2.45 ghz power fet suggestion needed?

[biff44]

I have a project to generate around 35 watts in an oscillator at 2.45 GHz. I normally don't deal with higher power active circuits, so I am not that familiar with modern fets. After some google searching.....I am having trouble finding a fet to do the job.

Google turns up a lot of devices, but many seem to be older Motorola, NEC, or Fujitsu parts that I suspect are either obsolete or "not recommended for new designes". Things like the MRF286. I can find new devices from places like Cree or Polyfet, but they are pretty expensive (>$100).

So, who makes a modern low cost (maybe $35) FET that can be used as an efficient 35 watt 2.45 ghz oscillator? I am not particular about the type (GaAs, MOS fet, etc), so long as I can make an oscillator out of it.

Thanks,
Rich

 

[Mazz]

LDMOS is the only possible solution, I guess, with that price target. It is a stable technology that can be pushed up to 2-3GHz.

Freescale has a large catalog: RF LDMOS Power Transistors.

Usually those parts are intended for amplifiers, I wonder how you'll design an oscillator with them. Why not use a more traditional oscillator and amplify up to 35W?

Mazz

 

[biff44]

Because a single FET circuit is going to be cheaper than an oscillator and some gain stages. Also, the voltage supply will be simpler because I need only one 28 V battery voltage, vs lower voltages for driver stages/oscillator AND the 28V output stage.

 

[vfone]

Would be not cheaper, because to make it work you have to use a much higher operating frequency transistor (due to higher gain and lower drain capacitance at oscillation frequency).
For example for an 8W 450MHz power oscillator, I had to use a power transistor dedicated for 900MHz.