The paper addresses a new approach to the integrated design of RF/Microwave receivers for power harvesting and conversion systems for ultra-low power densities. Such systems can be very useful in typical humanized environments in the presence of existing wireless systems with power densities as low as a few uW/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 an incident field is used in the joint design of a rectifier stage and of a boost converter that can dynamically track the maximum pow-er 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 control sub-system WE4A: RFID and Power Harvesting Technologies

Figure 1. (a) Structure of a piezoelectric cantilever beam with a tip mass;(b) a simplified equivalent circuit of a piezoelectric transducer.Abstract-This paper describes a reliable modeling technique for piezoelectric transducers and a procedure for identifying model parameters with few simple measurements and standard laboratory equipment. Direct measurements were taken on commercial Q220-A4-303YB piezoelectric transducers from Piezo Systems in a cantilever configuration with tip masses from 6 g to 18 g. For validation purposes, the behavior of the equivalent electromechanical circuits was simulated and compared to direct observations in real operating conditions. The model showed to predict with a high degree of accuracy both the frequency response of the transducers and the effects due to the presence of non-linear power converters which are usually ignored by conventional models presented in literature.978-1-4244-9289-3/11/$26.00 ©2011 IEEE