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
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|