SRM University 2007 B.Tech Electronics and Communications Engineering BANK : Digital Communication - Question Paper

S.R.M. INSTITUTE OF SCIENCE & TECHNOLOGY
School Of Electronics And Communication Engineering

ques. BANK

Subject Code : EC301
Subject Name : Digital Communication.
Class : fifth Semester ECE

Unit – I
Part – A
1. What is sampling?
2. State sampling theorem.
3. What is Nyquist rate?
4. What are the kinds of sampling?
5. What is interpolatory property?
6. What is aliasing / foldover?
7. What is aliasing error? Why is it caused?
8. What is aperture effect?
9. Why is equalizer needed during reconstruction?
10. What is the purpose of sample & hold circuit?
11. What is PAM?
12. What is PPM and PWM?
13. Define TDM & BW expansion factor.
14. What is reconstruction filter?
15. What is instantaneous sampling?
Part – B
1. State & prove sampling theorem.
2. Explain the distortion occurring during sampling.
3. What are protocol aspeels of sampling & recovery?
4. Explain PAM, PPM & PWM.
5. Explain time division multiplexing.
6. Write short notes on: a) Aliasing b) Natural samplling
7. Compare PAM, PPM & PWM.

Unit– II
Part – A
1. Mention the advantages of digital modulation.
2. What is ON-OFF signalling?
3. What bipolar signalling?
4. Mention the need for quantizer & encoder in PCM.
5. What is quantization fault / noise?
6. What are the advantages of PCM?
7. What are the various elements in PCM?
8. What is companding?
9. Write ? legal regulations & A legal regulations.
10. Why is synchronization needed in PAM?
11. How is synchronization achieved?
12. What is probability of error?
13. What is jitter?
14. What is regenerative repeater?
15. What is effect of ? in SNR?
16. What is idle channel noise?
17. Give the expression for probability of fault in PCM system.
18. What is fault threshold?
19. Give the channel capacity for PCM system.
20. What are errors of 1st type & 2nd type
Part – B
1. With neat block diagram discuss the different elements of PCM.
2. Explain the process of quantization. Derive signal to quantization noise ratio.
3. Derive the expression for probability of fault for PCM system
4. Write short notes on
a) Uniform quantization b) Companding
5. Write short notes on
a) Channel capacity b) Threshold effect
6. What is Companding. elaborate the 2 types?

Unit– III
Part – A
1. What is DPCM?
2. Define DM.
3. What is ADM?
4. Define ADPCM. Where is it used.
5. What is Slope overload?
6. What is granular noise?
7. Compare DPCM and DM.
8. What is adaptive sub band coding?
9. What are formants?
10. Write the expression for SNR of a DM.
11. Define AQF, AQB & compare.
12. Compare APF, APB.
13. What is a predictor?
14. Draw the block diagram of DPCM.
15. What is prediction error?
16. What are the advantages of DPCM and DM, ADM.
17. What are the Applications of DM
18. What is the Condition to select ?. with no overload.
19. What is adaptive prediction?
20. What are the kinds of digital multiplexers?

Part – B
1. With a near block diagram discuss about delta modulation?
2. With a neat block diagram discuss about DPCM?
3. Explain with a neat diagram, the various blocks of adaptive differential pulse code modulation.
4. With a block diagram discuss about Adaptive sub band coding.
5. Write short notes on : a) Quantization noise b) Digital multiplexers.
6. Derive an expression for SNR in delta modulation.
7. Compare PCM, DPCM and DM.


UNIT-IV
PART-A

1. What is baseband Channel?
2. When a channel is stated to be dispersive.
3. What is inter symbol interference?
4. Explain pulse shaping.
5. What is a matched filter?
6. What is Schwartz inequality?
7. Explain Raleigh’s energy theorem.
8. Explain Signal energy to noise spectral density ratio.
9. What is a decision device?
10. What is a receiver filter?
11. Explain Ideal nyquist channel.
12. Explain Sinc function.
13. What is timing error?
14. What is correlative level coding?
15. Explain Duobinary Signaling.
16. Give the characteristics of partial response signaling.
17. What is slicing?
18. Explain M-ary PAM.
19. What is temporal autocorrelation function?
20. Explain decision feedback amplifier..
21. What is eye pattern?
22. What is eyeopening?

PART-B
1. Explain in detail about matched filters.
2. Explain the Nyquist criterion for distortionless baseband data transmission.
3. Explain Correlative level coding for combating the effects of intersymbolinterferernce.
4. Write in detail about equalization of a dispersive baseband channel.
5. Explain eye trend for displaying the effects of inter symbol interference and channel noise in data transmission.


UNIT V

PART A
1. Define ASK and draw its waveform.
2. Define FSK and draw its waveform.
3. Define PSK and draw its waveform.
4. Write down the 2 Characteristics of Band Pass Communication channel?
5. Define Additive white gaussian noise.
6. Draw the block diagram of QPSK receiver.
7. Which is called as memory less channel.
8. Write down the optimum decision rule of maximum likelihood decoder.
9. Write any 2 properties of Matched filter.
10. Which is called as antipodal signal.
11. What is data compression?
12. Define the data compression techniques?
PART B

1. Explain the model of Band Pass data Transmission System with neat diagram.
2. Derive Probability of fault for QPSK System.
3. Derive Probability of fault for DPSK System.
4. Explain DPSK receiver with neat diagram.
5. Explain QPSK receiver with neat diagram.
6. Explain the detection techniques for DPSK System?
7. Explain the detection techniques for QPSK System?
8. Explain elementary ideas of sample domain technique for data compression?
9. Explain elementary ideas of transform domain technique for data compression?

Earning:   Approval pending.