Class D amplifier

[audioguru]

Hi Sig,
I don't bother with lousy-sounding AM radio.
If "harmonics of the baseband signal will be present in the output" of my favourite FM station or my FM radios, then they wouldn't have 0.1% or less harmonic distortion, would they?

The harmonics occur at radio frequencies and are reduced with tuned circuits to avoid interference.

 

[Sig239]

OK, I think I see what is happening here. We are talking about two different things. I am saying that it is not linear because the function that is applied to the signal is not a linear function(multiplication) ie. For an FM modulator: An increase in the AMPLITUDE of the baseband causes an increase in the FREQUENCY of the carrier. Though this happens at a linear rate(which is what audioguru is refering to right?), it is not caused by a linear function(which is what I was refering to). To clarify what I believe you are talking about... a given percentage of increase in amplitude of the baseband signal gives a linear responce in frequency of the carrier.

The book seems very badly written?, to suggest that the two original frequencies disappear is nonesense!

This was my fault. In an attempt to Illistrate what I was talking about, I mistakenly posted an example of a mixer. Modulators are all mixers but that type of mixer was the wrong illustration for an AM or FM modulator. IMHO the book is well written and very informative. If you care it is the ARRL handbook for radio communications. As you correctly stated, in an AM signal, the original frequency is obviosly present!

To clarify what I was talking about, the act of mixing or modulating is not a linear function, but it obviosly occurs at a linear rate.