A Bandwidth-Enhanced Metasurface-Based RF Energy Harvester With Wide-Angle Reception

This article presents an efficiency enhancement strategy for the bandwidth-enhanced metasurface-based harvester operating at wide incidence angles. A current-constrained strategy, combined with a bandwidth-enhancement scheme, is first employed to achieve a high harvesting efficiency over a wide frequency range. Subsequently, by adjusting the positions of through-vias in adjacent metasurface units, the effective coupling at large incidence angles is enhanced, and the collected energy is driven toward the output ports. As a result, the harvesting efficiency at large angles is significantly improved, thus enabling wide incidence angle reception. To validate the proposed strategy, a bandwidth-enhanced metasurface with different through-via positions and a DC combining network consisting of$2\times 2$rectifiers has been designed, fabricated, and measured. At normal incidence and an incident power density of$16.4~\mu $W/cm2, the measured total harvesting efficiency (RF–DC) remains above 27.2% (TE) and 26.6% (TM) at 3.425–3.7 GHz, corresponding to a relative bandwidth (RBW) of 7.72%. At the maximum incidence angle of 75°, the peak total efficiency reaches 19.9% under TE polarization and 24.5% under TM polarization. The proposed harvester has high efficiency, bandwidth enhancement, and wide incidence angle reception characteristics, which are expected to provide supplementary power to wireless sensing nodes in the complex electromagnetic (EM) environment.