All-Polarized Wideband Rectenna Array for Omnidirectional Wireless Energy Harvesting

In this work, a 3-D omnidirectional multiple polarized radio-frequency (RF) energy harvester (rectenna) array with broadband frequency coverages (2.4-3.1 GHz) is presented. The rectenna array strategically combines 12 single microstrip slot antenna elements placed in a transparent octahedral box. A broadband microstrip slot antenna based on multiple resonant stubs is proposed and studied. By utilizing two pairs of stubs embedded on a defective ground, a reflection coefficient of less than -10 dB can be achieved with broadband characteristics for applications of wireless local area network (WLAN). A broadband rectifier array is designed with 12 rectifier elements arranged in a 360-degree array. All elements are connected in parallel to achieve maximum DC combining and reduce losses caused by feed lines during array formation. The RF-DC conversation efficiency of the rectifier array is 75 % at an input power of 13 dBm. The experimental results show that this rectenna array works well with RF radiations at either horizontal or vertical polarization from various directions.