Simulation accuracy in HFSS

Ansoft HFSS Antenna Design kit creates HFSS model of rectangular patch antenna with edge feed at 2.45GHz. In that model I set narrower frequency sweep, add additional analysis with more adaptive passes, adjust Return loss raport to see booth analysis results.

It is normal, that return loss resonances are at different frequencies? S11 graph is attached, red line - original analysis, magenta line - analysis with 30 adaptive passes.

what is your problem exactly?
HFSS is a software based on the Finite Element Method (FEM) in the frequency domain.
changing the number of the tetrahedrons can be affected on the numerical results that obtained from the HFSS.
so your analysis with 30 adaptive passes can be slightly changed from the the first analysis.
one method to check the numerical results is increasing the number of meshes and tracking the results. the final results should be similar to themselves.

HR Karami