Hi,
It's recently come to my attention that the FM index of modulation is also the peak phase deviation in radians. This was in regards to a question about the linear region of phase/frequency detector.
My question is (and excuse me if the answer is simple):
How can you show that this is indeed the case? A mathematical proof would be interesting.
Thanks!
Slick
Any GOOD engineering book covering FM will go into what you are asking. FM and PM (phase modulation) are the same EXCEPT that in phase modulation, the peak phase deviation is proportional to the modulation frequency for a given modulation amplitude.
What this means practically is that the bandwidth of a PM signal increases with the modulation bandwidth. That is, the number of sidebands is not dependent upon the modulation frequency (for a sine wave).
In an FM signal, the bandwidth is independent of the modulation frequency. As the modulation frequency increases, the number of sidebands decreases.
In short, FM and PM are the same except that in FM the phase deviation is inversely proportional to the modulation frequency.
Bill
Look up FM Modulation and Bessel Functions. Various mathmetical descriptions are available.
Beachcomber
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