RF/baseband co-design of switching receivers for multiband microwave energy harvesting

The paper addresses a new integrated design of RF/Microwave receivers and conversion systems for energy harvesting to be adopted in ultra-low power density environments. Such systems can be very useful in typical humanized scenarios in the presence of existing wireless systems with power densities as low as a few μW/cm2. Despite of the scarce RF power available, energy usable to extend battery life or to self-power low-duty cycle electronics may be scavenged by highly efficient receivers and power converter circuits designed in a unique design process. A multi-band antenna is used as the RF power receiver. Its rigorous frequency-dependent equivalent circuit in the presence of incident fields, simultaneously radiated in several bands, is used in the joint design of a rectifier stage and of a boost converter that can dynamically track the maximum power point. This is obtained by a new simulation platform combining SPICE-like time-domain models of dispersive multiport components with the transient analysis of the storage and control sub-systems. The system operation is fully measured in a practical application and predicted and measured stored energy and system efficiency are discussed. As preliminary results the converter is realized by discrete components, but a significant reduction in power consumption is expected by an integrated circuit design.