Analysis of resolution for an amplitude steered array

In 1976, Hughes and Thompson introduced the amplitude-steered array, which steered the maximum response of the linear array by amplitude weighting the output signals of the elements, thus eliminating the need for time delays or phase-shift networks. Currently that amplitude-steered array concept is being extended to a broadband two-dimensional array which can be used for real-time three-dimensional imaging. In shifting the use of the amplitude-steered array from underwater acoustic communications to imaging, one must consider different issues of the array's performance such as lateral and axial resolution. The authors show that both lateral and axial resolution are limited by the length of the array. The dependence of axial resolution on the length of the array is a unique feature of the amplitude-steered array, leading to an interesting tradeoff between lateral and axial resolution. The authors develop a theoretical basis for the dependence and give simulation results.