Communication System

(b) The first stage of two stage amplifier has a voltage gain of 10, a 600  input resistor,a 1600 equivalent noise resistance and 27 k output resistor. For the second stage these values are 25, 81 k, 10 k and 1 M respectively. Calculate the equivalent input noise resistance of this two stage amplifier. 

(a) Calculate the percentage power saving when the carrier and one of the sidebands are suppressed in an AM wave modulated to a depth of (a) 100 percent and (b) 50 percent.

Write short note on:

(c) Noise in DSB-SC receivers

Write short note on:

(b) Noise figure

Write short note on:

(a) Noise temperature 

Explain:

(i) Thermal agitation noise

Explain:

(iii) Transit time noise

Explain:

(ii) Short noise 

(c) Explain Armstrong frequency modulation system.

(b) What are the reasons for use and function of RF amplifiers?

(a) Discuss the merits of delayed AGC as compared with simple AGC.

(b) What is pre-emphasis? Why is it used? Sketch a typical pre-emphasis circuit and explain why de-emphasis must be used also.

(a) Derive the formula for the instantaneous value of an FM voltage and define the modulation index. 

 (b) Derive the relation between the output power of an AM transmitter and depth of modulation.  

(a) List the basic function of a radio transmitter and the corresponding function of receiver. 

(c) Discuss how a grid modulated class C amplifier generates AM.

(b) Discuss the filter method of sideband suppression.

(a) A 360 W carrier is simultaneously modulated by two audio waves with modulation percentage of 55 and 65 respectively. What is the total side band power radiated?

 (b) Define random variables and differentiate between discrete and continuous random variables.

(a) Define ergodic process. Explain the difference between ergodic process and stationary process.

(b) A random variable follows Gaussian probability density function with parameters  and  Find its probability distribution function.

(a) Define CDP and PDF. Explain the properties of CDF and PDF

(g)  Compare NBFM and WBFM.

(f) A receiver connected to an antenna whose resistance is 50 has a equivalent noise resistance of 30 2. Calculate the receiver noise figure in decibels and equivalent noise temperature

 (e) With the help of block diagram of receiver explain the basic super heterodyne principle.

(c) Define and describe vestigial sideband transmission. What is its application.

(b) What is binomial distribution? Explain.