Phaseless metrology of earth station antennas from satellite borne sources

Holographic antenna metrology has been proved successful for diagnosing parabolic reflector antennas, in particular large earth station reflectors. Inversion of the complex far-field data by Fourier transformation can reveal surface imperfections, feed misalignments, and other phase error terms. We address the problem of direct far-field measurements in which the data is essentially the Fourier modulus. If the aperture amplitude could be measured, then the Gerchberg and Saxton (1972) algorithm could be applied directly. The problem is therefore to find an acceptable aperture estimate and measurement conditions from which a modified algorithm will deliver the phase. A convenient far-field source is a geostationary satellite, which could be a direct broadcasting satellite. Antennas have already successfully been diagnosed using a geostationary source by holographic techniques or more recently using the Misell algorithm. Our ultimate objective is to demonstrate aperture phase recovery using a single intensity data scan from a satellite source. We report our progress with simulated data and far field data obtained via cylindrical near field measurements