Advances in phase retrieval antenna metrology

Near-field scanning is a widely employed measurement technique for the characterisation of microwave antennas and is most commonly used to produce accurate far-field pattern predictions. In addition, the technique also provides powerful diagnostic capabilities allowing detailed reconstruction of the aperture field to be made, from which surface profile and feed alignment information may be derived. Conventional near-field scanning techniques rely on the measurement of complex (phase and amplitude) data. However, at millimetre and sub-millimetre wavelengths accurate phase measurement is difficult and new phase retrieval strategies based on intensity only measurements become attractive. The authors examine phase retrieval techniques based on both planar and cylindrical geometries and present the results of measurements at 94 GHz