Anna University Coimbatore 2010 B.E ,/B.TECH s :/e - Question Paper

ANNA UNIVERSITY COIMBATORE

B.E / B.TECH. DEGREE exams : MAY/JUNE 2010

REGULATION : 2008

4th SEMESTER -ELECTRONICS AND COMMUNICATION ENGG.

080290020- COMMUNICATION THEORY

TIME :3Hours Max.Mark:100



PART A

(20*2=40 MARKS)

ans ALL ques.


1. What is amplitude MOdulation?

2. Sketch the spectrum of AM wave.

3. Mention the 2 major limitations of AM

4. What is Donald Duck voice effect?

5. obtain the value of modulation index if the total

transmitted power is 150W and carrier power

is 100 W in AM.

6. Differentite FM & PM.

7. What is frequency deviation?

8. A certain FM signal is represented by

v(t) = 10 sin(10^8t+15sin2000t)volt, where t is in seconds. obtain the

carrier frequency and modulation index.

9. describe random process.

10. What is white noise?

11. describe noise temperature.

12. What is the basic principle of working

of superheterodyne receiver?

13. describe AM threshold effect.

14. elaborate the methods used to achieve FM

threshold reduction?

15. What is the need for pre-emphasis and

de-emphasis in FM?

16. State source coding theorem.

17. Mention the properties of entropy?

18. describe info capacity.

19. What is rate distortion theory?

20. compute the entropy of the source with

symbol probabilities of 0.25,0.25 and 0.5.



PART B

(5*12 = 60 MARKS)


ans ANY 5 ques.



21. discuss the transmission of television signals

using modultion.

22.(a) Write short notes on FDM. (6 Marks)

(b) discuss the Demodulation of SSb signals.

(6 Marks)

23.(a) explain WBFM in detail and derive an expression

for FM signal using bessel function. (10 Marks)

(b) Why frequency modulation is stated to be

non-linear modulation method. (2 Marks)

24. discuss Armstrong method of FM generation

in detail with a neat block diagram.

25.(a) Write short notes on Shot noise. (6 Marks)

(b) Write short notes on Thermal noise. (6 Marks)

26. explain the noise performance in AM

system using envelope detection.

27. describe mutual info. obtain the relation

ranging from mutual info and joint

probability of the channel input and channel

output.

28.(a) discuss Huffman coding in detail with an

example. (8 Marks)

(b) explain the significance of channel capacity

theorem. (4 Marks)

Earning:   Approval pending.