  We present a multi-node, multi-objective 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 of the array. In
this work, we demonstrate multi-objective distributed beamforming from a
three-node distributed phased array consisting of software-defined radios that
leverages high-accuracy wireless time coordination for both time
synchronization and two-dimensional localization of the elements. We use a
spectrally-sparse two-tone waveform for high-accuracy inter-node 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 multi-objective
beamformer based on the location estimates, which enables the simultaneous
steering of a beam and a null to two receiving antennas. Multi-objective
beamforming of pulsed waveforms at a carrier frequency of 2.1 GHz 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.
