RF Energy Harvesting for LED Lighting

Abstract

Due to the widespread application of RF communication and transmission, such as mobile communications, television, and WiFi etc., RF signals are widely available almost in every corners of the city and RF energy harvesting has been considered as one of the viable technologies for powering some low-power remote devices or systems. In the wearable and implanted electronics sectors, it has been considered as the best technological option for powering these devices although there are still a lot of challenges in compromising the power level, size and safety requirement. This project demonstrates the design, based on the readily available commercial electronic components, of an RF energy harvesting system operated at 2.4 GHz which is able to light up a 1.6 V LED. The final product consists of a tailor-made cross-dipole PCB antenna, a 7-stage charge pump realized with HSMS2852 high-frequency Schottky diodes. The harvested energy was stored in a capacitor and the experimental result showed that system can turn on a 1.6 V LED with RF signal of -8dBm although the system did not include a regulator. With RF power at 0 dBm, the system can output a DC voltage in the range of 3.3 V to around 6 V from signal frequency deceasing from 2.4GHz to 1.2 GHz. The decrease of the power conversion ratio with frequency mainly due to the parasitic capacitances associated with the Schottky diodes and the PCB. Since in a real environment the RF signal level is much lower, it is thus important to optimize the performance of every parts of the system including the antenna, the matching circuit, and the PCB layout. The performance of the system can be significantly boosted if tailor-made switching diodes with lower conduction losses are available. In short, the present work has demonstrated that for remote powering of low-power electronic system based on RF energy harvesting is feasible. Better power conversion efficiency can be achieved with high-gain and multiple antenna, lower loss switching devices, and higher efficient integrated charge pump.