| With the rapid development of Io T technology and wireless sensor network technology,people’s demand for low-power electronic devices is increasing day by day.Environmentally friendly and efficient RF energy harvesting technology,which can collect free wireless RF energy in free space,may become the most ideal way to supply energy for low-power devices in the future.Currently,the technology in high-power transmission technology can also be applied to a variety of scenarios such as microwave-driven drones,radio frequency identification,remote area energy supply.RF rectifier circuit is the most critical part of the RF energy harvesting system,which will directly determine the performance of the wireless RF energy harvesting system,and is also affected by the integration efficiency of the system’s receiving antenna and charging circuit.In order to meet the micropower requirements in Io T scenario applications,the paper focuses on the detection sensitivity and detection efficiency under micropower input conditions,and models the rectifier diode under small signal conditions to improve the accuracy of the design;designs a wide input power rectifier circuit and its conjugate matched receiving antenna to reduce the reflected energy loss from intermediate impedance transformation;designs a millivolt-level DC boost charging circuit that The overall system solution for micro-energy harvesting is constituted,and the system operates in the 2.45 GHz band;the main research contents and the results obtained include the following three parts.（1）A diode circuit model for small signal input conditions is developed.Since the simulation model used in the simulation software does not consider the package parameters,there is a certain error with the measured results,especially under the input conditions of micropower,the paper designed the relevant calibration pieces,measured the diode S parameters,and modeled based on the relevant parameters;the Matlab simulation software was used to fit the data and obtain the relevant parameters of the diode self-built model.（2）Rectifier circuit for Wireless Energy Harvesting（WEH）with wide input power range is proposed in this paper.We build up accurate models of the diodes to improve the accuracy of the design of the rectifier.Due to the nonlinear characteristics of the diodes,a new band-stop structure is introduced to reduce the imaginary part impedance and suppress harmonics.A novel structure with double branches and an optimized λ/4 microstrip line is proposed to realize the power division ratio adjustment by the input power automatically.The proposed two branches can satisfy the two cases with input power of-20 to 0 d Bm and 0 to 15 d Bm respectively.An impedance compression network（ICN）is correspondingly designed to maintain the input impedance stability over the wide input power range.Finally,a rectifier that works at 2.45 GHz is implemented.The measured results show that the highest efficiency can reach 51.5% at 0 d Bm and over 40% in-5 to 12 d Bm input power.（3）A DC/DC step-up charging circuit based on LTC3108 chip is designed.The basic structure and step-up principle of the charging chip are introduced,the applicable scenarios of the two charging chips are compared and analyzed,the LTC3108 with lower cold start voltage is selected as the chip of the charging circuit,the Spice model of the chip is imported in LTspice and the external circuit is connected,the simulation is realized to increase the DC input voltage as low as 20 mv to3.3V output,the super capacitor is selected to store The system is finally integrated with rectifier circuit,receiving antenna and charging circuit to realize a wide input power range RF energy harvesting system and analyze the feasibility and effect of the system. |
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