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 functions.

Answer 1

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 of square law device is, `y(t) = Bx(t) + Cx^(2)(t)`
where B and C are constants and x(t) = message signal `(A_(m)sin omega_(m)t)` + carrier signal `(A_(c)sin omega_(c)t)`