Manfred,
Your amplifier reminds me of something I worked on in the 80s,
trying to improve efficiency in military manpack transmitters. One
approach which was promising came out of an article:
F. H. Raab, “The class BD high-efficiency RF power amplifier”,
IEEE Journal of Solid-State Circuits, vol. SC-12, no. 3, June 1977
I can't find a full version online to link to; I'm sure I still
have a paper copy somewhere which I'll scan if/when I find it.
Steve
coughdiplexer
No go! While it's true that a diplexer would nicely terminate all harmonics and
thus avoid impedance transformation in the line, it would also negate the main
advantage of an ET transmitter, which is the high efficiency. With a near
square wave voltage at the drains, a diplexer would dissipate a considerable
amount of power in the load resistor.
The game is making an amplifier that does not dissipate power generated at
harmonic frequencies, but that simply doesn't generate any power there. To that
end the low-pass filter cannot be a diplexer.
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