I modeled a microstrip patch antenna in HFSS with airbox only lambda by 4 over the patch antenna. The airbox sidewalls and base touched the antenna, so none of the substrate edge scattering ripples are seen in the S11 results.
I, then, fabricated the antenna and saw bunch of ripples in the S11 results, though the pattern matched well with the simulation. The ripples, though, affect the S11 bandwidth since they go above -10dB.
I, then, simulated the microstrip patch antenna in HFSS with a bigger airbox that has its sidewalls and base some distance away from the sidewalls and the base of the microstrip antenna. The S11 results showed almost the same ripples seen in the measurement results and both results agreed well.
My question is: is it more accurate to simulate the airbox where the sidewalls are a distance away from the sidewalls and base of the antenna to capture the substrate edge scattering effect? Or, the substrate edge scattering ripples in measurement could have been avoided if measurement was done some other way?
Thanks.