I am designing a Class-E power amplifier in UHF band using ADS. Now I have 20dBm fundamental output power with 13% PAE, which is low for this class of PA. The problem is that I have thermal dissipation and DC power consumption and harmonics. How can I reduce these?

Schematic of the designed PA

Results obtained

  • $\begingroup$ Perhaps you could show us the design you have so far? As it is, I don't see how anyone could help you. $\endgroup$ – Kevin Reid AG6YO Dec 29 '15 at 2:47
  • $\begingroup$ Those are different questions. You need to decide what specific question you're asking, and then give enough information about your design for people to understand it, not just say “I have an amplifier, how do I make it better”. Edit your question so that it is specific and answerable. $\endgroup$ – Kevin Reid AG6YO Dec 29 '15 at 15:31
  • $\begingroup$ Thanks for your advice. I have edited the question. If still there's missing info in my question, please remind me to make it as clear as possible. $\endgroup$ – user4621 Dec 29 '15 at 15:33
  • $\begingroup$ I don't have the background in RF design to confirm, but that seems like enough information, yes. Thanks. But in the comments you said you fixed your power dissipation issue and you want to make other improvements. It's OK to post a question you now know the answer to, but if you're looking for some other information, please edit the question accordingly. $\endgroup$ – Kevin Reid AG6YO Dec 29 '15 at 15:37
  • $\begingroup$ I take back my first comment and now I just need an answer to the edited question. So, the above structure is working based on class-E power amplifier design, but it's not giving expected power and efficiency based on calculations because there's much power dissipation and large harmonics. How can I improve power dissipation and decrease harmonics? Thanks again! $\endgroup$ – user4621 Dec 29 '15 at 15:39

Class-E implies switching a transistor on and off, rather than operating it linearly. This implies a rectangular signal shape, which implies a sinc spectrum, which implies high out-of-band emissions. You counteract that correctly by using High-Q LC filters. Make sure you measure efficiency at the right point -- that is, including these filters, as they convert harmonic energy to in-band energy, if you want so.

  • $\begingroup$ I improved the design and now have 40% PAE which is not good at all. I also changed the filter to LC-bandpass filter which sounds to work better. Still I have 1watt power dissipation. Don't know how to handle with it... $\endgroup$ – user4621 Jan 18 '16 at 16:22
  • $\begingroup$ I'm not really sure you using a GHzs wide transistor is the right choice for your relatively low frequency signal. $\endgroup$ – Marcus Müller Jan 18 '16 at 16:54

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