Diagnosis of antenna-arrays using near-field antenna measurements and a priori information

Nowadays antenna measurements are often carried out by exploiting the benefits of near-field transformation techniques. However, as spherical near-field measurements are very time consuming it is desirable to use the near-field data being measured in order to determine an antenna's far-field characteristic also for diagnostic purposes, especially if the far-field characteristic differs from the expected one. This paper explains how to gain diagnostic information from measured near-field data. For this purpose, the standard microwave holography as well as the limits of its spatial resolution are discussed. Following this a new equivalent-source method is introduced allowing the reconstruction of electromagnetic near-fields with enhanced resolution as compared to the holographic approach. The quality of the reconstructed near-field data will be significantly enhanced when applying the proposed diagnostic algorithm.