How to set port impedance in HFSS to simulate RFID antenna

[abdessalam]

Hello,
I am confused by a RFID antenna simulation problem for many days. If the chip's impedance is 20-j160, the antenna designed should have a impedance of 20+j160 for max power transfor. However, in HFSS, version 10, the port impedance is 50 ohm.Can I set the port imepdance to be 20-j160 which is the impedance of the chip? If can't, how to set the port's impedance if I want to simulate the RFID antenna attached with a chip correctly.Especially the Gain, S11 and bandwith?
Here must be many people who are familar with the RFID antenna simulation using HFSS.Please help me and give your suggetstions. Thank you a lot.

 

[PlanarMetamaterials]

in HFSS, version 10

Sorry, I'm not that old. You know that version 17 is out now, right?

 

[Daniel_G]

I cannot refer to HFSS 10 neigher, but in newer versions there is an option in the port properties to renormalize the port impedance.
Anyways, if you tell HFSS to assume a certain impedance at the antenna port, which does not equal the real Z_0 of your design, your simulation might work, but certainly gives you wrong results regarding S11, gain etc.

As far as I know, the magnitude of Z_0 should be matched to the feeding network. Therfore, you should modify your antenna design in order to match your mag(Z_0)=|20-j160|~=161 Ohm.

If you feed your antenna through a microstrip line, you might use a microstrip line imedance calculator (to be found a google) to get an idea about the dimensions necessary to match this port impedance.