Hello, Element!
Structure was double ridged horn simulated (and also working there) 200MHz-2GHz
Global mesh settings was If I remember 12 cells/lambda and some mesh refinement around coax to H waveguide. I'm satisfied with automesh, I only make fine refinement if needed. I also look visually at the mesh.
We only make comparison with measurements of reflection coef. and we plan also compare far field pattern.
Regards,
Eirp

I am interested in the radiation pattern simulation vs measured info as well for the ridged horn. Was it waveguide or coax fed? Did you have good input impedance agreement?
I have had trouble in the past HFSS with the run time of medium size structures and correlation of radiation performance for radiating structures (horn, helix, patch).

Input impedance fits well with computed one.
Radiation I still don't know, I will ask my friend.
It was coaxial fed. (Coaxial - H waveguide - ridged horn).
Best,
Eirp

If impedance is good, then radiation pattern would agree better.
A tougher case would be a problem combining large scattering body and some small or curved features. Any experience on this?

According the horn I'm sending far field.. H plane @1GHz
BLUE - measured
DOTTED RED - calculated MWS.
From curves I think distance when measuring hasn't adequate enough to be in real far field.
Best,
Eirp

The overlay in the forward region looks pretty good. The simulation issues I have had (HFSS) have been with the calculated response in different regions -backlobes, x-pol, radiated axial ratio ect. In some cases I have had better correlation with WIPL although it can be a bear and you can't rely on it for dielectrics. If you have any x-pol overlays (in the principle and 45 degree planes) I would like to see how well CST calculates the data. It would also be nice to see the variation in calculated response for these parameters between cst and hfss. ------- I have done a fair amount of fooling around with the rad boundaries, sym axis, mesh seeding and pml but still haven't seen the results that the actual data shows. I could send you a model if you don't mind running it.
H3O

In attachment is VSWR (dotted red - MWS and the rest DRhorn - 2 slightly modified types). Note - antennas were quite tuned (to extend to lower frequencies) when built so experiment doesn't 100% fit the measurement.
Dear H30, if you have interesting project in HFSS, please export it as .sat and I can import and calculate via MWS.. + send the model in HFSS
Best regards,
Eirp
PS: Antenna has been measured at next few frequencies, I will provide the comparison soon

The rest of radiation patterns (E/H planes at 1GHz, 500MHz and layout of the antenna)...