Reduction of truncation errors in planar near-field aperture antenna measurements using the method of alternating orthogonal projections

A simple and effective procedure for the reduction of truncation error in planar near-field to far-field transformations is presented. The starting point is the consideration that the actual scan plane truncation implies a reliability of the reconstructed plane wave spectrum of the field radiated by the antenna only within a certain region inside the visible range. Then, the truncation error is reduced by a Maxwellian continuation of the reliable portion of the spectrum: after back propagating the measured field to the antenna plane, a condition of spatial concentration of the primary field is exploited to define a convergent iterative process which is also stable against moderately noisy data. Far-field patterns reconstructed from both simulated and measured near-field data demonstrate the effectiveness of the proposed procedure.