Accurate and Efficient Time-Domain Model for Generic Wireless Power Rectennas

The efficiency of an energy receiver of a Wireless Power Transfer (WPT) system is intricately influenced by many factors such as frequency, power, topology, and the parameters of the rectifying diode. Developing an efficient and accurate model is critical for effective design. Unlike analytical models that rely on signal approximation and circuit simplification, the time-domain model can comprehensively incorporate all diode parameters and provide a complete view of the circuit with all time-domain signals available. However, to ensure accuracy and rapid convergence, the output low-pass section has to be handled carefully due to its DC voltage bias for the diodes and its long time constant. Furthermore, scaling the time-domain model for diverse rectenna topologies presents challenges. In this work, we propose a recursive time-domain model suitable for half-wave and any-stage voltage multiplier rectennas. The output low pass section is addressed by replacing it with an equivalent DC voltage source, thus avoiding the long settling time and ensuring accurate DC bias for the diodes. An analytical model for converting input voltage to DC calculates the equivalent source. Our proposed model is scalable for any number of multiplier stages and can accommodate the effect of matching networks. We validate the accuracy of calculated power conversion efficiency and rectifier input impedance by comparing them with results from Harmonic Balance simulations.