Structural Optimizatoin Of Buried Wireless Sensor Antenna Based On Material Enhancement

The main difference between the propagation of electromagnetic waves in the ground and in the air is that the attenuation is more severe and the communication distance is greatly limited.In order to overcome the attenuation of the earth,,it is necessary to use very low frequency or ultra-low frequency electromagnetic waves for communication,but this not only makes the channel capacity small,but also requires a very large antenna.The research in this paper is based on the negative permeability metamaterials design and optimization of the antenna structure.Its main basis is the principle of magnetic induction communication.It focuses on solving two problems:the antenna area is too large and the communication distance is too short.The main research content of this topic is to optimize the coil antenna structure with a radius of 0.05m and the number of turns is 8 on the premise of operating frequency of 2MHz.The radius of the inner coil of the optimized antenna is 0.015m,and the radius of the antenna ball after optimization is 0.05m.The work of the dissertation is divided into three stages:(1)Select the appropriate coil type,verify the enhancement of the metamaterial shell,and determine the thickness of the metamaterial shell.The simulation uses the round and square coils respectively to analyze the antenna structure inside the metamaterial shell and verified that the magnetic field distribution of the circular coil is more uniform;Then from the theoretical point of view,the optimum thickness of the metamaterial shell is analyzed,and verified that the metamaterial antenna ball with radius of 0.05m,its best thickness of the metamaterial shell is 0.025m.(2)The internal coil is optimized by adding ferrite and steel rods.The nickel-zinc ferrite was selected for the ferrite,the stainless steel rod was selected for the steel rod,and then the related model was established and optimized based on the FEKO software,and the optimum size was obtained.Finally,the complete optimization model was brought into the Comsol software for Simulation of the underground model,simulation results verify that the optimized antenna is larger than the antenna of the same size,the magnetic field strength is improved by about two orders of magnitude.Under the premise of magnetic field intensity higher than 10-10A/m,optimized antenna increases transmission distance from 3m to 5m.(3)Antenna performance is analyzed.According to the previous antenna model analysis of the overall system characteristics,the influence of the antenna placement direction on the communication intensity was analyzed,and the effect was better when the antenna placement direction was consistent with the signal propagation direction;then the point-to-point and magnetic relay modeling of the metamaterial antenna was performed.The simulation results verified the superiority of the magnetic relay communication and the advantage of using the optimized structure at the transmitting end.Finally,the role and principle of the antenna matching were analyzed.The matching of the antenna was performed based on 2 MHz and the matching circuit was obtained.