How Do Microwave Chokes Work?

[MadScience]

Does anyone know how microwaves chokes work?

Or have any references with simple explanations?

 

[berkeman]

Does anyone know how microwaves chokes work?

Or have any references with simple explanations?

Welcome to the PF.

Can you be more specific? What frequencies are you asking about? And what is the microwave propagation mechanism you are addressing? Do you mean inductive impedance on a PCB microwave frequency circuit? Or are you referring to something in a waveguide structure?

 

[yungman]

What are you trying to do? Need more info. Are you referring to using it as a dc source to supply power to say collector of a transistor but like an open circuit at the microwave frequency? Also it serve as isolation from the other stages.

From circuit I've seen, in theory, it is same as an inductor that is short circuit at dc and high impedance at desired rf frequency. There is no difference between rf or lf, a choke is a choke. You just need to worry a lot about parasitic and distributing effect due physical dimension.

 

[MadScience]

Some more details:

I'm trying to understand how a choke would work for an axially segmented wave guide (with circumferential slots) in the 20 - 40 GHz region. Eventually I want to do it for a cylindrical wave guide but to start just understanding the cartesian version would be good.

I had a look at some of the original papers on chokes but the best understanding I was able to get was that they work something like lecher lines.

For instance, I can see intuitively why a choke stub should be about 1/4 wavelength long, but I don't know concretely why. Also, why have many stubs with small gaps between them? And how is the dimension of the slot chosen to minimize leakage?