I need to know the mean of set a value of solution frequency in setup dialog box in HFSS, for example I solve my antenna and setup the solution frequency at 2.45GHz and I get that the resonance occurs at 2GHZ with input impedance 68 ohm, then I change the solution frequency to 2GHz to get more result but when I solve it again, the input impedance has changed to 19 ohm at 2GHz instead of 68ohm, can you please help me in this regards.