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Question
In the block diagram of a simple modulator for obtaining an AM signal, shown in the figure, identify the boxes A and B. Write their function.
Solution
In the block diagram of modulator, A is Square Law Device and B is Band pass filter.
Band pass filter rejects low and high frequencies and allows a band of frequencies to pass through.
Square law device is a non linear device. It produces a non-linear output of message and carrier signals. The output from square law device is,
y(t)=Bx(t)+Cx2(t)
Where, B and C are constants and x(t)=message signal (Amsinωmt) + carrier signal (Acsinωct)
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