[Amps] worthwhile patents on RF amplifiers?

[jtml at losalamos.com]

I was looking through some recent solid state RF amplifier patents, and 
2 stood out for comment here. You may be able to view these or at least 
the cover sheet and abstracts with online free patent viewers now that 
you have these numbers:

US0285168 was awarded by the USPO around Dec. of 2007, invented by 
Steven Dishop of Bellefontaine, OH. The address is given Pearce and 
Gordon LLP in Cleveland. In it claims are made for a solid state module 
that has push pull MOSFETs operating at least 200 watts and 50 volts. An 
input and output transformer or balun is used to convert single ended to 
balanced for the transistors and match (1:4 on output). Then there is a 
claim for a four FET similar amplifier where a pair of FETs are operated 
in push pull, with drains tied together, and these are then operated 
push pull with another similar par, driven out of phase with the first. 
This one is 400 watts. I don't understand what is unique about any of 
this, and have seen similar amplifier constructions for decades. How can 
this patent hold valid?

The second one, US5187580, assigned to Advanced Energy Industries in Ft 
Collins (a real RF company, BTW) was awarded in Feb. of 1993. In this 
one the inventors suggest making a single ended MOSFET class E amplifier 
that works better without a shunt capacitor across D to S of the output 
device. They claim that the varactor capacitance of the Cds alone is 
sufficient, even better, and that the larger devices can be made to work 
at higher power and frequencies this way. Multi-kilowatts and 65 MHz. 
Normally in class E the voltage at the device is forced to zero before 
it switches, in this one it switches with substantial voltage across it, 
even suggests this is better. I don't see mention of improved efficiency 
with this technique, just very high power availability. Something 
bothersome is the claim that it must operate in a different class than 
A, B, AB, C, D, E, F...but no real math or proof of anything other than 
a suboptimal class E. Its the first RF amplifier patent I have seen 
where the invention is of a strange performance without sufficient 
explanation. Maybe I am being stupid and should just take these at face 
value? One has to wonder if their wattmeters were tricked, or harmonics 
were excessive, or whatever. None of this is described.

Solid state RF amplifier experts, chime in!

73
John