In Libra we very often used the REFNET component for S-parameter simulations of various circuits. This allowed us to set the reference impedance to the impedance of a circuit rather than a value, e.g. 50 ohm. In ADS there is no REFNET component at this time to my knowledge. However, is there a (tricky?) way to perform the same type of simulations using a workaround? Any ideas are welcome on this topic. I have tried to use a dataset together with an expression for the impedance in the ADS TERM component. It works fine as long as the termination impedance has a positive real part. But what to do if this is not the case? :-/
Refnet - file based termination
Assume the following circuit:
You simulate the S-parameters into the base of the transistor and save it in a 1-port dataset. You then want to design your input matching network, using the S-parameters from the simulation above as a load:
This will fail in case the real part of the impedance that is read by the REFNET is negative.
Instead of using a REFNET approach, which asssigns the impedance to a Term, you could use a S1P block. That way you can terminate your circuit with any impedance and at least do the impedance matching of the input network. The drawback with this method is that it is limited to a impdedance match only. Loss in the matching network etc cannot be measured.
This may or may not help, depending on what you are trying to do.
Any other ideas / comments ?