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Load-pull limitations in PA design?

Hi All,

I will be tasked with finding the proper Zin and Zout for a 1W RF power transistor's maximum Pout, gain, and PAE on a Maury load-pull station, but something has just occurred to me: won't any results coming from such a PA load-pull tuning method be relatively inaccurate? The reason why I say this is that the final (non-linear) PA circuit, when eventually placed in the RF transmitter itself, will be seeing a bandpass filter and/or an antenna, both of which mean that the PA will no longer be seeing the very wideband 50 ohm termination it saw in the load-pull tuning station. This means that the non- linear's PA harmonics will be strongly reflecting back off of the filter's and/or antenna's stopbands and back into the PA's output, affecting its PAE, stability, gain, etc. Aren't I correct about this? And if so, how do I address this problem??

Thanks for any help!

-Bill

Reply to
billcalley
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In ANY design, the nicely manicured specs, achieved on bench should be derated about 50% once you produce more than one unit on production line. Happens in all designs. And it is NOT a problem, this IS reality.

HTH

Stanislaw

Reply to
Stanislaw Flatto

personally i am much opposed to using non-linear amplifiers without truly compelling requirements to the otherwise. efficiency is more dependant on circuit topology to the point that is is unreasonable to be non-linear.

--
 JosephKK
 Gegen dummheit kampfen die Gotter Selbst, vergebens.  
  --Schiller
Reply to
joseph2k

Power amplifier are pretty much all non-linear, except for classic single-sideband or TV power amps. But even there tricks such as pulse modulation had made some inroads. However, in this age of spread spectrum comms and digital TV (if and when it really comes...) their days may be numbered.

Just think about it: The big final power amp of an AM transmitter usually has an efficiency well north of 80%. That wouldn't be possible if this was a linear amp. These days it's basically a very fast switch with it's supply voltage modulated via a PWM stage.

--
Regards, Joerg

http://www.analogconsultants.com
Reply to
Joerg

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