1. If the peak message signal amplitude is half the peak amplitude of the carrier signal, the signal is modulated.
Correct : C. 50%
2. A percentage of modulation greater than
Correct : D. 100%
3. Single sideband AM systems occupy same bandwidth as of conventional AM systems.
Correct : B. false
4. How is the performance of SSB AM systems in fading channels?
Correct : A. poor
5. Which of the following is a disadvantage of tone-in-band SSB system?
Correct : D. generation and reception of signal is complicated
6. FFSR in AM systems stands for
Correct : A. feedforward signal regeneration
7. AM demodulation technique can be divided into and demodulation.
Correct : C. coherent, noncoherent
8. Non coherent detection requires the knowledge of transmitted carrier frequency and phase at the receiver.
Correct : B. false
9. A product detector in AM systems is also called
Correct : D. phase detector
10. AM system use only product detector for demodulation. They never use envelope detectors.
Correct : B. false
11. LCD uses
Correct : B. twisted nematic crystals
12. Which of the following stage is present in FM receiver but not in AM receiver?
Correct : A. amplitude limiter
13. Function of duplexer in a RADAR is to permit the use of same antenna for transmission and reception.
Correct : A. true
14. Single Sideband Modulation (SSB) is generally reserved for point-to-point communication.
Correct : A. true
15. For an AM transmitter, class C amplifier can be used after the modulation stage.
Correct : B. false
16. For which of the modulated system, the linear amplified modulated stage is used?
Correct : A. low level amplitude modulated system
17. When noise is passed through a narrow band filter, the output of filter should be?
Correct : D. sinusoidal
18. A narrow band noise can exist in
Correct : D. am and fm both
19. The upper and lower sideband frequencies for 5KHz amplitude modulation with a 30KHz carrier frequency will be?
Correct : A. 35khz and 25khz
20. Phase array radar can track many targets together.
Correct : A. true
21. A duplex arrangement use separate frequencies for transmission.
Correct : A. true
22. VSB modulation is used in televisions because it avoids phase distortion at low frequencies.
Correct : B. false
23. A cordless telephone that uses separate frequencies for transmission in base and portable units is called
Correct : B. duplex
24. Which polarization is used to reduce the depolarization effect on received waves?
Correct : A. circular polarization
25. Circular polarization involves critical alignment between transmitting and receiving antenna.
Correct : B. false
26. It is only the reflected color that decided the color of an object.
Correct : B. false
27. What do you understand by the term “carrier” in modulation?
Correct : C. voltage for which amplitude, phase or frequency can be varied
28. Carrier wave in modulation is a resultant wave.
Correct : B. false
29. For a low level AM system, amplifier modulated stage must have
Correct : B. linear devices
30. Which is the greatest disadvantage of Pulse Code Modulation?
Correct : D. large bandwidth is required for it
31. Inductance and capacitance of a line is 0.8
Correct : A. 158
32. Quantization noise occurs in
Correct : D. amplitude modulation
33. What the main advantage of PCM?
Correct : C. lower noise
34. In AM pilot carrier, transmission has
Correct : B. two side bands and a carrier
35. Quantization noise depends upon both sampling rate and number of quantization levels.
Correct : B. false
36. Which of the following frequency is not transmitted in AM transmission?
Correct : D. audio frequency
37. Companding is used in PCM transmitters to allow amplitude limiting in the receivers.
Correct : B. false
38. What is the use of Companding?
Correct : D. to protect small signals in pcm from quantizing distortion
39. 5 PSD MODULATORS AND DEMODULATORS
Correct : B. false
40. Which of the following is not an advantage of digital modulation?
Correct : D. less bandwidth requirement
41. The performance of modulation scheme is not measured in terms of
Correct : D. transmitted power
42. In digital communication system, in order to increase noise immunity, it is necessary to increase
Correct : A. signal power
43. Which of the following is the ratio of signal energy per bit to noise power spectral density?
Correct : C. power efficiency
44. Increasing the data rate implies the increase in pulse width of digital symbol.
Correct : B. false
45. Which of the following is the ratio of the throughput data rate per Hertz?
Correct : A. bandwidth efficiency
46. Which of the following is defined as the range of frequencies over which the signal has a non zero power spectral density?
Correct : D. absolute bandwidth
47. is equal to width of main spectral lobe.
Correct : A. null to null bandwidth
48. Half power bandwidth is also called
Correct : C. 3 db bandwidth
49. FM is a part of general class of modulation known as
Correct : A. angle modulation
50. Frequency modulated signal is regarded as the phase modulated signal in which the modulating wave is differentiated before modulation.
Correct : B. false
51. Frequency modulation index defines the relationship between the and bandwidth of transmitted signal.
Correct : B. amplitude of message signal
52. Which of the following are two methods for generating FM signal?
Correct : C. direct method, indirect method
53. In indirect method, the carrier frequency is directly varied in accordance with the input modulating signal.
Correct : B. false
54. Which of the following is used to vary the frequency of the carrier frequency in accordance with the baseband signal amplitude variations in direct method of FM generation?
Correct : D. voltage controlled oscillators
55. Frequency demodulator is a frequency to amplitude converter circuit.
Correct : A. true
56. Which of the following is not a technique for FM demodulation?
Correct : C. product detector
57. Which of the following FM demodulator is sometimes known as pulse averaging discriminator?
Correct : B. zero crossing detection
58. PLL in FM detection stands for
Correct : A. phase locked loop
59. In angle modulation, signal to noise ratio before detection is a function of
Correct : D. if filter bandwidth
60. FM can improve the receiver performance through adjustment of transmitted power.
Correct : B. false
61. De-emphasis circuit is used
Correct : B. after detection
62. Why frequency fogging is used in a carrier system?
Correct : B. to reduce cross talk
63. For a phase modulated signal, the frequency deviation is proportional to
Correct : B. amplitude only
64. The frequency deviation is proportional to frequency in phase modulated signal.
Correct : B. false
65. Which of the following is not necessarily an advantage of FM over AM?
Correct : C. higher bandwidth is required
66. What is number of possible outputs if there is 7 line digital input?
Correct : D. 128
67. What is the frequency of the stereo sub carrier signal in FM broadcasting?
Correct : D. 38 khz
68. What is the bandwidth required in SSB signal?
Correct : A. fm
69. One of the advantage of using a high frequency carrier wave is that it dissipates very small power.
Correct : A. true
70. The antenna current is 10A. Find the percentage of modulation when the antenna current increases to 10.4A?
Correct : C. 28.5%
71. Find the total power, if the carrier of an AM transmitter is 800W and it is modulated to 50%?
Correct : D. 900w
72. Spread spectrum is used for
Correct : C. encrypting & hiding signal
73. Which is a quantization process?
Correct : C. rounding & truncation
74. Quantization is a process.
Correct : C. many to few mapping
75. Which conveys more information?
Correct : B. low probability event
76. If the channel is noiseless information conveyed is and if it is useless channel information conveyed is
Correct : D. 1,0
77. The mutual information between a pair of events is
Correct : D. all of the mentioned
78. 2 QUANTIZATION
Correct : B. false
79. The output of an information source is
Correct : A. random
80. When the base of the logarithm is e, the unit of measure of information is
Correct : C. nats
81. Flat top sampling of low pass signals
Correct : A. gives rise to aperture effect
82. In a delta modulation system, granular noise occurs when the
Correct : D. modulating signal remains constant
83. A PAM signal can be detected using
Correct : A. low pass filter
84. Coherent demodulation of FSK signal can be performed using
Correct : A. matched filter
85. The use of non uniform quantization leads to
Correct : C. increase in snr for low level signals
86. A PWM signal can be generated by
Correct : B. a monostable multi vibrator
87. TDM is less immune to cross-talk in channel than FDM.
Correct : B. false
88. In an ideal TDM system, the cross correlation between two users of the system is
Correct : B. 0
89. TDM requires
Correct : B. transmission of data samples
90. Which waveforms are also called as line codes?
Correct : A. pcm
91. When pulse code modulation is applied to non binary symbols we obtain waveform called as
Correct : C. m-ary
92. Examples of PCM waveforms are
Correct : D. all of the mentioned
93. Which type is used and preferred in digital logic circuits?
Correct : A. nrz-l
94. Which method is called as differential encoding?
Correct : B. nrz-m
95. Which method is preferred in magnetic tape recording?
Correct : B. nrz-m
96. NRZ-S is complement of
Correct : B. nrz-m
97. The return to zero waveform consists of
Correct : D. all of the mentioned
98. Phase encoded group consists of
Correct : D. all of the mentioned
99. In which waveform logic 1 is represented by half bit wide pulse and logic 0 is represented by absence of pulse?
Correct : A. unipolar rz
100. In which waveform logic 1 and logic 0 are represented by opposite one half bit wide pulses?