# Electronic Communication Past Papers Exam Questions

## Guess Paper 1: Electric Machines Fall – 2020 Past Papers

Time Allowed: 3 hours

Total Marks:    70, Passing Marks (35)

Q.1 Fill in the Blanks. (14)
i. ___________ of a signal is the range of frequencies that it can be transmits.
ii. Area under a signal is a measure of its ________________.
iii. Power of the angle modulated signal is always ____________.
iv. Various information sources produced_____________ signal.
v. Power of the power signal is __________________.
vi. In envelope detector, output of the detector follows envelope of _____________ signal.
vii. A signal can be reconstructed from its samples if R>________.

Q.2 Differentiate between signal to noise ratio (SNR) and bandwidth of a signal, write and explain the relationship between two signals SNR and bandwidth. (14)

Q.3 Explain periodic signal, a periodic signal, energy and power signal with equations. (14)

Q.4 What is mean by time reversal of a signal, explain with graphs and equations. (14)

Q.5 A baseband signal (S(t)= A2COSωt ) has to be modulated, explain the modulation process with diagrams and equations. (14)

Q.6 Find and plot the Fourier transform of unit impulse (s(t)=u(t)) and Sine (s(t)=sin(t)) function. (14)

Q.7 What is sampling theorem, explain Nyquist criteria for reconstruction of a signal. (14)

Q.8: Write short note on the following. (14)
i. Demodulation of FM.
ii. Scrambling in digital communication.