Help! Multi-layer PCB simulation problem with HFSS

hfss multilayer

Hi,
I am trying to simulate the s-parameter of multi-layer PCB but meet a problem how to add port.

The PCB consists of three metal layers and two substrate as shown in following:

================ < --- metal layer : microstrip line
Rogers 4350
================ < --- metal layer : microstrip GND
FR-4
================ < -- metla layer : reference GND
The "microstrip GND" connected "reference GND" by metal vias.
See the details in attached hfss file.

Now I intend to simulate s-parameter of microstrip lines on top layer which reference is the bottom layer "reference GND" (Not the middle layer "microstrip GND"). I try to add wave ports in Driven Modal but find its s-parameter is very strange and seems wrong obviously. I really appreciate one can tell me how to add a proper port at this case.
Thank you in advance.

Please find HFSS project file in attachment. (HFSS v9.2)

pcb simulation

What are the results you expect?

I expect the reasonable s-parameter should vary smoothly with frequency.
But s-parameter I get now seems not like what I expect.