Investigation of complex excitation errors at single element and sub-array level in large array antennas by inverse source technique

This paper describes the practical application of the inverse-source or source-reconstruction technique as a detailed antenna diagnostic tool [1-5]. The investigated antenna is intended as part of the European Navigation System GALILEO and is a pre-development model flying on the InOrbit Validation Element, GIOVE-B satellite. The array antenna, developed by EADS-CASA Espacio, consists of 42 patch elements, divided into six sectors and is fed by a two level beam forming network (BFN). The BFN provide complex excitation coefficients of each array element to obtain the desired iso-flux shaped beam pattern [8]. The inverse-source technique has been applied to identify the realized excitation law at sub-array level to identify possible errors. The measurements have been performed in the new hybrid (Near Field and Compact Range) facility in the ESTEC CPTR as part of the installation and validation procedure [7]. The investigation has been performed without any prior information of the array and intended excitation. The input data for the analysis is the measured spherical NF data and the array topology and reference coordinate system.