Flexible phased arrays potentially enable diverse applications not permitted by rigid systems; however, they introduce ambiguity in antenna element positions. If this position ambiguity can be overcome, flexible arrays can perform the full suite of array functions: beam steering, wavefront engineering, and beam focusing. Furthermore, shape reconstructions of arrays can be used for applications beyond beamforming. We propose a framework to reconstruct the shape of a flexible array that only uses mutual coupling measurements and does not require additional sensors or functionalities in the system. We discuss the approach, a two-step algorithm, which is highly modular and can be implemented in a variety of phased array systems. To demonstrate the accuracy of the approach, we present results from two passive 2.5-GHz phased array setups using dipole and patch antennas, as well as a 10-GHz (active) integrated circuit flexible phased array, and demonstrate the accuracy of the approach in this system. In all cases, the algorithm reconstructs the antenna shape accurately, with average position errors of approximately 6% of the wavelength. This article can serve as the beginning of the broad study of shape reconstruction algorithms and their applications.
We present a ray-tracing analysis of a smart motion detector based on a dynamically reconfigurable metasurface antenna (DMA). A DMA consists of an array of metamaterial radiators excited by a single-port waveguide or cavity. By incorporating simple switchable components into each element and addressing them individually, DMAs can generate a myriad of spatially distinct radiation patterns and alter them as a function of an applied voltage. These patterns have the potential to probe all regions of a room or set of rooms and detect motion, even when operating over an extremely narrow bandwidth. Through the acquisition of time-resolved measurements, the DMA sensor can retrieve temporal signatures and distinguish between different sources of movements. We investigate this sensing paradigm using a ray tracing simulation. We first replicate the trends obtained from recent experiments using our simulation platform to ensure that numerical ray tracing generates data that is a faithful representation of the reallife physics. We then demonstrate that temporal signals obtained in this manner carry information about the nature of the movement. Specifically, by using power spectra and filtering, we are able to extract features that correspond to specific motion patterns. These results constitute the first step toward incorporating DMAs into a smart sensor equipped with learning algorithms that can distinguish between human and non-human motion with high fidelity.INDEX TERMS Ray tracing, antenna radiation patterns, cavity resonators, radio frequency (RF), sensors, antenna arrays.
We demonstrate that dynamic metasurface apertures (DMAs) are capable of generating a multitude of highly uncorrelated speckle patterns in a typical residential environment at a single frequency. We use a DMA implemented as an electrically-large cavity excited by a single port and loaded with many individually-addressable tunable metamaterial radiators. We placed such a DMA in one corner of a plywood-walled L-shape room transmitting microwave signals at 19 GHz as we changed the tuning states of the metamaterial radiators. In another corner, in the non-line-of-sight of the DMA, we conducted a scan of the field generated by the DMA. For comparison, we also performed a similar test where the DMA was replaced by a simple dipole antenna with fixed pattern but generating a signal that spanned 19 − 24 GHz. Using singular value decomposition of the scanned data, we demonstrate that the DMA can generate a multitude of highly uncorrelated speckle patterns at a single frequency. In contrast, a dipole antenna with a fixed pattern can only generate such a highly uncorrelated set of patterns when operating over a large bandwidth. The experimental results of this paper suggest that DMAs can be used to capture a diversity of information at a single frequency which can be used for single frequency computational imaging systems, NLOS motion detection, gesture recognition systems, and more. INDEX TERMS Antenna radiation patterns, radio frequency, sensors, antenna arrays, metamaterials.
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