Frequency And Time Domain Integral Equation Methods For Bodies Of Revolution, Their Software Implementation And Applications

The usage of the axisymmetric property of the bodies of revolution (BoR) can convert an original electrically large BoR-problem into a series problems with small size of matrix equations, which can greatly reduce the computational cost and we call each small problem a Fourier component or mode of the original one. This dissertation is focused on both the frequency and time domain integral equation methods for computing the scattering and radiation property of the bodies of revolution. What we have done are listed below:In frequency domain, several basis functions are applied to investigate the scattering and radiation property of the bodies of revolution, including perfectly electric conducting objects, dielectric objects, coated objects, more complex muti-region objects and chiral media, etc.. Several key points which can greatly affect the efficiency and robustness of the moment method for bodies of revolution (BoRMoM) are investigated. The method are greatly improved by several new techniques, which include:An accuracy controllable method has been proposed to truncate the number of Fourier components when the plane wave incidents obliquely, which we call a partly iterative method. One can get the least number of Fourier components required for a given accuracy of the currents. A costless convergence criteria is proposed by investigating the distribution property of the mode currents (currents corresponding to each Fourier component) along the generating curve.The computation of the modal Green's function forms a bottleneck to further enhance the efficiency and robustness of the BoRMoM. Based on a spectrum estimation, a qusi-adaptive integral scheme is proposed to fast compute a group of extremely oscillating integrals of the modal Green's function (a special Green's function for the BoR-problems). It is based on the Filon algorithm and a formulation is derived to smartly determine the required number of sampling points for applying Gaussian quadrature in the whole range of [0,Ï€] along the circumferential direction. Source and field points with different geometric parameters have different number of sampling points. This method is smart, fast, robust and still of high accuracy.A mode reduction technique is proposed to enhance the computational efficiency of high order Fourier components. We found that, as the index of the mode increases, some elements of the impedance matrix are neglegible. A formulation is proposed to determine whether an element of the impedance matrix can be set as zero directly.A closed form expressions for near-axis, far-distance modal Green's functions are proposed, which can be used to accelerate the computation of the BoR-problems especially when the BoR is slim.A good method is proposed to verify whether the higher order impedance boundary condition (HOIBC) can be applied to a coated BoR. Based on the local property of the HOIBC and the costless of the MIE series solution, the method applies HOIBC in the MIE series solution for several special objects, e.g. sphere, and embeds the program into the software, which can be run for verification before the application of HOIBC to the coated BoR. The procedure for verification is costless.In time domain, a marching-on-in-degree (MoD) procedure based time-domain integral equation method has been proposed for solving BoR-problems. Compared with the previous work based on a marching-on-in-time (MoT) procedure, this method can not only utilize the symmetric property of BoR indeed, but also retain the stable property of the common MoD method. Compared with the MoD method without using the symmetric property and the conventional MoT method, it can significantly enhance the computational efficiency.A software BoRMoMModeler1.0 has been developed based on the frequency domain method (BoRFDMoM). The kernel of version 2.0 has also been finished which includes time domain integral equation methods and a more efficient and robust frequency domain method with more wide range of utility.The software BoRMoMModeler1.0 has been applied to model the electromagnetic scattering from the radar targets by the users. In our own group, a horn antenna with ripples and airborne radome are optimized as a whole to obtain a special radiation pattern which we call hollow beam. All its performances can answer to the requirements.