HFSS is a FINITE element method. I.e. there is a space segmentation. It naturally leads to missing the target. The original feature of HFSS is adaptive meshing algorithm, which iteratively finds important areas for denser meshing, bringing you closer to truth, without requiring a supercomputer cluster and terabytes of RAM.nI would say, your plots are almost equal to your theoretical computation. The fit is really good in important areas. You would not get better in experiment. nYou can get better result with denser meshing.nBut the power of HFSS is in solving arbitrary geometry with arbitrary properties, which no analytic method can solve. nSo you are just too picky to unimportant details, missing the main thing.n