Reconstruction of radiating sources.
Thesis DisciplineElectrical Engineering
Degree GrantorUniversity of Canterbury
Degree NameDoctor of Philosophy
The problem of obtaining phase information when radiating source distributions are reconstructed by Fourier transforming their measured radiated field patterns is examined. The two cases examined in detail are those of determining an antenna aperture distribution from its far-field radiation pattern and of reconstruction an astronomical brightness temperature distribution from data obtained using an interferometer. New techniques are presented which allow the aperture distribution of an antenna to be reconstructed from only the modules of a far-field radiation pattern. The techniques, which are based on the principle of holography, are described theoretically and are shown to be practical using the results of experiments performed with acoustic antennas. The methods are also shown to be applicable in the near-field of an antenna. Using the concept of the complex zeros of an interferogram, it is shown how phase errors can be identified in the data obtained from astronomical interferometers. In those cases in which the measure intensity is more accurate than the measured phase (it is shown how to process the measured date to determine this) it is shown how to compute an improved phase from the measured intensity. The problem of reconstructing brightness-temperature distributions from intensity only interferometer measurements is also discussed. The results obtained by processing actual measured data using the new techniques demonstrates their usefulness.