Physically Large Apertures for Wireless Power Transfer: Performance and Regulatory Aspects

Benjamin J. B. Deutschmann; Ulrich Muehlmann; Ahmet Kaplan; Gilles Callebaut; Thomas Wilding; Bert Cox; Liesbet Van der Perre; Fredrik Tufvesson; Erik G. Larsson; Klaus Witrisal

doi:10.1109/mwc.2025.3636246

arXiv · 2503.06807

Physically Large Apertures for Wireless Power Transfer: Performance and Regulatory Aspects

Benjamin J. B. Deutschmann·Ulrich Muehlmann·Ahmet Kaplan·Gilles Callebaut·Thomas Wilding·Bert Cox·Liesbet Van der Perre·Fredrik Tufvesson·Erik G. Larsson·Klaus Witrisal

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Abstract

Wireless power transfer (WPT) is a promising service for the Internet of Things, providing a cost-effective and sustainable solution to deploy so-called energy-neutral devices on a massive scale. The power received at the device side from a conventional transmit antenna with a physically small aperture decays rapidly with the distance. New opportunities arise from the transition from conventional far-field beamforming to near-field beam focusing. We argue that a physically large aperture, i.e., large with respect to the distance to the receiver, enables a power budget that remains practically independent of distance. Distance-dependent array gain patterns allow focusing the power density maximum precisely at the device location, while reducing the power density near the infrastructure. Physical aperture size is a key resource in enabling efficient yet regulatory-compliant WPT. We use real-world measurements to demonstrate that a regulatory-compliant system operating at sub-10GHz frequencies can increase the power received at the device into the milliwatt range. Our empirical demonstration shows that power-optimal near-field beam focusing inherently exploits multipath propagation, yielding both increased WPT efficiency and improved human exposure safety.

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BibTeX RIS

Benjamin J. B. Deutschmann, Ulrich Muehlmann, Ahmet Kaplan, Gilles Callebaut, Thomas Wilding, Bert Cox, Liesbet Van der Perre, Fredrik Tufvesson, Erik G. Larsson, Klaus Witrisal. 2025-03-09. Physically Large Apertures for Wireless Power Transfer: Performance and Regulatory Aspects. https://doi.org/10.1109/mwc.2025.3636246

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