Research On Magnetic Field Measurement Of Radio Energy Transmission System Based On Lock-in Amplifier

After the human society entered the age of electrification,science and technology continued to develop,and electric energy played an increasingly important role in people's daily lives.Most of the electrical equipment in life uses electrical wires for power supply,and there are many drawbacks.Since MIT proposed the realization of magnetic resonant wireless power transfer technology in 2007,it has set off a worldwide research boom on this topic.So far,the theoretical analysis of magnetic resonance wireless power transfer technology is still controversial,so the study of the magnetic field distribution under magnetic resonance conditions contributes to the theoretical analysis of magnetic resonance wireless power transfer technology,space magnetic field measurement under magnetic resonance conditions.It has a very important significance.At present,there are many types of magnetic field measuring instruments on the market.The more sophisticated instruments are expensive,bulky,have a low measurement frequency range.Moreover,it has poor applicability to the measurement of spatial magnetic fields of wireless power transfer systems.At the same time,there are few studies on the magnetic field measurement of magnetic resonance-type wireless power transfer systems.Therefore,it is necessary and practical to study the magnetic field measurement system for magnetic resonant radio energy transmission.This paper studies a set of magnetic field measurement system,including the design and fabrication of three-dimensional magnetic field probes,the collection of analog signals,the study of digital signal processing,and the design of measurement schemes.The spatial magnetic field of a magnetic resonance type infinite power transmission system at a fixed frequency was measured,and a three-dimensional distribution map of magnetic induction intensity was plotted.The simulation result was used as a standard value of the magnetic induction probe,and the measurement value was compared with the measurement value and the measurement was given.The system can provide a conclusion for the research of wireless power transfer technology.In this paper,firstly,the circuit model of one-dimensional magnetic induction probe is studied,the transfer function relationship of one-dimensional magnetic field probe is given,and the size of the induction coil is determined.Then it is generalized to three-dimensional situation,and a three-dimensional design is made according to the circuit model.Magnetic induction probes,finally simulated analysis of the influence of induction voltage on the mutual inductance parameters between the sensing probe coils.Secondly,because the induced voltage of the magnetic field probe is small,the analog lock-in amplifier and the digital lock-in amplifier are studied to demodulate the signal,and an accurate extraction of the voltage signal is achieved.The analog lock-in amplifier performs detailed research and analysis on the pre-amplifier,multiplier,and low-pass filter,and creates a hardware circuit;the research of the digital lock-in amplifier is performed on the FPGA development board and mainly includes A/D conversion.Module data acquisition,DDS reference signal generation,FIR filter design and square root computing module,data reading mainly rely on the serial port tool to read.Finally,using the fabricated analog lock-in amplifier to complete the measurement of the axial component of the magnetic resonance of the magnetic resonance type wireless power transmission system,the three-dimensional measurement of the magnetic induction intensity of the magnetic resonance type wireless energy transmission system was completed using a digital lock-in amplifier,and the measurement data was processed by MATLAB.Processing,and draw a magnetic induction intensity distribution state diagram.At the same time,using Maxwell 3D software to build the corresponding simulation model,and using this as a benchmark compared with measured values.The measurement results are in good agreement with the simulation results in terms of trend,and the error of the measurement values is small in the places where the magnetic field strength is weak.