Ansys Employee

The Scatter or noise might be due to improper excitations. 
here is possible solution, Please refer HFSS PDF in the help menu.

You can instruct the solvers to reduce the maximum size of tetrahedral elements on a surface or within a volume, until they are below a certain value (length-based mesh refinement) or you can instruct solvers to refine the surface triangle length of all tetrahedral elements on a surface orvolume to within a specified value (skin depth-based mesh refinement). These types of mesh operations are performed on the current mesh, that is, the most recently generated mesh.In a few circumstances, you may also want to create a mesh operation that modifies a solver's surface approximation settings for one or more faces. Surface approximation settings are only applied to the initial mesh, that is, the mesh that is generated the first time a design variation is