Analog Communication

a. Define the terms:

ii) band width

c. An FM signal with a deviation of 75 KHz is applied to an FM demodulator. When the input SNR is 15 dB, the modulating frequency is 10 KHz, estimate the SNR at the demodulator output. 

b. Describe the pre-emphasis and de emphasis in FM.

a. Derive the expression for the figure of merit of DSB-SC receiver.

c.Two 2-port devices are connected in cascade. For the first stage, the noise Figure and available power gain are 5 dB and 12 dB respectively. For the second stage, the noise figure and available power gain are 15 dB and 10 dB respectively. Determine the overall noise figure in dB.

b. Define noise equivalent band width and derive the expression for the same.

a. Define :shot noise, thermal noise, white noise.

c. Explain non-linearity and its effects in FM system.

b. With relevant block diagram, explain FM stereo multiplexing.

a. With the help of circuit diagram, explain demodulation of FM wave using balanced frequency discriminator. 

c. An angle modulated signal is defined by s(t) = 10 cosvolts find the following:

i) The power in modulated signal

ii) The frequency deviation 

iii) Phase deviation 

iv) The approximate transmission bandwidth.

b. Explain the direct method of generating FM waves. 

a. Define the terms:

iii) frequency deviation in the case of frequency modulation

a. Explain mean, correlation and covariance functions of a random process x(t)

a. Define the terms:

i) modulation index

c. With a neat block diagram, explain the operation of AM super heterodyne receiver.

b. Explain the scheme for generation and demodulation of VSB waves with relevant block diagrams, and mathematical expressions.

a. Derive the time domain expression of VSB modulated wave s(t) containing a vestige of upper side band.

c. Consider a message signal m(t) containing the frequency complents 100, 200 and 400 Hz.This message signal is applied to an SSB modulator together with a carrier at 100 KHz with only USB retained. The coherent detector employed at the receiver uses a local oscillator that gives a sine wave of frequency 100.02 KHz.

i) Determine the frequency component of the detector output

ii) Repeat your analysis assuming only LSB is transmitted,

b. Describe phase discrimination method of generating SSB waves.

a. With the neat diagram, explain the operation of quadrature carrier multiplexing.

c. A 250 W carrier of 1000 KHz is simultaneously modulated by sinusoidal signals of 2 KHz,6 KHz and 8 KHz with modulation indices of 35%, 55% and 75% respectively. What are the frequencies present in the modulated wave and what the radiated power? 

b. Explain the generation of DSB -SC wave using ring modulator.

a. Define demodulation and show that a square law device can be used to detect AM waves.

b. Explain the properties of auto correlation function and power spectral density.