difference in electric field pattern obtained in ie3d and hfss

hi
i,ve designed a pifa antenna and simulated it with both ie3d and hfss, gain, s parameters, impedance and directivity are the same but electric field pattern are not!,
i know this is caused by difference in method of MOM and FEM but how can i scale voltage source in IE3D or power source in HFSS to get the same electric field pattern
regards.

is this question so hard or so easy !!!!