Strange HFSS impedance smith chart

Hi, I use HFSS to draw impedance smith chart and get a strange chart, from previous post somebody also meet with such problem and said it was due to |s11|>1, in my case I don't think so,because all my simulation projects show such strange chart...

Plot S11 on a rectangular graph and you may get the answer.

Thanks, but I plot |s11| in dB and it is lower than 0 on the whole frequency band, I don't think it is |s11| that causes the problem, also all the projects that work well show the same problem, it maybe impossible they all go wrong...

Why do you think the impedance plot is strange? |S11| > 1 would refer to negative real impedance, it's obviously not the case here, impedance locus stays in right half plane.

But I hope to return to normal smith chart format...I don't know why the chart appears like that

Use S11 for the chart, not Z11

So s11 is complete same as Zin for single port network...thanks very much

No, S11 is S-parameters and not impedance. Smith chart usually expects S-parameters (not impedance) for input data.

OK, thanks