rectangular waveguide to coax transition design

Referring to the following article, I simulate Rectangular Waveguide to Coax Transition Design with HFSS 11.

http://www.w1ghz.org/QEX/Rectangular...ion_Design.pdf

I expect VSWR from 8 to 12.4 GHz will be under 1.25. But it is difficult. Is it possible?

I attach HFSS file and the result after optimization.

Your Teflon goes all the way to the bottom of the waveguide. In the article, there is Teflon only in the coax cylinder, it does not extend into the waveguide cylinder. Look at the picture on the second-to-last page.

Hi, shlomo22. Thank you for your reply.

Surely Teflon doesn't extend into the waveguide cylinder on Figure 13.
But I try Full height like Figure 7. It seems to be a measurement result.

Full height seems to improve VSWR compared with Bare. So I apply Full height.
I also tried with the size(diameter and length) on Figure 7.

But I couldn't get good results.

Hi,

It is not difficult! Just thinking and do more, wish you success.

Hi,
I tried do this transition from this paper too, I used CST MWS, but the result was not good too, I dont know why... Bare or Full height, the Figure 7 is "
strange", so I have the same experience as you