Research On Time-varying Plasma And Layered Medium Based On FDTD Algorithm

Plasma as the fourth state of nature in addition to solid,liquid and gaseous state.Refers to a substance by the ionized gas atoms and atomic groups after being deprived of part of the electronic component is positive and negative ions produced by ionizing,macroscopically neutralized ionized gas,scale is longer than Debye long.Because of its good electrical conductivity,and through the role of the magnetic field can capture,move,accelerate.Therefore,in the material,energy,aerospace and other aspects occupy a pivotal role.In the future may occur in electronic warfare,information warfare,the study of plasma is also very important.However,the FDTD method has been widely studied in the field of electromagnetic calculation since it was proposed and has developed into a mature numerical method.Because its method is to directly associate the field value of the sample point with the surrounding field values directly,it is of great advantage in dealing with the electromagnetic scattering and radiation problems of complex shape targets and inhomogeneous medium objects,and' thus has the advantages of being convenient for analysis and design.Therefore,the research content of this paper is to apply FDTD in plasma development,and mainly do the following work.(1)Based on the high-order FDTD method,the high-order FDTD method is improved by applying ampere-loop law and a set of optimization coefficients is obtained.Compared with the traditional FDTD method,this improved high-order FDTD calculation has higher accuracy and wider application.(2)ADE-FDTD method is used to investigate the propagation characteristics of time-varying plasma in terahertz band.The reflection,transmission and absorption coefficients of different electron density,particle concentration,rise time,plasma thickness and collision frequency were studied.Corresponding conclusions were given,which provided some technical support for aeronautical communication.(3)Due to the change of the flight path,the transmitting antenna,the receiving position of the antenna and so on during the reentry of the aircraft,the electromagnetic wave always enters the plasma at an angle.In addition,air-plasma layered media are formed in two-dimensional models.In the medium interface will produce reflected waves and transmitted waves from different interfaces.As a result,the general method of oblique incidence of plane wave in vacuum will not be suitable for layered media.In order to deal with this problem,a two-dimensional model was constructed and the oblique incident incidence method of plane wave in layered media was studied.Combined with the optimized high-order FDTD,the accuracy was improved.