Analog Communication - May 2013

Electronics & Telecomm. (Semester 5)

TOTAL MARKS: 80
TOTAL TIME: 3 HOURS (1) Question 1 is compulsory.
(2) Attempt any three from the remaining questions.
(3) Assume data if required.
(4) Figures to the right indicate full marks.

Answer the following (any four) :-

1 (a) Explain Tracking in AM receiver(5 marks) 1 (b) What are the causes of fold over distortion? How can it overcome(5 marks) 1 (c) Explain how PPM is generated from PWM(5 marks) 1 (d) List the advantages of digital communication over analog communication system. Explain in brief(5 marks) 1 (e) Explain pre-emphasis and De-emphasis in brief with the help of circuit diagram.(5 marks) 2 (a) Why is frequency modulation preferred for stereophonic broadcasting? Explain in brief(5 marks) 2 (b) An AM broad casting operates at its maximum allowed total output of 100 kW at 90% modulation. How much of this power is the intelligence signal?(5 marks) 2 (c) Explain high power AM-DSBFC modulator with schematic diagram(10 marks) 3 (a) Explain measurements of Receiver Performance in detail(10 marks) 3 (b) What is noise? List the types of noise and explain each in brief(10 marks) 4 (a) Explain in detail pulse width modulation (PWM) with the help of circuit diagram(10 marks) 4 (b) Explain Delta modulation. Draw the output signal waveform? Also differentiate Delta modulation and Adaptive Delta Modulation(10 marks) 5 (a) The Signal to Noise ratio of an AM system is 25dB. The highest audio frequency transmitted is 30 KHz. If the trasnmitted carrier power is reduced by one-tenth and FM with a deviation of ± 15 KHz is employed, what signal to noise ratio is obtained(10 marks) 5 (b) Explain foster Seeley discriminator with the help of schematic diagram(10 marks) 6 (a) Explain VSB transmission (5 marks) 6 (b) What is superheterodyne dune tracking. Explain in brief(5 marks) 6 (c) The output voltage of a tranmitter is given by 500(1+0?4 sin 3140 t) sin6.28t. This voltage is fed to be load of 600 ? resistance . Then calculate -
(i) Carrier frequency
(ii) Modulation frequency
(iii) Carrier Power
(iv) Mean power output
(v) Peak power output(10 marks)

Write short notes (any four) :-

7 (a) FM noise triangle(5 marks) 7 (b) Ratio Detector(5 marks) 7 (c) Squetch Circuit(5 marks) 7 (d) Primam causes of ISI(5 marks) 7 (e) AVC and AGC(5 marks)