How to defne the radiation boundary?

Dear Sir:

I want to define a radiation boundary out of the patch antenna. Some people told me that it should be quarter lamda away from patch edges. But I cannot define the wave port inside the radiation boundary so that one face of radiation boundary should be overlap the wave port. But if I do that, the distance from that face to antenna will be shorter than quarter lamda. Could you help me?


Thank you very much!

Regards,

I hope I depicted your structure in mind correctly. Try to extend your radiation box so that all structure including the wave port located inside. And then use the pec cap behind your port.

Extend your feeding line (I suppose coaxial line or microstrip line) to the radiation boundary. Make port at same position as radiation boundary and design feeding line to be at least λ/4 far from structure..
From what you wrote I suppose you're using HFSS.. However in MWS you don't have to care if your port is inside or whatever located. Radiation boundary is created automatically and port could be inside the bounding box.

Regards

eirp

I also agree this kind of method to build up waveport and radiation boundary. About using metal cap behind the waveport and inside the radiation boudary, the size and the distance of this metal cap is very critical to the simulation results.
I dont think λ /4 away from the microstrip antenna, we set up the metal cap, it will not spoil the original radiation pattern, but I have no idea about how far it will spoil the simulation results, any one did some simulations to compare them?

Best Regards,