Resonant Circuit Topology for Radio Frequency Energy Harvesting

In this work the operation of a MOSFET based rectifier, composed of multiple stages of voltage doubler circuits used for radio frequency (RF) energy harvesting, is investigated. Analytical modeling of the input stage of the rectifier consisting of short-channel diode-connected transistors is carried out, and the equivalent input resistance obtained is used along with simulation results to improve impedance matching in the harvester. The criteria for voltage boosting and impedance matching, that are essential in the operation of energy harvester under low ambient RF levels, as well as the design considerations for a pi-match network to achieve matching to 50 Ohms, are elaborated on. In addition their application is demonstrated through simulations carried out using Advanced Design System (ADS) simulator. Furthermore, measurement results of an already fabricated dual-band RF harvester are presented, and the approach taken to improve the antenna design from the harvester chip measured input impedance is discussed. The integrated antenna-harvester system tested was capable of harvesting ambient RF power and generating DC output voltage levels above 1 V

Analog Front End for RF Energy Harvesting

This thesis proposes a design for ultra low power sensitive single and dual band RF energy harvesting system for UHF microwave frequencies at 2.4-GHz and 865-MHz to 960- MHz(ISM band). The system is designed to power a load and generate a constant 1-V output voltage for a battery-less passive energy harvesting circuit. Input power is fed from 50 RF source to emulate antenna at UHF microwave band. The design includes single band and dual band off-chip RF matching circuit, RF limiter, Differential Rectifier, Power On Reset (POR), Band Gap Reference (BGR) and Low Drop Out Regulator (LDO). The number of rectifier stages is optimized to obtain a better efficiency to generate 1V output voltage. The full system performance has been verified by simulations for equivalent received power from -20-dBm to -10-dBm. The overall RF energy harvesting system efficiency at -14-dBm (10 m Distance from 4W EIRP source) input power for single band matching at 2.4-GHz is 46.9% with 54Kohm load and for dual band matching at 953-MHz and 2.4-GHz we achieve an efficiency of 41.5% with 61K ohm load and 46% with load 54.4Kohm respectively. The technology node employed is 0.18_m technology. The simulations are carried out at schematic level with bond wire parasitic’s and verified by post layout simulation. At the last we conclude by proposing a novel architecture for constant voltage battery charging