Wireless power transfer (WPT) has been an active topic of research, with anumber of WPT schemes implemented in the near-field (coupling) and far-field(radiation) regimes. Here, we consider a beamed WPT scheme based on adynamically reconfigurable source aperture transferring power to receivingdevices within the Fresnel (near-zone) region. In this context, the dynamicaperture resembles a reconfigurable lens capable of focusing power to awell-defined spot, whose dimension can be related to a point spread function(PSF). Near-zone focusing can be achieved by generating different amplitude orphase profiles over the aperture, which can be realized using traditionalarchitectures, such as phased arrays. Alternatively, metasurface guided-waveapertures can achieve dynamic focusing, with potentially lower costimplementations. We present an initial tradeoff analysis of the near-zone WPTconcept, relating key parameters such as spot size, aperture size, wavelength,focal distance, and availability of sources. We find that approximate designformulas derived from the Gaussian optics approximation provide usefulestimates of system performance, including transfer efficiency and coveragevolume. The accuracy of these formulas is confirmed using numericalcalculations.
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