ibutter
Newbie level 2
HFSS - 50 Ohm Coaxial line terminated with 50 Ohm impedance boundary. |S11| too large
I'm modelling a 50 Ohm coaxial cable in HFSS that is excited with a waveport and terminated with a 50 Ohm impedance boundary.
The Z0 of the wave port is 50 Ohms (refined through tweaking dimensions of the teflon and pin size around standard SMA 50 Ohm cable designs).
The problem is that S11 mag in dB (at 4 GHz) is only -3.26 dB.. I'd expect that to be much lower given the 50 Ohm impedance boundary.
This result doesn't change when changing the following:
Any ideas?
Ian
- - - Updated - - -
I've realized that the "impedance" boundary is designed for sheet impedances, defined as ohm/square.. So I tried with a "radiation" boundary and got -70dB S11 mag.. But I feel like that's cheating, however it does demonstrate what I hoped to demonstrate
I'm modelling a 50 Ohm coaxial cable in HFSS that is excited with a waveport and terminated with a 50 Ohm impedance boundary.
The Z0 of the wave port is 50 Ohms (refined through tweaking dimensions of the teflon and pin size around standard SMA 50 Ohm cable designs).
The problem is that S11 mag in dB (at 4 GHz) is only -3.26 dB.. I'd expect that to be much lower given the 50 Ohm impedance boundary.
This result doesn't change when changing the following:
- Changing the length of the cable (S11 mag doesn't change, but phase does, as expected)
- Changing port characteristic impedance - Zpi, Zpv, Zvi, Zwave
- Changing PEC to copper
- Using curvilinear coordinates for curved surfaces
- Deembedding (same on and off)
- Normalizing port to 50 Ohms (no change, as expected due to Z0 being very close to 50 already)
- Mesh density (smallest tried is Lambda refinement of 0.25)
Any ideas?
Ian
- - - Updated - - -
I've realized that the "impedance" boundary is designed for sheet impedances, defined as ohm/square.. So I tried with a "radiation" boundary and got -70dB S11 mag.. But I feel like that's cheating, however it does demonstrate what I hoped to demonstrate
Last edited: