Digital Communications Unit-4 FAQ

Digital Communications

Unit-4 (FAQ)

Short Answer Questions:-

  1. What is meant by Probability of Error Pe?
  2. what is meant by Bit Error Rate BER? how BER and Eb/No ( approximately known as SNR) related to each other?
  3. what is matched filter? give the impulse response of it.
  4. Differentiate the following.                                                                                                     i. Base band transmission( or Communication) systems and Pass band Transmission systems.                        ii. coherent and Non-coherent systems.
  5. what is the need for MSK modulation?
  6. Draw the signal space diagrams of  i. ASK  ii. PSK  iii. FSK    iv. QPSK   v. DPSK
  7. what is meant by gaussian error probability?
  8. write a short note on M-ary QPSK?
  9. Define error function, complementary error function and Q-function. Give the relation between Q- function and  complementary error function.
  10. Compare digital modulation schemes in terms of Bandwidth and Pe.
  11. Give the meaning of QPSK. how it is different from PSK?
  12. write a short note about QPSK.
  13. what is meant by singal space or signal constellation diagram . give its significance
  14. draw the wave forms of ASK ,PSK and FSK when data input is 1100101.
  15. problems on the impulse response of matched filter.
  16. advantages of pass band over base band transmission?
  17. applications of ASK, PSK and FSK ,QPSK and DPSK.
  18. what are the advantages and disadvantages of all modulation schemes?
  19. advantages of QPSK.

long Answer Questions:-

  1. compare different digital modulation schemes.
  2. Draw the block diagram of Correlation receiver. Explain the working of it in detail.
  3. Draw the block diagram of integrate and dump receiver (base band Receiver). Explain the working of it in detail.
  4. Explain the working of DPSK system with an example.
  5. Derive the expression for Pe of the following     i. QPSK      ii. PSK      iii. matched filter    iv.  DPSK     v. Optimum receiver     vi. Integrate and dump receiver.
  6. write a short note on synchronization methods.
  7. derive the transfer function of optimum receiver.
  8. derive the impulse response of matched filter.
  9. draw block diagrams of modulator and de-modulator  for the following  coherent modulation schemes and explain its working in detail       i. FSK     ii. QPSK     iii. PSK        iv.ASK
  10. draw block diagrams of modulator and de-modulator  for the following  non-coherent modulation schemes and explain its working in detail                i. FSK     ii.  non coherent PSK or DPSK       iii.ASK
  11. Derivations of Pe of   i. coherent ASK/BASK/ASK        ii coherent PSK /BPSK/PSK         iii.coherent FSK/BFSK/FSK.
  12. Derivations of Pe of   i.Non- coherent ASK/Non- coherent BASK        ii  non-coherent PSK /Non- coherent BPSK         iii.coherent FSK/ Non- coherentBFSK.
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Author: Lakshmi Prasanna

Completed M.Tech in Digital Electronics and Communication Systems and currently working as a faculty.