Hey folks,
I've been working on a microstrip board layout in ADS for a relatively simple PA. As part of the design I have a stabilization resistor that shunts the gate of the active device to ground. My problem lies in performing a momentum simulation of the input matching network with this shunt branch. When I perform the simulation on the schematic level in ADS I get one response, upon trying to verify the same response in the EM simulation I find it behaves completely differently.
After some investigation, I've found that the same behaviour that results in the EM simulator can be duplicated in the schematic simulator by deleting the ground symbol that is at the bottom of the shunt stabilizing resistor. What this boils down to is that the EM simulator will not recognize my shorts to ground and is leaving one end of the shunt resistor floating.
I've tried a few things to get a working short to ground: Short-circuit stubs and vias to ground.
My question to you all is: To use the VIAGND element in layout for a microstrip design in ADS what layers should I be using for conductor (I've tried cond) and hole (I've tried cond and hole)? If one of the things I mentioned above was actually right, is there something else that I'm missing?
Thanks in advance,
Steve