Conditions for Near-Field Phase Retrieval Measurements of Reflector Antennas in the MM and Sub-MM Wave Ranges

The performance of a double-intensity near-field phase retrieval algorithm is investigated. In addition to previously noted advantages of phase retrieval, it is shown from computer simulation that the accuracy of far-field prediction of a reflector antenna by the algorithm may be better than the conventional near-field measurement when the probe is scanned on a non-perfect planar surface. The concept of 'phase encoding power' is introduced from which the scan distances for the algorithm to converge satisfactorily are derived by simulation. Near-field phase retrieval is validated by measurement of an offset reflector at 32GHz. The result illustrates the practicability and capability for application in the mm and sub-mm wave ranges.