Learning Forum

[Krishna Prasath]

Hi,

What is format to give complex port impedance for RFID antenna designs? Sometimes I get positive S11 value when change reactance number format, like if I include i in complex part or leaving i in complex part. Which one is correct?

 

Thanks

[slouie]

The format for entering in a complex value under Port Impedance is: 

resistance + 1i * reactance

 

[Krishna Prasath]

The format for entering in a complex value under Port Impedance is: 

resistance + 1i * reactance

 

Hi Slouie,

I am using lumped port. I am giving real value for resistance and (1i*(imaginary value)) for reactance. Say 21 ohm for resistance and 1i*196 ohm for reactance. Still I am getting positive S11 over some frequencies. 

Thanks

[asamaiyar]

Positive S11 in dB?

What is your convergence criteria? 

[Krishna Prasath]

Positive S11 in dB?

What is your convergence criteria? 

 

Yes, Positive S11 in dB (over certain frequency range). Criteria is delta S <0.02.

[dprestau]

When dealing wit complex impedance, you should also  select " Generalized" for S parameters definition in HFSS Design settings. This definition will provide the expected S parameters.

 

[shanmei]

Can you explain more about the "generalized" option? 

 

Do you know choose the port setting to be " renormalize all modes" to be 50 ohms? Thanks. 

[jmnolan]

The Zo value in the solution matrix does not match the lumped port complex impedance. I am using 2019 R3. Is something broken with it? When I use real values such as 50 or 80, the Zo value matches in the solution matrix, however with complex it is very different. 

[AndyJP]

"1i*" oh, I use it for years, but didn't know this.

 

Wait a minute! Do you mean, I can enter a complex permeability(mu) tensor in Transient solver? Or it will still tell me that "ferrites are not supported"?