WAVE PROPAGATION & COMMUNICATION ENGG.
Questions of 2012
1. (i) What is the difference between AM & PAM?
(ii) How ground
wave propagation takes place
(iii) What do you mean by radiation pattern &
bandwidth of an antenna?
(iv) Write down disadvantages of FM & AM.
(v) What are
the causes & effects of solar noise?
2. (i) Explain need of modulation in a radio
communication system. Classify various modulation schemes.
(ii) Discuss
the concept of skip distance & MUF in ionosphere propagation
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3. (i) Explain operating principle of a log
periodic antenna. Why is the bandwidth of log periodic antenna much greater
than YAGI antenna?
(ii) (a) Derive
the relation between the output power of an AM transmitter
and
its modulation index
(b) An 400
watt carrier is AM modulated to a depth of 75 %. Calculate
the
total power in the modulated wave.
4. (i) Explain with the help of block diagram, the
Armstrong method of
generating
FM signal.
(ii) Define noise. Give the classification and explain
various types of noise.
5. (i) Draw block diagram of FM receiver and explain
its working.
(ii) Explain working of a BJT collector amplitude
modulator with suitable
circuit
diagram.
6. (i) What is space wave propagation? Why is this
limited to line of sight
distance?
Derive formula for range of space wave propagation.
(ii) Define PAM, PWM and PCM.
7. (i) Define effective aperture of an antenna.
Derive relationship between
maximum
effective aperture and antenna again.
(ii) Derive the formula for the instantaneous value of
an FM voltage and
Define the
modulation index (mf). What is transmission band width for
FM.
8. Write short
notes on any two:
(i)
Parabolic antenna.
(ii)
Super heterodyne Receiver.
(iii)
Balanced modulator using diode.
Questions of 2011
1. (i) What are different types of transmission
lines?
(ii) Explain
what is meant by traveling wave and standing wave.
(iii) What do you mean by fading?
(iv) Define Directive gain of an antenna.
(v) Explain in
brief the term – polarization
2. (i) Define Reflection, Refraction and
polarization of Electromagnetic wave.
(ii) State
Maxwell equation in free space.
3. (i) What is SWR in transmission line and how it
is eliminated by stub
matching?
(ii) Explain the behavior of open circuited and
closed circuited transmission
lines.
4. (i) A high frequency radio link has to be
established between two points at
a distance of 2500 km on earth’s
surface. Considering ionospheric
height to be 200 km and its critical
frequency, 5 MHz . Calculate MUF
for given path.
(ii) Derive the expression for characteristic
impedance (Z0), attenuation
constant (
), velocity of propagation (Vp) and wavelength (
) of
transmission line in terms of primary
constant.
5. (i) Define Voltage Standing Wave Ratio (VSWR)
for a terminated
transmission line. Under what loading
condition VSWR will be unity and
infinite.
(ii) Explain antenna efficiency (n), beam width
and radiation resistance
with reference to antenna.
6. (i) Give difference between Broadside array and
Endfire array.
(ii) R = 100
The value of primary constants of an open
wire line per km are R = 100
,
C = 0.008
for f = 1kHz. Find:
a) Propagation
constant (P)
b) Characteristic
Impedance (Z0)
7. (i) Explain slotted line method (VSWR method )
of input impedance
measurement of antenna at high
frequency.
(ii) Explain principle of pattern and find array
factor of two element array.
8. Write short
note on following (Any two):
(i)
Yagi – Uda antenna
(ii)
Line of sight distance.
(iii)
Log periodic antenna
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