Open-Loop Distributed Beamforming Using Scalable High Accuracy Localization

TL;DR

This paper demonstrates open-loop distributed beamforming at 1.5 GHz using high-accuracy localization to precisely control phase alignment among multiple nodes without feedback, enabling dynamic beamforming as nodes move.

Contribution

It introduces a scalable high-accuracy ranging waveform and methods that enable open-loop beamforming with multiple nodes at microwave frequencies, without relying on feedback.

Findings

Achieved open-loop beamforming at 1.5 GHz with three nodes.

Demonstrated dynamic phase correction for moving nodes.

Showed high-accuracy ranging with centimeter-level precision.

Abstract

We present a distributed antenna array supporting open-loop distributed beamforming at 1.5 GHz. Based on a scalable, high-accuracy internode ranging technique, we demonstrate open-loop beamforming experiments using three transmitting nodes. To support distributed beamforming without feedback from the destination, the relative positions of the nodes in the distributed array must be known with accuracies below $\lambda/15$ of the beamforming carrier frequency to ensure that the array maintains at least 90\% coherent beamforming gain at the receive location. For operations in the microwave range, this leads to range estimation accuracies of centimeters or lower. We present a scalable, high-accuracy waveform and new approaches to refine range measurements to significantly improve the estimation accuracy. Using this waveform with a three-node array, we demonstrate high-accuracy ranging simultaneously between multiple nodes, from which phase corrections on two secondary nodes are implemented to maintain beamforming with the primary node, thereby supporting open-loop distributed beamforming. Upon movement of the nodes, the range estimation is used to dynamically update the phase correction, maintaining beamforming as the nodes move. We show the first open-loop distributed beamforming at 1.5 GHz with two-node and three-node arrays, demonstrating the ability to implement and maintain phase-based beamforming without feedback from the destination.