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Questions:

1. What is the mostly used modulation technique in digital transmission that

includes many different methods of converting information into pulse form for

transferring pulses from a source to a destination?

Ans. Pulse Modulation

2. What are the four most common methods of pulse modulation?

Ans. Pulse Width Modulation (PWM), Pulse Position Modulation (PPM),

Pulse Amplitude Modulation (PAM), Pulse Code Modulation (PCM)

3. It is a series of pulses, in which the amplitude of the information signal at a give

time is coded as a binary number.

Ans. Pulse Code Modulation (PCM)

4. It is a series of pulses, in which the amplitude of each pulse represents the

amplitude of the information signal at a given time.

Ans. Pulse Amplitude Modulation (PAM)

5. It is a method of Pulse Modulation wherein the maximum analog signal amplitudeproduces the widest pulse, and the minimum analog signal amplitude produces

the narrowest pulse.

Ans. Pulse Width Modulation (PWM)

6. It is a sampling of analog signal using a sample-and-hold circuit such that the

sample has the same amplitude for its whole duration.

Ans. Flat-topped Sampling (Blake), Flat-top Sampling (Tomasi)

7. What is Sampling Rate?

Ans. It is a process of taking samples of information signal at a rate based on the

Nyquist Sampling Theorem.

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8. It is a method of Pulse Modulation wherein the highest amplitude sample

produces a pulse to the far right, and the lowest amplitude sample produces a

pulse to the far left.

Ans. Pulse Position Modulation (PPM)

9. What is the error produced during the quantization process due to the difference

between the original signal and quantized signal magnitudes?

Ans.Quantization Error/ Quantization Noise

10. What is the process of assigning the analog signal samples to a pre-determined

discrete level?

Ans. Quantization

11. The Quantization levels are separated by a value ofV. What is V stands for?

Ans. the resolution or step size of the quantization level

12. It is a sampling function technique where the sample time is made longer and the

analog-to-digital conversion takes place with a changing analog signal.

Ans. Natural Sampling

13. It is a device that periodically samples the continually changing analog input

signal and converts those samples to a series of constant-amplitude PAM levels.

Ans. sample-and-hold circuit

14. The term Pulse Code Modulation is a type of modulation and a form of digitally

coding analog systems.

Ans. False

15. With PCM, Pulses are of fixed length and non-fixed amplitude.

Ans. False

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16. What are the two functions of Codec?

Ans. Coding and Decoding

17. What are the two methods of analog Companding?

Ans. -law and A-law Cmpanding

18. In the _______ today, PCM is referred method of communications within the

public switch telephone network.

Ans. United States

19. Numerical indication of how efficiently a PCM ode is utilized.

Ans. Coding Efficiently

20. It is implemented with diodes thaw re placed after the low pass filter in e PCM

receiver.

Ans. Analog Expansion

21. What parameter determines the range of signal power in which the SQR is

relatively constant?

Ans. Mu ()

22. What is the most recent digitally compressed PCM systems use?

Ans. 12-bit linear PCM code and an 8-bit compressed PCM code

23. Dependent on the sample rate and number of bits in the compressed PCM code.

Ans. Line Coding

24. It is designed specifically to take advantage of the sample-to-sample

redundancies in typical speech waveforms.

Ans. Differential PCM (DPCM)

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25. In the receiver, the PCM code is converted into a PAM signal, filtered, and then

expanded back to its original dynamic range.

Ans. Analog Companding

26. In the receiver, the compressed PCM code is expanded and then decoded.

Ans. digital Companding

27. The process of compressing and expanding to improve the dynamic range of a

communication system.

Ans. Companding

28. In getting the coding efficiency, number of bits should be including the sign bit?

Ans. Yes

29. For a linear PCM codes, all quantization intervals does have equal magnitudes?

Ans. Yes

30. The transmission line _______ are placed at prescribed distances to regenerate

the digital pulses.

Ans. repeaters

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PROBLEM SOLVING:

1. What is the Nyquist sample rate for a maximum analog frequency of 4kHz and 10

kHz?

Ans. fs 8 kHz, fs 20 kHz

2. Find the number of bits per sample when the maximum dynamic range for a

linear PCM system is 99.9dB.

Ans. 16.3 bits per sample

3. Determine the minimum number of bits required in a PCM code for a dynamic

range of 80 dB. What is the coding efficiency?

Ans. 14 bits, coding efficiency = 94.91%

4. Determine the SQR for a 1-vrms signal and a quantization interval of 0.01 V.

Ans. SQR = 50.8 dB

5. Determine the minimum number of bits required for PCM codes with the following

dynamic ranges and determine the coding efficiencies: DR = 24 dB, 48 dB, and

72 dB.Ans. For DR= 24 dB: 5 bits, coding efficiency= 81.5%

For DR= 48 dB: 8 bits, coding efficiency= 99.7%

For DR= 72 dB: 12 bits, coding efficiency= 99.7%