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1 kilowatt Power Amplifier at 430 MHz

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Shoma Chandorkar

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I wand to design 1kilowatt of SSPA using phillips- BLF578 in class AB operation. which type of impedance matching is required . can anybody help me to design I/P and O/ P matching circuitary? What are all the steps to design PA?
 
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With making Loadpull or source pull analysis you can determine which output/input impedance gives the appropriate power at the output of the PA. You can even simulate it with very accurately using most popular EDA softwares like agilent ads. I prefer to read Gonzales' Amplifiers book.

Kind Regards,
ALP
 

For these higher power levels, using several lower power amplifiers which are combined is cheaper, and much more reliable. The most optimum way is push-pull initial stages which are combined with quarature hybrids. Possiby in a "tree" of several stages.
 

The price of BLF578 is about $350. To burn it (due to incorrect design) needs just couple of seconds.
As was mentioned, I would go for combined amplifiers, or use a metalo-ceramic tube.
 

A 1kW PA at 430MHz is quite a beast. With class AB bias you will need to think carefully about thermal management issues. This unit will get hot due to the efficiency of class AB.

Also you will need a very big power supply to test it. Also you have health and safety issues during development.

Have you addressed all the above already?

I'm still uncertain why there is a need for a class AB amplifier at this power level at 430MHz. Are you designing it for amateur radio use?
 

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