Electronics and Communication Engineering - Exam Questions Papers

41. 

The current I for the network

A. 0 mA
B. 10.72 mA
C. 10.94 mA
D. 11.32 mA

Answer: Option B

Explanation:

.


42. 

A switch tail ring counter is made by using a single D FF. The resulting circuit is a

A. SR FF
B. JK FF
C. D FF
D. T FF

Answer: Option C

Explanation:

In both case input will always opposite to each other hence it is D FF.


43. 

The driving point impedance of the following network is given by . The component values are

A. L = 5H, R = 0.5Ω, C = 0.1F
B. L = 0.1H, R = 0.5Ω, C = 5F
C. L = 5H, R = 2Ω, C = 0.1F
D. L = 0.1H, R = 2Ω, C = 5F

Answer: Option A

Explanation:

Comparing it with given equation

C = 0.1

RC = 0.05

R = 0.54

.


44. 

Consider a baseband binary PAM receiver shown below. The additive channel noise n(t) is whit with power spectral density SN(f) = N0/2 = 10-20 W/Hz. The low-pass filter is ideal with unity gain and cutoff frequency 1 MHz. Let Yk represent the random variable y(tk).
Yk = nNk if transmitted bit bk = 0
Yk = a + Nk if transmitted bit bk = 1
Where Nk represents the noise sample value. The noise sample has a probability density function, PNk(n) = 0.5ae-a|n| (This has mean zero and variance 2/a2). Assume transmitted bits to be equiprobable and threshold z is set to a/2 = 10-6 V.

The probability of bit error is

A. 0.5 x e-3.5
B. 0.5 x e-5
C. 0.5 x e-7
D. 0.5 x e-10

Answer: Option D

Explanation:

Probability of error

= 0.5e-107 x 10 -6 = 0.5e-10.


45. 

In a synchro error detector, the output voltage is proportional to [ω(t)]n, where ω(t) is the rotor velocity and n equals :

A. -2
B. -1
C. 1
D. 2

Answer: Option C

Explanation:

In a synchro detector, output voltage is proportional to ω(t)

v0 a ω(t)

So, n must be equal to one.