Full Hemisphere Aperture-Antenna Far-Field Patterns From Planar Near-Field Measurements

A simple geometrical estimate resulting from rigorous asymptotic evaluation of the Fourier transform integral leads one to conclude that the angular range of the far-field obtainable using planar near-field measurement techniques is limited by the extent of the scan plane and the separation of this plane from the antenna under test. Here, it is shown that this angular range can be extended to a full hemisphere through proper selection of the measurement parameters and careful treatment of the transform integral. In particular, it is noted that the transverse spectrum of the field can possess singularities. These singularities are spectrally filtered by the finite size of the scan plane resulting in a muting effect that must be accounted for in the data processing. This is accomplished through the analytic approximation of the bandlimited singularities. Three hardware examples are shown that demonstrate this more detailed approach comparing the results with corresponding patterns obtained using spherical near-field measurement.