Research On Design Technology Of Rectenna In Wireless Power Harvesting System

The wireless power harvesting system(WPH)converts electromagnetic energy distributed in space into direct current energy to supply power to low-power devices,which is a hot spot of current electromagnetic field research.The core component of WPH is the rectenna.The current research direction of the rectenna focuses on the miniaturization,multi-frequency and broadband of the rectenna and the improvement of the rectification efficiency of the system.This paper makes a detailed theoretical analysis and simulation comparison of the components of the rectenna system.Focusing on the above research directions,this paper designs three types of wireless energy harvesting systems.The main work is as follows:First,a miniaturized rectifier circuit working at 5.8GHz is proposed,focusing on the analysis of rectifier diodes and the choice of rectifier network topology.The 5.8GHz rectifier circuit composed of a single-stage voltage doubling rectifier network,a microstrip single-segment short-circuit matching network and a 1/4-wavelength microstrip line filter,which meets the requirements of circuit miniaturization.The physical measurement results show that the rectification efficiency of the circuit is above 40% in the input frequency range of 14 d Bm ? 20 d Bm.Secondly,a dual-frequency rectenna system operating at 2.45 GHz and 5.8GHz is designed to receive multi-band radio frequency energy.The receiving antenna adopts a microstrip dual-frequency monopole antenna,which is composed of two L-shaped high and low frequency monopole antennas and a microstrip feeder.The impedance bandwidth of the measured antenna at2.45 GHz and 5.8GHz is 8.2% and 47.5% respectively;The dual-frequency rectifier circuit consists of a single-order voltage doubling rectifier network,a sector-shaped open-circuit stub DC filter and a microstrip double-branch open-circuit stub matching network.The simulation and actual measurement results show that the circuit and the signal source are at the dual frequency points of2.45 GHz and 5.8GHz Good impedance matching can be achieved at the place,and the rectification efficiency of the circuit is above 40% within the input power range of 16 d Bm ? 20 d Bm.It is proved that the designed rectifier circuit meets the design requirements of dual-frequency wireless energy harvesting system.Finally,on the basis of the two systems previously designed,we designed a broadband circularly polarized rectifier antenna based on the reflected power recovery network,which can receive electromagnetic signals in any polarization direction.The receiving antenna adopts a double-sided cross dipole structure,and the antenna has a larger impedance bandwidth by increasing the width of the output end of the dipole antenna;In order to realize the circular polarization characteristics of the antenna,the dipole antennas on the same plane are connected through a three-quarter circular ring to produce a phase difference.At the same time,a rectangular branch line is added to each dipole arm of the antenna to broaden the axial ratio bandwidth of the antenna.The actual test results show that the designed broadband circularly polarized antenna can achieve right-handed circular polarization in the operating frequency range of 2.18 GHz ? 3.6 GHz.Then,a rectifier circuit with a working frequency of 2.45 GHz is designed,which uses a microstrip open-circuit stub harmonic suppression network as a DC filter,and the rectifier network topology uses a diode in parallel to increase the output voltage of the circuit.In order to broaden the input power and operating frequency of the rectifier circuit,a power recovery network structure is inserted between the receiving antenna and the rectifier circuit,and the design of the structure is completed by splitting its working principle and formula derivation.When the rectifier circuit causes impedance mismatch due to changes in input power and operating frequency,this structure can reuse the reflected energy generated by the impedance mismatch and improve the rectification efficiency.The simulation results show that the 2.45 GHz rectifier circuit based on the reflected power recovery network achieves more than 50% rectification efficiency in the range of input power of 12.6d Bm ? 21 d Bm and operating frequency of 2.10 GHz ? 2.72 GHz.The measured results of the circuit are basically consistent with the simulation results,which proves that the designed rectifier circuit based on the power recovery network can achieve high-efficiency rectification in a wide range of input power and operating frequency.