matched termination of coax in hfss

[warran]

Hi everyone,

I hope everyone is doing well. I am facing a problem in measuring the phase of the electric field coupled to coax via a waveguide. Precisely, I have to read the electric field of antenna at near field by a rectangular waveguide probe.
I get some spike points on a phase values compared to its neighbouring point (approximately 180 out of phase) while letting coax end open. How can I terminate coax in hfss such that impedances matches the coax impedance ? Can I just solve the simulation for near field on a line at two points on the end face of the co-ax?
I would like to thank for any help in advance!!

 

[PlanarMetamaterials]

I get some spike points on a phase values compared to its neighbouring point (approximately 180 out of phase) while letting coax end open.

Two questions:
1) Is phase wrapping being used? This could cause sudden 180-degree phase differences.
2) Are there any particular reasons your coax is left open instead of terminated (with, e.g., 50 ohms)?

 

[warran]

Two questions:
1) Is phase wrapping being used? This could cause sudden 180-degree phase differences.
2) Are there any particular reasons your coax is left open instead of terminated (with, e.g., 50 ohms)?

Hi, yes phase wrapping is used. Regarding letting it open is just because I was not confidence about how to make 50 ohms termination. I tried to terminate the coax by assigning an impedance boundary at the end of the coax with values for impedance (50 0hm) and reactance (0). But, I did not get the expected results. should I calculate the reactance of coax also and put that value for reactance?

In addition, if I just consider one point in the face of coax for phase and magnitude of the electric field, where could be the best position (I mean near the inner conductor, in the between inner and outer conductor, or near the outer conductor)?

 

[PlanarMetamaterials]

Hi, yes phase wrapping is used. Regarding letting it open is just because I was not confidence about how to make 50 ohms termination. I tried to terminate the coax by assigning an impedance boundary at the end of the coax with values for impedance (50 0hm) and reactance (0). But, I did not get the expected results. should I calculate the reactance of coax also and put that value for reactance?

In addition, if I just consider one point in the face of coax for phase and magnitude of the electric field, where could be the best position (I mean near the inner conductor, in the between inner and outer conductor, or near the outer conductor)?

Can you confirm that the "spikes" you observe are not just phase-wrapping points (e.g., between 180 and -180 degrees?)
The typical method is to terminate the coax with a port. It will not only match the impedance properly, but will also tell you how much power it is absorbing.
I would probably average the phase across the transverse plane.