Excitation Coefficient Determination for an Antenna Elevation Network Using Installed Performance Radiation Measurements

Abstract

Phased array antennas are typically designed from a set of largely similar radiating elements that are fed by a beam forming network (BFN). The ambient structure thereby impacts the installed performance and needs to be considered in the excitation coefficients determination. However, obtaining reliable results with purely numerical tools for aerospace composite material structures is questionable without electromagnetic parameter investigation. This work describes a method based on individual far-field measurements of the radiating sub-arrays in a Compact Antenna Test Range (CATR). The full array pattern is synthesized by planar near -field (PNF) techniques. Thereby, the excitation coefficients are optimized to mitigate the actual structure influence without the need for additional electromagnetic material properties investigation. The procedure is exemplified with a linear polarized Ka-band phased array for an airborne synthetic aperture radar application. Individual on structure slotted waveguide antenna (SWA) element measurements, excitation coefficients determination and the synthesized radiation pattern are shown. In a proof of concept with structures that are assumed perfectly conductive, measurementbased processing results are compared with simulations.