B.E./B.Tech. DEGREE EXAMINATION, NOVEMBER/DECEMBER 2010
Third Semester

Information Technology
IT 2202 — PRINCIPLES OF COMMUNICATION
(Regulation 2008)

Time : Three hours Maximum : 100 Marks
PART A — (10 × 2 = 20 Marks)

1. Why should the modulation index of AM be less than 1?
2. Draw FM and PM waveforms.
3. What is Shannon limit for information capacity?
4. Draw Costas loop circuit.
5. Define Companding.
6. Distinguish between DM and ADM.
7. What is the significance of PN sequence?
8. What are the types of FH spread spectrum technique?
9. What is a transponder?
10. Derive the velocity of a Geo Synchronous Satellite.

PART B — (5 × 16 = 80 Marks)

11. (a) (i) What is the principle of Amplitude modulation? Derive expression for the AM wave and draw its spectrum. (Marks 8)
(ii) Describe the frequency analysis of Angle modulated waves. Explain their Bandwidth requirements. (Marks 8)

Or
(b) (i) A modulating signal of 2 cos5000t is amplitude modulated over a carrier signal of 5cos20000t . Derive expressions for the modulation index, LSB and VSB frequencies, Bandwidth and the ratio of Side
Band Power in the Total Power of AM wave. (Marks 8)
(ii) Explain the principle of Angle Modulation. Derive and explain phase deviation, Modulation index, frequency deviation and percent modulation. (Marks 8)

12. (a) (i) Draw FSK Transmitter and explain. Describe its Bandwidth Considerations. (Marks 8)
(ii) For a BPSK modulator with a Carrier frequency of 70 MHz and an input bit rate of 10 Mbps, determine the maximum and minimum upper and lower side frequencies, draw the output spectrum, determine the minimum Nyquist bandwidth, and calculate the baud (Assume fa = 5 MHz). (Marks 8)

Or
(b) (i) Draw and explain the operations of Non-coherent and coherent FSK modulators. (Marks 8)
(ii) Draw QPSK modulator and explain. Describe its Bandwidth considerations. (Marks 8)

13. (a) (i) Describe in detail the PCM technique with focus on its sampling rate, and signal to quantization Noise ratio. (Marks 8)
(ii) What is ISI? Explain the applications of eye pattern to detect ISI. (Marks 8)

Or

(b) (i) With a block diagram, explain the adaptive Delta Modulation technique. (Marks 8)
(ii) What is DPCM? Explain its principle with neat block diagram. (Marks 8)

14. (a) (i) Draw the circuit of a P-N sequence generator and explain. (Marks 8)

(ii) Describe the concept of FHSS in detail. (Marks 8)
Or
(b) (i) Explain the principle of DSSS with coherent binary PSK. (Marks 8)
(ii) Compare between the TDMA and CDMA wireless communication systems. (Marks 8)

15. (a) (i) List any four advantages and disadvantages of Geo Synchronous Satellites. (Marks 4)
(ii) Describe in detail the operation of Optical Sources. (Marks 12)

Or
(b) (i) State and describe Kepler's laws. (Marks 4)
(ii) Describe in detail the operations of various types of optical detectors. (Marks 12)