Research On Key Techonologies Of Near-Field Electromagnetic Positioning System

In recent years,the rapid development of science and technology has brought positioning technology into people’s daily life.Traditional satellite navigation and positioning methods have been unable to meet people’s positioning needs in indoor and complicated environments.To achieve accurate indoor positioning,there have been many ways of using high-frequency electromagnetic signals to achieve indoor positioning,such as WIFI positioning,Bluetooth positioning,and ultra-wideband positioning.However,high frequency electromagnetic signals face problems such as multipath interference and severe path loss in indoor environments,which will lead to a decrease in positioning accuracy and a reduction in positioning range.Considering that low-frequency electromagnetic signals:can better penetrate buildings and bypass obstacles,and can effectively reduce multipath interference,this paper will mainly study the near-field electromagnetic positioning system based on low frequency electromagnetic signals.Starting from the principle of the near-field electromagnetic positioning system,the paper displays the key technologies used by the system in detail through theoretical analysis,modeling simulation and practical testing.The paper firstly analyzes the propagation characteristics of electromagnetic waves in the near-field region by establishing electric dipole and magnetic dipole models,and summarizes the relationship between the phase changes of the electric and magnetic with distance when the electromagnetic wave propagates in the near-field region,the effectiveness of using this changing relationship to realize the ranging function is verified by the results of simulation and test.Secondly,this paper proposes the basic frame structure of the near-field electromagnetic positioning system.According to the working characteristics of the system,the combination of the trilateration positioning algorithm and the near-field electromagnetic ranging technology is selected,and the test environment is arranged in the underground warehouse with instruments and meters.By extracting the phase difference-distance data and converting it into coordinate information,the feasibility of realizing the positioning function through this technology is verified.Finally,according to the equipment characteristics of the near-field electromagnetic positioning system,this paper proposes two miniaturized antennas suitable for the near-field electromagnetic positioning system.Both of antennas use coil structure as radiating element,and use capacitance and inductance to achieve impedance matching,which effectively reduces the size of the antenna.The first antenna adopts the method of double-sided etching,and the radiators are arranged on both sides of the dielectric substrate.The maximum size of the antenna is only five thousandths of the working wavelength.The design of the second antenna is combined with the wearable concept,the antenna is arranged on the back of the human body,the maximum size is 1%of the working wavelength,and the antenna meets the radiation safety performance requirements.The simulation results and actual test results show that both antennas can meet the working requirements of the near-field electromagnetic positioning system while achieving the goal of miniaturization.