| Radio Frequency Energy Harvesting(RFEH)systems can replace traditional batteries to harvest and utilize RF energy in the natural environment.Currently,research on this system has attracted widespread attention in academia and practical engineering applications.For the circuit of the RFEH system,this article has carried out relevant principle analysis,designed the receiving antenna,matching circuit,RF-DC rectifier circuit,and power management unit(PMU).The important system parameter values have been calculated and simulated,and the power consumption model of the system has been established.The overall power consumption of the circuit has been analyzed.The specific content includes the following three parts:(1)Aiming at the low gain and low efficiency of the receiving antenna in RFEH system,a planar inverted F antenna(PIFA)with high gain and low return loss operating in GSM 900 band is designed.The simulation results show that the return loss of the antenna is 0.6,the bandwidth is 130 MHz,the directional gain directly above the antenna is 3.2 d Bi,the efficiency is 93%,the energy value collected in the ordinary environment is-6 d Bm,and the voltage value is 300 m V,which can provide power for subsequent circuits.(2)Aiming at the problems of high forward conduction threshold voltage,low output voltage,and low power conversion efficiency(PCE)in traditional RF-DC rectifier circuits,a novel synchronous self-threshold compensated voltage doubling rectifier circuit based on Dickson charge pump is proposed.The LC matching circuit is designed to amplify the input signal to 1.04 V,ensuring the start of the rectifier circuit;A new circuit structure combining switch and voltage divider is proposed to solve the problems of high forward threshold loss and high reverse leakage current;A synchronous signal control scheme is designed to replace the external clock signal,which solves the problem of additional power consumption;The effects of input power level,load resistance,and the number of stages of the rectifier circuit on the rectifier performance are studied.A high-precision power consumption model of the rectifier circuit is established,and the parameter values and power consumption values of each component when the rectifier circuit can reach the PCE peak value are determined.The simulation results show that the equivalent threshold voltage of the rectifier transistor is 0.05 V and the power consumption of the rectifier circuit is 13.94 μW.PCE is 58%.(3)Aiming at the problems that the output voltage ripple of the RF-DC rectifier circuit is large and cannot directly supply power to the load,a new type of PMU is designed,which can control the output voltage of the rectifier circuit with high accuracy,achieving the purpose of directly supplying power to the load.The PMU system block diagram is proposed,in which the specific modules include improved starting circuit,bandgap reference circuit,voltage detection circuit and voltage stabilizing circuit;The logic control circuit is designed to control the working voltage of the circuit to realize the maximum power transmission of load energy;The power consumption model of the PMU circuit is established,and the power consumption values of each component are analyzed and verified by simulation.The simulation results show that the power consumption of the PMU circuit is 9.52 μW,the PCE is 62%.The overall simulation results of RFEH system show that the PCE of the micro-watt level RF energy collection system designed in this paper is 31.77%,which has potential application value in the fields of wireless energy transmission and portable equipment power supply. |
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