Quiznetik

Communication Engineering | Set 2

1. In which waveform logic 1 is represented by equal amplitude alternating pulses?

Correct : C. rz-ami

2. The signals which are obtained by encoding each quantized signal into a digital word is called as

Correct : B. pcm signal

3. The length of the code-word obtained by encoding quantized sample is equal to

Correct : A. l=log(to the base 2)l

4. In PCM encoding, quantization level varies as a function of

Correct : B. amplitude

5. What is bit depth?

Correct : C. number of possible digital values to represent each sample

6. Choosing a discrete value that is near but not exactly at the analog signal level leads to

Correct : B. quantization error

7. In PCM the samples are dependent on

Correct : A. time

8. DPCM encodes the PCM values based on

Correct : B. difference between the current and predicted value

9. Delta modulation uses            bits per sample.

Correct : A. one

10. Sample resolution for LPCM          bits per sample.

Correct : D. all of the mentioned

11. Adaptive DPCM is used to

Correct : B. decrease bandwidth

12. Vocoders analyse the speech signals at

Correct : A. transmitter

13. Vocoders                      the voice at the receiver.

Correct : B. synthesize

14. 6 CHANNEL VOCODER

Correct : B. false

15. Which of the following is not a vocoding system?

Correct : C. waveform coder

16. Which of the following pronunciations lead to voiced sound?

Correct : D. ‘m’

17. Channel vocoders are the time domain vocoders.

Correct : B. false

18. is often called the formant of the speech signal.

Correct : C. pole frequency

19. Formant vocoders use large number of control signals.

Correct : B. false

20. Cepstrum vocoder uses

Correct : D. inverse fourier transform

21. The real part of an antenna’s input impedance is due to

Correct : B. radiated signal

22. What is the other name for half-wave dipole antenna?

Correct : C. hertz antenna

23. Measured on the ground, the field strength of a horizontally polarized half wave dipole antenna is strongest

Correct : B. in two directions

24. When an antenna radiates more energy in one direction than in other directions, it is called

Correct : B. directivity

25. What is the full form of ERP?

Correct : A. effective radiated power

26. The polarization of plane waves received from satellite is changed by

Correct : A. faraday rotation

27. What is the input impedance to a lossless antenna, at resonance?

Correct : C. resistive

28. TDMA stands for

Correct : A. time division multiple access

29. Which term is used when signals move from one line to another?

Correct : B. space switching

30. PSK stands for Pulse Shift Keying.

Correct : B. false

31. Which term is used for moving PCM samples from one time slot to another?

Correct : A. time switching

32. Power can be coupled into or out of a waveguide with a magnetic field probe.

Correct : B. false

33. What is the full form of LOS?

Correct : B. line of sight

34. How we can define the satisfactory performance of an analog microwave system?

Correct : A. carrier to noise ratio that exceeds a given value

35. RGB stands for

Correct : D. red green blue

36. How many lines are there in an NTSC signal?

Correct : D. 525

37. Luminance refers to

Correct : C. brightness

38. Linear modulation techniques are not bandwidth efficient.

Correct : B. false

39. Which of the following is not a linear modulation technique?

Correct : C. fsk

40. In BPSK, the                  of constant amplitude carrier signal is switched between two values according to the two possible values.

Correct : B. phase

41. BPSK uses non-coherent demodulator.

Correct : B. false

42. DPSK uses coherent form of PSK.

Correct : B. false

43. In DPSK system, input signal is differentially encoded and then modulated using a                  modulator.

Correct : C. bpsk

44. QPSK has                  the bandwidth efficiency of BPSK.

Correct : A. twice

45. QPSK provides twice the bandwidth efficiency and                energy efficiency as compared to BPSK.

Correct : C. same

46. What is the full form of OQPSK?

Correct : D. offset quadrature phase shift keying

47. The bandwidth of OQPSK is                to QPSK.

Correct : A. identical

48. QPSK signals perform better than OQPSK in the presence of phase jitter.

Correct : B. false

49. Which of the following is not a detection technique used for detection of π/4 QPSK signals?

Correct : D. envelope detection

50. Which of the following is a combined linear and constant envelope technique?

Correct : A. mpsk

51. In an M-ary signalling scheme two or more bits are grouped together to form a

Correct : B. symbol

52. M-ary signalling techniques are not sensitive to timing jitters.

Correct : B. false

53. M-ary modulation schemes have very good power efficiency.

Correct : B. false

54. What is the radius of the circle in M-ary PSK on which message points are equaly spaced?

Correct : A. √es

55. As the value of M                    the bandwidth efficiency

Correct : C. increases, increases

56. The power efficiency of the M ary PSK decreases because of the

Correct : D. densely packed constellation

57. In QAM, the amplitude is                and phase is

Correct : B. varied, varied

58. M-ary QAM signal have constant energy per symbol.

Correct : B. false

59. In comparison to M-ary PSK, M-ary QAM bandwidth efficiency is            and power efficiency is

Correct : A. identical, superior

60. The bandwidth efficiency of an M-ary FSK signal                  with                  in M.

Correct : C. decreases, increase

61. Power efficiency of M-ary FSK increases, since

Correct : D. m-signals are orthogonal

62. The method in which the tail of one pulse smears into adjacent symbol interval is called as

Correct : A. intersymbol interference

63. If each pulse of the sequence to be detected is in            shape, the pulse can be detected without ISI.

Correct : C. sinc

64. What is symbol rate packing?

Correct : A. maximum possible symbol transmission rate

65. A nyquist pulse is the one which can be represented by            shaped pulse multiplied by another time function.

Correct : C. sinc

66. Examples of nyquist filters are

Correct : C. root raised & raised cosine filter

67. The minimum nyquist bandwidth for the rectangular spectrum in raised cosine filter is

Correct : B. 1/2t

68. Roll off factor is the fraction of

Correct : B. excess bandwidth and minimum nyquist bandwidth

69. A pulse shaping filter should satisfy two requirements. They are

Correct : C. should be realizable & have proper roll off factor

70. Examples of double side band signals are

Correct : C. ask & psk

71. ISI is                  by increasing channel bandwidth.

Correct : B. minimized

72. Why is pulse shaping technique used?

Correct : C. to reduce isi

73. Raised cosine filter does not satisfy Nyquist criteria.

Correct : B. false

74. As the roll off factor in raised cosine rolloff filter                      the occupied bandwidth

Correct : D. nyquist

75. Gaussian pulse shaping filter follows Nyquist criterion.

Correct : B. false

76. Gaussian filter has zero crossings at adjacent symbol peaks.

Correct : B. false

77. Which of the following is true for a Gaussian filter?

Correct : D. sharp cut off

78. Gaussian pulse shaping filter reduces the spectral occupancy and ISI.

Correct : B. false

79. Gaussian pulses are used when cost and power efficiency are major factors.

Correct : A. true

80. The method in which small amount of controlled ISI is introduced into the data stream rather than trying to eliminate it completely is called as

Correct : D. all of the mentioned

81. From digital filter we will get the output pulse as the                of the current and the previous pulse.

Correct : A. summation

82. In duobinary signalling method, for M-ary transmission, the number of output obtained is

Correct : C. 2m-1

83. The method using which the error propagation in dubinary signalling can be avoided is

Correct : B. precoding

84. In precoding technique, the binary sequence is            with the previous precoded bit.

Correct : C. exor-ed

85. The duobinary filter, He (f) is called as

Correct : B. cosine filter

86. The method which has greater bandwidth efficiency is called as

Correct : B. polybinary signalling

87. In polybinary signalling method the present bit of binary sequence is algebraically added with              number of previous bits.

Correct : D. j-2

88. The primary advantage of this method is

Correct : C. redistribution of spectral density & to favor low frequencies

89. Source encoding procedure does

Correct : D. all of the mentioned

90. The range of amplitude difference gives the value of

Correct : B. distortion

91. As the eye opens, ISI

Correct : B. decreases

92. The index value n, in transversal filter can be used as.

Correct : C. time offset & filter coefficient identifier

93. The over-determined set of equations can be solved using

Correct : C. zero forcing & minimum mean square error

94. If the filter’s tap weight remains fixed during transmission of data, then the equalization is called as

Correct : A. preset equalization

95. Equalization method which is done by tracking a slowly time varying channel response is

Correct : B. adaptive equalization

96. Preamble is used for

Correct : D. all of the mentioned

97. The disadvantage of preset equalizer is that

Correct : B. time varying channel degrades the performance of the system

98. For AWGN, the noise variance is

Correct : B. n0/2

99. A Gaussian distribution into the non linear envelope detector yields

Correct : A. rayleigh distribution

100. The DPSK needs                  Eb/N0 than BPSK.

Correct : A. 1db more