How to determine the reference plane in MW0ffice EM Simu

I want to simulate a microstrip filter in EM sight of MW0.
In the filter,the first section and the last section microstrip is 50 Ohm line.
After I add a edge port,I wonder where should I put the ref. plane.

Thanks for any suggestion!

When you add an edge port in MW0 EM Simulation,you should draw the arrow of edge port into the structure.
But I don't know how long the arrow should be drawn?
Has anyone experience in such detail?

Thanks.

The reference plain passes through the end of arrow. You can place the reference plain only into the port's homogeneous transmission line to obtain the correct results. If Your filter was designed for 50 Ohm ports, the reference plane location (and I/O 50 Ohm microstrip line length, of course) don't affects the results (except the filter's electrical length and small losses in the line). Otherwise, You should put the reference plane on the edge of structure.

Best regards,
Kit-the-great