Communication Engineering - Online Test

Q1.
Consider the frequency modulated signal with carrier frequency of 105 Hz. The modulation index is
Answer : Option B
Explaination / Solution:



Q2. Let f(x) be a real, periodic function satisfying f(−x) = −f(x). The general form of its Fourier series representation would be
Answer : Option B
Explaination / Solution:



Q3. A white noise process X(t) with two-sided power spectral density 1 X 10-10  W/HZ is input to a filter whose magnitude squared response is shown below.


Answer : Option C
Explaination / Solution:
No Explaination.


Q4. Consider a linear time invariant system x = Ax, with initial condition x(0) at t = 0. Suppose α and β are eigenvectors of (2 x 2) matrix A corresponding to distinct eigenvalues λ1 and λ2 respectively. Then the response x(t) of the system due to initial condition x(0) = α is
Answer : Option A
Explaination / Solution:



Q5. The signal  is
Answer : Option C
Explaination / Solution:
No Explaination.


Q6. Let z(t) = x(t) * y(t), where "*" denotes convolution. Let C be a positive real-valued constant. Choose the correct expression for z (ct).
Answer : Option A
Explaination / Solution:



Q7. A speed signal, band limited to 4 kHz and peak voltage varying between +5 V and -5 V, is sampled at the Nyquist rate. Each sample is quantized and represented by 8 bits. If the bits 0 and 1 are transmitted using bipolar pulses, the minimum bandwidth required for distortion free transmission is
Answer : Option B
Explaination / Solution:



Q8. Consider the system with following input-output relationwhere, x[n] is the input and y[n] is the output. The system is
Answer : Option D
Explaination / Solution:




Q9. Which of the following statements is true regarding the fundamental mode of the metallic waveguides shown ?

Answer : Option A
Explaination / Solution:

Rectangular and cylindrical waveguide doesn’t support TEM modes and have cut off frequency. Coaxial cable support TEM wave and doesn’t have cut off frequency.


Q10.
Let a causal LTI system be characterized by the following differential equation, with initial rest condition

Where x(t) and y(t) are the input and output respectively. The impulse response of the system is (u(t) is the unit step function)
Answer : Option B
Explaination / Solution: