ads inductor fitting

Hi,

In inductor modeling, I found that although Y parameters (my Q and L are extracted from Y parameters) fit well, the S parameters fittings are nasty (dB(S11) differs about 8dB). This really confuses me, which one should I use to fit my inductor?

What cause this kind of difference? doesn't the Y parameters derived from S parameters?

Thank you.

that shouldnot be so large difference,did you check the phase of the parameters?