How to set the impedance for the lumped port in HFSS

Hi

I am working on a patch antenna. The input impedance of the chip is 34-j810. I am simulating the antenna by HFSS. When I set the impedance of the lumped port, I found that the initial setting affects the result a lot. So what is the value I should put into? Is 34-j810 (source impedance) or 34+j810 (conjugate matching impedance)? Please help.

Thanks.