Design of an RF Voltage Doubler Circuit for Energy Harvesting Applications

An experimental RF energy harvester is proposed that uses a rectenna to harvest ambient energy at 7.5 GHz frequency. The circuit uses a Voltage Doubler (VD) rectifier that uses a Schottky diode for microwave (RF) to DC conversion. Firstly, a single-stage VD circuit is designed with an impedance matching (IM) network, later it is extended to a two-stage VD circuit, with simple optimization in the IM network. The single-stage VD circuit resulted in a DC voltage of 3.65 V for an input power of 20dBm, whereas the two-stage VD circuit yielded a 7.13 V DC output for the same input power. In both cases, the load resistance is optimized to provide the maximum Power Conversion Efficiency (PCE). In this way, the maximum PCE achieved for a two-stage VD rectifier is 73.83% for a load resistor of 100KΩ. The proposed rectifier design can prove to be an inexpensive device for wireless energy transfer and RF energy harvesting.