A Dual-Band Fractal Antenna Integrated with a 2D Voltage Multiplier for Enhanced RF Energy Harvesting

Ambient radio frequency (RF) energy harvesting has emerged as a promising sustainable power solution for low-power electronic devices, particularly in the context of rapidly expanding Internet of Things (IoT) ecosystems and wireless sensor networks. This study presents a novel RF energy harvesting system that integrates a dual-band fractal antenna with a two-dimensional (2D) Villard voltage multiplier to address the fundamental limitations of conventional energy harvesters, specifically the restricted output current and power conversion efficiency associated with traditional one-dimensional multiplier topologies. The fractal antenna, designed using a third-order Koch snowflake geometry on an FR4 substrate, operates at 2.25 GHz and 2.9 GHz, providing high gain (5.02 dBi and 5.48 dBi, respectively) with omnidirectional radiation characteristics suitable for capturing ambient RF signals from multiple directions. The 2D voltage multiplier architecture incorporates three parallel branches of 10-stage Villard doublers, utilizing HSMS-2850 Schottky diodes and high-frequency capacitors, configured to substantially enhance output current capacity while maintaining the same voltage multiplication factor as conventional designs. The complete system was fabricated using standard PCB manufacturing processes on FR4 and Rogers RO3010 substrates, with comprehensive characterization performed using vector network analysis and precision RF-DC conversion measurements. Experimental results demonstrate outstanding performance, achieving a peak power conversion efficiency (PCE) of 95% at 2.25 GHz with 0 dBm input power, significantly outperforming the conventional 1D multiplier baseline. The integrated system successfully powered an LED at a distance of 2 m from the transmitting source, confirming its practical viability. The synergistic combination of a high-performance dual-band fractal antenna and an innovative 2D voltage multiplier architecture presents a significant advancement in RF energy harvesting technology, offering a compact, efficient, and reproducible solution for powering next-generation IoT sensors, wearable devices, and remote monitoring systems operating in diverse environmental conditions.