finite-ground singlewire layout simulation in Momentum

I tried a finite-ground singlewire layout simulation in Momentum for a 7-metal process. I chose AM as the signal layer and M1 as the ground layer. The ground layer has the same length and a three-time width as the signal layer. Two 50ohm ports are made by AM layer. Then I ran S-parameter simulation in Momentum. However, the results were not consistent with those from the singlewire simulation in Cadence Spectre with using the same process.

Singlewire is so simple that I don't think there should be large difference between Momentum and Cadence results. But...

I doubt if I drew layout correctly in Momentum. The results in Momentum maintained the same if I removed the ground layer I drew. Does finite ground have big influence on the result?

thanks.

This problem is described in @DS momentum help.
You should use internal port and ground reference instead of single port.