Research On Surface Characteristics Of Frequency Selection Based On FDTD Algorithm

The frequency selective surface is essentially a spatial filter that interacts with the electromagnetic waves irradiated on its surface,so that these electromagnetic waves selectively pass through this plane,and within a certain frequency band,it will show total reflection or total transmission.The field of communication is widely used.Because of the characteristics of frequency selective surface,its research has always been a hot spot in the field of electromagnetics.For the study of the surface electromagnetic characteristics of plane and surface frequency selection,the thesis introduces the processing method of finite-difference time-domain algorithm,which starts from Maxwell's equations and discretes the electric field component and the magnetic field component in time and space to solve the space electromagnetic field.Under the condition that the plane wave is perpendicularly incident,the frequency selection surface for the plane can use periodic boundary conditions,and only one of the units can be calculated to analyze the transmission characteristics of the frequency selection surface;To select the surface according to the frequency of the curved surface,an algorithm can be used to calculate the entire model.The numerical analysis of the frequency selective surface is completed by applying the finite-difference time-domain algorithm,and compared with the results of the simulation software to verify the accuracy and efficiency of the time-domain finite difference algorithm.The main work of the thesis is carried out from the following aspects:Firstly,it introduces the research background of frequency selective surfaces and finite-difference time-domain algorithm,briefly describes the definition,classification,working mechanism of frequency selective surfaces,and some basic theoretical knowledge used by finite-difference time-domain algorithms in analyzing frequency selective surfaces,including Basic iteration formulas,absorption boundary conditions,periodic boundary conditions,and Floquet theorem in one and two dimensions;Secondly,when using the finite-difference time-domain algorithm to study the frequency selective surface transmission characteristics,it is compared with the software CST simulation results.For single-layer and double-layer frequency selection surfaces and dual-frequency frequency selection surfaces,two methods of algorithm calculation and software simulation are used to realize the study of planarfrequency selection surfaces.Through the analysis of its results,it is found that the calculation results of the two methods are in good agreement,which verifies the accuracy and applicability of the finite-difference time-domain algorithm;At the same time,by comparing the calculation time of the two methods and the size of the memory consumption,the efficiency of the algorithm is verified;Finally,the finite-difference time-domain algorithm is used to study the scattering characteristics of the frequency selective surface of the finite-period surface,and the results of the CST simulation are compared.It is difficult to select the surface modeling for the current surface frequency,and the calculation amount is relatively large,and the finite-difference time-domain algorithm is introduced.Aiming at the periodic surface frequency selection surface structure such as cylindrical surface and conical surface,through the calculation of the array unit,the scattering characteristic analysis of the surface frequency selection surface array is realized.The results are also analyzed first and compared with the CST simulation results.The results are in good agreement with each other,which verifies the accuracy and applicability of the finite-difference time-domain algorithm;The efficiency of the two methods is also compared,including the calculation time and the size of the consumed memory,which verifies the efficiency of the algorithm.