What is the significance of putting a check mark next to "Renormalize all Ports to 50 ohm" in Waveprt settings in HFSS? I am getting different results for S11 when I check/uncheck it? What should I do so that my Simulation graphs match the measured ones after fabrication? I'll be using SMA connector.
In HFSS it is good practice to always renormalize your impedance to 50 ohms to make sure your driving ports are independent of waveport/lumpedport size,substrate and transmission line widths.If you don't renormalize, HFSS calculates the port impedance based on the width of the line and substrate properties and even the ports dimensions(waveport or lumpedport),but if you renormalize the port impedance to 50 ohm, no matter whether the feedline is matched to 50 ohm or not, the port impedance is constant at 50 ohm for all the frequencies.Remember if you renormalize your impedance,your HFSS results should be the same to the results you can get using other software such as ADS,Multisim,etc.So for your case please renormalize all ports to 50 ,hope you know that your simulation graphs will be slightly different to the measured ones after fabrication.This can be due to multiple factors including fabrication error.One other important thing to mention,remember to use right size for your port dimensions(waveport,or lumped port).
Of course, if your ports aren't 50 ohms, then you shouldn't re-normalise. I use different impedance microstrip, non-conventional coaxial cable and also waveguide, and these aren't 50 ohms. It depends if the input is in the line you have modelled, or in 50 ohms.
If there is a junction with 50 ohm line it is best to model the join and have some 50 ohm line in the model, because re-normalising won't model the discontinuity (perhaps capacitance due to a step in width).
If the port you are using is 50 ohms then it is a normal practice to maintain that value by ticking the box. you also need to make sure that your feedline is relatively 50 ohm
Agreed with the learned colleagues. It depends if you intend to use 50 ohms source then make it re-normalised to 50Ohms otherwise just use the impedance equal to that of your source.
after reading the excellent reply of Jean Lambert Kubwimana, I have a question. If the ports are renormalized, why is it still important to correctly size the port dimensions? I can understand why this is true for wave ports, but for lumped ports this should not be an issue, am I correct? especially given that there is a de-embed option if you are worried about the 0.5 dB accuracy you can gain..
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