Analysis Of Loop On-off Detection Based On Magnetic Resonance Frequency Splitting

Magnetic coupling resonance technology has been a research hot spot of scholars both at home and abroad since it was put forward by MIT.The application of this technology greatly promotes the development of wireless power transmission technology.So far,the research of this technology focuses on improving the energy transmission characteristics of the system,including the optimal design of coils,impedance matching and frequency tracking,and etc.There are few reports about the application of this technology in other fields.For the advantages of strong coupling and anti-interference ability,the magnetic coupling resonance technology is introduced into the on-off detection of a loop in this paper,which expands the application of electromagnetic induction principle in near-field blind zone.Besides,this application introduces the magnetic coupling resonance technology from wireless power transmission to information detection.The research in this paper is carried out with the support of the National Natural Science Foundation of China “Magnetic Coupling Resonance Method for Ground Grid Detection and Experimental Research”(51577016).And the main research work and results is as follows.(1)Based on the equivalent circuit theory,the series-series structure is taken as an example to analyze the conditions and influencing factors of frequency splitting from the angle of input impedance in the system.In addition,the factors that affect the frequency splitting of the system are verified with the circuit simulation.(2)From the perspective of the high-frequency characteristics of the coil,the different resonant frequencies of the loop with two different states are analyzed.Based on this and combined with the frequency selection characteristics of magnetic coupling resonance technology,a loop on-off detection method based on frequency splitting phenomenon is proposed.The feasibility,maximum detection distance and anti-metal interference of this method are verified via the finite element simulation software HFSS.After that,this on-off detection method is introduced to the single mesh model of ground grid,which is verified by HFSS simulation.Finally,the loop on-off detection platform based magnetic resonance frequency splitting is built with relative equipment in laboratory,and the method is verified through the experiments.(3)As an important part of the integration of the detection platform,the power amplifier section is designed.Based on theoretical knowledge of radio frequency(RF)circuits and power amplifiers,a class E power amplifier design scheme with shunt capacitors is proposed.For the requirements of this paper,the design specifications of the power amplifier are put forward,and the overall circuit is designed and simulated through the RF circuit design software AWR.What’s more,the real object of class E power amplifier is debugged.Debugging results show that in the operating frequency band,the output power is 38dBm(6W)on average and the maximum output power is 38.77dBm(7.53W).The efficiency of the power amplifier is between 56% and 66%,which can meet the requirements of the detection system.