Communication Engineering - Online Test

Q1. A transmission line has a characteristic impedance of 50 Ω and a resistance of 0.1Ω/m . If the line is distortion less, the attenuation constant(in Np/m) is
Answer : Option D
Explaination / Solution:

For distortion less transmission line characteristics impedance


Q2.
Given the finite length input x[n] and the corresponding finite length output y[n] of an LTI system as shown below, the impulse response h[n] of the system is

Answer : Option C
Explaination / Solution:
No Explaination.


Q3.

For a message signal and carrier of frequency fc which of thefollowing represents a single side-band (SSB) signal ?

Answer : Option C
Explaination / Solution:



Q4. The system ẋ = Ax + Bu with  is
Answer : Option C
Explaination / Solution:
No Explaination.


Q5. The Nyquist sampling rate for the signal  is given by
Answer : Option C
Explaination / Solution:

S(t) = sinc(500t) sinc(700t)
S(f ) is convolution of two signals whose spectrum covers f1 = 250 Hz and f2 = 350 Hz. So convolution extends
f = 25 + 350 = 600 Hz
Nyquist sampling rate
N = 2f = 2#600 = 1200 Hz

Q6.
Given f(t) and g(t) as shown below:

g(t) can be expressed as
Answer : Option D
Explaination / Solution:
No Explaination.


Q7. X(t) is a stationary process with the power spectral density Sx(f)>0, for all f . The process is passed through a system shown below

Let Sy (f ) be the power spectral density of Y(t). Which one of the following statements is correct
Answer : Option D
Explaination / Solution:



Q8. Given f(t) and g(t) as shown below:

The Laplace transform of g(t) is
Answer : Option C
Explaination / Solution:
No Explaination.


Q9.
In the circuit shown, all the transmission line sections are lossless. The Voltage Standing Wave Ration(VSWR) on the 60 Ω line is

Answer : Option B
Explaination / Solution:




Q10. The two inputs of a CRO are fed with two stationary periodic signals. In the X-Y mode, the screen shows a figure which changes from ellipse to circle and back to ellipse with its major axis changing orientation slowly and repeatedly. The following inference can be made from this.
Answer : Option C
Explaination / Solution:
No Explaination.