microwave-radio and satellites communications
TRANSCRIPT
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BOOK REVIEW IN COMMUNICATIONS Electronic Communications System By Wayne Tomasi
Prepared By : MARY JANE R. ROGELIO 179
frequencies, microwave radio systems
can carry large quantities of information.
High frequencies mean short
wavelengths, which require relatively
small antennas.
Radio signals are more easily propagatedaround physical obstacles such as water
and high mountains
Fewer repeaters are necessary for
amplification.
Distances between switching centers are
less.
Underground facilities are minimized.
Minimum delays are introduced.
Minimal crosstalk exists between voice
channels.
Increased reliability and less
maintenance are important factors.
Disadvantages of Microwave Radio:
It is more difficult to analyze and design
circuits at microwave frequencies.
Measuring techniques are more difficult
to perfect
and implement at microwave
frequencies.
It is difficult to implement conventional
circuit components at microwave
frequencies. Transient time is more critical at
microwave frequencies.
It is often necessary to use specialized
components for microwave frequencies.
Microwave frequencies propagate in a
straight line, which limits their use to line-
of-sight applications.
8)
Propagates signals outside the Earths atmosphere and
are capable of carrying signals much farther whileutilizing fewer transmitters and receivers.
Satellite Systems
9)
It is used in microwave radio systems rather than
amplitude modulation because AM signals are more
sensitive to amplitude nonlinearities inherent in wide-
band microwave amplifiers.
Frequency Modulati
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BOOK REVIEW IN COMMUNICATIONS Electronic Communications System By Wayne Tomasi
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10)
Major factor when designing FM Radio systems. It is
caused by repeater amplitude nonlinearity in AM,
while in FM, it is caused by transmission gain and delay
distortion.
Intermodulation Noise
11)
The composite signal that modulates the FM carrier
and may comprise one or more of the following:
Frequency-division multiplexed voice-
band channels
Time-division-multiplexed voice-band
channels
Broadcast-quality composite video or
picture phone
Wideband data
Baseband
12)
It provides an artificial boost in amplitude to the higher
baseband frequencies.Preemphasis Network
13)
Frequency modulation index used in the FM deviator.
Typically, modulation indices are kept between 0.5 and
1.
Low-Index
14)FM signal that is produces at the output of the deviator
with a low-index frequency modulation.
Narrowband FM
15)A receiver and a transmitter placed back to back or in
tandem with the system.Microwave Repeaters
16)
It receives a signal, amplifies and reshapes it, and then
retransmit the signal to the next repeater or terminal
station down line from it.
Types of Microwave repeaters:
IF
Baseband
RF
Repeater Station
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BOOK REVIEW IN COMMUNICATIONS Electronic Communications System By Wayne Tomasi
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17)
The received RF carrier is down-converted to an IF
frequency, amplified, reshaped, up-converted to an RF
frequency, and then retransmitted.
IF Repeater
18) Generally less than 9 MHz. Baseband Frequencies
19) The range id 60 MHz to 80MHz.IF frequencies
20)
Another name for a Local oscillator, is considerably
lower in frequency than either the received or the
transmitted radio frequencies.
Shift Oscillator
21)Transmission used by microwave systems wherein adirect signal path must exist between the transmit
receive antennas.
Line-of Site Transmission
22)A temporary reduction in signal strength which last in
milliseconds for several hours or even days.
Radio Fade
23)
It suggests that there is more than one transmission
path or method of transmission available a transmitter
and a receiver.
Diversity
24)
It is simply modulating two different RF carrier
frequencies with the same IF intelligence, then
transmitting both RF signals to a given destination.
Frequency Diversity
25)
The output of a transmitter is fed to two or more
antennas that are physically separated by an
appreciable number of wavelengths.
Space Diversity
26)
A single RF carrier is propagated with two different
electromagnetic polarizations. It is generally used in
conjunction with space diversity.Polarization Diversity
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BOOK REVIEW IN COMMUNICATIONS Electronic Communications System By Wayne Tomasi
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27)
It is more than one receiver for a single radio-frequency
channel. With frequency diversity, it is necessary to also
use receiver diversity because each transmitted
frequency requires its own receiver
Receiver Diversity
28)
Another form of Hybrid diversity and undoubtly
provides the most reliable transmission but most
expensive. It combines frequency, space, polarization
and receiver diversity into one system.
Quad Diversity
29)
A specialized form of diversity that consist of a
standard frequency diversity path where the two
transmitter/ receiver pairs at one end of the path are
separated from each other and connected to differentantennas that are vertically separated as in space
diversity.
Hybrid Diversity
29)
Alternate facilities temporarily made to avoid a service
interruption during periods of deep fades or equipment
failures.
types of protection switching arrangements:
hotstandby
diversity
Protection Switching
Arrangement
30)Each working radio channel has a dedicated backup
or spare channel.Hot Standby Protection
31)A single backup channel is made available to as many
as 11 working channels.
Diversity Protection
32)
In hotstandby protection, it splits the signal power and
directs it to the working and the spare (standby)
microwave channels simultaneously.
Head-End Bridge
33) It has two working channels, one spare
channel, and an auxiliary channel.
Diversity Protection
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34)A low-capacity low-power microwave radio that is
designed to be used for a maintenance channel only.
Auxilliary Channel
35) It is where the number of repeater stations betweenprotection switches depends.
Reliability Objectives
of the Systems
36)
Points in the system where baseband signals either
originate or terminate.
four major sections:
baseband
wireline entrance link (WLEL)
FM-IF
RF sections
Terminal Stations
37)
Points in a system where baseband signals may be
reconfigured or where RF carriers are simply
repeated or amplified.
Repeater Stations
38)
Stands for WireLine Entrance Link, it serves as the
interface between the multiplex terminal equipment
and the FM_IF equipment.
WLEL
39)
A balanced modulator that, when used in conjunction
with a microwave generator, power amplifier, and
band-pass filter, up-converts the IF carrier to an RF
carrier and amplifies the RF to the desired output
power.
Transmod
40)
It must be capable of amplifying very high frequencies
and passing very wide bandwidth signals for
microwave radios.
devices used in microwaveamplifiers:
Klystron Tubes
Traveling-wave tubes (TWTs)
IMPATT (Impact avalanche and transit
time)
Power Amplifiers
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BOOK REVIEW IN COMMUNICATIONS Electronic Communications System By Wayne Tomasi
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41)
It provides the RF carrier input to the up-converter. It is
called as microwave generator rather than an
oscillator because it is difficult to construct a stable
circuit that will oscillate in the gigahertz range.
Microwave Generator
42)
It operates in the range 5 MHz to 25 MHz, used to
provide a base frequency that is multiplied up to the
desired RF carrier frequency.
Crystal-controlled
Oscillator
43)
A unidirectional device often made from ferrite
material. It used in conjunction with a channel-
combining network to prevent the output of one
transmitter from interfering with the output of another
transmitter.
Isolator
44)Stands for Automatic Gain Control, is a circuit in an
IF amplifier.
AGC
45)It occurs only when three stations are placed in a
geographical straight line in the system.Multi-hop Interference
46) It prevents the power that leaks out the back andsides of a transmit antenna from interfering with the
signal entering the input of a nearby receive antenna.
High/Low-FrequencyScheme
47)The signal entering the input of a nearby receive
antenna.
Ring around
48)It means that this channels are propagated with
vertical polarization.
V Channels
49)The line-of-sight directly between the transmit and
receive antenna. Also called as the Direct Wave.
Free-Space Path
50) It consists of the electric and magnetic fields
associated with the currents induced in earths surface.
Surface Wave
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BOOK REVIEW IN COMMUNICATIONS Electronic Communications System By Wayne Tomasi
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51)
The portion of the transmit signal that is reflected off
Earths surface and captured by the receive
antenna.
Ground-Reflected Wave
52)
The portion of the transmit signal that is returned back
to Earths surface by the ionized layers of earths
atmosphere.
Sky Wave
53)
The loss incurred by an electromagnetic wave as it
propagates in a straight line through a vacuum with no
absorption or reflection of energy from nearby objects.
Free-Space Path Loss
54) A phenomenon wherein electromagnetic energy isspread out as it propagates away from the source
resulting in lower relative power densities.
Spreading Loss
55)
The reduction in signal strength at the
input to a receiver.
Fading
56)
The difference between the nominal output power of a
transmitter and the minimum input power to a receivernecessary to achieve satisfactory performance. System Gain
57)
Sometimes called as Link Margin, is essentially a fudge
Factor included in system gain equations that
considers the non ideal and less predictable
characteristics of radio wave propagation and terrain
sensitivity.
Fade Margin
58)
He described ways of calculating outage time due to
fading on a non diversity path as a function of terrain,
climate, path length, and fade margin, in April 1969.
W.T. Barnett
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BOOK REVIEW IN COMMUNICATIONS Electronic Communications System By Wayne Tomasi
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59)
From Bell Laboratories, he derived formulas for
calculating the effective improvement achievable by
vertical space diversity as a function of the spacing
distance, path length, and frequency in June 1970.
Arvids Vignant
60)The ratio of the wideband carrier to the wideband
noise power.
Carrier-to-Noise
Ratio (C/N)
61)
Also called Receiver Sensitivity, is the minimum wide
band carrier power at the input to a receiver that will
provide a usable baseband output.
Receiver Threshold
62) The carrier-to-noise ratio before the FM demodulator.
Pre-detection Signal to-
Noise Ratio
63)The carrier-to-noise ratio after the FM demodulator.
Postdetection Signal-
to-Noise Ratio
64)A ratio of input signal-to-noise ratio to output signal to
noise ratio.
Noise Factor (F)
65) The noise factor stated in dB and is a parametercommonly used to indicate the quality of a receiver. Noise Figure
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BOOK REVIEW IN COMMUNICATIONS Electronic Communications System By Wayne Tomasi
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CHAPTER 25 SATELLITE COMMUNICATIONS
# DEFINITIONS TERMS
1) A celestial body that orbits around a planet.Satellite
2)
Man-made satellites that orbit earth, providing a
multitude of communication functions to a wide
variety of consumers, including military,
governmental, private and commercial subscriber.
Communications
Satellites
3)
A satellite radio repeater which a satellite may have
many.
Consists of :
input Bandlimiting device (BPF)
input low-noise amplifier (LNA)
frequency translator
low level amplifier
output bandpass filter
Transponder
4)
It consists of one or more satellite space vehicles, a
ground-based station to control the operation of the
system, and a user network of earth stations that
provides the interface facilities for the transmission
and reception of terrestrial communications traffic
through the satellite system.
Satellite System
5)It includes control mechanism that support the
payload operation.Bus
6)
The actual user information conveyed through the
system. Payload
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BOOK REVIEW IN COMMUNICATIONS Electronic Communications System By Wayne Tomasi
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17)
It was the first commercial telecommunications
satellite. It launched from Cape Kennedy in 1965 and
used two transponders. Also called as Early Birds.It
stands for International Telecommunications Sate-
llite.
Intelsat I
18)Domestic satellite launched by former Soviet Union in
1966. It means lighting.
Molya
19)A German astronomer who discovered the laws
thatgoverns satellite motion.
Johannes Kepler
20)
It may be simply stated as:
The planets move in ellipses with the sun at one
focus
The line joining the sun and the planet sweeps
out equal intervals of time.
The square of the time of revolution of a planet
divided by the cube of its mean distance from
the sun gives a number that is the same for all
planets.
Keplers Law
21) The point in an orbit closest to earth Perigee
22) The point in an orbit farthest from the earth.Apogee
23)
It states that the square of the periodic time
of orbit is proportional to the cube of the mean
distance between the primary and the satellite.
Harmonic Law
24)
High-altitude earth-orbit satellites operating primarily
in the 2-GHz to 18 GHz frequency spectrum with orbits
Satellite 22,300 miles above earths surface.
Geosynchronous
Satellite
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Advantages of Geosynchronous Satellite:
It remain almost stationary in respect to a
given earth station.
Available to earth within their shadows100% of the time.
No need to switch from one geosynchronous
satellite to another as they orbit overhead
The effects of Doppler shift are negligible
Disadvantages of geosynchronous Satellite:
It requires sophisticated and heavy propulsion
device onboard to keep them in a fixed orbit
Much longer propagation delays
Requires higher transmit power and more
sensitive receivers because of the longer
distances and greater path loss.
High precision spacemanship is required.
25)
The angle between the earths equatorial plane andthe orbital plane of a satellite measured counter
clockwise at the point in the orbit where it crosses the
equatorial plane traveling from south to north called
the ascending node.
Angle of Inclination
26)
The point where the polar or inclines orbit
crosses the equatorial plane travelling from north to
south
Descending Node
27)The line joining the ascending and descending node
Line of Nodes
28)
It is when the satellite rotates in an orbit directl
above the equator, usually in a circular path.Equatorial Orbit
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BOOK REVIEW IN COMMUNICATIONS Electronic Communications System By Wayne Tomasi
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29)
It is when the satellite rotates in path that takes over
the North and the South poles in an orbit that is close
to earth and passes over and very close to both the
North and South Poles.
Polar Orbit
30)The noise power normalized to a 1 Hz bandwidth, or
the noise power present in a 1Hz bandwidth
Noise Density
31)
It identifies the system parameters and is used to
determine the projected carrier-to-noise ratio and
energy Bit-to-noise density ratio at both the satellite
and earth station receivers for a given modulation
scheme.
Link Budget