70 TOP DIGITAL COMMUNICATION LAB VIVA Questions and Answers

DIGITAL COMMUNICATION LAB VIVA Questions and Answers :-

1. What is multiplexing?

2. What are different types of multiplexing?

3. What is TDM?

4. What do you mean by FDM?

5. What is Amplitude shift Keying (ASK) ?

6. What are different types of digital modulation?

7. What is Phase shift keying ( PSK)?

8. What is Frequency shift keying (FSK) ?

9. What is Binary Phase shift Keying (BPSK) ?

10. What is bandwidth of BPSK signal?

11. What do you mean by Differential Phase Shift Keying (DPSK)?

12. What is Bandwidth of DPSK?

13. Show the phase change in DPSK at the digital input 10111101.

14. What is PSK?

15. Why JK flip-flop is being used in this type if Keying?

16. What are the advantages over other types of keying?

17. What is a GUNN DIODE?

18. How would you find the propagation loss for two different known length and voltage of optical fiber.

19. What is the used formula to find out the bending loss for an optical fiber?

20.Differentiate ASK and FSK.?

21. What is meant by PLL?

22. Applications of PLL.?

23. Define pre-emphasis & de-emphasis?

24. Why is ASK called as ON-OFF keying?

25. What are the advantages of digital transmission?

26. What is meant by frequency synthesizer?

27. Applications of frequency synthesizer?

28. What is meant by line coding?

29. Define polar encoding?

30. Define bipolar encoding?

31. Define unipolar encoding?

32. Define Manchester encoding?

33. What are the two function of fast frequency hopping?

34. What are the features of code Division multiple Accesses?

35. What is called multipath Interference?

36. Explain ARQ,FEC.HARQ?

37. What is sampling?

38. State sampling theorem ?

39. What is aliasing?

40. How to avoid aliasing effect ?

41. Define Nyquist Criteria.

42. Purpose of sampling?

43. what is DTV?

44. How many digital television terrestrial broadcasting standards (DTTB) are used?

45. Difference in HDTV and SDTV?

46. What is aperture effect?

47. How aperture effect can be corrected?

48. what is pulse stuffing?

49. Explain nysquist criterion and interval?

50. Which kind of multiplexing used in digital communication?

51. Define Aperture effect . How it can be avoided

52. Why is Sample & Hold circuit used?

53. An Analog signal is given as
X(t) = 3cos 50pt + 10 sin 300 pt + cos 100pt
Calculate Nyquist rate

54. The spectrum of a signal g(t) has bandwidth 0.8KHZ and centered around 10 KHZ. Find Nyquist Rate

55. why pm is better than fm ?

56. Difference in digital and discrete signals?

57. why we need quantization?

58. A PCM system uses a uniform quantizer followed by a 7 bit encoder,with bit rate 50Mbps.What is the message bandwidth for system to operate satisfactorially?
59. Properties of Matched filter?
60. Difference between CDMA & TDMA
61. What is Pulse code modulation(PCM)?
62. How the performance of a PCM is corrupted?
63. What are the two types of Spread spectrum technique?
64. We need to send 3 bits at a time at a bit rate of 3Mbps.The carrier frequency is 10MHz.Calculate No of levels and Bandwidth
65. What is a Constellation Diagram?
66. Which modulation is a combination of other 2 schemes
67. Name two principles by which spread spectrum achieves its goal
68. Which of the 3 multiplexing techniques is common for fibre optic links
69. What is the minimum number of bits in a PN sequence if we use FHSS with a channel bandwidth of 5kHz and Bss=120kHz?
70. Which theorm gives Maximum Data Rate of a channel

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