will cause SWR on the feed cable b. will not receive d. all of the above
ANS: C
15. At resonance, the input impedance to a lossless antenna should be:
a. resistive c. capacitive b. inductive d. infinite
ANS: A
16. An antenna can be matched to a feed line using:
a. a shorted stub c. an LC network b. a loading coil d. all of the above
ANS: D
17. As the length of a "long-wire" antenna is increased:
a. the number of lobes increases c. efficiency decreases
b. the number of nodes decreases d. none of the above
ANS: A
18. Arrays can be:
a. phased c. parasitic b. driven d. all of the above
ANS: D
19. An array with one driven element, a reflector, and one or more directors is called a:
a. Marconi c. Log-Periodic Dipole b. Yagi d. stacked array
ANS: B
20. LPDA stands for:
a. Low-Power Dipole Array c. Log-Periodic Dipole Array b. Low-Power Directed Array d. Log Power Dipole Array
ANS: C
21. The radiated beam from a parabolic "dish" transmitting antenna is:
a. collimated c. dispersed b. phased d. none of the above
ANS: A
22. The energy picked up by a parabolic antenna is concentrated at the:
a. center c. focus b. edges d. horn
ANS: C
23. Antennas are often tested in:
a. an echo chamber c. a vacuum chamber b. an anechoic chamber d. an RF reflective chamber
ANS: B
24. Field strength at a distance from an antenna is measured with:
a. a slotted line c. an EIRP meter b. a dipole d. a field-strength meter
ANS: D
COMPLETION
1. An antenna is the interface between the transmission line and ____________________.
ANS: space
2. Hertz antenna is another name for a half-wave ____________________.
ANS: dipole
3. The length of a half-wave dipole is about ____________________ % of a half-wave in free space.
ANS: 95
4. The ____________________ resistance is the portion of an antenna's input impedance due to transmitted
radio waves leaving the antenna.
ANS: radiation
5. Input impedance at the center feed point of a resonant half-wave dipole is about ____________________
Ω.
ANS: 70
6. Input impedance at the center feed point of a resonant folded dipole is about ____________________ Ω.
ANS: 280 – 300
7. The vertical angle of radiation is called the angle of ____________________.
ANS: elevation
8. Antenna radiation patterns are typically drawn on graphs with ____________________ coordinates.
ANS: polar
9. As compared to a ____________________ source, a half-wave dipole has a gain of about 2 dBi.
ANS: point isotropic
10. Antenna gain measured in ____________________ is with reference to a half-wave dipole.
ANS: dBd
11. ____________________ is the same as the gain for a lossless antenna.
ANS: Directivity
12. The front-to-back ratio of a half-wave dipole is ____________________ dB.
ANS: 0
13. The ____________________ of a directional antenna is the angle between its half-power points.
ANS: beamwidth
14. ERP stands for ____________________ radiated power.
ANS: effective
15. ERP is the power input to the antenna multiplied by the antenna's ____________________.
ANS: gain
16. A ____________________ is required to connect a coaxial cable to a center-fed dipole antenna.
ANS: balun
17. A horizontally mounted dipole will radiate waves with ____________________ polarization.
ANS: horizontal
18. A folded dipole has ____________________ bandwidth than a standard dipole.
ANS: wider greater more
19. A monopole antenna is typically mounted in the ____________________ direction.
ANS: vertical
20. The length of a typical monopole antenna is ____________________ wavelength.
ANS: one-quarter 1/4
21. A monopole antenna mounted high on a tower typically uses a ____________________ plane.
ANS: ground
22. A vertical antenna has an _________________________ radiation pattern for ground-based receivers.
ANS: omnidirectional
23. The number of driven elements in a Yagi antenna is typically ____________________.
ANS: one
24. The reflector on a Yagi antenna is called a ____________________ element.
ANS: parasitic
25. An LPDA is a ____________________ dipole array.
ANS: log-periodic
26. If an LPDA had five elements, the number of driven elements it had would be ____________________.
ANS: five
27. All the waves that hit the surface of a parabolic antenna merge at the ____________________.
ANS: focus
28. A ____________________ beam has all its individual rays parallel to each other.
ANS: collimated
29. A microwave ____________________ antenna is essentially an extension of a waveguide.
ANS: horn
30. An ____________________ chamber is often used to test microwave antennas.
ANS: anechoic
SHORT ANSWER
1. Calculate the physical length of a half-wave dipole for use at 300 MHz.
ANS: 475 millimeters
2. How much power will a 95% efficient antenna radiate if driven with 100 watts?
ANS: 95 watts
3. If an antenna has 10.14 dB of gain compared to a point source, how much gain does it have compared to a
half-wave dipole?
ANS: 8 dB
4. What is the ERP of an antenna with 10 dBd of gain and driven by one watt?
ANS: 10 watts
5. A resonant antenna has an input impedance of 100 ohms and is driven by 100 watts. What is the RMS
current in the antenna?
ANS: 1 ampere
6. A resonant antenna has an input impedance of 100 ohms and is driven by 100 watts. What is the RMS
voltage at the feed-point of the antenna?
ANS: 100 volts
Chapter 17: Microwave Devices
MULTIPLE CHOICE
1. The microwave frequency range is considered to start at:
a. 100 MHz c. 10 GHz b. 1 GHz d. 100 GHz
ANS: B
2. The UHF range is:
a. below the microwave range c. above the microwave range b. inside the microwave range d. same as the microwave range
ANS: A
3. The dominant mode of a waveguide depends on:
a. the shape of the waveguide c. the point of signal injection b. the power level of the signal d. none of the above
ANS: A
4. The dominant mode of a rectangular waveguide is:
a. TE 01 c. TE 10 b. TM 01 d. TM10
ANS: C
5. The dominant mode of a circular waveguide is:
a. TE 01 c. TE 11 b. TM 01 d. TM11
ANS: C
6. Circular waveguides use TM 01 mode because:
a. it is dominant c. it is the only mode possible b. of its circular symmetry d. it is more efficient
ANS: B
7. The characteristic impedance of a waveguide:
a. is fixed b. depends on the frequency it carries c. depends on the longer dimension of its cross section d. both b and c
ANS: D
8. Power can be coupled into or out of a waveguide:
a. with a magnetic field probe c. through a hole in the waveguide b. with an electric field probe d. all of the above
ANS: D
9. Directional couplers for waveguides are characterized by:
a. their insertion loss c. their directivity b. their coupling specification d. all of the above
ANS: D
10. Striplines and microstrips are used to:
a. couple sections of waveguide c. couple components on a circuit board b. couple waveguides to antennas d. none of the above
ANS: C
11. A resonant cavity is a type of:
a. tuned circuit c. antenna b. defect in a waveguide d. none of the above
ANS: A
12. A TEE connector used with waveguides is:
a. an H-plane TEE c. a "magic" TEE b. an E-plane TEE d. all of the above
ANS: D
13. TWT stands for:
a. Transverse Wave Transmission c. Traveling-Wave Tube b. Transverse-Wave Tube d. Traveling-Wave Transmission
ANS: C
14. An "isolator" is a device that:
a. isolates frequencies in a waveguide b. allows a signal to pass in one direction only c. separates signals among various ports d. prevents microwaves from leaking out of a waveguide
ANS: B
15. A "circulator" is a device that:
a. rotates signal polarity in a waveguide b. allows a signal to pass in one direction only c. separates signals among various ports d. prevents microwaves from being "trapped" in a waveguide
ANS: C
16. GaAs stands for:
a. gallium arsenide c. gallium astenite b. gallium assembly d. none of the above
ANS: A
17. IMPATT stands for: a. impact avalanche and transit time c. implied power at transmission terminal b. induced mobility at transmission time d. none of the above
ANS: A
18. YIG stands for:
a. Yttrium-Iron-Gallium c. Yttrium-Iron-Garnet b. Yttrium-Iron-Germanium d. none of the above
ANS: C
19. A YIG can be tuned by applying:
a. an electric field c. mechanical pressure b. a magnetic field d. an "exciter" signal
ANS: B
20. The device commonly used in microwave ovens is the:
a. TWT c. magnetron b. klystron d. YIG
ANS: C
21. The device commonly used in satellite communications is the:
a. TWT c. magnetron b. klystron d. YIG
ANS: A
22. The device commonly used in UHF transmitters is the:
a. TWT c. magnetron b. klystron d. YIG
ANS: B
23. A microwave phased array is often made using:
a. slots c. Fresnel lenses b. Yagis d. all of the above
ANS: A
24. RADAR stands for:
a. radio ranging c. radio detection and ranging b. radio depth and ranging d. remote detection and ranging
ANS: C
25. RADAR uses:
a. pulsed transmission c. the Doppler effect b. continuous transmission d. all of the above
ANS: D
26. The maximum effective range for pulsed radar: a. increases with increasing repetition rate c. decreases with increasing pulse period b. decreases with increasing repetition rate d. none of the above
ANS: B
27. The minimum effective range for pulsed radar:
a. increases with increasing pulse duration c. is always a tenth of the maximum range b. decreases with increasing pulse duration d. none of the above
ANS: A
COMPLETION
1. ____________________ is the effect of a pulse "spreading out" as it travels through a waveguide.
ANS: Dispersion
2. The electric field is ____________________ along the walls of a rectangular waveguide.
ANS: zero
3. The waveguide mode with the lowest cutoff frequency is the ____________________ mode.
ANS: dominant
4. In TE10 mode, the ____________________ field peaks in the middle of the waveguide cross section.
ANS: electric
5. In TE20 mode, the electric field has ____________________ peaks in the waveguide cross section.
ANS: two
6. In a circular waveguide, ____________________ mode is used because of its circular symmetry.
ANS: TM01
7. A waveguide acts as a ____________________-pass filter.
ANS: high
8. In a waveguide, group velocity is always ____________________ than the speed of light.
ANS: slower
9. In a waveguide, phase velocity is always ____________________ than the speed of light.
ANS: faster
10. In a waveguide, impedance ____________________ as frequency increases.
ANS: decreases
11. A ____________________ TEE is a combination of E-plane and H-plane TEES.
ANS: hybrid
12. The Q of a resonant cavity is very ____________________ compared to lumped LC circuits.
ANS: high
13. A wavemeter is a resonant ____________________ with an adjustable plunger.
ANS: cavity
14. A Gunn device oscillates because of its negative ____________________.
ANS: resistance
15. Both magnetrons and TWTs are slow ____________________ tubes.
ANS: wave
16. Both klystrons and TWTs are ____________________-beam tubes.
ANS: linear
17. A ____________________ antenna is just a waveguide with a hole in it.
ANS: slot
18. A ____________________ antenna is a flat piece of copper on an insulating substrate with a ground
plane on the other side.
ANS: patch
19. The radar cross section of a target is typically ____________________ than its actual size.
ANS: smaller
20. The frequency of the returned signal will be ____________________ than the transmitted signal if the
target is moving toward the radar antenna.
ANS: higher
SHORT ANSWER
1. Calculate the TE10 cutoff frequency for a rectangular waveguide if the longer dimension of its cross
section is 5 cm.
ANS: 3 GHz
2. Calculate the group velocity in a waveguide carrying a signal that is twice its cutoff frequency.
ANS: 260 × 106 meters per second
3. Calculate the phase velocity in a waveguide carrying a signal that is twice its cutoff frequency.
ANS: 346 × 106 meters per second
4. Calculate the wavelength of a 2-GHz signal in a waveguide with a 1-GHz cutoff frequency.
ANS: 173 millimeters
5. Find the gain in dBi of a 10-GHz horn antenna with dE = dH= 60 mm.
ANS: 14.8
6. Find the maximum unambiguous range for a pulsed radar sending 10k pulses per second.
ANS: 15 km
7. Find the minimum unambiguous range for a pulsed radar sending 2-µsec duration pulses.
ANS: 300 meters
Chapter 18: Terrestrial Microwave Communication Systems
MULTIPLE CHOICE
1. Another term for a single microwave link is a:
a. section c. skip b. hop d. jump
ANS: B
2. Microwave systems use:
a. FM c. QAM b. SSB d. all of the above
ANS: D
3. The typical reliability of a microwave system is:
a. 90% c. 99.9% b. 99% d. 99.99%
ANS: D
4. A typical microwave system uses a transmitted power of about:
a. 2 watts c. 200 watts b. 20 watts d. none of the above
ANS: A
5. In analog microwave systems, additional repeaters increase the:
a. reliability c. jitter b. noise level d. all of the above
ANS: B
6. In digital microwave systems, additional repeaters increase the:
a. reliability c. jitter b. noise level d. all of the above
ANS: C
7. LOS stands for:
a. Loss Of Skip c. Line-Of-Sight b. Loss Of Signal d. Line-Of-Signal
ANS: C
8. Too much antenna gain causes:
a. a very narrow microwave beam c. excessive noise b. a very wide microwave beam d. jitter
ANS: A
9. The microwave signal path should clear obstacles by at least: a. 60% of the Faraday zone c. 60% of the height of the antenna tower b. 60% of the Fresnel zone d. 60% of the highest obstacle height
ANS: B
10. Satisfactory performance of an analog microwave system is defined as:
a. a carrier-to-noise ratio that exceeds a given value b. an ERP level that exceeds a given value c. an energy-per-hertz level that exceeds a given value d. none of the above
ANS: A
11. Satisfactory performance of a digital microwave system requires a:
a. low level of transmitted power b. high level of ERP c. good energy per bit per transmitted Watt ratio d. good energy per bit per noise density ratio
ANS: D
12. Fading is caused by:
a. multipath reception c. ducting b. attenuation due to weather d. all of the above
ANS: D
13. The effects of fading due to multipath reception are often reduced using:
a. diversity c. high-gain antennas b. power d. all of the above
ANS: A
14. Repeaters are used in a microwave system:
a. always c. above 10 GHz b. when distance exceeds line-of-sight d. below 10 GHz
ANS: B
15. Microwave repeaters can be:
a. IF type c. regenerative type b. baseband type d. all of the above
ANS: D
16. An advantage of digital techniques over analog in a microwave system is:
a. less bandwidth is required c. it requires less power b. accumulation of noise is reduced d. all of the above
ANS: B
17. MMDS stands for:
a. Multichannel Microwave Distribution System
b. Multipoint Microwave Distribution System c. Multichannel Multipoint Distribution System d. Multiple Microwave Distribution Systems
ANS: C
18. LMDS stands for:
a. Local Microwave Distribution System b. Local Multipoint Distribution System c. Local Multichannel Distribution System d. Low-power Microwave Distribution System
ANS: B
19. LMDS is:
a. bidirectional c. multidirectional b. unidirectional d. none of the above
ANS: A
COMPLETION
1. One microwave link is called a ____________________.
ANS: hop
2. STL stands for ____________________-to-transmitter links.
ANS: studio
3. A typical microwave system has about one hour per ____________________ or less of downtime.
ANS: year
4. Adding more links causes ____________________ in a digital microwave system.
ANS: jitter
5. In microwave systems, it is more convenient to use noise ____________________ than noise figure in
calculations.
ANS: temperature
6. In digital microwave systems, the energy per bit per ____________________ is a key parameter.
ANS: noise density
7. Multipath reception can cause 20 dB or more of ____________________.
ANS: fading
8. Two antennas stacked one above the other on a tower is an example of ____________________ diversity in a microwave system.
ANS: space
9. The ability to use two frequencies simultaneously is an example of ____________________.
ANS: diversity
10. Microwave systems generally use less than ____________________ watts of power.
ANS: ten
11. ____________________ are necessary in a microwave system that extends beyond the line-of-sight
distance.
ANS: Repeaters
12. Analog microwave systems use both IF and ____________________ repeaters.
ANS: baseband
13. Microwave digital radio techniques reduce the accumulation of ____________________ as a signal goes
from link to link.
ANS: noise
14. MMDS is unidirectional, but ____________________ is bidirectional.
ANS: LMDS
SHORT ANSWER
1. If the line-of-sight distance for an optical beam is 12 km, what would it be, approximately, for a
microwave beam?
ANS: 16 km
2. A line-of-sight microwave link operating at 4 GHz has a separation of 40 km between antennas. An
obstacle in the path is located midway between the two antennas. By how much must the beam clear the obstacle?
ANS: 16.4 meters
3. A transmitter and receiver operating at 1 GHz are separated by 10 km. How many dBm of power gets to
the receiver if the transmitter puts out 1 Watt, and both the sending and receiving antennas have a gain of 20 dBi?
ANS: –42.4 dBm
4. A microwave system has a feed-line loss of 2 dB and sees a sky temperature of 150 K. Calculate the noise
temperature of the antenna/feed-line system referenced to the receiver input.
ANS: 201 K
5. A microwave receiver receives –60 dBm of signal. The noise power is –100 dBm. What is the carrier-to-
noise power ratio?
ANS: 40 dB
Chapter 19: Television
MULTIPLE CHOICE
1. NTSC stands for:
a. National Television Systems Commission b. National Television Systems Committee c. National Television Systems Council d. Nippon Television Systems Commission
ANS: B
2. The NTSC specification was drawn up by the:
a. FCC c. EIA b. IRE d. IEEE
ANS: C
3. RGB stands for:
a. Red-Green Burst c. Red-Green Bandwidth b. Red-Green Brightness d. Red-Green-Blue
ANS: D
4. The number of scan lines in an NTSC signal is:
a. 525 c. 1024 b. 625 d. 1250
ANS: A
5. The number of NTSC frames sent per second is:
a. 25 c. 50 b. 30 d. 60
ANS: B
6. The number of NTSC fields sent per second is:
a. 25 c. 50 b. 30 d. 60
ANS: D
7. The aspect ratio of a standard TV receiver is:
a. 3 : 4 c. 525 : 625 b. 4 : 3 d. 625 : 525
ANS: B
8. Luminance refers to:
a. brightness c. chroma b. contrast d. raster
ANS: A
9. Luminance is measured in:
a. foot-candles c. IRE units b. lumins d. NTSC units
ANS: C
10. The maximum luminance level is called:
a. max white c. all white b. peak white d. whiter than white
ANS: B
11. The blanking level corresponds to a luminance of:
a. white c. whiter than white b. black d. blacker than black
ANS: B
12. The sync pulse level corresponds to a luminance of:
a. white c. whiter than white b. black d. blacker than black
ANS: D
13. The vertical blanking pulse is serrated to:
a. maintain horizontal sync c. equalize the DC level b. maintain vertical sync d. all of the above
ANS: A
14. When measured in lines, horizontal resolution:
a. is greater than vertical resolution b. is about the same as vertical resolution c. is less than vertical resolution d. horizontal resolution is not measured in lines
ANS: B
15. The smallest picture element is called a:
a. dot c. pixel b. pic d. none of the above
ANS: C
16. In a color TV receiver, Y I Q refers to:
a. luminance signal, in-phase color component, quadrature phase color component b. composite color signal, in-phase color component, quadrature phase color component c. composite video signal, in-phase video component, quadrature video color component d. a method of demodulating stereo sound
ANS: A
17. Compared to the luminance signal, the horizontal resolution for color is: a. much greater c. much less b. about the same d. resolution does not apply to color
ANS: C
18. The modulation used for the video signal in a standard NTSC color TV receiver is:
a. SSB c. suppressed-carrier AM b. vestigial sideband AM d. FM
ANS: B
19. The modulation used for the audio signal in a standard NTSC color TV receiver is:
a. SSB c. suppressed-carrier AM b. vestigial sideband AM d. FM
ANS: D
20. The modulation used for the chroma signal in a standard NTSC color TV receiver is:
a. SSB c. suppressed-carrier AM b. vestigial sideband AM d. FM
ANS: C
21. The function of the "color burst" is to:
a. detect the presence of a color video signal b. regenerate the color sub-carrier c. to synchronize the color demodulation line by line d. all of the above
ANS: D
22. SAP stands for:
a. separate audio program c. sync amplitude pulse b. separate audio pulse d. sync audio pulse
ANS: A
23. The horizontal output transformer is also called:
a. the isolation transformer c. the flyback transformer b. the video transformer d. the yoke
ANS: C
24. Compared to a monochrome CRT, the accelerating voltage on a color CRT is:
a. about the same c. much lower b. much higher d. color CRTs use magnetic acceleration
ANS: B
25. Deflection in CRTs used in TV receivers is done:
a. magnetically for both vertical and horizontal b. electrostatically for both vertical and horizontal c. electrostatically for vertical and magnetically for horizontal
d. magnetically for vertical and electrostatically for horizontal
ANS: A
26. AFPC stands for:
a. allowed full picture chroma c. automatic frequency and picture control b. automatic frequency and phase control d. none of the above
ANS: B
COMPLETION
1. ____________________ is a conductive coating on both the inside and outside of the CRT in a TV.
ANS: Aquadag
2. The ____________________ standard for TV has been in use since 1953.
ANS: NTSC
3. Video systems form pictures by a ____________________ process.
ANS: scanning
4. During the horizontal blanking interval, the electron beam ____________________ from right to left.
ANS: retraces
5. The NTSC specifies a ____________________ video signal.
ANS: composite
6. The ____________________ ratio of a CRT screen is the ratio of width to height.
ANS: aspect
7. Brightness information is called ____________________.
ANS: luma luminance
8. Color information is called ____________________.
ANS: chroma chrominance
9. The blanking period before the sync pulse is called the front ____________________.
ANS: porch
10. Odd and even fields are identified by the ____________________ of the vertical sync pulse.
ANS: position
11. Each horizontal scan line takes ____________________ microseconds, not including blanking.
ANS: 62.5
12. Horizontal blanking lasts ____________________ microseconds.
ANS: 10
13. Vertical blanking lasts about ____________________ milliseconds.
ANS: 1.3
14. Picture elements are called ____________________.
ANS: pixels
15. The maximum number of scan lines under NTSC is ____________________.
ANS: 525
16. The human eye is most sensitive to the color ____________________.
ANS: green
17. The color sub-carrier frequency is approximately ____________________ MHz.
ANS: 3.58
18. SAP stands for ____________________ audio program.
ANS: separate
19. The second anode of a CRT is often called the ____________________.
ANS: ultor
20. The accelerating voltage for a color CRT is about ____________________ kV.
ANS: 20 to 30
21. The inside of a CRT's face-plate is coated with ____________________ to generate the picture.
ANS: phosphor
22. The horizontal output transformer is called the ____________________ transformer.
ANS: flyback
23. A good way to separate luma from chroma is to use a ____________________ filter.
ANS: comb
24. The color ____________________ turns off the color circuitry when a color TV is receiving a
monochrome signal.
ANS: killer
25. Signal levels in cable TV systems are usually measured in ____________________.
ANS: dBmV
26. The antenna for a CATV system is located at the ____________________ end.
ANS: head
27. A ____________________ shows a color-bar signal with predetermined levels and phases.
ANS: vectorscope
28. Color intensity is called ____________________.
ANS: saturation
29. The ____________________ of the chroma signal represents the color hue.
ANS: phase
30. The ____________________ controls in a color TV adjust the electron beams to strike the correct color
phosphor dots.
ANS: purity
31. The ____________________ controls in a color TV adjust the electron beams to strike the correct triad of
phosphor dots.
ANS: convergence
Chapter 20: Satellite Communications
MULTIPLE CHOICE
1. The height of the geosynchronous orbit above the equator is about:
a. 3,578 km c. 357,800 km b. 35,780 km d. depends on satellite velocity
ANS: B
2. The high and low points of a satellite's orbit are called, respectively,:
a. apogee and perigee c. uplink and downlink b. perigee and apogee d. downlink and uplink
ANS: A
3. The area on the earth that is "covered" by a satellite is called its:
a. earth station c. footprint b. downlink d. plate
ANS: C
4. The velocity required to stay in orbit:
a. is constant b. is zero (freefall) c. is lower close to the earth than far from the earth d. is higher close to the earth than far from the earth
ANS: D
5. An antenna is aimed by adjusting the two "look angles" called:
a. azimuth and elevation c. declination and elevation b. azimuth and declination d. apogee and perigee
ANS: A
6. The power per transponder of a typical Ku-band satellite is in the range:
a. 5 to 25 watts c. 500 to 2500 watts b. 50 to 250 watts d. depends on its orbit
ANS: B
7. The power level for an earth station to transmit to a satellite is on the order of:
a. 101 watts c. 103 watts b. 102 watts d. 104 watts
ANS: C
8. The "payload" on a communications satellite consists of:
a. transponders c. solar cells b. batteries d. all of the above
ANS: A
9. "Station-keeping" refers to:
a. antenna maintenance c. orbital adjustments b. power-level adjustments d. none of the above
ANS: C
10. DBS stands for:
a. decibels of signal c. direct-broadcast system b. down-beam signal d. direct-broadcast satellite
ANS: D
11. LNA stands for:
a. low-noise amplifier c. low-noise amplitude b. low north angle d. low-noise array
ANS: A
12. A reduction in TWT power for linearity is called:
a. backdown c. power-down b. backoff d. EIRP drop
ANS: B
13. TVRO stands for:
a. television receive only c. television remote origin b. television repeater only d. none of the above
ANS: A
14. TDMA stands for:
a. transponder-directed multiple antennas c. time-division multiple access b. television distribution master antenna d. transmit delay minimum aperture
ANS: C
15. VSAT stands for:
a. video satellite c. very small antenna terminal b. video signal antenna terminal d. very small aperture terminal
ANS: D
16. On the uplink from a terminal, a VSAT system uses:
a. high power to a small antenna c. low power to a large antenna b. low power to a small antenna d. LEO satellites
ANS: B
17. A typical VSAT system is configured as a:
a. star c. ring b. mesh d. repeater
ANS: A
18. LEO stands for:
a. long elliptic orbit c. lateral earth orbit b. low-earth orbit d. longitudinal earth orbit
ANS: B
19. For real-time communication, LEO systems require:
a. a constellation of satellites c. very high power b. tracking dish antennas d. all of the above
ANS: A
20. The frequency bands used by Ku-band satellites are:
a. 4 GHz and 6 GHz c. 20 GHz and 30 GHz b. 12 GHz and 14 GHz d. none of the above
ANS: B
COMPLETION
1. A satellite in geosynchronous orbit takes ____________________ hours to complete one orbit.
ANS: 24
2. The ____________________ is the signal path from the earth station to the satellite.
ANS: uplink
3. The ____________________ is the signal path from the satellite to the earth station.
ANS: downlink
4. A satellite in a ____________________ orbit appears to stay directly above one spot on the equator.
ANS: geostationary
5. Non-geostationary satellites are sometimes called ____________________ satellites.
ANS: orbital
6. A geosynchronous orbit is about ____________________ km above the earth.
ANS: 35,780
7. A ____________________ is an outline of the area on the earth's surface that a satellite broadcasts to.
ANS: footprint
8. All satellite orbits are ____________________ in shape.
ANS: elliptical
9. The ____________________ is the distance of a satellite's closest approach to the earth.
ANS: perigee
10. The ____________________ is a satellite's farthest distance from the earth.
ANS: apogee
11. An antenna's ____________________ is its angular direction between east and west.
ANS: azimuth
12. An antenna's ____________________ is its vertical angle with respect to the earth's surface.
ANS: elevation
13. An antenna's ____________________ is the angle by which it is offset from the earth's axis.
ANS: declination
14. Satellites using the ____________________ band operate on 12 GHz.
ANS: Ku
15. The time for a signal to make a round trip via satellite is about ____________________ milliseconds.
ANS: 500
16. A ____________________ is a type of repeater used on communications satellites.
ANS: transponder
17. Both the gain and the beamwidth of a dish antenna depend on its ____________________.
ANS: diameter
18. VSAT systems commonly use a ____________________ network configuration.
ANS: star
19. To date, LEO satellite systems have been a financial ____________________.
ANS: failure
20. C-band antennas are ____________________ than Ku-band antennas.
ANS: larger
SHORT ANSWER
1. A receiving antenna with a gain of 44.4 dBi looks at a sky with a noise temperature of 15 K. The loss
between the output of the antenna and the input of the LNA is 0.4 dB, and the LNA has a noise temperature of 40 K. Calculate the G/T.
ANS: 25 dB
2. A receiver has a noise figure of 1.7 dB. Find its equivalent noise temperature.
ANS: 139 K.
3. A receiving antenna with a G/T of 25 dB is used to receive signals from a satellite 38,000 km away. The
satellite has a 100-watt transmitter and an antenna with a gain of 30 dBi. The signal has a bandwidth of 1 MHz at a frequency of 12 GHz. Calculate the C/N at the receiver.
ANS: 38 dB
Chapter 21: Cellular Radio
MULTIPLE CHOICE
1. AMPS stand for:
a. American Mobile Phone System c. Advanced Mobile Phone System b. Analog Mobile Phone Service d. Advanced Mobile Phone Service
ANS: D
2. PCS stands for:
a. Personal Communications Service c. Personal Cell phone Service b. Personal Communications Systems d. Portable Communications Systems
ANS: B
3. RCC stands for:
a. Radio Common Carrier c. Regional Cellular Carrier b. Radio Cellular Carrier d. none of the above
ANS: A
4. MSC stands for:
a. Mobile Switching Center c. Maximum Signal Carrier b. Mobile Service Cellular d. Minimum Signal Carrier
ANS: A
5. MTSO stands for:
a. Minimum Transmitted Signal Output c. Mobile Telephone Switching Office b. Maximum Transmitted Signal Output d. Mobile Transmission Time-Out
ANS: C
6. MIN stands for:
a. Manual Identification Number c. Maximum In-band Noise b. Mobile Identification Number d. Minimum In-band Noise
ANS: B
7. NAM stands for:
a. Numerical Access Mode c. Number Access Module b. Numerical Assignment Mode d. Number Assignment Module
ANS: D
8. ESN stands for:
a. Electronic Serial Number c. Emission Strength Number b. Emitted Signal Number d. none of the above
ANS: A
9. SCM stands for: a. Service Class Mark c. Signal Class Mark b. Station Class Mark d. Serial-Code Mode
ANS: B
10. SCM identifies the:
a. code number of a cell phone c. signal classification (analog or digital) b. base-station class d. maximum power level of a cell phone
ANS: D
11. SID stands for:
a. Sequential Interrupt Demand c. System Identification Number b. Standard Identification Number d. Signal Intensity Descriptor
ANS: C
12. The SID is used by a cell phone to:
a. identify the type of system (analog or digital) b. recognize an AMPS system c. set its transmitted power level d. recognize that it is "roaming"
ANS: D
13. DCC stands for:
a. Digital Color Code c. Digital Communications Carrier b. Digital Communications Code d. Direct Channel Code
ANS: A
14. SAT stands for:
a. Station Antenna Tower c. Supervisory Access Tone b. Supervisory Audio Tone d. none of the above
ANS: B
15. CMAC stands for:
a. Control Mobile Attenuation Code c. Central Mobile Access Control b. Control Mobile Access Code d. Carrier Mode Attenuation Control
ANS: A
16. The CMAC is used to:
a. control access to the cell site b. set the access code of the cell phone c. set the transmit power of the cell phone d. select the transmit channel for the cell phone
ANS: C
17. In an AMPS system, voice is sent using:
a. AM c. FSK
b. FM d. CDMA
ANS: B
18. In an AMPS system, control-channel signals are sent using:
a. AM c. FSK b. FM d. CDMA
ANS: C
19. The ERP of a typical handheld AMPS cell phone is:
a. less than 600 µW. c. between 1 and 2 watts b. less than 600 mW. d. 4 watts
ANS: B
20. BSC stands for:
a. Base Station Controller c. Basic Service Contract b. Base Signal Controller d. Basic Service Code
ANS: A
21. The combination of the mobile cell phone and the cell site radio equipment is called the:
a. BSC c. RF interface b. MTSO d. air interface
ANS: D
22. The optimum cell-site radius is:
a. 2 km c. as small as possible b. 0.5 km d. none of the above
ANS: D
23. Phone traffic is measured in:
a. calls c. number of users b. erlangs d. number of blocked calls
ANS: B
24. One way to increase the capacity of a cell phone system is:
a. increase the number of cells c. increase the ERP b. decrease the number of cells d. decrease the ERP
ANS: A
25. CDPD stands for:
a. Code-Division Packet Data c. Coded Digital Packet Data b. Cellular Digital Packet Data d. Cellular Digital Pulse Data
ANS: B
COMPLETION
1. AMPS uses the ____________________-MHz band.
ANS: 800
2. ____________________ is still the most common cellular phone system in North America.
ANS: AMPS
3. Frequency ____________________ is what makes cellular phone systems complex.
ANS: reuse
4. A ____________________ occurs when an in-use cell-phone moves from one cell site to another.
ANS: handoff
5. If a cell-site radius drops below ____________________ km, handoffs will occur too frequently.
ANS: 0.5
6. The number of ERP classes in AMPS is ____________________.
ANS: three
7. A cell phone permanently installed in a car would be ERP class ____________________.
ANS: I one
8. The maximum ERP of class III cell phones is ____________________.
ANS: 600 mW
9. A portable, handheld cell phone would be ERP class ____________________.
ANS: III three
10. Mobile transmitter power is controlled by the ____________________.
ANS: land station
11. A MAC is a mobile ____________________ code.
ANS: attenuation
12. For security, you should always assume that AMPS transmissions are ____________________.
ANS: public
13. A mobile switching center is also called an ____________________.
ANS: MTSO
14. The optimum size of a cell site depends on the amount of ____________________.
ANS: traffic
15. Telephone call traffic is measured in ____________________.
ANS: erlangs
16. A cell phone moving into a site with no available frequencies will have a ____________________ call.
ANS: dropped
17. The reduction in cell size to increase traffic is called cell ____________________.
ANS: splitting
18. A ____________________ site is a very small unit that can mount on a streetlight pole.
ANS: microcell
19. Very small cells called ____________________ are used for reliable indoor reception.
ANS: picocells
20. Compared with AMPS, digital cellular phones require ____________________ bandwidth.
ANS: less
SHORT ANSWER
1. Give two reasons why digital cell phone systems are more secure than analog cell phone systems.
ANS: 1. Digital is inherently more secure because of its format. 2. Digitized voice signals are easily encrypted.
2. If a 28.8-kbps modem is being used over a cell phone, how many words of text would be lost during a
100-msec handoff interruption assuming 10 bits per letter and 5 letters per word?
ANS: 57.6
3. A certain cell site contains 200 cell phones. The probability that a given cell phone is being used is 15%.
What is the traffic in erlangs?
ANS: 30
4. What is "trunking gain"?
ANS: For a given probability of being blocked, the maximum allowable traffic per channel increases as the number of channels increases.
Chapter 22: Personal Communications Systems
MULTIPLE CHOICE
1. Current PCS systems are referred to as:
a. first-generation c. third-generation b. second-generation d. digital-generation
ANS: B
2. The frequency band designated for PCS in North America is:
a. 800 MHz c. 1.9 GHz b. 900 MHz d. 12 GHz
ANS: C
3. The "forward" PCS channel is:
a. from the base to the mobile c. from mobile to mobile b. from the mobile to the base d. same as the uplink
ANS: A
4. Compared to AMPS, PCS cell sites are:
a. bigger c. distributed b. smaller d. higher-power
ANS: B
5. AMPS was designed for:
a. POTS c. use built into an automobile b. voice d. all of the above
ANS: D
6. The number of competing PCS systems in North America is:
a. 2 c. 4 b. 3 d. many
ANS: B
7. CDMA technology was invented by:
a. AT&T c. Bell Labs b. Lucent d. Qualcomm
ANS: D
8. GSM is used in:
a. Asia c. North America b. Europe d. all of the above
ANS: D
9. In GSM, voice channels are called:
a. traffic channels c. bearer channels b. voice channels d. talking channels
ANS: A
10. AMPS uses:
a. CDMA c. spread-spectrum b. TDMA d. none of the above
ANS: D
11. Other things being equal, battery life in a GSM phone should be:
a. less than in a TDMA phone c. greater than in a TDMA phone b. no better than in an AMPS phone d. no better than a TDMA phone
ANS: C
12. It is necessary to send control information on traffic channels in:
a. no PCS system c. TDMA only b. GSM only d. both GSM and TDMA
ANS: D
13. GSM uses:
a. frequency hopping c. CDMA b. direct-sequence modulation d. all of the above
ANS: A
14. In GSM, SIM stands for:
a. Short Inbound Message c. Subscriber ID Module b. Subscriber-Initiated Message d. Subscriber ID Method
ANS: C
15. IMSI stands for:
a. Integrated Mobile Subscriber Identification b. International Mobile Subscriber Identification c. Interim Mobile Subscriber Identification d. Intermodulation System Interference
ANS: B
16. IS-95 uses:
a. frequency hopping c. CDMA b. TDMA d. all of the above
ANS: C
17. IS-136 uses:
a. frequency hopping c. CDMA b. TDMA d. all of the above
ANS: B
18. In CDMA:
a. all frequencies are used in all cells b. each cell uses half the available frequencies c. each cell is assigned a frequency by the base d. the frequency is selected by the mobile phone
ANS: A
19. CDMA uses a set of PN sequences that are:
a. common c. rotating b. unique d. orthogonal
ANS: D
20. The next generation of PCS is expected to have:
a. faster data rates c. wider roaming area b. Internet access d. all of the above
ANS: D
COMPLETION
1. PCS stands for ____________________ Communications System.
ANS: Personal
2. Current PCS systems are called ____________________-generation systems.
ANS: second
3. In North America, PCS is assigned the ____________________-MHz band.
ANS: 1900
4. Compared to AMPS, PCS cells are ____________________ in size.
ANS: smaller
5. Besides TDMA and CDMA, ____________________ is also used in North America for PCS.
ANS: GSM
6. The spread-spectrum technique used in IS-95 PCS is ____________________.
ANS: CDMA direct sequence
7. The spread-spectrum technique used in GSM is _________________________.
ANS: frequency hopping
8. Unlike AMPS, CDMA allows for a ____________________ handoff.
ANS: soft
9. The orthogonal PN sequences used in CDMA are called a ____________________ code.
ANS: Walsh
10. Unlike other systems, in CDMA ____________________ frequencies are used in all cells.
ANS: all
11. PN stands for Pseudo-____________________ Noise.
ANS: random
12. ____________________ diversity is inherent in any spread-spectrum system.
ANS: Frequency
13. RF channel S/N ratios ____________________ than zero are typical in CDMA systems.
ANS: less
14. CDMA uses a ____________________-rate vocoder.
ANS: variable
15. A phone user typically talks less than ____________________% of the time during a conversation.
ANS: 50
16. CDMA requires ____________________-loop power control to work properly.
ANS: closed
17. GPRS stands for General ____________________ Radio Service.
ANS: Packet
18. IMT stands for International ____________________ Telecommunications.
ANS: Mobile
19. UPT stands for ____________________ Personal Telecommunications.
ANS: Universal
20. UWT stands for Universal ____________________ Telecommunications.
ANS: Wireless
21. W-CDMA stands for ____________________ CDMA.
ANS: Wideband
SHORT ANSWER
1. What is the advantage of a "soft" handoff?
ANS: No calls are dropped.
2. If CDMA receivers hear all frequencies all the time, how do they pick a specific frequency?
ANS: Each frequency is modulated using a separate orthogonal PN sequence. To demodulate, the receiver uses the PN sequence specific to the channel it wants.
3. What is the effect of cochannel interference in CDMA?
ANS: It increases the background noise level, but CDMA can tolerate a lot of such noise.
4. How does GSM achieve frequency diversity?
ANS: It uses limited frequency hopping.
5. Why was PCS assigned to 1.9 GHz instead of the 800-MHz band used for AMPS?
ANS: The 800 MHz band was already overcrowded.
6. Why would a battery in a GSM phone be expected to last longer than a battery in a TDMA phone?
ANS: A TDMA phone is active during one out of every three time slots. A GSM phone is active during one out of every eight.
7. What is the advantage of using offset QPSK over standard QPSK?
ANS: With standard QPSK, the transmitted power repeatedly goes to zero. With offset QPSK, it never goes to zero. Linearity requirements are less strict for offset QPSK transmitters.
8. What is the "near/far" effect in CDMA, and what causes it?
ANS: A stronger station farther away can "drown out" a weaker station that is near. This happens when the power transmitted by mobile units is not well controlled by the base.
Chapter 23: Paging and Wireless Data Networking
MULTIPLE CHOICE
1. Pagers use:
a. the VHF band only b. the UHF band only c. both the VHF and UHF bands d. the VHF band, the UHF band, and the ISM band
ANS: C
2. ISM stands for:
a. IEEE Standard Message c. Industrial, Scientific, and Messaging b. IEEE Secure Message d. Industrial, Scientific, and Medical
ANS: D
3. CAPCODE is:
a. an encryption scheme used for pagers b. an addressing scheme used for pagers c. an error-detection scheme used for pagers d. a digital modulation scheme used for pagers
ANS: B
4. In a one-way pager system:
a. all pages are sent from all transmitters b. each transmitting antenna covers a wide area c. transmitters use relatively high power d. all of the above
ANS: D
5. POCSAG stands for:
a. Pager Operations Common Standards Advisory Group b. Pager Operations Code Standardization Advisory Group c. Post Office Code Standardization Advisory Group d. Post Office Common Standards Advisory Group
ANS: C
6. A typical pager system does not:
a. require "handoffs" c. require error detection b. allow "roaming" d. all of the above
ANS: A
7. The IEEE specification covering wireless LANs is:
a. 802.10 c. 802.12
b. 802.11 d. 802.13
ANS: B
8. The IEEE 802 spec for wireless LANs uses the:
a. VHF band c. ISM band b. UHF band d. infrared band
ANS: C
9. The IEEE 802 document for wireless LANs specifies the use of:
a. CSMA/CA c. CDMA b. CSMA/CD d. all of the above
ANS: A
10. BSS stands for:
a. Basic Service Set c. Bluetooth Service System b. Basic Service System d. none of the above
ANS: A
11. Bluetooth uses:
a. CDMA c. QPSK b. frequency hopping d. all of the above
ANS: B
12. Bluetooth uses the:
a. VHF band c. ISM band b. UHF band d. infrared band
ANS: C
13. TDD stands for:
a. Time-Division Duplex c. Time Delay Difference b. Time-Delayed Duplex d. Total Distance Delay
ANS: A
14. A Bluetooth "piconet" has:
a. 2 nodes c. 2 to 8 nodes b. 2 to 4 nodes d. 2 to 16 nodes
ANS: C
15. Two or more connected piconets forms a:
a. micronet c. TDD net b. multinet d. scatternet
ANS: D
16. The basic range of a Bluetooth device is:
a. 10 cm to 1 meter c. 10 cm to 100 meters
b. 10 cm to 10 meters d. within 10 feet
ANS: B
17. IRDA stands for:
a. Infrared Data Association c. Infrared Restricted Data Area b. Infrared Digital Association d. Infrared Roaming Data Area
ANS: A
18. The range of an IRDA system is:
a. 1 meter c. 1 foot b. 10 meters d. 10 feet
ANS: A
19. Infrared networks:
a. cannot penetrate walls c. can use reflected infrared beams b. can use diffused infrared beams d. all of the above
ANS: D
20. The maximum range of a typical wireless modem is:
a. 1 meter c. several hundred meters b. several meters d. several thousand meters.
ANS: D
COMPLETION
1. Each pager has a unique address called a ____________________.
ANS: capcode
2. Many pagers can share a frequency using ____________________.
ANS: TDMA
3. The POCSAG was devised by the British ____________________ Office.
ANS: Post
4. A POCSAG message uses a ____________________-bit error correction code.
ANS: 10
5. IEEE ____________________ covers wireless LANs.
ANS: 802.11
6. The IEEE document specifies a maximum power of ____________________ for wireless LANs.
ANS: 1 watt
7. Bluetooth uses the ____________________ band.
ANS: ISM
8. A network of 2 to 8 Bluetooth devices is called a ____________________.
ANS: piconet
9. A Bluetooth scatternet consists of 2 or more ____________________.
ANS: piconets
10. An IRDA system is deliberately restricted to a range of ____________________.
ANS: 1 meter
Chapter 24: Fiber Optics
MULTIPLE CHOICE
1. Compared to the core, the index of refraction of the cladding must be:
a. the same c. less b. greater d. doesn't have an index of refraction
ANS: C
2. Fiber-optic cables do not:
a. carry current c. generate EMI b. cause crosstalk d. all of the above
ANS: D
3. Single-mode fiber is made from:
a. glass c. both a and b b. plastic d. none of the above
ANS: A
4. Fiber-optic cable cannot be used:
a. in an explosive environment b. to connect a transmitter to an antenna c. to isolate a medical patient from a shock hazard d. none of the above
ANS: B
5. A single-mode cable does not suffer from:
a. modal dispersion c. waveguide dispersion b. chromatic dispersion d. all of the above
ANS: A
6. Scattering causes:
a. loss c. intersymbol interference b. dispersion d. all of the above
ANS: A
7. The loss in single-mode fiber-optic cable due to the glass is about:
a. 40 dB per km c. 0.4 dB per km b. 4 db per km d. zero loss
ANS: C
8. The loss in single-mode fiber-optic cable due to a splice is about:
a. 0.02 dB c. 1 dB
b. 0.2 db d. 3 dB
ANS: A
9. The loss in single-mode fiber-optic cable due to a connector is about:
a. 0.02 dB c. 1 dB b. 0.2 db d. 3 dB
ANS: B
10. Which of the following is a type of fiber connector:
a. ST c. SMA b. SC d. all of the above
ANS: D
11. The quantum of light is called:
a. an erg c. a photon b. an e-v d. a phonon
ANS: C
12. LASER stands for:
a. Light Amplification by Simulated Emission of Radiation b. Light Amplification by Stimulated Emission of Radiation c. Light Amplification by Simulated Emitted Rays d. Light Amplification by Stimulated Emitted Rays
ANS: B
13. APD stands for:
a. Avalanche Photodiode c. Avalanche Photo Detector b. Advanced Photodiode d. Advanced Photo Detector
ANS: A
14. In a PIN diode, leakage current in the absence of light is called:
a. baseline current c. dark current b. zero-point current d. E-H current
ANS: C
15. For a light detector, responsivity is measured in:
a. amps per watt c. mA per joule b. µW per amp d. µsec per µW
ANS: A
COMPLETION
1. In the core, the angle of incidence equals the angle of ____________________.
ANS: reflection
2. The core is surrounded by the ____________________.
ANS: cladding
3. The ____________________ angle is where refraction changes to reflection.
ANS: critical
4. An electron-volt is a measure of ____________________.
ANS: energy
5. The numerical aperture is the ____________________ of the angle of acceptance.
ANS: sine
6. Optical fiber relies on total ____________________ reflection.
ANS: internal
7. Chromatic dispersion is also called ____________________ dispersion.
ANS: intramodal
8. With optical fiber, ____________________ light is more common than visible light.
ANS: infrared
9. In multimode fiber, ____________________ index has less dispersion than step index.
ANS: graded
10. For laser diodes, the term ____________________ is used instead of bandwidth.
ANS: linewidth
11. Dispersion can be expressed in units of ____________________ rather than bandwidth.
ANS: time
12. ____________________ interference is when one pulse merges with the next pulse.
ANS: Intersymbol
13. The optical fiber is free to move around in a ____________________ cable.
ANS: loose-tube
14. The optical fiber is not free to move around in a ____________________ cable.
ANS: tight-buffer
15. A ____________________ is a short length of fiber that carries the light away from the source.
ANS: pigtail
16. Good connections are more critical with ____________________-mode fiber.
ANS: single
17. A ____________________ diode is the usual light source for single-mode cable.
ANS: laser
18. The quantum of light is called the ____________________.
ANS: photon
19. A ____________________ diode is the usual light detector for single-mode cable.
ANS: PIN
20. For safety, you should never ____________________ at the end of an optical fiber unless you know it is
not connected to a light source.
ANS: look
Chapter 25: Fiber-Optic Systems
MULTIPLE CHOICE
1. FDDI stands for:
a. Fiber Digital Data Interface c. Fiber Distribution Delay Interface b. Fiber Distributed Data Interface d. Frequency-Division Data Interface
ANS: B
2. FITL stands for:
a. Fiber In The Loop c. Frequency Input to The Loop b. Fiber Input Timing Loss d. Fiber Input Timing Loop
ANS: A
3. FTTC stands for:
a. Fiber Transmission Timing Constraint b. Fiber Transmission Technology Committee c. Fiber Telephone Transmission Cable d. Fiber To The Curb
ANS: D
4. SONET stands for:
a. Simple Optical Network c. Synchronous Optical Network b. Standard Optical Network d. none of the above
ANS: C
5. DWDM stands for:
a. Digital Wavelength-Division Modulation b. Dense Wavelength-Division Modulation c. Double Wavelength-Division Modulation d. Dense Wavelength-Division Multiplexing
ANS: D
6. A Soliton is a:
a. defect in the glass c. type of pulse b. type of particle d. type of optical network
ANS: C
7. Adding bits to synchronize one digital signal to another is called:
a. bit stuffing c. SDH b. bit-synch d. WDM
ANS: A
8. Power above the minimum required by an optical receiver is called:
a. gain margin c. excess gain
b. system margin d. overdrive
ANS: B
9. Typically, repeaters are not required for fiber-optic cable lengths up to:
a. 1000 miles c. 100 km b. 100 miles d. 10 km
ANS: C
10. In SONET, OC-1 stands for:
a. Optical Carrier level one c. Optical Channel one b. Optical Coupler unidirectional d. Optical Cable type 1
ANS: A
11. In SONET, STS stands for:
a. Synchronous Transport Signal c. Synchronous Transmission Signal b. Synchronous Transport System d. Synchronous Transmission System
ANS: A
12. A commonly used fiber-based system for LANs is:
a. FDDI c. gigabit Ethernet b. high-speed Ethernet d. all of the above
ANS: D
13. The use of solitons on fiber-optic cables is:
a. common c. obsolete b. experimental d. not possible
ANS: B
14. OTDR stands for:
a. Optical Time-Delay Response c. Optical Time-Domain Reflectometer b. Optical Timing Delay Requirement d. Optical Time-Division Relay
ANS: C
15. Using fiber-optic cable in a telephone system except for the connection to the subscriber's phone is called:
a. FDDI c. FITL b. FTTC d. SONET
ANS: B
COMPLETION
1. FTTC stands for Fiber To The ____________________.
ANS: Curb
2. FITL stands for Fiber In The ____________________.
ANS: Loop
3. SDH stands for Synchronous Data ____________________.
ANS: Hierarchy
4. WDM stands for ____________________-division multiplexing.
ANS: Wavelength
5. SONET stands for ____________________ Optical Network.
ANS: Synchronous
6. FDDI stands for Fiber ____________________ Data Interface.
ANS: Distributed
7. Optical amplifiers use ____________________-doped glass.
ANS: erbium
8. Optical amplifiers use a ____________________ laser.
ANS: pump
9. Dense ____________________ allows many different wavelengths of light to share a cable.
ANS: WDM
10. The OC-1 line rate is ____________________ Mbps.
ANS: 51.84
11. SONET does not use bit ____________________ to synchronize two digital signals.
ANS: stuffing
12. SONET uses a ____________________ to denote the starting position of an information frame.
ANS: pointer
13. FDDI systems use two ____________________ rings to carry signals.
ANS: token
14. The two rings of an FDDI system carry data in ____________________ directions.
ANS: opposite
15. Each ____________________ in an FDDI system acts as a regenerative repeater.
ANS: node
16. FDDI uses ____________________ mode cables.
ANS: multi
17. The data rate of an FDDI system is ____________________ bps.
ANS: 100 M
18. SONET frames have considerably more ____________________ than do DS frames for information
about signal routing and setup.
ANS: overhead
19. The number of bytes in a SONET frame is ____________________.
ANS: 810
20. The number of bytes in the payload of a SONET frame is ____________________.
ANS: 774
21. The number of rows in a SONET frame is ____________________.
ANS: 9
22. The total number of overhead bytes in a SONET frame row is ____________________.
ANS: 4
23. The number of path overhead bytes in a SONET frame row is ____________________.
ANS: 1
24. SONET frame rows contain path overhead and ____________________ overhead.
ANS: transport
25. In SONET, SPE stands for synchronous payload ____________________.
ANS: envelope
SHORT ANSWER
1. What is the bandwidth of a first-order LPF with a rise time of 350 nanoseconds?
ANS:
1 MHz
2. Calculate the total rise time for a fiber-optic system if the transmitter, receiver, and cable each have a rise
time of 50 nanoseconds.
ANS: 86.6 nanoseconds