Angle-of-Arrival Detection in Series-Fed Modular Hybrid Beamforming Arrays Exploiting the Analogy Between Frequency and Spatial Responses

Phased arrays in wireless systems typically use corporate-fed architectures and estimate the direction of incoming signals by scanning beams with controllable phase shifters. While this is adequate for communications within the -3 dB beamwidth of a single signal, multiuser systems, as well as sensing and localization applications, benefit from finer steering resolutions. In wideband systems, the beam squint phenomenon enables simultaneous observations of nearby directions within a single look and can be exploited to improve the angle-of-arrival (AoA) estimation. However, while conventional corporate-fed arrays exhibit a limited beam squint, asymmetrical routed ones can instead amplify this effect significantly, thus enabling the observation of multiple directions while still supporting a reliable communication, when properly designed. This article presents a method that exploits the analogy between the frequency response and the beam pattern of asymmetrically routed arrays to estimate the AoA from the measured spectrum, using a single look. An analytical solution is derived that relates the steering error, and thus the AoA, to the shape of the frequency response. The method is validated through simulations and over-the-air (OTA) experiments using a 27 GHz, 12-element modular phased-array transceiver. The system comprises three 2× 2 subarrays, each driven by an individual RFIC and interconnected through an asymmetric series-fed routing on the PCB. Experimental results demonstrate a steering-error estimation accuracy of 0.3°-5° over a 20° beamwidth using a single observation. This enables real-time steering-error tracking without beam rescanning, making the approach highly relevant for future communication and sensing systems. © 1963-2012 IEEE.