The high cost of high-resolution phase shifters required to maintain precise control over the array beam pattern in traditional phased arrays preclude their use in a variety of emerging millimeter-wave applications. We develop a phased array architecture that obviates the need for such precise phase shifters, based on the use of sub-half-wavelength array element spacing and novel spatial domain delta-sigma processing. We characterize the performance of this architecture in terms of the array signal-to-quantization-noise ratio (SQNR) and the array power transfer efficiency, and demonstrate a tradeoff between these two metrics. As an illustrative design, we show that when constrained to two-bit phase shifters, a four-fold increase in the array density can provide a roughly 6 dB improvement in SQNR over standard design techniques, with an average efficiency loss of less than 1.5 dB with respect to a perfectly tuned ideal array. In our analysis, we account for the effects of mutual coupling, and describe a simple, practical impedance matching network for this architecture. The resulting framework allows a system designer with a given set of circuit, device, and antenna fabrication and integration technologies to choose from a spectrum of tradeoffs between array density and RF component complexity.

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An efficient sparse antenna array architecture is developed for coherent imaging of sparse but otherwise unknown scenes. In this architecture, the array elements form a periodic nonuniform pattern. Using analysis that explicitly takes into account the presence of noise, we develop an efficient pattern design procedure based on co-arrays, describe an efficient scene support recovery algorithm as part of image reconstruction in the form of a modification to the MUSIC algorithm, and discuss a failure detection technique based on evaluating "back-projection" error. Since our development exploits a close connection to multi-coset sampling of bandlimited waveforms, our results may in turn may also be useful in the design of those systems.

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Abstract-We develop an efficient structured sparse antenna array architecture for coherent imaging of sparse but otherwise unknown scenes. In this architecture, the array elements are configured in a periodic nonuniform pattern that can be viewed as the superposition of multiple sparse uniform arrays. For this architecture, we develop an efficient pattern design procedure using co-array analysis. Moreover, we describe robust and efficient algorithms implementing the associated array processing needed for this architecture, which comprise scene support recovery, followed by image reconstruction. Finally, we develop a practical method for detecting reconstruction failures when the scene density exceeds the level for which the array was designed to accommodate, so that false images are not produced. Finally, as a demonstration of its viability, the architecture is used to reconstruct a simulated natural scene.Index Terms-Phased-array antennas, sparse arrays, compressed sensing, MUSIC algorithm, millimeter-wave imaging.