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
1.c.
Why AGC is required in radio receivers?
(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
Upper and lower side frequency
Modulation co-efficient and percent modulation
Draw o/p frequency spectrum
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
Double spotting
Three point tracking
Image frequency rejection ratio
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