Anna University Chennai 2012-3rd Sem B.E Computer Science and Engineering ./B.Tech , /E (ester, )-ANALOG AND DIGITAL COMMUNICATION - Question Paper

B.E./B.Tech. DEGREE EXAMINATION, MAY/JUNE 2012.
Third Semester
Computer Science and Engineering
CS2204/141304/CS36/EC1207/10144 CS 305/080230008-ANALOG AND DIGITAL COMMUNICATION
(Regulation 2008)
Time : 3 hours
Maximum : 100 marks
ans all ques..
PART A-(10*2 = 20 marks)
1. describe modulation and modulation index.
2. What is the purpose of limiter in FM receiver?
3. Draw 8-QAM phasor diagram.
4. Determine the peak frequency deviation and minimum bandwidth for a binary FSK signal with a mark frequency of 49 KHz, a space frequency of 51KHz.
5. Determine the Nyquist rate for analog input frequency of
(a) 4KHz.
(b) 10KHz.
6. describe companding.
7. What is the need for data modems?
8. Mention the differnce ranging from line coding and channel coding.
9. describe Process gain and Jamming margin.
10. provide an example to PN sequence.
PART B-(5*16 = 80 marks)
11. (a) Draw the block diagram and discuss generation of DSB-SC signal using balanced modulator. If the percentage modulation is 100%, how much percentage of the total power is current in the signal when DSB-SC is used.
Or
(b) describe FM and PM modulation and write their equations. define the generation of FM wave using Armstrong method.
12. (a) discuss the generation and detection of PSK system with the help of block diagrams.
Or
(b) define the coherent detection procedure of M-ary PSK and find the expression for the probability of symbol fault.
13. (a) Draw the block diagram and discuss the operation of a PCM system. A binary channel with bit rate = 36000 bits/sec is available for PCM voice transmission. obtain number of bits per sample, number of quantization levels and sampling frequency assuming highest frequency component of voice signal is 3.2KHz.
Or
(b) explain linear delta modulation using block diagram and derive expression for S/N ratio.
14. (a) discuss source coding theorem . Consider 5 messages S0,S1,S2,S3,S4 provided by the probabilities 1/2,1/4,1/8,1/16,1/16. Use the Shanon-Fano algorithm to develop an efficient code.
Or
(b) explain asynchronous modem requirements. discuss working principle of these modems. discuss fault correction capability of block codes.
15. (a) define the structure of feedback shift register for generating PN sequences. provide the advantages associated with spreading a signal sprectrum.
Or
(b) (i) discuss the concept of synchronization and tracking of frequency hopping spread spectrum signals. (10)
(ii) Mention merits and demerits of time divison multiplexing. (6)

Earning:   Approval pending.