Performance study of an ultra wideband multifunction phased array

Abstract

This paper proposes and evaluates an advanced ultra wideband multifunction phased array. Ultra wideband phased arrays have to make use of true time delay into an array of phase shifters, in order to avoid strong limitations in the system field of view[1]. The methodology applied relies on a mixed beamforming technique, based on true time delay behind each subarray and phase shifters down to the T/R module level. True time delay can be implemented by using analog switched delay lines, optical fiber delays or digital filters. Whichever technology is considered, the use of a mixed beamforming methodology introduces signal distortion and antenna pattern corruption. Therefore, suitable array tapering is necessary, in order to reshape the antenna pattern. The performance study focuses on an ultra wideband phased array (2-18 GHz), with the goal to show pattern degradation, sidelobe level and grating lobe level in a typical implementation and to study how to improve the ultra wideband array figures.