Electronics and Communication Engineering - Exam Questions Papers

1. 

In a communication system, a process in which statistical averages and time averages are equal is called as,

A. stationary
B. ergodic
C. Gaussian
D. BIBO stable

Answer: Option B

Explanation:

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2. 

The materials not having negative temperature coefficient of resistivity are

A. metals
B. semiconductors
C. insulators
D. none of the above

Answer: Option A

Explanation:

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3. 

The input to a binary communication system, denoted by a random variable x, takes on one of the two values 0 or 1 with probabilities and . The behaviour of the communication system is modelled by
P(Y = 1 |x = 1|) = and P(Y = 0|x = 0) =
Find P(Y = 1)

A.
B.
C. 1
D.

Answer: Option B

Explanation:

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4. 

Consider an AM system using a square law detector as shown in figure.

XC(t) = AC[1 + u x (t)] cos ωct, |ux(t)| << 1
The signal power at the output is :

A. A2Cu2 E[x2(t)]
B. A2Cu2 E(x)
C.
D. None

Answer: Option A

Explanation:

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5. 

Thermal noise is passed through an ideal low-pass filter having cut-off at fc = ωHz. The auto correlation value of the noise at the output of the filter is given as

A. Triangular function over the range
B. Gaussian over the range -∞ ≤ t ≤ ∞
C. A Delta function at t = 0
D. Sin c function over the range - ∞ ≤ t ≤ ∞

Answer: Option D

Explanation:

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