Electronics

Electronics

Complex port impedance for RFID chips

    • Krishna Prasath
      Subscriber

      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
      Ansys Employee

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


      resistance + 1i * reactance


       

    • Krishna Prasath
      Subscriber

      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
      Subscriber

      Positive S11 in dB?


      What is your convergence criteria? 

    • Krishna Prasath
      Subscriber

      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
      Ansys Employee

      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
      Subscriber

      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
      Subscriber

      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
      Subscriber

      "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"?

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