# What's the difference between FM and PM?

1. ## Diff bet FM and PM

what is the diff bet FM and PM?
i read from a book that freq diff of FM depends on freq of modulating signal but phase dev of PM is indep of freq of modulating signal.
pl give the respective formulas for freq & phase dev also.

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2. ## 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.

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3. ## Re: Diff bet FM and PM

HELLO checkmate

orthogonal codes which provide error correction capabilities in a noisy transmission channel

plz ur word orthogonal codes are less prone to noise.............
what about antipodal signals/codes...............

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4. ## Re: Diff bet FM and PM

hi frd

there is a basic difference betweem FM and PM

in FM, modulation index is inversely proportional to the modulating frequency but

in PM that is independent of the modulating frequency.

regards

puneet bansal

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