What's the definition of rE in the Far-Field in HFSS?

Hi, everyone. I have a question about the far-field simulation in HFSS.

What's the definition of rE in the Far-Field in HFSS? Is it corresponding to the 1 Amp current source? or is it related to the feeding impedance?

Thanks.

it is related to feeding impedance (normalised w.r.t. it)