S-parameters of a varicap doesn't make no sense due to its nonlinear nature.
OK, s-parameters can be measured but they cannot be used in a simulator because as you know well varicap is voltage controlled capacitor and tightly bias depended.
So, s-parameters of a varicap do not seem very logical to me.
Scattering parameters are still well-defined for nonlinear devices; they'd just be bias-dependant.
If you want to measure it, just embed the varactor in series with a TL such as a microstrip, and DC bias the two sides. Remember to use a decoupling capacitor or DC block when connecting your VNA!
S2p or zap model is accuracy model of elements.
The model spice in datasheet is refer to the Skyworks Application Note, Varactor SPICE Model for Approved RF VCO Applications that works in 2.5GHz.
In my designed filter, the frequency is more than 2.5GHz (4 GHz)
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I don't want to measure. I just want to find in the internet