Phase retrieval in the radio holography of reflector antennas and radio telescopes

Abstract
Methods of phase retrieval from simulated intensity information have been tested for use in the radio holography of reflector antennas. In numerical simulations the Misell algorithm has been used successfully to retrieve the aperture phase distribution from two numerically simulated power polar diagrams, one in focus and the second defocused. The technique uses no auxilliary reference antenna. However, it does need a high signal to noise ratio, typically 50 dB if a60 \times 60array is to be measured to a precision such that the gain is within 1 percent of ideal. It should be most useful where no direct phase measurements are possible and ground-based or satellite transmitters can be used as sources. The use of astronomical maser sources (22 GHz) can give information on large scale deformations.