Re: flow of designing LNA, if no compenent in the @DS librar
U should not use another Transistor cause then u have different S parameters. What u want to do is a linear analysis of the Amplifier and find the optimal Zin for minimum noise figure, S parameters are enough for that. Just use the S2P 2 terminal Block on the Data Items in ADS. Inside it u can just point to the file where u have your S parameters for a specific bias condition and do the rest of the analysis. ADS library models are exactly the same just that your component model looks like a transistor and not a Box like the one u will use.
For bias u just need to gurantee Ic and Vce , u dont need much info for the Tansistor for that, datasheet is enough.