Flexible Meta-Patch Rectenna Array for Energizing Low-Power Wearable Medical Sensors

Abstract

This article presents a low-cost $2\times 2$ metasurface-based rectenna array operating at the 2.45 GHz industrial, scientific, and medical (ISM) band, designed to power low-power wearable medical sensors (WMS). The proposed antenna is a novel textile-based metasurface interlayer patch (meta-patch) antenna fabricated on a felt fabric substrate, which replaces the conventional ground plane with a grounded metasurface consisting of a $3\times 3$ unit cell array. A single excitation port is used for both the patch antenna and the metasurface to improve gain, efficiency, and bandwidth. The meta-patch antenna achieved a high gain of 7 dB, an efficiency of 77%, and an enhanced bandwidth of 120 MHz. The rectifier employs a seven-stage Cockcroft-Walton Voltage Multiplier (CWVM) topology, fabricated on a rigid substrate. To evaluate the performance of the meta-patch rectenna array and the effect of adding more elements, the proposed meta-patch rectenna was tested in single-element, $2\times 1$ array, and $2\times 2$ array configurations under continuous RF power. The single-element, $2\times 1$ rectenna array, and $2\times 2$ rectenna array achieved power conversion efficiencies (PCE) of 52%, 53%, and 56%, with DC output powers of $414~\mu $ W, $429~\mu $ W, and $450~\mu $ W, respectively, at an input power of -1 dBm. The results demonstrate the potential of the proposed rectenna arrays for efficiently energizing low-power WMS.

Keywords

• Cockcroft-Walton rectifier
• meta-patch rectenna array
• meta-patch textile antenna
• metasurface-based antenna
• RF energy harvesting
• seven-stage rectifier