Waveguide Step Impedance

[Rf engineer]

Dear Friends,

I have to do the impedance matching of a ridged waveguide with a standard Ku band rectangular waveguide, as impedance step transformer. May be chebyshev tranformers.

I have studied a lot of text and research papers on these topic where i just got the theoratical formulaes....to find reflection coefficiencts and impedances......

Can anybody share to the point examples , which states how to take lengths of each section and height of each section, furthermore.....I need to model ti in HFSS, I tried yesterday with equal quarter wavelength steps.....and then tried to optimized it.....but it took so much hours and result was not good.....

So I request you guys to share some rule of thumbs and an example tutorial to optimize such steps in HFSS as well......

I really thank you all for reading this.

Best regards

 

[at.sdsu]

What i understand from your question is you want to introduce impedance matching transformer in a rectangular waveguide, is that so?

 

[hgc1979]

I know a little about ridged waveguide, my opinion is to make a preliminary model by formula you have got from papers first ,and then you can do some simulation by hfss or cst. If you want to do some profermance optimizations , you can set some parameters of the ridged waveguide variables, then the software will do the variable sweep and help you to find the good results.

BR

 

[zhul3]

For the same operating frequency, ridged WG is much smaller than regular rec.WG and it is sensitive, especially for your Ku-band case.

Thus to realise the transfomer, you probably need several steps (at least 3), and ridged structure should also be included in the first few transformer steps.

e.g, the first step of your transformer: bigger WG and lower ridge
the second step of your transformer: biggerbigger WG and lowerlower ridge
.
.
.
.
the last step of your transformer: regular Ku-band (WR75) Rec. WG and no ridge.


The length of the ridge could be optimized for impedance matching. Theoritically quarter wavelength transformer should work, but you need to calculate the impendance of your each transformer step by HFSS first.

Calculation must have some errors, then you have to use optimization. I know there is a pain by HFSS....