NCERT Class XII Chapter
Communication Systems
Questions With Solutions
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Question : 8
Total: 8
Due to economic reasons, only the upper sideband of an AM wave is transmitted, but at the receiving station, there is a facility for generating the carrier. Show that if a device is available which can multiply two signals, then it is possible to recover the modulating signal at the receiver station.
Solution:
Let, the received signal be A 1 ( ω c + ω m ) t
The carrier signal available at the receiving station isA c ω c
Multiplying the two signals, we getA 1 A c ( ω c + ω m ) ω c
=
[ c o s ( 2 ω c + ω m ) t + c o s ω m t ]
If this signal is passed through a low pass filter, we can recover the modulating signal
ω m t
The carrier signal available at the receiving station is
Multiplying the two signals, we get
=
If this signal is passed through a low pass filter, we can recover the modulating signal
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