I'm using EMPOWER Simulator for UHF planar PCB antennas in free space. Two questions:
1) I'm not sure how to set air height and box size for most accurate results. I get different results depending on the air height used and size of EMPOWER box. One design is a flat broadband dipole with 7" x 8" elements. It's model looks reasonable with air height set to 8 inches, but varies considerably with larger values. I need to simulate smaller elements, but I don't trust that the air height setting is correct for smaller geometry/higher frequencies.
2) Box covers. Since I'm trying to simulate free space, I tried to set covers to semi-infinte waveguides, per help instructions. This didn't seem to work - I only get reasonable results using an electrical cover model with 377 ohm impedance. What is best free space model?
1) I'm not sure how to set air height and box size for most accurate results. I get different results depending on the air height used and size of EMPOWER box. One design is a flat broadband dipole with 7" x 8" elements. It's model looks reasonable with air height set to 8 inches, but varies considerably with larger values. I need to simulate smaller elements, but I don't trust that the air height setting is correct for smaller geometry/higher frequencies.
2) Box covers. Since I'm trying to simulate free space, I tried to set covers to semi-infinte waveguides, per help instructions. This didn't seem to work - I only get reasonable results using an electrical cover model with 377 ohm impedance. What is best free space model?
The more air height you use, the higher box walls it creates, screening EM field in X and Y directions, and changing far field.
The box is a part of antenna construction. If your antenna does not have a box, you need minimize it height disabling air, and use wide box. The box is needed for Empower analysis - Empower works only in box mode.
If you have a MomenumGX license, than you can disable the box at all: MomentumGX works in both modes: with or without box, and if you construction does not have box, just do not use it.
2) To simulate radiation effects you need use "electrical" cover with 377 ohm impedance. It simulate freespace impedance. Using "open" cover is incorrect for that.