Re: Diff bet FM and PM
In FM, the information of a signal is encoded in its frequency. Similarly for PM, the information is encoded in its phase. Both modulation schemes use a carrier frequency as a reference.
A FM modulated signal with message signal x(t) has the form
A sin(2*pi*(fc+delta(f))*t) where delta(f) is the frequency deviation and is a function of x(t).
A PM modulated signal with message signal x(t) has the form
A sin(2*pi*fc*t + p) where p is the phase and is a function of x(t).
Digital signals usually use PM as its possbile to formulate orthogonal codes which provide error correction capabilities in a noisy transmission channel.