Put a capacitance in parallel with tag in hfss

I m simulating a antenna, and in my model I need put a capacitance in parallel with chip, for this I use a lumped port to excite the circuit and put one a lumped rlc in parallel with this.
I use to calculate a Z11 the simple formula.
The problem is that with this lumped port move my ressonance frequency to right, 50MHz more less of the real measure
Anybody knows how I can correct this?
thanks

Do you insert DC block ?

I didn insert dc block, I put one rlc port and set a value of the capacitance

Show me schematic or netlist.

I tried put de file ".aedt", but was impossible, and how I can send for you or generate netlist?

the folder