RF energy scavenging system for DC power from FM broadcasting based on an optimized Cockcroft-Walton voltage multiplier

The potential utilization of RF signals from a commercial FM band (88-108MHz) is explored for DC power. In this paper, an RF energy scavenger has been developed which is able to power up low power consumption devices. The RF-DC conversion stage is based on a six-stage Cockcroft-Walton voltage multiplier (CWVM), and its performance is analyzed by rating the maximum power delivered in the load via its output impedance. Several models have been previously proposed in order to predict the output impedance of CWVMs in lieu of optimizing the maximum power delivered to the load; nevertheless all of them were inaccurate. Here, a new approach based on the CWVM transmission line model, which accurately predicts output impedance, is proposed. Under this framework, the output impedance of the CWVM depends only on junction capacitance and resistance of the diodes rather than stage capacitors, as considered formerly.