# harmonics suppression and impedance matching for harmonics

Thread Starter

#### PuPuuuuu10

Joined Jun 30, 2021
23
Recently, i am doing projects of class E PA in radio frequency. I got about two concepts which are about harmonics suppression and impedance matching for harmonics.
Things i know is not quite much. I have known that one method for harmonics suppression is through 1/4lamda microstrip. We can make some open microstrips at 1/4lamda wavelength so that this can short the harmonics which we probably only get the fundamental wave at the load.
But what is about impedance matching for harmonics, things i know is that it can improve the efficiency of the power amplifier but by what kind of way.
Is there some relationships between these two concepts? I mean they both can be achieved by microstrips. So i just a little confused.
Anyway, might need your guidance. Thanks!

#### Papabravo

Joined Feb 24, 2006
17,551
Recently, i am doing projects of class E PA in radio frequency. I got about two concepts which are about harmonics suppression and impedance matching for harmonics.
Things i know is not quite much. I have known that one method for harmonics suppression is through 1/4lamda microstrip. We can make some open microstrips at 1/4lamda wavelength so that this can short the harmonics which we probably only get the fundamental wave at the load.
But what is about impedance matching for harmonics, things i know is that it can improve the efficiency of the power amplifier but by what kind of way.
Is there some relationships between these two concepts? I mean they both can be achieved by microstrips. So i just a little confused.
Anyway, might need your guidance. Thanks!
So for the fundamental frequency you want a terminated microstrip which absorbs the input signal energy with no reflections.
In addition you want unterminated microstrips to absorb the harmonics. I think that if you ponder for a moment you may remember that both open and shorted microstrips will produce reflections and this seems contrary to you goals. Maybe you have some clever arrangement that is not obvious to me from your verbal description. Could you perhaps share a drawing of what you have in mind.

Thread Starter

#### PuPuuuuu10

Joined Jun 30, 2021
23
For harmonics suppression. This one is to use TL2nd、TL3rd、 TL4th、TL5th microstrips to short the harmonics at 2f 3f 4f 5f.
And for impedance matching for harmonics. this is something i found on youtube which a teaching vedio by keysight.

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Thread Starter

#### PuPuuuuu10

Joined Jun 30, 2021
23
So for the fundamental frequency you want a terminated microstrip which absorbs the input signal energy with no reflections.
In addition you want unterminated microstrips to absorb the harmonics. I think that if you ponder for a moment you may remember that both open and shorted microstrips will produce reflections and this seems contrary to you goals. Maybe you have some clever arrangement that is not obvious to me from your verbal description. Could you perhaps share a drawing of what you have in mind.
yes i have attached some topologies, thanks!

#### Papabravo

Joined Feb 24, 2006
17,551
OK. so now I can see what you are up to. Is it still your intention to leave the harmonic stubs unterminated, or do you plan to terminate them in such a way as to absorb most of the energy that arrives in each stub?
I'm not able to read any of the details from the impedance computation screen shot.

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