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# EC6501 Digital Communication Question Bank

## Sample EC6501 Digital Communication Question Bank:

Part A 2 Marks

1. State sampling theorem for low pass signals..

2. Compare uniform and non-uniform quantization.

3. Why is pre-filtering done before sampling?

4. What is natural sampling and flat-top sampling?

5. List out the components required for signal reconstruction

6. Define the term aliasing. (EC6501 Digital Communication question bank)

7. Compare DM and PCM.

8. What is meant by quantization?

9. What is the need for non-uniform quantization?

10. State any two non-uniform quantization rules.

11. Define quantization noise power. (EC6501 Digital Communication question bank)

12. Define Nyquist rate and Nyquist interval.

13. A signal is sampled at Nyquist rate of 8 KHz and is quantized using 8 bit
uniform quantizer. Assuming SNR for a sinusoidal signal, calculate the bit
rate, SNR and BW.

14. What is Companding?

15. Write μ-law of compression.

16. What is TDM? (EC6501 Digital Communication question bank)

17. Draw the block diagram of TDM.

18. What is the need for synchronization in TDM?

19. Define PAM

### PART-B 16 Marks (EC6501 Digital Communication question bank)

1. State the sampling theorem. Explain the ideal sampling process with necessary
expressions and diagrams. (16)

2. Explain
(i) Natural Sampling and Flat-top Sampling (10)
(ii) Sample and Hold circuit. (6)

3. The signal g(t) = 10 cos(20πt) cos(200πt) is sampled at the rate of 250 samples per second. (EC6501 Digital Communication question bank)

(a) Determine the spectrum of the resulting sampled signal.

(b) Specify the cut-off frequency of the ideal reconstruction filter so as to recover
g(t) from its sampled version.

(c) What is the Nyquist rate for g(t). (EC6501 Digital Communication question bank)

(d) Explain the reconstruction process of a message from its samples. (16)

4. Explain the process of quantization and obtain an expression for signal to
Quantization ratio in the case of a uniform quantizer. (16)

5. Explain the characteristics of Non-uniform quantization with diagrams.
Also compare uniform and non-uniform quantization methods. (16)

expression for SDR. (16)

7. Write short notes on (EC6501 question bank)

(i) Analog companding and (8)
(ii) Digital companding. (8)

8. With neat diagrams, Pulse Code Modulation and demodulation system.(16)

9. A compact disc (CD) records audio signals digitally using PCM. Assume the
audio signal bandwidth to be 15 KHz. (a) What is the Nyquist rate?

(EC6501 Digital Communication question bank)

 Subject Name Digital Communication Subject Code EC6501 Regulation 2013