An extremely ultrathin flexible Huygens's transformer

Abstract

The current study aims to present the physical perception of a meta-surface energy harvester's (MEH's) design based on space-time physics of a traveling wave. Regarding the relation between the wave-velocity and field-impedance, the balance condition in Huygens's meta-atoms is provided. Accordingly, it was demonstrated that MEH behaves as a transformer at far-field. It was observed that the location of the metallic-via is mimicked by the number of loop coils in the secondary of the transformer in the unit-cell. In addition, the impedance matching between the wave impedance in a lossless medium and MEH's load was to be tuned by adjusting the size parameters of the unit-cell at a desired resonance frequency. For this purpose, the present study developed a simple design framework to achieve the resonance frequency at a more optimum pace based on surrogate modeling. The theoretical analyses are validated by the results of full-wave and circuit simulations. Finally, a recently developed flexible MEH was further extended to a multi-polarization structure using more compact cells. The fabricated flexible MEH has 10 × 10 number of deep subwavelength thick cells (≈0.004λ0), while traditional MEH was basically designed only to fit on the planar surface. The new design paves the way for the multi-polarized MEH to wrap around the cylindrical surface as a 2D-isotropic MEH. The results of the data analyses show that the simulation and experimental results enjoy an acceptable agreement.