A 1-to-2.5GHz phased-array IC based on gm-RC all-pass time-delay cells

Abstract

Electronically variable delays for beamforming are generally realized by phase shifters. Although a constant phase shift can approximate a time delay in a limited frequency band, this does not hold for larger arrays that scan over wide angles and have a large instantaneous bandwidth. In this case true time delays are wanted to avoid effects such as beam-squinting. In this paper we aim at compactly integrating a delay based phased-array receiver in standard CMOS IC technology. This is for instance relevant for synthetic aperture radars, which require large instantaneous bandwidths often in excess of 1GHz, either as RF or as IF bandwidth in a superheterodyne system. We target low-GHz radar frequencies, assuming sub-arrays of four elements and up to 550ps delay.