Wednesday, November 4, 2009
| IF 244 PRINCIPLES OF COMMUNICATION |
| Time: 3 Hours Max Marks: 100 |
| Answer all questions |
| PART – A |
| (10 x 2 = 20 Marks) |
| 1. Determine the Fourier Series representation of x(t)=Cos4?t + sin 8?t. |
| 2. What is the relation between the autocorrelation and power spectral density of a |
| random signal? Explain. |
| 3. Calculate the transmission bandwidths required when voice signal having a |
| bandwidth of 4KHZ is transmitted using amplitude modulation and frequency |
| modulation. Assume ?=5. |
| 4. What do you understand by FM threshold? Explain. |
| 5. State and explain sampling theorem for band limited signals. |
| 6. What are the causes of Inter Symbol Interface(ISI)?. Explain how eye pattern is |
| used to measure ISI. |
| 7. Differentiate between coherent and non-coherent demodulation. |
| 8. Compare the performances of M-ary PSK and M-ary PSK modulation schemes. |
| 9. List the properties of Pseudo Noise Sequence used in direct sequence spread |
| spectrum system. |
| 10. What are the advantage of cyclic block codes over linear block codes? |
| PART - B |
| (5 x 16=80 Marks) |
| 11. Consider an amplitude modulated signal S(t)=5 (1+0.5 cos 2000?t +0.5 cos |
| 4000?t+cos 6000?t) cos 25,000?t. |
| a. Sketch the frequency of spectrum of S(t) |
| b. Find the total power , the sideband power and power efficiency |
| c. Find the modulation index. |
| 12a. i) State the Dirichlet condition to be satisfied for Fourier Series and Transform |
| representation . |
| ii) Find the Fourier co-efficient of a periodic pulse train of period T0. |
| (OR) |
12b. Explain direct method FM signals generation and slope detector for
| demodulation. |
| 13a. i) Draw the block diagram of Pulse code Modulator and explain. |
| ii) Differentiate between granular noise and slope overload noise and slope overload |
| noise in delta modulation. |
| (OR) |
| 13b. Derive an expression for the impulse response of a matched filter working under |
| white noise and hence show that it is equivalent to the time. correlate |
| 14a. Explain Binary PSK and Binary FSK modulation and demodulation with the help |
| of block diagrams. |
| (OR) |
| 14b. Derive an expression for bit error probability for quadrate PSK receiver and draw |
| the block diagrams for the modulator and demodulator. |
| 15a. Draw the block diagrams of Direct Sequence and Frequency Hopping spread |
| spectrum transmitters and explain. |
| (OR) |
| 15b. Write notes on the following |
| i. Cyclic codes |
| ii. Adaptive Delta Modulation. |
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