Integrated design of RF energy harvesting systems and converters for wearable applications

The combination of EM theory, full-wave numerical analysis, and nonlinear circuit techniques into an integrated numerical tool for the RF/base-band co-simulation and co-design of RF/microwave harvester systems operating in a multiband environment is considered. Electromagnetic theory and software tools typical of an RF design environment, such as harmonic balance, are used to rigorously analyze the receiving antenna subject to multiple incident fields and loaded by the rectifier, and to design the antenna-rectifier interstage network. The results provide guidelines to be followed in the design of the baseband portion of the system. A novel boost converter circuit allows the rectified energy to be transferred to a storage capacitor in an optimal way, i.e., keeping the rectifier dynamically close to the load situation providing maximum rectified power. The overall result is very general, allowing harvester performance to be accurately described in virtually any practical humanized scenario.. . A novel wearable, triple-band ring-antenna, designed to harvest RF energy from GSM 900, GSM 1800 and WiFi sources available in the ambient, is discussed. It consists of a single annular ring suitable modified with appropriate slots to be operated as a resonant radiator at all the bands of interest, thus well performing with respect of both radiation efficiency and circular polarization in compact dimensions. A multilayer configuration is exploited making use of textiles and flexible substrates whose integration issues are also discussed.