Noncooperative Sub-6GHz Reconfigurable Antenna DoA Estimation to Aid mmWave Analog Beamforming: Algorithm and Measurements

Envisioned analog beamforming, high-gain, phased antenna array systems operating at millimeter-wave (mmWave) frequencies require a fast beam selection process for practical implementation in mobile units in a changing propagation environment. This paper proposes a novel direction of arrival (DoA) estimation technique using a single RF chain reconfigurable Alford loop antenna at sub-6GHz frequencies to facilitate a rapid optimal beam selection process at mmWave frequencies. Measurement-based DoA estimation, demonstration of reduced beam scanning overhead at mmWave frequencies, and design of a software-defined-radio (SDR)-based testbed for evaluating the proposed integrated system are addressed.