Communication Engineering - Online Test
Q1. The state variable description of an LTI system is given by
where y is the output and u is the input. The system is controllable for
Answer : Option D
Explaination / Solution:
Q2. A load of 50 Ω is connected in shunt in a 2-wire transmission line of Z0 = 50Ω as shown in the figure. The 2-port scattering parameter matrix (s-matrix) of the
shunt element is
Answer : Option C
Explaination / Solution:
Q3. A band-limited signal with a maximum frequency of 5 kHz is to be sampled. According to the sampling theorem, the sampling frequency in kHz which is not valid is
Answer : Option A
Explaination / Solution:
No Explaination.
Q4. The parallel branches of a 2-wire transmission line re terminated in 100Ω and
200Ω resistors as shown in the figure. The characteristic impedance of the
line is Z0 = Ω and each section has a length of λ/4. The voltage reflection
coefficient Γ at the input is
Answer : Option D
Explaination / Solution:
Q5. For a periodic signal 
the
fundamental frequency in radians/s is
the
fundamental frequency in radians/s is
Answer : Option A
Explaination / Solution:
No Explaination.
Q6. A λ/2 dipole is kept horizontally at a height of λ0/2 above a perfectly conducting
infinite ground plane. The radiation pattern in the lane of the dipole (
plane)
looks approximately as
plane)
looks approximately as
Answer : Option B
Explaination / Solution:
Q7. A continuous random variable X has a probability density function 
is
is
Answer : Option A
Explaination / Solution:
No Explaination.
Q8. A right circularly polarized (RCP) plane wave is incident at an angle 600 to the
normal, on an air-dielectric interface. If the reflected wave is linearly polarized,
the relative dielectric constant ξr is.
Answer : Option D
Explaination / Solution:
No Explaination.
Q9. Two systems with impulse responses h1(t) and h2(t) are connected in cascade.
Then the overall impulse response of the cascaded system is given by
Answer : Option C
Explaination / Solution:
No Explaination.
Q10. Two 4-array signal constellations are shown. It is given that φ1 and φ2 constitute
an orthonormal basis for the two constellation. Assume that the four symbols
in both the constellations are equiprobable. Let N0/2 denote the power spectral
density of white Gaussian noise.
The if ratio or the average energy of Constellation 1 to the average energy of
Constellation 2 is
Answer : Option B
Explaination / Solution:
