Question

Inductor is the main cause which deviates the center frequency regardless of message
signal. Due to the reason use of inductor in FM Modulator is critical. Similarly, in case of
IC modulators inductor induces a process called gyration. An alternate approach to solve
the above mentioned problem is the use of Wien Bridge Oscillator.
Design a FM modulator with the help of Wien Bridge Oscillator for pure sinusoidal
output. Choose minimum number of passive components to minimize harmonics. The
output of modulator would be in Narrow Band FM.

Answer 1

An FM Modulator can be designed using many methods. Let's discuss about one of those methods which includes 1) Sine wave generator 2) Positive clamper 3) 555 Frequency modulator. The first part sine wave generator includes Weinbridge oscillator in our design. The design of FM Modulator with the help of weinbridge oscillator for pure sinusoidal output is as shown below: