Multiobjective Distributed Beamforming Using High-Accuracy Synchronization and Localization

Abstract

We present a multinode, multiobjective open-loop microwave distributed beamforming system based on high-accuracy wireless synchronization and localization. Distributed beamforming requires accurate coordination of the spatial and electrical states of the individual elements within the array to achieve and maintain coherent beamforming at intended destinations. Of the basic coordination aspects, time synchronization and localization of the elements are among the most critical to support beamforming of modulated waveforms to destinations in both the near-field and far-field relative to the array. In this work, we demonstrate multiobjective distributed beamforming from a three-node software-defined radio distributed phased array system that leverages high-accuracy wireless time coordination for both time synchronization and 2-D localization of the elements. We use a spectrally sparse two-tone waveform for high-accuracy internode range estimation combined with a linear frequency-modulated waveform to mitigate multipath interference. Localization is performed in a centralized format, where one node is designated as the origin and the remaining nodes build the array geometry relative to the origin, from which we obtain localization accuracy of less than 1 cm. We implement a near-field multiobjective beamformer based on the location estimates, which enables simultaneous steering of a beam and a null to two receiving antennas. Multiobjective beamforming of pulsed waveforms at a carrier frequency of 2.1GHz is demonstrated in cases where one of the nodes in the distributed antenna array is moved, and where the targets (the two receiving antennas) are moved, demonstrating multiobjective with steerable beamforming and displacement of the array elements.