West Bengal Institute of Technology (WBIT) 2011-4th Sem B.Tech Electronics and Communications Engineering B-TECH ,Analog Communication,,ester,WBUT - Question Paper

GROUP-A
(Multiple option questions)
1. select the accurate options from any ten of the following: 10*1=10

i) The image frequency of a superheterodyne receiver is
a) created within the receiver itself
b) due to sufficient adjacent channel rejection
c) not rejected by IF tuned circuits
d) independent of the frequency to which the receiver is tuned.
ii) The input of the mixer stage is
a) Local oscillator signals only
b) RF signals only
c) Small carrier power
d) Very small carrier power.
iii) A carrier is amplitude modulated by 2 sine waves of various frequencies up
to 40% and 60%. The resulting overall modulation index is
a) 1
b) 0.72
c) 0.4
d) 0.6.
iv) When modulating frequency is doubled, the modulation index is halved and the
modulating voltage remains constant. The modulation system is
a) AM
b) FM
c) PM
d) any 1 of them.
v) Which of the subsequent stages has AGC bias?
a) Local oscillator
b) Mixer
c) RF amplifier
d) AFT discriminator
vi) A 10 kW transmitter is modulated to 80%. The avg. sideband power will be
a) 1.8kW
b) 8kW
c) 3.2kW
d) 9.6kW.
vii) Varactor diode is used for
a) FM
b) PM
c) PULSE Modulation
d) AM.
viii) If the radiated power of AM transmitter is 10 kW, the power in the carrier for
modulation index of 0.6 is nearly
a) 8.24
b) 8.47
c) 9.26
d) 9.6
ix) The envelope detector is a/an
a) Synchronous detector
b) Asynchronous detector
c) Product demodulator
d) Coherent detector.
x) De-emphasis in FM system involves
a) Compression of modulating signal
b) Expansion of the modulating signal
c) Amplification of the lower frequency signal of modulating signal
d) Amplification of the higher frequency signal of the modulating signal
xi) A PAM signal can be detected by using
a) an ADC
b) an integrator
c) a bandpass filter
d) a high pass filter
xii) The modulation system inherently most noise resistant is
a) SSB-SC
b) FM
c) PPM
d) PCM
xiii)Entropy is basically a measure of
a) rate of info
b) avg. info
c) probability of info
d) disorder of info
xiv) Thermal noise power in resistor R is proportional to
a) T
b) T^2

Earning:   Approval pending.