Conformal high-efficiency ultra-thin flexible rectifying metasurface with a simple structure

This paper proposes a conformal high-efficiency ultra-thin flexible rectifying metasurface (RMS) with a simple structure applied for wireless power transferring (WPT), featuring polarization insensitivity and wide-angle incidence capabilities. The RMS unit adopts a rotationally symmetric structure consisting of double rings and cross-shaped elements, with two diodes placed in the gap of the cross-shaped to achieve polarization insensitivity. Simultaneously, by adjusting the dimensions of the "double ring and cross" structure, its output impedance is varied to achieve conjugate matching with the diode input impedance, thereby eliminating the impedance matching network. Furthermore, a diode and an inductor are series-connected at the ends of one horizontal branch and one vertical branch of each unit's cross-shaped structure to enable interconnection between the RMS units and to form a direct current (DC) pathway. Simplifying the power combining network and reducing the complexity of the RMS system structure. The RMS of 6 × 6 units was designed and fabricated using a 0.6 mm flexible polyimide substrate, with overall dimensions of 114.6mm × 114.6 mm. Measurement results demonstrate that at 5.8 GHz, the proposed RMS achieves a system efficiency exceeding 66.26% under different polarizations. System efficiency exceeds 50.42% over an incident angle range of 0° to 30° and reaches 68.18% at an incident power density of 0.796 mW/cm². Even with a conformal cylindrical radius of 100 mm, system efficiency remains above 35.44%.