Solution for Analog Communication for Analog Communication May 2016 Index Q.1) a) . 2 b) . 2 c) . 3-4 d ) . 5 Q.2) a) . 6-7 b) ... Explain block diagram of adaptive delta modulator

Mumbai University EXTC (Semester -V)

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Solution for Analog Communication

May 2016

Index

Q.1)

a) …………………………………………………………………………. 2

b) …………………………………………………………………………. 2

c) …………………………………………………………………………. 3-4

d) …………………………………………………………………………. 5

Q.2)

a) …………………………………………………………………………. 6-7

b) …………………………………………………………………………. 8-9

Q.3)

a) …………………………………………………………………………. 10-14

b) …………………………………………………………………………. 15-16

Q.4)

a) …………………………………………………………………………. 17-18

b) …………………………………………………………………………. 19-21

Q.5)

a) …………………………………………………………………………. 22-23

b) …………………………………………………………………………. 24-25

Q.6)

a) …………………………………………………………………………. 25-26

b) …………………………………………………………………………. 26-28

c) …………………………………………………………………………. 28-30

d) …………………………………………………………………………. 31

e) …………………………………………………………………………. 32-33



Q1) (a) Why IF is selected as 455 KHz in AM? Solution:

(b) Distinguish between narrow band FM and wideband FM. Solution:



(c) What are the causes of fold over distortion? How it can be prevented?

Solution:



(d) Explain double spotting with reference to radio receiver. Solution:



(e) Define noise figure and signal to noise ratio. Solution:

Q2)



(a) One input to AM modulation is 500 KHz carries with an amplitude of 20 Vp.The second input is 10 KHz modulation signal that is of sufficient amplitude to cause in o/p wave of ± 7.5 Vp .Determine.

(i) Upper and Lower side frequency. (ii) Expression for modulated wave. (iii) Draw o/p spectrum. (iv) Modulation co-efficient and prevent modulation. (v) Total transmitted power.

Solution:





(b) Explain practical diode detector with delayed AGC. Solution:



Q3) (a) Explain indirect method of FM generation.

Solution:









Part 4: Use of frequency Multipliers Mixer and Amplifier: The FM signal produced at the output of phase modulator has a low carrier frequency and low modulation index. They are increased to an adequately high value with help of frequency multipliers and mixer. The power level is raised to the desired level by the amplifier.



(b) Explain ratio detector in detail with suitable diagram. Solution:





Q4) (a) Explain independent sideband technique in detail.



(b) Explain Super Heterodyne radio receiver in detail with block diagram. Solution:

Operation :-



In order to maintain a constant difference between the local oscillator frequency and the incoming frequency, ganged tuning is used .This is simultaneous tuning of RF amplifier, mixer and local oscillator and it is achieved by using ganged tuning capacitors



Q5)



(a) Explain block diagram of adaptive delta modulator with waveform. Solution:

As shown in Fig due to variable step size, the slope overload error is

reduced. But quantization error is increased. Due to the adjustable step size, the slope overload problem is solved. Hence ADM system has a low bit rate than the PCM system. Therefore the BW required is also less than a comparable PCM system.





(b) State and prove sampling theorem for pass band signal. Solution:



Q6)Write short note on any four of the following. (a) PLL FM demodulator. Solution:



(b) Quadrature Amplitude Modulation. Solution:





(c) TDM and FDM. Solution:



TDM :-



(d) Companding Solution:



(e) Aliasing error and aperture effect.

Solution:



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Solution for Analog Communication for Analog Communication May 2016 Index Q.1) a) . 2 b) . 2 c) . 3-4 d ) . 5 Q.2) a) . 6-7 b) ... Explain block diagram of adaptive delta modulator