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Design >> RF Design >> how this FM modulator works?
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Message started by sapphire on Jan 20^th, 2009, 12:55pm

Title: how this FM modulator works?
Post by sapphire on Jan 20^th, 2009, 12:55pm

I am not sure whether this circuit can work as a FM modulator, because the modulation point and the output are the same.

Anyone has seen this before? Thanks for your help

Title: Re: how this FM modulator works?
Post by didac on Jan 21^st, 2009, 2:23am

Hi,
It looks like a direct FM modulator. If Vin(t) is the information signal and Cdiode(that i's a varactor I assume) and L are the tank of an oscillator, the amplitude of V(t) is changing the ressonant frequency with time so its changing the carrier frequency, thus directly making an AM to FM conversion.
Hope it helps,