Quiznetik

Digital Communication | Set 1

1. In uniform quantization process

Correct : D. both a and c are correct

2. The process of converting the analog sample into discrete form is called

Correct : C. quantization

3. The characteristics of compressor in μ-law companding are

Correct : A. continuous in nature

4. The modulation techniques used to convert analog signal into digital signal are

Correct : D. all of the above

5. The sequence of operations in which PCM is done is

Correct : A. sampling, quantizing, encoding

6. In PCM, the parameter varied in accordance with the amplitude of the modulating signal is

Correct : D. none of the above

7. One of the disadvantages of PCM is

Correct : A. it requires large bandwidth

8. The expression for bandwidth BW of a PCM system, where v is the number of bits per sample and fm is the modulating frequency, is given by

Correct : A. bw ≥ vfm

9. The error probability of a PCM is

Correct : D. all of the above

10. In Delta modulation,

Correct : D. both a and c are correct

11. In digital transmission, the modulation technique that requires minimum bandwidth is

Correct : A. delta modulation

12. In Delta Modulation, the bit rate is

Correct : A. n times the sampling frequency

13. In Differential Pulse Code Modulation techniques, the decoding is performed by

Correct : A. accumulator

14. DPCM suffers from

Correct : C. both a & b

15. The noise that affects PCM

Correct : D. both a and b are correct

16. The factors that cause quantizing error in delta modulation are

Correct : D. both a and b are correct

17. Granular noise occurs when

Correct : B. step size is too large

18. The crest factor of a waveform is given as –

Correct : C. peak value/ rms value

19. The digital modulation technique in which the step size is varied according to the variation in the slope of the input is called

Correct : C. adaptive delta modulation

20. The digital modulation scheme in which the step size is not fixed is

Correct : B. adaptive delta modulation

21. In Adaptive Delta Modulation, the slope error reduces and

Correct : B. quantization error increases

22. The number of voice channels that can be accommodated for transmission in T1 carrier system is

Correct : A. 24

23. The maximum data transmission rate in T1 carrier system is

Correct : C. 1.544 megabits per second

24. T1 carrier system is used

Correct : A. for pcm voice transmission

25. Matched filter may be optimally used only for

Correct : A. gaussian noise

26. Matched filters may be used

Correct : D. all of the above

27. The process of coding multiplexer output into electrical pulses or waveforms for transmission is called

Correct : A. line coding

28. For a line code, the transmission bandwidth must be

Correct : B. as small as possible

29. Regenerative repeaters are used for

Correct : D. all of the above

30. Scrambling of data is

Correct : A. removing long strings of 1’s and 0’s

31. In polar RZ format for coding, symbol ‘0’ is represented by

Correct : D. both b and c are correct

32. Polar coding is a technique in which

Correct : A. 1 is transmitted by a positive pulse and 0 is transmitted by negative pulse

33. The polarities in NRZ format use

Correct : A. complete pulse duration

34. The format in which the positive half interval pulse is followed by a negative half interval pulse for transmission of ‘1’ is

Correct : C. manchester format

35. The maximum synchronizing capability in coding techniques is present in

Correct : A. manchester format

36. The advantage of using Manchester format of coding is

Correct : A. power saving

37. Alternate Mark Inversion (AMI) is also known as

Correct : A. pseudo ternary coding

38. In DPSK technique, the technique used to encode bits is

Correct : B. differential code

39. Overhead bits are

Correct : A. framing and synchronizing bits

40. ISI may be removed by using

Correct : A. differential coding

41. Timing jitter is

Correct : C. deviation in location of the pulses

42. Probability density function defines

Correct : A. amplitudes of random noise

43. Impulse noise is caused due to

Correct : D. all of the above

44. In coherent detection of signals,

Correct : D. all of the above

45. Synchronization of signals is done using

Correct : D. all of the above

46. Orthogonality of two codes means

Correct : A. the integrated product of two different code words is zero

47. In Alternate Mark Inversion (AMI) is

Correct : B. 0 is encoded as no pulse and 1 is encoded as negative pulse

48. Advantages of using AMI

Correct : D. all of the above

49. The interference caused by the adjacent pulses in digital transmission is called

Correct : A. inter symbol interference

50. Eye pattern is

Correct : D. all of the above

51. The time interval over which the received signal may be sampled without error may be explained by

Correct : A. width of eye opening of eye pattern

52. For a noise to be white Gaussian noise, the optimum filter is known as

Correct : C. matched filter

53. Matched filters are used

Correct : D. all of the above

54. The number of bits of data transmitted per second is called

Correct : A. data signaling rate

55. Pulse shaping is done

Correct : D. all of the above

56. The criterion used for pulse shaping to avoid ISI is

Correct : A. nyquist criterion

57. The filter used for pulse shaping is

Correct : D. all of the above

58. Roll – off factor is defined as

Correct : A. the bandwidth occupied beyond the nyquist bandwidth of the filter

59. Nyquist criterion helps in

Correct : D. both a and b

60. The Nyquist theorem is

Correct : D. both a and c

61. The difficulty in achieving the Nyquist criterion for system design is

Correct : A. there are abrupt transitions obtained at edges of the bands

62. Equalization in digital communication

Correct : D. all of the above

63. Zero forced equalizers are used for

Correct : A. reducing isi to zero

64. The transmission bandwidth of the raised cosine spectrum is given by

Correct : A. bt = 2w(1 + α)

65. The preferred orthogonalization process for its numerical stability is

Correct : B. house holder transformation

66. For two vectors to be orthonormal, the vectors are also said to be orthogonal. The reverse of the same

Correct : B. is not true

67. Orthonormal set is a set of all vectors that are

Correct : A. mutually orthonormal and are of unit length

68. In On-Off keying, the carrier signal is transmitted with signal value ‘1’ and ‘0’ indicates

Correct : A. no carrier

69. ASK modulated signal has the bandwidth

Correct : A. same as the bandwidth of baseband signal

70. Coherent detection of binary ASK signal requires

Correct : D. both a and b

71. The probability of error of DPSK is ______________ than that of BPSK.

Correct : A. higher

72. In Binary Phase Shift Keying system, the binary symbols 1 and 0 are represented by carrier with phase shift of

Correct : B. Π

73. BPSK system modulates at the rate of

Correct : A. 1 bit/ symbol

74. The BPSK signal has +V volts and -V volts respectively to represent

Correct : A. 1 and 0 logic levels

75. The binary waveform used to generate BPSK signal is encoded in

Correct : A. bipolar nrz format

76. The bandwidth of BFSK is ______________ than BPSK.

Correct : C. higher

77. In Binary FSK, mark and space respectively represent

Correct : A. 1 and 0

78. The frequency shifts in the BFSK usually lies in the range

Correct : A. 50 to 1000 hz

79. The spectrum of BFSK may be viewed as the sum of

Correct : A. two ask spectra

80. The maximum bandwidth is occupied by

Correct : C. fsk

81. QPSK is a modulation scheme where each symbol consists of

Correct : B. 2 bits

82. The data rate of QPSK is ___________ of BPSK.

Correct : C. twice

83. QPSK system uses a phase shift of

Correct : B. Π/2

84. Minimum shift keying is similar to

Correct : A. continuous phase frequency shift keying

85. In MSK, the difference between the higher and lower frequency is

Correct : B. half of the bit rate

86. The technique that may be used to reduce the side band power is

Correct : C. gaussian minimum shift keying

87. Analog to digital conversion includes

Correct : C. sampling & quantization

88. The process of converting the analog sample into discrete form is called

Correct : C. quantization

89. The modulation techniques used to convert analog signal into digital signal are

Correct : D. all of above

90. In Delta modulation,

Correct : D. both a and c are correct

91. In digital transmission, the modulation technique that requires minimum bandwidth is

Correct : A. delta modulation

92. In Delta Modulation, the bit rate is

Correct : A. n times the sampling frequency

93. In Differential Pulse Code Modulation techniques, the decoding is performed by

Correct : A. accumulator

94. The crest factor of a waveform is given as –

Correct : C. peak value/ rms value

95. The digital modulation technique in which the step size is varied according to the variation in the slope of the input is called

Correct : C. adaptive delta modulation

96. Impulse sampling is also called as

Correct : D. both a & b

97. Nyquist Rate is given by

Correct : A. 2w

98. The number of voice channels that can be accommodated for transmission in T1 carrier system is

Correct : A. 24

99. For a line code, the transmission bandwidth must be

Correct : B. as small as possible

100. Scrambling of data is

Correct : A. removing long strings of 1’s and 0’s