# EC2252 MJ2014 Communication Theory 4th Semester Question Paper - Reg2008

Anna University
Question Paper Code :51399
B.E./B.Tech. DEGREE EXAMINATION, MAY/JUNE 2014.
Fourth Semester
Electronics and Communication Engineering
EC 2252/EC 42/EC 1252/080290020 -- COMMUNICATION THEORY
(Regulation 2008)
(Common to PTEC 2252 Communication Theory for B.E. (Part-Time) Third Semester ECE – Regulation 2009)

PART A — (10 X, 2 = 20 marks)

1. State the differences between single side band and vestigial side band transmission systems.
2. For an AM system, the instantaneous values of carrier and modulating signal. are 60 sin wct and 40 sin wnt respectively. Determine the modulation index.
3. Define white noise.
4. If the maximum phase deviation in a phase modulation the when a modulating signal of 10 V is applied is 0.1 radian, determine the value of phase deviation constant.
5. State the Shannon's theorem.
6. State the need for pre-emphasis and de-emphasis circuits in the field of communication.
7. Derive an equation for the modulated signal of an AM system.
8. Why is frequency modulation preferable for voice transmission?
9. Define noise figure.