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Posted By: sridhar.v Member Level: Silver Posted Date: 03 Dec 2007
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2006 Anna University B.E Electrical and Electronics COMMUNICATION ENGINEERING (EC 256) Question paper
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BE/B.TECH. DEGREE EXAMINATION, MAY/JUNE 2006
FOURTH SEMESTER
REGULATION 2001
ELECTRICAL AND ELECTRONICS ENGINEERING
EC 256- COMMUNICATION ENGINEERING
Time : Three hours Maximum : 100 marks
Answer ALL questions.
PART A-(10*2=20 MARKS)
1. Define AM and FM.
2.What are the frequencies judiciously selected in C-band microwave satellite communication and why?
3. Draw the waveforms for PPM and PDM.Explain.
4. Explain slope overload error in delta modulation.
5. What is BER? Explain.
6. What is matched filter? Give its use.
7. Compare step index single mode fiber with graded index and step index multimode fibres in terms of optical characteristics.
8. List the characteristics of coaxial cable.
9. How color information is sent through composite video signal? Illustrate your answer with diagram.
10. What do you understand by horizontal and vertical synchronization in TV?
PART B-(5*16=80 MARKS)
11. (i) Explain the following :
(1) Narrow band and wideband FM signal. (3 marks)
(2) Direct and indirect methods of FM generation. (3 marks)
(3) Merits of satellite communication. (3 marks)
(ii) An amplitude modulated signal with modulating frequency of 4 KHz and modulation index of 0.3 is to be detected using a simple linear diode detector with C= 0.2 micro farad. Find the value of RL.(7 marks)
12. (a) (i) Distinguish between PDM and PPM. Explain the generation of PPM waveform from PDM signal with help of a block diagram. (12 marks)
(ii) State and explain sampling theorem for band pass signals. (4 marks)
OR
(b) (i) With help of neat block diagram explain differential PCM. (10 marks)
(ii) Explain the merits and demerits of differential PCM compared to linear PCM. (6 marks)
13. (a) (i) Explain the following :
(1) integrate and dump receiver. (4 marks)
(2) optimum filter. (4 marks)
(ii) Explain with diagram a coherent system of signal reception and show that the correlation receiver and matched filter receiver are identical. (8 marks)
OR
(b) (i) Explain FSK. Derive the expression for probability of error. (8 marks)
(ii) Compare the performances of PSK with FSK. (8 marks)
14. (a) (i) Explain, with diagram, FDM and TDM transmitter and receiver. (8 marks)
(ii) Give an experimental setup for measurement of thermal noise. (8 marks)
OR
(b) (i) Explain characteritics impedance and VSWR of a transmission line. (6 marks)
(ii) A glass fiber with nc=1.5 and nc1=1.45 has a core diameter of 9 micrometer and is used at lambda=1.3 micrometer. Find its normalised frequency. (10 marks)
15. (a) (i) Explain, with diagram, the television system transmitter and receiver. (8 marks)
(ii) Discuss the principle of interlaced scanning and why this is mostly preffered. (8 marks)
OR
(b) (i) Explain hue,saturation and brightness. What are colour-difference signals? (8 marks)
(ii) Distinguish clearly between delta gun and PIL gun picture tube used in colour telivision. (8 marks)
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