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Reg. No. Name:

B4E571 Pages: 2

APJ ABDUL KALAM TECHNOLOGICAL UNIVERSITY
FOURTH SEMESTER B.TECH DEGREE EXAMINATION, JUNE 2017
Course Code: EC 208
Course Name: ANALOG COMMUNICATION ENGINEERING (EC)

Max. Marks:100 Duration: 3 Hours

PARTA
Answer any 2 questions. Question No.1 is compulsory.

. (a) The noise output of a resistor is amplified by a noiseless amplifier having a gain of

60 and a bandwidth of 20kHz, A meter is connected to the output of the amplifier
reads 171 rms (a) The bandwidth of the amplifier is reduced 10 5kHz, its gain
remaining constant .What does the meter read now? If the resistor is operated at 80°C,

what is its resistance? (8)

(b)When the percentage modulation is 75, an AM transmitter produces 10kW. How
much of this is carrier power? What would be the percentage saving in power if the

carrier & one of the sidebands were suppressed before transmission took place? (7)

. (a) Define Noise Figure & Noise factor. Derive the expression for overall Noise

Factor (F) of cascaded amplifiers. (8)

(b) Why modulation used in analog communication? What are the sources of noise

that affect the communication quality? (7)

. (a) Derive the equation for AM wave. Plot the frequency spectrum of AM if the

carrier is of maximum amplitude 5V, 100 kHz is simultaneously modulated by three
modulating signals of amplitude 2V, 51117; 1.5V, 2kHz ಹ 1۷, 11117 respectively.
Obtain the bandwidth &effective modulation index. (8)

(b)With neat diagram explain working of envelope detector. The output of a diode
envelope detector with a load resistance of 5 kQ, is fed through a de blocking
capacitor to an amplifying stage which has an input resistance of 10kQ. Determine the
maximum depth of modulation the detector can handle without negative peak
clipping? What is the other error associated with envelope detector? How it can be

avoided? (7)

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