ANALOG COMMUNICATION SYSTEMS (B.Tech EC)
B.Tech. (Semester-5th)
December 2007
ANALOG COMMUNICATION SYSTEMS (EC-301)
Time : 03 Hours
Maximum Marks : 60
Instruction to Candidates:
1) Section - A is compulsory
2) Attempt any Four questions from Section-B.
3) Attempt any two questions from Section-c
Section – A
(10 * 2 = 20)
Q1)
a) Modulation Index of AM.
b) Frequency Deviation of FM.
c) Selectivity.
d) Transistor Mixer.
e) Sample and Hold Circuits.
f) SPATTER
g) Relation between SNR & BW
h) Multiplexing
i) Pulse Position Modulation.
j) Narrow banding.
Section - B
(4 * 5 = 20)
Q2) What do you mean by a word Communication in general? Explain an electronic
communication systems block diagram.
Q3) Explain the Quadrature Detector Circuit with the help of block diagram.
Q4) (a) Obtain a General expression for average power in a complex wave in a
amplitude modulated wave where total modulation index is give by
(b) An AM Voltage is represented by the expression
V=5[1+0.6 cos(6280t)]sin(2 * 3.14 * 10 t) volts
State: (1) Modulation Depth (2) f m (3) period of Carrier wave (4) the
peak instantaneous value of the modulated wave.
Expand the expression and calculate the rms voltage of lower side
frequency component. The modulated wave is applied across the
resistance of 1 K Ohms. What is the power dissipated?
Q5) (a) Describe FM stereo system and mono system.
(b) For a FM wave presented by voltage equation
V(t)=10sin(8 * 10 t+7sin6 *10 t)
Determine the carrier frequency, modulating frequency, modulating
index, maximum deviation, power dissipated in 8 ohm load.
Q6) Explain the High- level Amplitude Modulation? Technique with suitable diagram.
Section - C
(2 * 10 = 20)
Q7) What is Filter method? Describe the working of Filter method.
What is the principle for Generation of SSBSC waves?
Q8) (a) An amplitude modulated wave is represented by
The wave is passed through a filter which removes the Carrier. Then
this carrier is re inserted with a phase change of 90 degree. Show that
the resulting wave is phase modulated. Determine the peak deviation,
peak frequency deviation, depth of residual amplitude modulation and
frequency of residual amplitude modulation.
(b) Obtain Compare AM and FM methods.
Q9) (a) Explain the working of PLL FM Detector.
(b) A PM transmitter is operating at a carrier of 100 MHz with a carrier
voltage of 8 V, the modulation Signal has an amplitude of 3 V and a
frequency of 6khz, resulting in deviation of 60khz. Write the voltage
equation for the following conditions.
(1) Original Values.
(2) Audio amplitude increased to 4 V.
(3) Audio frequency increased to 8khz.
(4) Audio changed to 2 V and 3khz.