For greatest efficiency and accuracy in measuring patterns of a circularly polarized antenna on a planar near field range (NFR), a recommended procedure is to use a fast switched, dual circularily polarized probe. With such equipment one obtains complete pattern and polarization data from a single scan of the antenna aperture. For our task of measuring high gain shaped beam apertures, measurement efficiency is further improved by using a moderately high gain (about 12 dBi) probe that has been accurately calibrated for patterns, polarization, and gain over the test frequency band. Such a probe allows scan data point spacing to be typically at least one wavelength, thus keeping scan time minimized with acceptably small aliasing (data spacing) error. The measured near field amplitude and phase data is transformed via computer to produce the angular spectrum that is further processed to remove the effect of the probe patterns, i.e. probe correction. The final output is a set of (principal and cross) circular-polarized far field patterns.
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