s parameter of transistor

dear sir/madam

i got S parameter of NEC3210S01 pHEMT device from the datasheet. but when i bias the transistor for the state bias condidtion in the datasheet, i didnot get the S parameters which was stated in the datasheet for that bias condition. i done the simulation in ADS2011.10. KINDLY help me

thank you

You use a model of the transistor and compare the results with presented s-parameters? Are results better or worse or totally different? Post maybe your schematic and results.