Question Paper: Priniciples of Communication Engineering Question Paper - Dec 18 - Electronics And Telecomm (Semester 4) - Mumbai University (MU)
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## Priniciples of Communication Engineering - Dec 18

### Electronics And Telecomm (Semester 4)

Total marks: 80
Total time: 3 Hours
INSTRUCTIONS
(1) Question 1 is compulsory.
(2) Attempt any three from the remaining questions.
(3) Draw neat diagrams wherever necessary.

Q1 Solve any Four

1.a. Modulation Index for AM should be less than one. Justify/Contradict.
(5 marks) 12125

1.b. What is aliasing? How it can be prevented?
(5 marks) 12146

(5 marks) 12127

1.d. Justify, why FM is more immune to noise?
(5 marks) 12128

1.e. Define noise figure and noise factor.
(5 marks) 12129

2.a. State and prove sampling theorem for low pass bandlinited signals.
(10 marks) 12130

2.b. One input to AM modulation is 800 KHz carries with an amplitude of 10 $V_p$. The second input is 10KHz modulating signal that is of sufficient amplitude to cause a change in o/p wave of $\pm$5.5 $V_p$. Determine

1. Upper and lower side frequency

2. Modulation co-efficient and percent modulation

3. Draw o/p frequency spectrum

4. Draw modulated wave showing maxima and minima of waveforms

(10 marks) 12131

3.a. Explain the operation of Foster Seeley discriminator with the help of circuit diagram and phasor diagram.
(10 marks) 12132

3.b. Explain the working of stabilized reactance modulator with suitable diagram.
(10 marks) 12133

4.a. With help of neat diagram and waveforms explain generation and demodulation of PWM.
(10 marks) 12134

4.b. Explain phase shift method for suppression of unwanted carrier with neat block diagram.
(10 marks) 12135

5.a. Explain the following with reference to AM receiver

1. Double spotting

2. Three point tracking

3. Image frequency rejection ratio

4. Fidelity

(10 marks) 12136

5.b. Explain Indirect FM transmitter with suitable diagram.
(10 marks) 12137

Q6 Write short note on (any four)

6.a. Vestigial side band transmission (VSB) and its application
(5 marks) 12138

6.b. $\mu$-law and A-law companding
(5 marks) 12139

6.c. Frequency division Multiplexing (FDM)
(5 marks) 12140

6.d. Amplitude limiting and thresholding.
(5 marks) 12141

6.e. Pre emphasis and de-emphaisis circuits and its need
(5 marks) 12142