Diagnostics of an SSR array antenna from the measured near-field intensity using phase retrieval

A new possibility for array diagnostics is to apply the phase retrieval approach. It is now established that the aperture phase of a reflector antenna and its complex aperture field can be determined from scans of the radiated or received intensity patterns. It is envisaged that such a measurement procedure, which dispenses with the reference channel therefore removing the requirement for access to the antenna system under test, might be applied to operational antennas, for example, to diagnose the condition of a radar array in service. A phase retrieval algorithm to recover the discrete source distribution of array antennas has been formulated and applied to the diagnosis of a waveguide array by Lord et al. (see IEE Proc. H, vol.139, no.4, p.392, 1992). In the paper the algorithm is applied to scan cylindrical near-field data of a Marconi secondary surveillance radar (SSR) antenna