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DR. BABASAHEB AMBEDKAR TECHNOLOGICAL UNIVERSITY, LONERE –
Semester Examination May - 2019
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Branch: Electronics and Telecommunication Engineering
Sem.:- IV
Subject with Subject Code:- Analog Communication Engineering Marks: 60
BTEXC402]
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Date:- 16/05/2019
Time:- 3 Hr.
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Instructions to the Students
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2
3
4
. Each question carries 12 marks.
. Attempt any five questions of the following.
. If some part or parameter is noticed to be missing, you may appropriately
assume it and should mention it clearly
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(Marks)
Q.1. A) State and explain Sampling Theorem. What is Nyquist (06)
Criteria? A continuous time signal x (t) = 7 sin 2500πt + 5 sin
7
500πt is to be sampled. Calculate the minimum sampling
frequency.
B) With the help of neat diagram explain a typical radio (06)
transmitter.
Q.2. A) Explain double sideband suppressed carrier technique of AM. (12)
Also explain generation of the same using Balanced Modulator.
OR
B) 1. Derive an expression for power relation in an AM wave. (06)
Assuming that a 750 W carrier is modulated to the depth of
5
0 percent. Calculate the total power in modulated wave.
2
. Explain VSB technique of AM, What are its advantages over (06)
other AM Techniques
Q.3.
Answer any two of the following
A) Explain generation of Frequency modulation with the help of (06)
basic reactance modulator.
B) In an FM system, when the audio frequency (AF) is 750 Hz, and (06)
AF voltage is 2.6 V, the deviation is 5.2 kHz. If the AF voltage is
now increased to 8V what is new deviation? If the AF voltage is
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further raised to 10V while AF is dropped to 200 Hz, what is the
deviation? Find Modulation index in each case.
C) Explain concept of Pre-emphasis and De-emphasis.
(06)
Q.4. A) What is superheterodyne principle? Explain operation of (08)
superheterodyne receiver with the help of block diagram. Also
B) Define: Sensitivity, Selectivity, Fidelity, Image frequency
(04)
Q.5. A) Draw and explain the circuit diagram of practical diode (06)
detector. How AGC obtained from the detector
B) Draw and explain the circuit diagram of ratio detector. How (06)
amplitude limiting can be achieved using ratio detector? What
Q.6.
Answer any two of the following
A) Define Noise. What are different sources of noise? Explain in (06)
detail.
B) Two Resistors 15KΩ and 60KΩ are at room temperature, for (06)
the bandwidth of 100kHz, calculate thermal noise for following
conditions. (a) for each resistor (b) for series connection (c) for
parallel connections.
C) Define: Noise Figure, Noise Factor
(06)
The signal power and noise power measured at the input of an
amplifier are 200 μW and 2μW respectively. If the signal power
at the output is 1.5W and noise power is 40mW, calculate the
amplifier noise factor and noise figure
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