Hi
I have a question about the Radiation Boundary in HFSS itself. I am simulating a dipole with a lumped port feed and I notice changes in the resonant impedance/frequency when I change the size of the Radiation Boundary. According to the design requirements, I gathered that the minimum distance of the radiation boundary away from the radiating structure should be lambda/4.
I modeled my dipole for IR wavelengths, it's 5um in length (including the feed gap) and for the lambda/4 design I get a resonant frequency of 25.05THz. Whereas when I increase the radiation boundary to around twice more (in height, length and width) I get a resonant frequency of 24.7THz. Although the difference is small why is there a difference at all if both case abide by the lambda/4 rule? It feels like the first case has a sort of cavity mode associated with it or something.
Does anyone have a solution to determine the right medium dimensions for accurate resonant results?
Thanks in advance