Electronically Steered Arrays

Abstract

This chapter discusses electronically steered arrays (ESAs), also commonly called phased arrays. These antennas have beams that can be electronically steered in pointing direction or beam shape, without mechanical motion, and accomplished in microseconds. Although the operation of all arrays depends on the proper phasing of the individual array elements, the terms ESA and phased array have by usage come to mean an array in which the beam is steered in direction and shape by varying the phasing of the elements. Present day ESA (or phased array) technology includes adaptive beam forming (ABF), which merges rapid beam pointing and shaping with digital signal processing separately. With ABF arrays, the phasing and time delaying of the signals from individual elements are jointly adaptively adjusted and then summed to rapidly beam point, beam shape, and Doppler filter desired received signals. In this way, the received signal output, from the summed individual array signals, may be optimized, simultaneously, for both the strength of the desired signal relative to thermal noise and relative to interference from undesired signals.