Study On Computation And Measurement Methods Of EM Scattering For Arbtrary Shaped Targets In Time Domain

The recently developments in the areas of high resolution radar technology, electromagnetic pulse simulation studies, and target identification techniques related problems where the transient response plays major role. In order to obtain the wide-band electromagnetic scattering characteristics of arbitrary shaped conducting structures, a computation method which based on the Time-Domain-Integral-Equation (TDIE) and measurement method in transient electromagnetic scattering laboratory for electromagnetic scattering were investigated in this thesis. As two important reasons which restrict the the progress of the TDIE arithmetic, the late-time instabilites and large quantity of computation of TDIE method were studied deeply. Measurement theory and technique in a shielded anechoic chamber were researched, stable methods based on TDIE were developed, the fast analysis for electrically large structures were implemented successfully, and accurate wide-band scattering data for some complex shaped targets were measured.Firstly, the derivations of time domain EFIE, MFIE and CFIE for transient electromagnetic scattering from arbritrary shaped perfect electrically conducting bodies and Marching-On-In-Time(MOT) method for solving TDIE were reviewed, modeling and partitioning method for scatterers were presented, and some scale model radar targets are designed and manufactured. Some questions in MOT method including integral singularity, late-time-instabilites and computation complexity were analized, and some feasible schemes were advised.Secondly, aiming at the late-time-instabilites of the MOT, two improved algorithms, named marching on in order(MOO) algorithm which based on the weighed Laguerre polynomials and implicit method(IMPT) which based on implicit time recursion, were investigated for electromagnetic scattering. We proposed a new method to detemine the orders of the weighted Laguerre polynomial which are needed in the time variable expansion through approaching the temporal coefficients of the Hertz vector. And we also proposed an approach to reduce the oscillations which emerged in low energy region according to the Fourier transforms relation between frequency responses and time responses and oscillation character of laguerre polynomial in time and frequency domain, respectively. Implicit expressions were deduced from magnetic field integral equation using different kinds of finite differences, and nine kinds of integral equations were obtained through combine electric field integral equation with magnetic field integral equation with different kinds of finite differences, comparisons of performance with different kinds of differences were presented through simulation for different targets by using different kinds of incident pulse. A stable and accelerated procedure for EFIE was developed, the procedure employs implicit method in conjunction with a time averaging scheme to solve EFIE with the second order time derivatives, it has the superior stability and great efficiency for electromagnetic scattering compution for arbitrary surface of a closed or open PEC body.Thirdly, in order to reduce the computational complexity for the electrically large structures, the plane-wave-time-domain(PWTD) method was used to enhanced MOT algorithm by associated PWTD with IMPT method using CFIE, and both the two level PWTD(TLPWTD) and multilevel PWTD(MLPWTD) methods were used to enhanced MOT algorithm by associated them with second-order-time-derivatives IMPT method using EFIE which was proposed by the author in this thesis. It farther enhanced the ability to solve the electromagnetic scattering from arbitrary closed or open PEC surface of the electrically large structures using TDIE.At last, a system for measurement of ultra-wideband impulse scattering responses from scale models of radar targets in time domain is described. The method of acquisition of the scattering signal, and signal processing technique for measurement data are investigated in detail. Three scatterers, including a PEC sphere, a missile scale-model and a plane scale-model, are measured using this system. Compared the measured data with the numerical data, the result shows a good agreement.