Study Of Some Key Problems Of The Multidomain Pseudospectral Time-Domain Algorithm And Its Applications

In order to improve the stability and accuracy of the multidomain pseudospectral time-domain (MPSTD) algorithm and expand its application, some key problems of its theories and applications are studied in this paper. With respect to the theories, the absorbing boundary conditions (ABCs) and matching conditions of the interfaces are studied. With respect to the applications, two kinds of electromagnetic problems are analyzed and some key technologies are studied.In this paper, the convolutional perfectly matched layers (CPML) ABC which performance is much better than the traditional PML ABC is applied to the pseudospectral time-domain (PSTD) algorithm. Due to the values of the CPML's parameters are different in the PSTD and the finite-difference time-domain (FDTD), the setting principles of these parameters are studied by using the Fourier PSTD algorithm and the value range of these parameters is obtained when the CPML's performance is optimal. Based on these principles, the CPML is applied to the MPSTD, and the absorbing performances on different conditions are studied. Finally, principles of dealing with the CPML ABC in the MPSTD are presented as a conclusion.The matching conditions are studied for the type of interfaces which separating two subdomains with the same material. Firstly, for the characteristic variables (CV) matching condition and the physical boundary (PB) matching condition which all presently used in this type of interface, the stability of them is compared and analyzed. The numerical results indicate that the CV matching condition is more stable than the PB matching condition. Secondly, for overcoming the limitations of the CV matching condition, the improved characteristic variables (ICV) matching condition is presented,which makes the CV matching condition perfect. Finally, based on the ICV matching condition, the boundary connecting condition of total-scattered fields is deduced for the interfaces of subdomains, and a scheme of the introduction of incident wave is proposed, which easily realized the introduction of the incident wave and the extraction of the scattering field.The matching conditions are studied for the type of the interfaces which separating two subdomains with different material. Firstly,a characteristic variables-physical boundary (CV-PB) matching condition is proposed by combining the characteristic variables of Maxwell's equations and physical boundary condition, and it proves that the CV matching condition is a special case of the CV-PB matching condition. Secondly, stability and accuracy of the CV-PB matching condition and the PB matching condition are compared and analyzed. The numerical results indicate that the CV-PB matching condition is more stable and accurate than the PB matching conditions.Two different introduction methods of incident wave are studied, as well as a new setting method of excitation source when the waveguide is analyzed using the MPSTD. Based on these schemes, the broad wall slot's characteristics in rectangular waveguide are analyzed, and the numerical results indicate that the MPSTD is more accurate and efficient to analyze this type of problems. It offers an approach for analyzing the broad-band characteristic of complex waveguide problems accurately and efficiently.For accurately and quickly analyzing the microstrip antennas or the similar electromagnetic structures, a hybrid MPSTD-FDTD algorithm is proposed which combines the MPSTD and the FDTD. Firstly, the accuracy of the hybrid algorithm is analyzed and discussed. Secondly, two kinds of microstrip antennas are analyzed by using the algorithm, and the numerical results verified the hybrid algorithm is valid and accurate. It offers an approach for accurately and quickly analyzing microstrip antennas or similar electromagnetic structures.