Electronic and Communication — Winter 2021

Define term modulation in context to communication process. Describe needs of modulation process in detail.

With suitable circuit diagram describe the working of envelope detector circuit for demodulating the AM wave.

Derive the expression of sinusoidal AM wave. Amodulating signal m (t)= 10cos (2π×103t) is amplitude modulated with a carrier signal c (t) =50cos (2π×105t). Find the modulation index, the carrier power, and the power required for transmitting AM wave. Also draw the amplitude spectrum of AM wave. Describe the significance of Carson’s rule used in FM wave bandwidth

07 approximation process. Also with help of the neat block diagram explain Armstrong method for generating FM waves.

Compare FM and AM processes.

Enlist at least four FM demodulator circuits. Also describe working of Foster-Seeley discriminator with required details. Define noise factor and noise temperature. Derive the Friss formulae for deriving

07 the value of noise factor with cascaded amplifiers connection scenario.

List out main functions of the communication radio receiver circuits. Also define the following terms related to radio receiver: (1) Selectivity (2) Fidelity (3) Sensitivity.

Draw block diagram of Super-heterodyne receiver and explain the functionality of its each block with necessary details.

Briefly describe different noise types related to overall communication process. 0 Explain the process of an SSB-SC signal generation using phase shifting method

07 with relevant mathematical expressions.

Explain the importance of pre-emphasis and de-emphasis circuits. Also describe functioning of pre-emphasis and de-emphasis circuits with necessary details.

Explain the direct method to generate FM signal with necessary details.

A FM wave is given by s(t)=20cos(8π×106t+9sin(2π×103t)). Compute the frequency deviation, bandwidth, and power of the given FM wave. Derive an equation for impedance of series tuned circuit in terms of quality factor.

07 Also define term skin effect and suggest possible ways to reduce it.

Define the terms. Signal Bandwidth (ii) Power Spectral Density (iii) Distortion Also state and prove time shifting property of Fourier transform.

List out different types of noise existing during the working of a communication

system. Also briefly describe about shot noise, partition noise and flicker noise.

Describe Ham radio concept with required details. Also describe the usage significance of Ham radio during the occurrence of natural calamines.