Hi, thanks for all your reply.
Actually right now I have figured out how to get the simulation right in Momentum. I need to assign the finite ground plane with a port as "GND reference port".
However, once I generate the "Layout Component" and do the "EM-circuit" co-simulation, the problems come up again. The "GND reference port" setting is auto-disabled. Moreover, even I connect the "GND reference port" manually to the schematic "GND" symbol together with other circuit element, the results still not be good.
For example, for the Wikison Power Divider, the infinite GND plane layout component together with the schematic resistor can generate a resonable results, but once I use the finite GND plane layout component in schematic and did the EM-circuit co-simulation, the results go bad again.
If someone meet this problem before, please let me know how to solve it. Thanks.