It means that your cap's resonance frequency is lower than your working frequency and caps begin to behavior like inductors.
Hi yanfeng, thanks for your reply.
From picture in attach to my previous question (about negative C lumped model in Hyperlynx 3d EM) I connect two finite
ground plane with vias. There is an alternative method to tell the simulator that I have two finite ground layers without use vias?
As showed in the User's Manual, to have a finite ground layer, in basic parameters
I changed No. 0 G (infinite perfect ground) substrate layer to dielectric layer.