Rashtrasant Tukadoji Maharaj Nagpur University 2010 B.E Electronics

part A

1. (a) List the various kinds of noise existing in a receiver circuit. discuss every of them.
(b) discuss noise figure and derive the formula for the identical for a 2 stage amplifier.
(c) Why is high frequency carrier needed for a communication system?

2. (a) discuss subsequent terms as related to ionospheric propagation:
(i) Critical frequency
(ii) MUF
(iii) Skip distance
(b) discuss tropospheric wave propagation. Also derive the expression for range of tropospheric propagation.


3. (a) discuss plate modulated class-C amplifier with the help of circuit diagram.
(b) With the help of block diagram discuss as to how SSB-SC signal is generated by phase shift method.

4. (a) What is frequency modulation? Derive the expression for the instantaneous value of FM signal. Also draw necessary waveforms and comment on the significant side bands in FM.
(b) An AM signal has the equation:
V(t)= {[ 15 + 4sin??(44*?10?^3 t)] sin??46.5*?10?^6 t]V? ?
Find:
(i) Carrier frequency
(ii) Frequency of modulating signal
(iii) Modulation index
(iv) Sketch the signal in time domain and in frequency domain
(v) Transmission efficiency.

5. (a) Draw the circuit diagram of square legal regulations diode detector and discuss its working with suitable diagram.
(b) Draw the complete block diagram of the Armstrong frequency modulation system and discuss the function of the miner, multiplier and balanced modulator.

part B

6. (a) discuss generation of PWM signal. How it is demodulated?
(b) discuss generation of PPM and discuss with waveforms how it is derived from PWM.

7. (a) Draw and discuss the block diagram of superheterodyne radio receiver.
(b) discuss PCM with neat waveforms. Also discuss Quantization in brief.

8. (a) Draw the block diagram of communication receiver and discuss the working of Squelch system in detail.
(b) describe the subsequent terms with respect to radio receiver:
(i) Sensitivity
(ii) Selectivity
(iii) Image frequency rejection

9. (a) discuss telephone transmitter and telephone receiver circuit in detail.
(b) Write the various tones used in automatic exchange.
(c) discuss time division multiplexing used in telephony.

10. (a) Write short notes on any TWO:
(i) Adaptive Delta Modulation
(ii) Double spotting
(iii) Central Battery Exchange.

Earning:   Approval pending.