A Compact Self-Powered WSN Enabled by Miniaturized 3-D Wideband Rectenna

Ambient radio frequency (RF) energy harvesting offers an innovative solution for powering low-power wireless sensor nodes (WSNs). Existing RF self-powered WSNs face a critical trade-off between frequency coverage, power conversion efficiency (PCE), and structural simplicity, which constrains their practical deployment in IoT scenarios. This paper proposes a broadband RF self-powered WSN within 30x60x45 mm3, achieved through a 4-layer 3D synergistic design that integrates the antenna, rectifier, and load circuits. A miniaturized 3D wideband rectenna featuring a semi-circular radiating patch and a three-section transmission line (TL) impedance matching network (IMN) based on conjugate-complex matching is designed to capture RF energy across the 1.8–2.8 GHz band. The rectifier achieves an overall PCE of 40% with a peak of 50% at 2.3 GHz under 0 dBm input. The proposed WSN realizes intermittent operation with a 100.9-s cycle at 2 m from a household Wi-Fi source and enables self-powered operation at 24 m from a 36 dBm directional RF energy transmitter. It demonstrates significant potential as a sustainable, maintenance-free, and eco-friendly solution for battery-less IoT sensing systems.