SWIPT Module for Battery-Less Ultra-Low-Power Sensor Nodes

This letter proposes a simultaneous wireless information and power transfer (SWIPT) module capable of operating a battery-less ultra-low-power wireless sensor node (WSN). This module features a miniaturized circular patch antenna that utilizes a proximity-coupled feed to enable wireless information transfer (WIT) in the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\text{5}$</tex-math></inline-formula> GHz WiFi band (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\text{5.15}$</tex-math></inline-formula>–<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\text{5.825}$</tex-math></inline-formula> GHz). The WIT operation can be powered through wireless power transfer (WPT) to the proposed module using a capacitive coupled feed. The WPT is realized using a dedicated RF shower, which transmits RF energy in the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${4.9}$</tex-math></inline-formula>–<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\text{5.1}$</tex-math></inline-formula> GHz band. The different frequency bands are chosen for WIT and WPT to reduce the mutual coupling effect. Moreover, the use of orthogonal-polarized feeds for WIT and WPT further enhances the isolation between information and power signals. The design incorporates two conjugate matched shunt Schottky diodes, a stepped impedance low-pass filter, and a parallel dc combining network for full-wave rectification (FWR) of the incident RF waves. Therefore, the proposed module ensures high power conversion efficiency (PCE) with a smaller footprint making it an ideal candidate for implementing battery-less WSN operation for Internet-of-Things (IoT) applications.