In a scatter-case simulation, an object is illuminated by a plane wave. The far field is computed by transforming the near field of total E field (scattered field + incident field) into far field (I believe, please correct me if I'm wrong). How can I obtain the far field of the scattered field ONLY?

(Here by "near field", I mean the E field inside the boundary box.)

One way I can think of is to compute the near field of scattered field at first (by subtracting incident E field from total E field). But CST Studio Suite ​​​​​​​ doesn't offer the option to compute far field from near field.

Does anyone have a solution? Many thanks!