Graded-Index-Fiber-Inspired 3-D Printed Surface Focusing Porous Dielectric Structure With GaAs MMIC Rectenna Toward Millimeter-Wave Wireless Power Transfer Application

Borrowing the idea of the graded-index (GRIN) fiber, we propose an all-dielectric porous structure with a unique surface focusing feature to improve the performance of the rectenna for millimeter-wave (mm-Wave) wireless power transfer (WPT) applications in this letter. The on- and off-axis focusing properties of the proposed structure are analyzed by the full-wave electromagnetic simulation. Moreover, benefitting from the low-cost 3-D printing technique, the designed GRIN structure prototype with different pore densities of the polylactic acid material is fabricated. The near-field phase transform experiment at 28 GHz was carried out to verify the excellent focusing performance of the fabricated structure prototype. Besides, the characteristics of multifocal spots on the surface of the proposed structure are further confirmed by the mm-Wave WPT experiments with a GaAs monolithic microwave integrated circuit rectenna using a
${\text{0.5}}\ \mu \mathrm{m}$
enhancement-mode pseudomorphic-HEMT gated anode diode, which reveals the great potential of the proposed structure for improving the applicability of the rectenna array in practical mm-Wave WPT applications by reducing its sensitivity to an incident angle of the transmitted beam.