Electronics and Communication Engineering - Exam Questions Papers

26. 

Consider the signal flow graph shown in figure below. The gain is :

A.
B.
C.
D.

Answer: Option C

Explanation:

P1 = abcd

L1 = be, L2 = cf, L3 = dg

Δ1 = 1

.


27. 

During transmission over a communicate channel, bit errors occur independently with probability . If a block of 3 bits are transmitted, the probability of at most one bit error is equal to

A.
B.
C.
D. none

Answer: Option D

Explanation:

Probability of no-error + probability one error

.


28. 

If x1[n] x1(z) with ROC = R1 and x2[n] x2(z) with ROC = R2 then ROC for x1[n] + x2[n] will be __________ (where Ri → Region of convergence and x1[n] and x2[n] are causal).

A. R1 ∩ R2
B. R1 ∪ R2
C. (R1 ∪ R2) ∩ (R1)
D. (R1 ∩ R2) ∪ (R1)

Answer: Option A

Explanation:

R1 ∩ R2, Suppose R1 for x1(n) be

Then ROC for x1(n) + x2(n)

R1 ∩ R2 (R1 < R2)

Then ROC for x1(n) + x2(n)

R1 ∩ R2(R1 < R2)


29. 

Consider a unity feedback control system with open-loop transfer function The steady state error of the system due to a unity step input is :

A. zero
B. K
C. 1/K
D. infinite

Answer: Option A

Explanation:

.


30. 

The analog signal given below is sampled at 1200 samples per second. m(t) = 2 sin 120 pt + 3 sin 240 pt + 4 sin 360 pt + 5 sin 480 pt + 6 sin 600 pt + 7 sin 720 pt. The folding (maximum) frequency is __________ .

A. 300 Hz
B. 360 Hz
C. 600 Hz
D. 480 Hz

Answer: Option C

Explanation:

Folding frequency (max.) = = 600 Hz.