Communication Systems MCQ Questions & Answers

71

The outputs of two noise sources each producing uniformly distributed noise over the range -a to +a are added. What is the p.d.f. of the added noise?

A) Uniformly distributed over the range -2a to +2a B) Triangular over the range -2a to 2a C) Gaussian over the range -∞ to ∞ D) None of the above

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Answer & Solution

Answer: Option B

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72

In a FM demodulator,

A) capacitors are charged to amplitude of FM wave B) frequency deviations are converted into voltage variations C) simple diode is employed D) carrier frequency is doubled

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Answer & Solution

Answer: Option B

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73

The power spectral density of the stationary noise process N(t) having auto correlation R_uu(τ) = Ke^-3|τ| is

A) $$\frac{{3K}}{{3 + {\omega ^2}}}$$ B) $$\frac{{3K}}{{3 - {\omega ^2}}}$$ C) $$\frac{{6K}}{{9 + {\omega ^2}}}$$ D) $$\frac{{6K}}{{9 - {\omega ^2}}}$$

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Answer & Solution

Answer: Option C

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74

Noise figure is defined as

A) $$F = \frac{{\frac{{{S_i}}}{{{N_i}}}}}{{\frac{{{S_0}}}{{{N_0}}}}}$$ B) $$F = \frac{{\frac{{{S_0}}}{{{N_0}}}}}{{\frac{{{S_i}}}{{{N_i}}}}}$$ C) $$F = \frac{{\frac{{{S_0}}}{{{N_0}}}}}{{\sqrt {\frac{{{S_i}}}{{{N_i}}}} }}$$ D) $$F = \frac{{\frac{{{S_i}}}{{{N_i}}}}}{{\sqrt {\frac{{{S_0}}}{{{N_0}}}} }}$$

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Answer & Solution

Answer: Option A

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75

The List-I and the list-II. Match the attribute to the modulation system that best meets it.

List-I (lists the attributes)	List-II (lists of the modulation systems)
a. Power efficient transmission of signals	1. Conventions AM
b. Most bandwidth efficient transmission of voice signals	2. FM
c. Simplest receiver structure	3. VSB
d. Bandwidth efficient transmission of signals with significant dc component	4. SSB-SC

A) a-4, b-2, c-1, d-3 B) a-2, b-4, c-1, d-3 C) a-3, b-2, c-1, d-4 D) a-2, b-4, c-3, d-1

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Answer & Solution

Answer: Option B

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76

Noise in FM receiver is reduced by

A) Amplifier B) AFC C) Limiter D) Detector

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Answer & Solution

Answer: Option C

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77

The most common detector used in an AM radio broadcast receiver is:

A) Coherent detector B) Envelope detector C) Ratio detector D) Discriminator

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Answer & Solution

Answer: Option A

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78

A random process obeys Poisson's distribution. It is given that the mean of the process is 5. Then the variance of the process is

A) 5 B) 0.5 C) 25 D) 0

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Answer & Solution

Answer: Option A

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79

For an AM signal, the bandwidth is 20 kHz and the highest frequency component present is 800 kHz. The carrier frequency used for this AM signal is

A) 710 kHz B) 705 kHz C) 700 kHz D) 790 kHz

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Answer & Solution

Answer: Option D

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80

Consider the following types of modulation
1. Amplitude modulation
2. Frequency modulation
3. Pulse modulation
4. Phase modulation
Which of the above modulation are used for telecasting TV programmes?

A) 3 and 4 B) 2 and 3 C) 1 and 2 D) 1 and 4

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Answer & Solution

Answer: Option C

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Communication Systems MCQ Questions & Answers | ECE