Matching a rectangular waveguide with a circular resonator

[HeavyIon]

Good day to the forum participants! I need to match a WR-284 rectangular waveguide with a 2.46 GHz circular resonator (about 50 mm diameter). The source is located in a rectangular waveguide. Do I understand correctly that I should use the RF window to match the waveguide with the resonator? The step transition does not give me the opportunity to improve the QSWR, but only expands the frequency range. I managed to get a QSWR of -20 dB at this frequency. What do you advise?

 

[biff44]

i must admit i do not understand what you are trying to do.
a resonator...."resonates". It can be a one port, or two port resonator.
if it is a two port resonator, lets assume it is a bandpass type of resonator. so the amount of coupling into the resonator, and the amount of coupling out of the resonator at the 2nd port, mostly determine the input to output insertion loss (along with the resonator unloaded Q), and peripherally the VSWR.

the process is to determine the bandwidth needed (lets assume it is narrow bandwidth), set the input and output coupling to achieve that (possibly with a window iris), and then if you somehow need better vswr, maybe a single post tuner in front of the window?

if you need a variable coupling, you can combine a window iris with a screw that lowers or raises into the iris, or a set of horizontal inductive posts, and so on

usually, you would only care about VSWR if you were making a bandpass filtering device, usually out of several "resonators"

 

[HeavyIon]

Of course, I was mistaken about VSWR, in fact I mean the S1,1 parameter. It shows how efficient the power input is.
First, the window size is determined, then the post-tuner is added. What should the post tuner look like?

The picture shows approximately what I am modeling. Electrodes in a circular waveguide for matching to the required frequency.