The Research On Key Techniques Of MOT And MOD Methods

Till now we have two methods for the calculations of computational electromagnetics: Frequency domain and timedomain calculation method. Compared to the frequency domain method, time domain method has great advantage when wide-band issuesarerevolved. And we can directly calculate the antenna radiation, time domain current of target scattering, change of electric field. It is easy to know the physical meaning and to obtain a lot of valid data used in practical engineering design. In this paper, we study the two solutions for Time Domain Integral Equation which are Marching-On-in-Time and Marching-On-in-Degreesy stematically. Realizing the calculation of the linear structure of the scattering current with MOD.We first introduce the theoretical basis of the method of MOT. This paper describes the thin wire approximation, one-dimensional model space subdivision, impedance coefficient calculation and Fourier Transform. Then MOT formulas derivation is obtained and used to calculate the current linear model plane electromagnetic wave scattering, combined with Fourier Transform to analysis thespectrum characteristics finite of straight wire current. After deep research on the MOD method, the analysis time basis function-associated laguerre polynomials properties, then derive the orthogonal and conductive properties of polynomial family, and come in time domain pulse expansion formulas of the order. And gained the expand order of the domain pulse. This paper discussed the effects of total time and the pulse parameters to the expansion of the order, and expandsome kinds of time domain pulse to determine theleast order which makes the expansion of the pulse satisfy the threshold range. The use of laguerre polynomials as a time-weighted basis functions resulting in a verycomplex double integraloperation of impedance matrix elements, that also makes original function hard to calculate, so we need to use approximate numerical integration methods.This paper introduces the basic theory of Newton-Cotes integration formula and Gauss quadrature formula. The trapezoid formula, Simpson formula and Gauss-Legendre quadrature formula is displayed. And then extended them to a double integral formula. Later, we verify calculation accuracy of several quadrature formula by examples, and choose the proper formula tocalculates the impedance matrix elements. Finally, we studied the MOD method systematically. And introduced the discrete units of one-dimensional model, split method and space basis function. Then the base function is used to expand the time domain electric field integral equation, and solved it by the method of moments. The details of calculation involves stretching factor selection, impedance matrix element calculation meticulous is presented. The results of the two methods to calculate the thin wire scattering were compared, which test the correctness of MOD. And we finally realize one-dimensional calculation of MOD.