Full-wave analysis of the GALILEO System Navigation Antenna by means of the generalized scattering matrix of a finite array

A full-wave methodology has been used to analyse the GALILEO system navigation antenna for the space segment of the global positioning system. It is a multilayer array structure composed by cavity-backed microstrip patches in stacked configuration, and coaxial probe feeding. It follows a hexagonal regular lattice that makes possible to perform a modular analysis in two steps. First, each isolated array element is modeled considering a finite hexagonal metallic flange. A generalized scattering matrix (GSM) of each element is obtained in terms of coax and spherical modal expansions from a hybrid 3-D finite elements-modal analysis method (SFELP). Next, the GSM´s of the array elements are analytically connected by using properties of rotation and translation of spherical modes to obtain the overall GSM of the array. This matrix provides the impedance, coupling and radiating characteristics of the array on a finite ground plane. Radiation patterns of the isolated element and the array have been obtained and compared with measurements.