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Posted By: Sree.... Member Level: Diamond Posted Date: 21 May 2008
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2007 Andhra Pradesh State Jawaharlal Nehru Technological University B.Tech COMMUNICATION ENGINEERING Set No. 2 Question paper
Code No: RR321001 Set No. 2
III B.Tech II Semester Regular Examinations, Apr/May 2007
COMMUNICATION ENGINEERING
(Electronics & Instrumentation Engineering)
Time: 3 hours Max Marks: 80
Answer any FIVE Questions
All Questions carry equal marks
? ? ? ? ?
1. (a) An AM transmitter has antenna current of 2A with modulation index of 60
percent. What will be the total antenna current if one more identical antenna
is connected in parallel with the previous one, keeping the transmitter output
same? Will it affect the modulation index?
(b) An audio frequency signal 10 sin(2p × 500t) is used to amplitude modulate a
carrier of 50 sin 2p105t to Calculate
i. Modulation index
ii. Side band frequencies
iii. Amplitude of each side band frequencies
iv. Bandwidth required
v. Total power delivered to the load of 600 ohms
vi. Transmission efficiency. [8+8]
2. (a) The sinusoidal modulating wave m(t) = Am cos(2pfmt) is applied to a phase
modulation with phase sensitivity Kp . The unmodulated carrier wave has
frequency fc and amlititude Ac . Determine the spectrum of the resulting
phase modulated wave, assuming that the maximum phase deviation ßp =
KpAm does not exceed 0.5 radians.
(b) A carrier wave of frequency 100 MHz is frequency modulated by sine wave of
amplitude 20 volts and frequency 100 KHz. The frequency sensitivity of the
modulation is 25 KHz per volt. Determine the approximate bandwidth of FM
wave using Carson’s rule. [10+6]
3. (a) Write about the classification of transmitters.
(b) Draw the block diagram of Amplitude modulated transmitter and explain the
functions of each block. [8+8]
4. (a) Write about tone and volume control in a radio receiver.
(b) Bring out the draw backs of TRF receiver.
(c) 3-point tracking. [5+6+5]
5. (a) Explain clearly the phenomenon of shot noise generation in active devices.
(b) Derive expression for noise figure of a cascade system of amplifiers. [8+8]
6. (a) Draw the conceptual diagram of multiplexing-demultiplexing and explain.
(b) Distinguish between sampling and quantization. [8+8]
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Code No: RR321001 Set No. 2
7. (a) What is companding? Why is it used? Why is it preferable to quantizing with
tapered steps? Illustrate your answer with a sketch of typical companding
curves.
(b) What are the advantages and applications of Pulse-code Modulation? [8+8]
8. (a) Which is more efficient, circuit switching or virtual circuits switching? Why?
(b) What are the three switching methods? Explain [8+8]
? ? ? ? ?
2 of 2
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