spiral inductor simulation with HFSS

I am doing on-chip spiral inductor characterization with HFSS. I found that if metal 1 ground shield is added into the simulation, both Q and the achieved inductance get worse, which doesn't seem reasonable to me. Does anyone know if I'm missing anything, or if there is any special setting needed to do this kind of simulation with HFSS? Thanks a lot.

Is it a patterned ground shield? If it is only a solid metal plane, the Q will surely go down due to the induced current.

in my opnion, the decreased Q is the result of increased parasitic capacitance.

Has anyone managed to simulate a spiral antenna below 30 MHz using HFSS?

I have the same problem. When I put a "Floating" patterned groud shield bellow the inductor, the Q value decreases. I'm using HFSS. What should I assign to PGS or where should I link it?

thanks

how to connect two layers of multilayer inductor in hfss?via?