SRM University 2007 B.Tech Electronics and Communications Engineering BANK : EC200 ANALOG COMMUNICATION - Question Paper

UNIT – II ( EXPONENTIAL MODULATION)

PART – A
1. Write an expression for FM signal.
2. Define Modulation index in FM.
3. State Carson’s rule.
4. Explain how PM can be generated using frequency Modulator.
5. Compare AM and FM?
6. Compare FM and PM?
7. Compare NBFM and WBFM?
8. What are advantages & disadvantage of FM over AM?
9. What is Pre – emphasis & De-emphasis?
10. Define frequency deviation.
11. Draw the phasor diagram of FM.
12. Explain how FM can be generated from phase modulator.
13. Write about the power content in FM signal?
14. Write down the expression for the bandwidth of PM.
15. Write down the demerits of direct method of FM generation.
16. What are the methods involved in FM wave generation?
17. Describe the 2 steps involved in FM detection.
18. What are the kinds of Discriminators used for FM wave Detection?
19. Give the 2 kinds of Phase Discriminator.
20. Write down the demerits of single – tuned discriminator circuit.
21. Write down the disadvantages of balanced slope discriminator.
22. Give the demerits of Foster-Seeley discriminator.
23. Give the merits of & demerits of ratio detector.
24. When does a frequency modulator behave like an Amplitude modulator?
25. What do you understand by NBFM?
26. What do you understand by WBFM?
27. Distinguish ranging from Direct and Indirect method of FM generation.
28. State the principle of Reactance Tube modulator.
29. Define the modulation index for PM.
30. Enumerate the major blocks which constitute Armstrong modulator.


PART - B
1. Derive an expression for Narrow Band Frequency Modulation.
2. Derive an expression for Wide Band Frequency Modulation
3. With neat sketch discuss the direct method of FM generation.
4. Explain the Armstrong method of FM Generation..
5. In an FM system, when the audio frequency (AF) is 500Hz and the AF voltage is 2.4V, the deviation is 4.8 KHz. If the AF voltage is now increased to 7.2V, what is the new deviation? If the AF Voltage is raised to 10V while the AF is dropped to 200Hz, What is the deviation? obtain the modulation index in every case?.
6. Explain PLL method of FM demodulation.
7. Find the carrier and modulating frequency, the modulation index and the maximum deviation of the FM wave represented by the voltage formula ?
V=12Sin (6?108 t +5 sin 1250t).
What power this FM wave will dissipate in 10 ohm resistor?.
8. Draw the diagram of Foster – Seeley discriminator & discuss its operation.

Earning:   Approval pending.