[Amps] Non-linear subharmonics was: Nonsense, AL-1500 parasitic

[Steve Thompson]

Here's a message received from a guy I knew at university aeons ago. He reads 
the archives but is not a subscriber. I'm not sending it because it carries 
any personal baggage for me but because it's an input from a highly qualified 
and very experienced rf engineer.

Steve

----------  Forwarded Message  ----------

Subject: Amps Reflector
Date: Tue, 21 May 2002 12:50:04 +0100

I saw the comments on the amps reflector archive (I'm not a list member)
about sub harmonic generation and the assertions that it cannot happen. It 
does happen and is often referred to as half carrier regen or parametric 
division. There are numerous references around on parametric dividers.

It is a nonlinear phenomenon and happens particularly with low voltage
semiconductor PAs when driven hard with the right/wrong kind of matching
environment. You need assymetrical waveform clipping to take place in
order to halve the period of what started out as a sine wave. It's also
a major pain the the ass!