Yep, tuned with a scope. There's a pdf of class E on the net somewhere and shows a whole page of 'half sine' traces indicating what state the tuning is in.
From the person who is considered perhaps the inventor, or at least someone who spent a lot of time advocating for Class E, Nathan Sokol. Refer to page 16. I took a short course from him years ago and still have the book.
Sokol, N., Class-E RF Power Amplifiers, QEX January/February 2001.
https://people.physics.anu.edu.au/~dxt103/160m/class_E_amplifier_design.pdfMax power and max eff never meet alas.
That's often the case with RF power amplifiers though. OP1dB is , for example, peaked at a different tuning than best OIP3, than the tuning for the the best gain or S11/S22, etc.
Btw parasitic capacitance from the PCB will be minimal but the devices C will have a strong influence.
Here's my problem with that statement: if that were true, then the tuning of my builds would have been close to spot on after simulation with the transistor models straight from the transistor vendor and they
never are. Then I change PCB layout with the same transistor and passives and then the tuning is a bit different yet again. So, no, that doesn't agree with my experience. In theory, proper Class-E design is supposed to "absorb" the transistor Cds and resonate against it. Either the models aren't accurate at 7 MHz (which would not surprise me at all) and/or something else is going on, like, oh, for example, unmodeled parasitic C on the passives and the PCB.
Speaking of transistor models - they should be "accurate" in a sense and they extracted parasitics and put them into their models but in many cases they are apparently not planning on you running their transistors at 4, 6, 10, etc. MHz, even though the published rise and fall times would seem to allow it. These are meant for switching power supplies and inverters and, though this is starting to change, a lot of the applications for these inexpensive transistors we (I) use are not going go any higher than 1 MHz, if that. As a result, the models from some manufacturers create "convergence errors" in a normal Class E and sometimes Current-Mode Class D circuit above maybe 1 MHz. A convergence error basically means that the computer can't converge on a solution to the math problem you are asking it to solve and it generates an error. (Transient simulations are essentially solutions to differential equations.) No simulation is possible in that case.
I figured this out about a year ago. A lot of very simple circuits (not even Class E circuits) generate convergence errors at my frequencies of interest. But then I can reduce the operating frequency (or slow the slew rate, or whatever) and then they start to work. Some Nexperia and TI transistors have been a pain in the backside this way. Infineon transistor models have been pretty good and I have yet to have serious issues with them. (They are my new favorite transistor company.) I have had good luck so far with Cree and Transphorm too, though Cree makes you create a place for their thermal model in order to configure their transistors.
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