Explanation on E-class in SSB TNX

[in3elx]

Good morning, everyone.
Can anyone explain how Class-E works in SSB?!... I have found very little info. Is there also a block diagram? Thanks

[N6YWU]

Guido posted an explanation of his basic concept here (9 years ago in 2013):
http://pe1nnz.nl.eu.org/2013/05/direct- ... n-pll.html

A block diagram of the signal flow for the uSDX is here:
https://github.com/threeme3/usdx/blob/master/block.png

Here's my random guess at a rough explanation:

A signal with a very narrow bandwidth in relation to its center frequency looks, from a distance, very similar to just a pure sinewave, with any modifications or modulation happening fairly slowly, e.g. over a very large number of RF sinewave periods. An SSB modulation of 3 kHz audio into at 3 MHz or higher RF band is a ratio of 1000:1 or more, or a very slow rate of change compared to the RF frequency. So the SSB result is almost a pure sinewave with close to no visible changes if you look at just several dozens to hundreds of RF periods (of non-silence).

The rate of change is slow enough that it can be bit-banged as occasional phase adjustments to the output of a frequency synthesizer IC (or a Raspberry Pi timer) feeding a class-E amplifier. A class E amp is similar to a digital switch driving a (very carefully tuned) phase synchronized resonant load. Then the harmonics need to be filtered out to produce legal HF RF.

The whole path just an approximation to pure analog SSB modulation, but close enough for humans to understand its demodulation, and not perceive it to be too distorted.

73, Ron, n6ywu
http://www.nicholson.com/rhn/dsp.html