Optimized Beam Steering Approach for Improved Sidelobes in Phased Array Radars Using a Minimal Number of Control Bits

Abstract

As active electronically steerable arrays become more prominent, a new paradigm of assigning bits to a set of digital phase shifters, necessary for analog and digital beamforming, is proposed. It is well known that a modern day digital phase shifter which is associated with each transmit/receive module typically relies on three to seven bits. Each of these phase shifters provide a desired resolution of 45° to 2.8125°, respectively. When an array is steered with a fixed precision set of phase shifters, there are some angles where results are significantly better than others. For example, six bit phase shifters can provide exact 11.25° differential phases in a linear array, but not 15°, and subsequent quantization errors lead to reduced pointing accuracy and increased sidelobe levels. However, these errors can be minimized if the set of shifters operate collectively instead of independently with “blind” quantization. In particular this study seeks the solution for the following problem: for a set of N phase shifters, each defined by B bits, determine the optimal way to distribute the N×B bits so that the array performance is maximized.