Hi! Praneeth,

Regarding the simulation geometry and setup, The setings for the two cases are similar.

The solving space Box1 size: Position: (-500, -500, 0); (Xsize, Ysize, Zsize) = (1000, 1000, 600). It is larger than the suggested size: Lambda/4.

Solution types: HFSS-Network Analysis-Terminal (ANSYS 2022 R2)

Analysis Setup: Freq = 4 GHz, Maximum number of passes: 20, Maximum Delta Energy: 0.1. Others: Default. Sweep: discrete-single point at 200 MHz.

A screenshot:

It is also noticed that the sizes of the solving space can affect the result of case 1, but cannot affect the result of case 2. The result of case 2 is constant and is always equal to the one obtained from the theoritical calculations. Therefore, I guess the difference is due to the pec GND of case 1. But I don't know the reason.

I hope the information is enough and I look forward to your feedback/suggestions.

Thanks and best regards,

Xinglong