University of Mumbai 2008-4th Sem B.E Electrical and Electronics Engineering Comnication Engineering -I - Question Paper
Con/5248-07. ......( REViSEb' COURSE'Y 1' "J CD-5769
( 3 Hours ) [Total Marks : 100
N.B. : (1) Question No. 1 is compulsory.
(2) Attempt any four questions from the remaining six questions.
(3) Figures to the right indicate full marks. , . c
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1. (a) Draw block diagram-of FM receiver Explain each block. Draw waveform at 7
various stages. 2-j 11 0 &
(b) Explain capture effect. 3
(c) Define fourier transform and inverse fourier transform. Prove the time shifting 6 property of fourier transform.
(d) Explain the use of companding in PCM. 4
2. (a) Consider an angle modulated signal Xc(t) = 10cos (Wc t + 3cos Wm() 10
fm = 1000 Hz. Assume the modulation to be FM -
(i) Determine the modulation index and transmission bandwidth - when Wm is increased by factor of 4.
(ii) Determine the modulation inder and transmission bandwidth when Wm is decreased by factor of 4.
Give your inference on modulation index and bandwidth.
(b) Draw the (SB Receiver. Explain in brief the operation of receiver. Give its 10 application.
3. (a) Design a practical diode dectector for Amplitude Modulation. Derive maximum 10
modulation index and derive modulation index to avoid distortion.
(b) Derive expression for amplitude modulated wave and the total power transmitted. 10
4. (a) Define the following terms - 5
(i) Bit/frame
(ii) Frame synchronization
(iii) Bit rate.
(b) A PCM system uses a 7-bit binary encoder following a uniform quantizer. 10 If the bit rate of the system is 49 Mb/sec determine the maximum message bandwidth for a satisfactory system operation.
(c) A PCM system samples the signal at the rate of 8000 Frames/Sec. for a given 5 condition draw a PCM transmitter and receiver system.
5. Write short notes on (any four): 20
(a) VSB transmission
(b) Squelch circuit
(c| Balance slope detector
(d) Adjacent and Co-channel interference
(e) Inospheric propagation
(f) Self exited mixer.
6. (a) State and explain the sampling theorem. 10
(b) Draw PWM system. Explain and draw the wave forms. 10
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| Earning: Approval pending. |
