An Efficiency Optimization Technique for RF Energy Harvesting Circuits

An analytical approach to maximize efficiency in RF rectifiers is presented in this paper. In particular, the equations to calculate input impedance and input power with parasitic effects are derived. The losses associated with the Matching Network (MN) are discussed and an efficiency optimization technique using the derived equations is given. A prototype rectifier is designed using the given approach for the 915 MHz Industrial, Scientific, and Medical (ISM) radio band. The prototype shows a rectification efficiency of 57% for an input power of -10 dBm (100 μW), which is a 7% improvement over the state-of-art solutions. The prototype powered an LED using a DC/DC converter and is tested using an antenna. A commercial 1W (4W EIRP) transmitter is used to power the prototype from 15.5 meters away.