JNTU Kakinada B-Tech 2-2 RT22045 ANALOG COMMUNICATIONS R13 April 2018 Question Paper

Code No: RT22045
II B. Tech II Semester Supplementary Examinations, April-2018
ANALOG COMMUNICATIONS
(Electronics and communication Engineering)Time: 3 hours Max. Marks: 70
Note: 1. Question Paper consists of two parts (Part-A and Part-B) 2. Answer ALL the question in Part-A
3. Answer any THREE Questions from Part-B
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PART ?A
1. a) What are the basic constituents of a communication system? (4M)
b) How can you obtain a DSB-SC signal? What is the Band-width of DSB-SC
signal? (4M)
c) What do you mean by angle modulation? What are the types of angle modulation? (4M)
d) Write down the expression for the signal to noise ratio at the output of angle
modulation systems. (4M)
e) Define the term distributor or de-commutator? (2M)
f) Write the main functions of a radio receiver? (4M)
PART -B
2. a) With suitable diagram explain the square-law diode modulation method for AM
generation? (8M)
b) An amplitude modulated voltage is given by V = 50 (1 + 0.2 cos 100 t + 0.001 cos
3500t) cos 10
6
t. State all frequency components present in the voltage, and find
modulation index for each modulating voltage term. What is the effective
modulation index of V? (8M)
3. a) List out the methods for generation of SSB-SC signal and explain any one of the
method in detail. (8M)
b) Find the various frequency components and their amplitudes in the voltage given
by v (t) = 50 (1+ 0.7 Cos 5000t- 0.3 Cos 1000t) sin 5×10
6
t. Draw the single sided
spectrum. Also evaluate the modulated and sideband power. (8M)
4. a) Explain in detail about NBFM and WBFM. Derive the expression for bandwidth
of wideband FM. (8M)
b) An angle modulated signal is represented in time domain as s (t) = 10 Cos (2p.10
6
t
+ 3 Sin 2p.10
3
t). Assuming the given signal as PM,
i) Calculate the frequency deviation, modulation index, B.W and power.
ii) Repeat the above calculations when the message frequency is doubled. (8M)
5. a) Derive the expression and explain how pre-emphasis/de-emphasis filtering
improves the signal to noise ratio? (8M)
b) Find Figure of merit and signal to noise ratio for the Ring modulator. (8M)
6. a) With neat sketch explain the generation of PWM and PPM? (8M)
b) Three signals m
1
, m
2
and m
3
are to be multiplexed, m
1
and m
2
have a 50 kHz
bandwidth, and m
3
has a 10 KHz bandwidth. Design a commutator switching
system so that each signal is sampled at its Nyquist rate. (8M)
7. a) Draw the block diagram of amplitude modulated transmitter and explain functions
of various blocks. (8M)
b) Briefly discuss about the frequency stability in FM Transmitter? (8M)
1 of 1
SET – 1
R13