Dr. Hiroaki Ikeda in Tokyo has been a long time developer of high
power solid state amplifiers for broadcast. I met him in 1980, at a
conference, when he was pushing MOSFETS from Hitachi and NEC to
deliver RF power for MW frequencies. He worked for the Japanese
Broadcasting Corp (NHK) and was a professor at Shizuoka Univ until
1998. His transmitter work was published in IEEE Transactions on
Broadcast in Dec 1980 and in Proc IEE International Broadcasting
Convention, 1980. Also more RF developments with FETs in several
Transactions of IEE Japan in 1986.
In December 1999, Ikeda published a paper in IEEE Trans. on
Industrial Electronics titled:
Megasonic Transducer Drive Utilizing MOSFET DC-to-RF Inverter with
Output Power of 600 W at 1 MHz. For those trying to push RF MOSFETS
and combine them in Class D, check this out. They use the RF to drive
a cleaner for LCDs and semiconductor wafers.
In an unrelated but similar (!) set if papers, H. Fujita presents
work on a 2 KW 2 MHz RF system, using MOSFETS to drive a low
temperature plasma for surface treatment. This is in IEEE Trans on
Power Electronics, Nov 1999 and in IEEE Trans on Industry
Applications, Jan 1999. He uses a third harmonic resonant circuit in
the load to help square up the waveforms in the FETS to lower losses
and surges/spikes.
Just wanted to point out that a lot of interesting high power RF
stuff is done under the guise of 'industry' applications, not just in
medical, communications, or scientific work as most of us are
familiar. Although this isn't 28 MHZ stuff, and it certainly isn't
linear, the circuit evaluation and the combiner techniques are of
interest.
73
John
K5PRO
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