Small signal model of HEMT using ADS

Hello

I would like to replace the VCCS by a SDD component in the small signal model of GaN HEMT(Using ADS). Could somebody help me in this? How many ports should the SDD be and what should be the equations?

Like this ?

Yes but how do you set the transconductance G and time delay T values? Here is the circuit with VCCS. R1 and R" will be constant resistor values.