| COMMUNICATION SYSTEM-1 |
| PAPER NO. 1 |
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EC-309 COMMUNICATION SYSTEM-1 (B.Tech 5th Semester,2122) Time : 3 Hours Maximum Marks : 60 NOTE:- This paper consist of Three Sections. Section A is compulsory. Do any Four questions from Section B and any two questions from Section C Section-A Marks : 20 1(a) Why modulation is required in a communication system? (b) Differentiaite between energy signal and power signal. (c) List various forms of external noise. (d) Where and why class C amplifier is preffered? (e) Why arte linear amplifers used in SSB transmitters? (f) What is Pre-emphasis ? Why is it used? (g) What are the advantages that the super hetrodyne reciever has over the TRF radio recievers? (h) State the sampling theorem. (i) List the factors influencing the choise of the intermediate frequency for a radio reciever. (j) Define the terms sensitivity, selectivity and image frequency. Section-B Marks:5 Each 2. A certain transmitter radiates 9kW with the carrier unmodulated, and 10.125 kW when the carrier is sinosoidal modualted. Calculate the modulation index. If another sine wave, corresponding to 40% modulation, is transmitted simultaneously, determine the total radiated power. 3. Explain the generation of carrier suppressed AM signal. 4. Compaer the three main systems of SSB generation by drawing up a table of outstanding characteristics of each system. 5. Find the carrier and modulating frequencies, the modulating index, and the maximum deviation of the FM wave representated by the voltage equation: v = 12 sin (6 × 108 t + 5 sin 1250 t) 6. Explain the generation of FM by direct method. Section-C Marks : 10 Each 7. Explain the working of AM reciever using a phased locked loop. 8. Explain the operation of a phase discriminator with the help of a circuit diagram. 9. With the help of a block diagram, describe the Pilot carrier SSB reciever. |