internal coplanar wave guide in HFSS

hello

I'm looking for an example of a design of an internal CPW in a PCB with HFSS, my problem is that I calculated the dimensions of my CPW using Appcad but after simulation I don't get my impedance of 50 Ohms knowing that there is no errors in dimensions calculations


help plz, I noticed that when I add perfect E boundary to my metal conductor (copper) I get an impedance of 43 Ohms, is that the solution?

help , I 'm beginner in HFSS


many thanks