Applications Of Compressive Sensing And Reciprocity Theorem In Target And Composite EM Scattering

This dissertation consists of two parts of research work:the introduction of the compressive sensing?CS?to the electromagnetic scattering from target and the introduction of the reciprocity theorem to the composite scattering from a target located above a rough surface.Firstly,this dissertation integrates the CS with the method of moments?MoM?to analysis the bistatic scattering from a two dimensional target efficiently.Then the CS is combined with the fast multipole method?FMM?for the purpose of fast analyzing the mono-and multi-static scattering from a target.To further improve the efficiency in solving the multi-static scattering from a target,the CS is introduced into the commercial software FEKO.Finally,this dissertation proposed a new method based on the reciprocity theorem and the physical optics?PO?to calculate the composite backscattering from a dielectric-coated conducting target located above a dielectric rough surface.The principal contributions of this dissertation are as follows:1.Two new methods based on CS and MoM has been proposed and validated to efficiently calculate the bistatic scattering from two dimensional targets.To perform a bistatic scattering analysis by the two new methods,the induced currents over the surface of the object is treated as the original signal.And the matrix form equations derived from MoM are converted to underdetermined equations by introducing a lower dimensional measurement matrix and filling just m rows of the matrix equation,for the two hybrid methods respectively.Finally,a CS reversion is employed to reconstruct the original signal from the lower dimensional measurement data.The numerical results show that two hybrid methods can both save a lot of computing time while provide good results.2.A new hybrid method?CS-FMM-Mono?that introduced ideas from CS to the FMM is proposed for fast analysis of electromagnetic monostatic scattering from two-and three-dimensional targets.In CS-FMM-Mono,the CS is utilized to decrease the number of angular sampling,which also introduces a set of lower dimensional excitations,and the FMM worked as an electromagnetic field solver.By solving the electromagnetic problems under the new set of excitations,one can derive the samples of the signals.Finally,the induced currents can be reconstructed by solving an optimal problem.3.For the purpose of solving the multi-static scattering from two-and three-dimensional targets efficiently,a new method?CS-FMM-Multi?that combining the CS with the FMM is proposed.CS-FMM-Multi treats the scattered far field generated by all excitations in one scattering angle as the signal of interest.Based on the CS theory,the signal is measured directly.And then the measurement of the scattered field is converted to the measure of the induced currents and the matrix equation by the relationships between the scattered field,the induced currents and the excitations.Finally,the FMM and orthogonal matching pursuit?OMP?are utilized to solve the m easured matrix equations and the optimal?₁norm equations,respectively.4.To further improve the computational efficiency of the multi-static scattering from three dimensional targets,the CS is introduced into the commercial software FEKO,and a new method called CS-FEKO is proposed.In CS-FEKO,FEKO is treated as a black box,which worked as an electromagnetic simulating kernel,while CS is the pre-and post-ends of FEKO.The pre-end of the CS is utilized to form the new excitations that the FEKO needs,and the post-end of the CS is for the purpose of reading and recovering the scattered fields.Based on the special characteristics of the FEKO software,two measurement matrixes are proposed in this thesis.Numerical results show that CS can be applied with relatively minor modifications to FEKO,while improving the computational efficiency dramatically.5.A new hybrid method based on the reciprocity theorem and the PO is proposed and validated to calculate the electromagnetic backscattering from dielectric-coated conducting target located above dielectric randomly rough surface.The results obtained from the hybrid method show a good agreement with the numerical results derived from the conventional MoM in a special case of a perfectly electric conducting target located above a dielectric rough surface.Finally,the influence of some parameters related to the coating material on the composite scattering is investigated and discussed in detail.