Error when doing S-parameter fitting using ADS optimization

Hi Guys,

Now I am doing S-parameter fitting using ADS optimization(fit the response of the equivalent circuit model to the measurement result). While I had a problem here: when the error function goes very close to zero, the optimized curves are much more different.

I am confused here. Do you guys know what's going on? Thanks for help!

Hi. I am so confused in how to do this fitting. I got the s parameters from HFSS and had built the equivalent circuits for my model. Could you please give me a detailed structure of how to get the value of equivalent L and C. If you got a manual for this, that would be better. I looked up on the internet, but the information is so limited. I appreciate your help.