Communication Systems MCQ Questions & Answers

Communication Systems MCQ Questions & Answers | ECE

Learn Communication Systems MCQ questions & answers are available for a Electronics and Communications Engineering(ECE) students to clear GATE exams, various technical interview, competitive examination, and another entrance exam. Communication Systems MCQ question is the important chapter for a Electronics and Communications Engineering(ECE) and GATE students. Page-3 section-3

A signal m(t), band-limited to a maximum frequency of 20 kHz is sampled at a frequency f_s kHz to generate s(t). An ideal low pass filter having cut-off frequency 37 kHz is used to reconstruct m(t) from s(t). The minimum of f_s required to reconstruct m(t) without distortion is

A) 20 kHz B) 40 kHz C) 57 kHz D) 77 kHz

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Answer & Solution

Answer: Option C

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A message signal m(t) = A_msin(2πf_mt) is used to modulate the phase of carrier A_ccos(2πf_ct) to get the modulated signal y(t) = A_ccos(2πf_ct + m(t)). The bandwidth of y(t)

A) depends of A_m but not on f_m B) depends of f_m but not on A_m C) depends of A_m and f_m D) does not depends on A_m or f_m

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Answer & Solution

Answer: Option C

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A bandlimited signal is sampled at the Nyquist rate. The signal can be recovered by passing the samples through

A) an RC filter B) an envelope detector C) a PLL D) an ideal low-pass filter with the appropriate bandwidth

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Answer & Solution

Answer: Option D

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An FM signal is being broadcast in the 88-108 MHz band having a carrier swing of 125 kHz. The percentage of modulation is

A) 100% B) 83% C) 67% D) 50%

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Answer & Solution

Answer: Option B

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Hilbert transform of Acos(2πf₀t + θ) is

A) -Asin(2πf₀t + θ) B) Acos(2πf₀t + θ) C) -Acos(2πf₀t + θ) D) Asin(2πf₀t + θ)

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Answer & Solution

Answer: Option D

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Boosting of higher frequency at the transmitter is done by using

A) De-emphasis B) AGC circuit C) Pre-emphasis D) Armstrong method

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Answer & Solution

Answer: Option C

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A signal contains components at 400 Hz and 2400 Hz. This signal modulates a carrier of frequency 100 MHz. However after demodulation it is found that the 400 Hz signal component is present. The channel Bandwidth is 15 KHz. What is the reason for the higher frequency signal not to be detected properly.

A) Modulation used in FM and BW B) Modulation used in AM and BW is insufficient C) Modulation used in FM but pre emphasis is not used D) Modulation used in AM but detector is for FM

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Answer & Solution

Answer: Option C

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Match List-I with List-II and select the correct answer using the options given below:

List-I	List-II
a. SSB	1. Envelope detector
b. AM	2. Integrate and dump
c. BPSK	3. Hilbert transform

A) a-3, b-1, c-2 B) a-3, b-2, c-1 C) a-2, b-3, c-1 D) a-1, b-2, c-3

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Answer & Solution

Answer: Option A

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