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Design >> RF Design >> class E PA
https://designers-guide.org/forum/YaBB.pl?num=1374257138

Message started by grosser on Jul 19^th, 2013, 11:05am

Title: class E PA
Post by grosser on Jul 19^th, 2013, 11:05am

hello,

Can you advice any circuit solution which could help achieve good harmonics supression in such circuit ?
I mean harmonics in RFC current.

bests

grosser

Title: Re: class E PA
Post by aaron_do on Jul 21^st, 2013, 8:15pm

I thought RF chokes normally give a constant current?

Aaron

Title: Re: class E PA
Post by grosser on Jul 22^nd, 2013, 12:54am

and that's it ?
is that all of your help ?

it gives a constant current if it's not switched like in this case.

grosser

Title: Re: class E PA
Post by aaron_do on Jul 22^nd, 2013, 1:58am

OK fair enough, it wasn't much help :P

But if it is really acting like an RFC, I think it is still supposed to provide constant current right? What I'm getting at is are you really using an RFC? Because I've seen several works using bonding wires trying to emulate RFCs. Or maybe you're saying that it is an RFC, but its not ideal, so there's still some harmonic current flowing through? Correct me if I'm wrong here.

In terms of minimizing harmonics, the methods that come to mind involve Push-Pull structures, changing the terminating impedance, using a more linear class of operation, some kind of pre-distortion, or negative feedback. For class E PAs, I'm not sure which of those apply, because you need specific current and voltage waveforms to get good efficiency. Maybe you could define the scope of your problem more completely...

Aaron

Title: Re: class E PA
Post by grosser on Jul 22^nd, 2013, 2:38am

OK fair enough, it wasn't much help :P

;)

aaron_do wrote on Jul 22^nd, 2013, 1:58am:

But if it is really acting like an RFC, I think it is still supposed to provide constant current right? What I'm getting at is are you really using an RFC? Because I've seen several works using bonding wires trying to emulate RFCs. Or maybe you're saying that it is an RFC, but its not ideal, so there's still some harmonic current flowing through? Correct me if I'm wrong here.

Aaron

Yes. You're completely right. I forgot to remove RFC from jpeg.

In terms of minimizing harmonics, the methods that come to mind involve Push-Pull structures, changing the terminating impedance, using a more linear class of operation, some kind of pre-distortion, or negative feedback. For class E PAs, I'm not sure which of those apply, because you need specific current and voltage waveforms to get good efficiency. Maybe you could define the scope of your problem more completely...

The inductance i use is specified to be a short range antenna, to power up sensors when are in its range.
It's driven by 10MHz sqare wave and the antenna propagates awful harmonics upto 1G

grosser

Title: Re: class E PA
Post by aaron_do on Jul 22^nd, 2013, 4:51am

Hi,

it looks like whatever you do you are gonna sacrifice efficiency. Is the design supposed to be fully integrated or are you simply trying to patch up your current design? Also, how much power are we talking?

If its only 10 MHz, you can use SMD capacitors/inductors to design an LC filter. Or maybe you can just not drive it so hard (or not with a square wave).

Anyway, I think you will need to give more information if you want a better answer.

cheers,
Aaron