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 particular band of frequencies to pass through.
Square law device is a non-linear device. It produces a non-linear output of messages and carrier signals. The output of square law device is
$y\left(t\right)=Bx\left(t\right)+C{x}^2\left(t\right)$
Where B and C are constants and
x(t) = message signal $\left(A_{m}sin{\omega }_{m}t\right)$+ carrier signal $\left(A_{c}sin{\omega }_{c}t\right)$