Simulating the effect of a SAW filter in spectre?

Hi,

I am working on a receiver in the transistor level using cadence. The receiver employs off-chip SAW filters in the signal path.

How can I simulate the behavior of the SAW filters accurately? If I have the s-parameter files(such as .s4p), can I import it into cadence? If so, how do I do it?

For now, I am just using the input/output impedance of the SAW as the source/load impedance of the preceding/following block. However, this is accurate only if I provide the SAW with matched source and load impedances. I would like to simulate the SAW behavior under mismatched conditions.

Thanks in advance,