Theory_Questions:
1.The power required to transmit an SSB
signal and DSB-SC signal are?
a)PmPc/2, PmPc
b) PmPc/2, PmPc/2
c) PmPc, PmPc
d) PmPc ,PmPc/2
Answer: [A] PmPc/2, PmPc
2) In an Envelope detector, the load
resistance is 1KΩ, carrier frequency is 1MHz and the message signal
is having a B.W of 4 KHz, then what is the appropriate value of the
capacitor?
A)50nF
B) 300nF
C) 250nF
d) 1nF
Answer: [A] 50nF
3)What must be the condition on the
charging time for the proper operation of Envelope Detector?
a)1/fc<<RsC<<1/fm
b)1/fc<<RsC
c) RsC<<1/fc
d) 1/fm<<RsC<<1/fc
Answer: [C] RsC<<1/fc
4)Receiver Complexity is less in case
of which modulation scheme?
a)VSB
b)SSB
c)DSB-SC
d)AM
Answer: [D] AM
5)What is the Auto correlation function
and spectral density of White Noise?
a) constant & impulse function
b) impulse function & constant
c) Ramp function & constant
d) impulse function & ramp function
Answer: [B] impulse function &
constant
6)In AM ,if the carrier amplitude is
10V and message signal is sinusoidal, having peak value 2V,what is
the modulation index and total transmitted power?
a)0.8,36W
b)0.8,72W
c)0.2,51W
d)0.2,52W
Answer: [C] 0.2,51W
7)suppose a voice signal is having peak
value of 2V and power of 2W,with carrier peak value of 6V,is DSB
modulated,then what is the total power in side bands?
a)36W
b)72W
c)1W
d)2W
Answer: [A] 36W
8)In the above problem,if the message
is Amplitude modulated,instead of DSB-SC,then what is the total power
in Side bands?
a)36W
b)72W
c)1W
d)2W
Answer: [C] 1W
9)if the input to the Envelope detector
is m(t)cos(2πfct)+mh(t)sin(2πfct),then what is the output of the
envelope detector?(Assume m(t)=Amcos(2πfmt) and mh(t) is the hilbert
transform of m(t))
a) Amcos(2πfmt)
b) Amsin(2πfmt)
c)Am
d) Am/2
Answer: [C] Am
10)Two DSB signals with bandwidth 20
KHz is passed using quadrature carrier multiplexing,then what is the
bandwidth of resulting signal?
a)10KHz
b)20KHz
c)40KHz
d)30KHz
Answer: [B] 20KHz
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