Differences between modal expansion and integral equation methods for planar near-field to far-field transformation (Summary)

The objective of this paper is to present the classical modal expansion and the recently developed integral equation approach for performing a planar near-field to far- field transformation. It is shown that if the measurement plane is an infinite plane both the methods yield the same answer, however when the measurement plane is finite the truncation error for the integral equation approach is much less than that for the modal expansion. However, computationally the modal expansion is much faster. Examples are presented to illustrate each technique.