Dual-Polarized Wide-Angle Energy Harvester for Self-Powered IoT Devices

In this work, a dual-polarized wide-angle energy harvester operating at 3.75 GHz is proposed for ambient RF energy harvesting applications. A 4 x 4 array harvester can efficiently harvest incident RF waves from all polarizations, resulting in high RF-AC efficiency of 94% and final RF-DC efficiency of 34% at 0.02 W/m(2) input power density, or -15 dBm input power. This performance is preserved under a wide incident angle up to 65 degrees in TE mode and 75 degrees in TM mode. Owing to its simple power combining configuration, the array can be easily expanded to incorporate more unit cells, increasing the amount of collected power. Not only having the RF-DC conversion function, it is also equipped with a power management circuit to create a usable output voltage level. With this advantage, the harvester is suitable to be employed in real-life applications in which the polarization and angle of incidence are unknown and the incident power is very low.