Advanced Radio Frequency Energy Harvesting with Power Management from Multiple Sources for Low Power Sensors and Mobile Charging Applications

Abstract

—A complete energy harvesting system via Radio Frequency (RF) is designed in a broadcast station where multiple frequency sources are readily available. These frequency sources are the Intermediate Frequency (IF), 70MHz, Wi-Fi frequency band, 2.4GHz, and the Ku-band frequency, 13 GHz. The RF source via the Wi-Fi band (2.4 GHz) is harvested via a microstrip patch antenna designed with its matching network. The harvested RF energy is transformed into usable DC power via an 8-stage Villard voltage doubler circuit. The DC power is managed by a power management system handled by the BQ25570 circuit which gives a regulated output of 3V, powers up a low power motion sensor, and charges a battery at the same time. This system comes with a backup source which is the battery and able to take over the system in case the incoming RF signal fails. The RF energy harvested from the IF 70MHz and Ku-band at 13GHz is derived from coupler outputs which are available in broadcast stations, transmission lines, etc. Both these RF signals are converted to DC signals via a 5-stage Villard voltage doubler circuit with different matching networks. The DC power is managed by a power mux via the TPS2122 which selects the highest available power. Over the years, no works on RF harvesting have focused on smart phone charging as its application, due to the limitation in power availability. This work strives to provide enough power to charge phones and effectively gives a 5V output to charge smart phones with a charging current of 0.5A which is similar to a USB charging port.