[ADS] Correlation between circuit and layout simulation in keysight ADS

I'm designing an amplifier in ADS. I simulated the amplifier circuit and I got acceptable values. after that, I have done the layout and did layout simulation in ADS. however, ADS layout simulation values do not correlate with ADS circuit simulation. moreover, ADS layout simulation doesnt make sense! so i decided to probe the DC voltage values. i did DC voltage annotation and find out that the transistor/device DC bias volatge between circuit simulation and layout simulation is way different. Moreover the Ground is not zero potential but its negative voltage for layout simulation!

1) how to make the ground to be 0V in layout simulation?
2) is there any better way to correlate DC bias voltage between layout and circuit simulation than just increasing the voltages in layout simulation? Looks like there is a substantial DC voltage drop in layout simulation as compared to circuit simulation.

If the negative port terminal is floating (not connected to circuit ground)ADS assumes symmetric feed and uses +1/2Vin and -1/2Vin at the port terminals. You can connect minus terminal of port 1 to schematic ground using the ground symbol.

one of the negative port is connected to the ground symbol.

please see the attachment. i already connected one ground port to the ground symbol. However, the issue is still happening!

hi volker,
i think i get what u meant. i need to connect every ground port in the design to a ground symbol? is that correct?

Is this layout or look-alike symbol? I meant connection at schematic level where you use your S-params.

As far as I know, it depends how you have defined your ports. If you have defined all your ports with explicit ground reference pin (2 pins = 1 port) then I think your S-params don't pass any external currents, so they don't pass the external ground connection. But if you have 1 pin = 1 port, it should be enough to connect just port 1 reference to schematic ground.

yes.

hi volker, make alot of sense. since i dont have infinite ground plane at the bottom, i defined all my ports with explicit ground reference pin (2pins = 1port). due to this, i only getting sensible data if i connect ground symbols for every other ground pin in the layout or look-alike. you are very true. thanks.

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