Algorithm Studies And Application Of Time-Domain Integral Equation On The Combined Problem Of Metal/Dielectric And EM-Circuit Simulation

The objective of studying and developing modern computing electromagnetic theory and algorithm is to solve all kinds of engineering electromagnetic problems. In the areas of computing radar cross section(RCS) of complex objects and broadband antenna design and Electromagnetic Compatibility(EMC) analysis, we often have to simulate the electromagnetic characteristics of some objects with complex metallic/ dielectric structures. Under these backgrounds, this thesis choses time domain integral equation (TDIE) theory as the theoretical foundation, marching-on-in-time(MOT) scheme as numerical solver, and investigates the scattering, radiation of the complex metallic/dielectric structures and mixed electromagnetic(EM)-circuit Simulation, and develops general electromagnetic computing software to solve the electromagnetic computing problems in engineering. The content of this thesis is made up of two parts, the first part expounds TDIE theory for complex metallic/dielectric structures and its resolving technique based on MOT; the second part expounds a formulation for mixed EM-circuit simulation using TDIE.In the first part of this thesis, the TDIE including time-domain electric field integral equation (TD-EFIE), time-domain magnetic field integral equation (TD-MFIE), time- domain combined field integral equation (TD-CFIE) and time-domain combining PMCHW(Poggio, Miller, Chang, Harrington, Wu) formulation for complex metallic/dielectric structures are elaborated uniformly based on the surface equivalence principle and boundary conditions firstly. For an attempt to choose optimal TDIE for different structures, the applicability and excellence as well as disadvantages of different TDIEs are compared. Then the solving procedures of these TDIEs based on the RWG function using MOT are elaborated, including the model building of complex objects, data extraction, some mathematical formulations in realizing the algorithm, calculating the matrix elements, the parameter extraction and the post processing after the simulation, etc.Different temporal bases functions are evaluated and their high frequency components are compared for the cause of their impact on late-time stability in this thesis. In addition, the method of impedance matrix prestorage for composite structures is presented, which largely saves the time of repeatedly computing impedance elements, and the required memory is formulated. In the procedure of computing impedance matrix elements, an improved method of accurate evaluation of retarded time integrals with singularity in self-impedance elements in MOT scheme is presented, which improve the late-time stability of MOT scheme. Some numerical results of practical complex antenna and scattering problems are presented to illustrate the validity of the method and better stability of TD-E-PMCHW compared with TD-EFIE for complex metallic/dielectric structures.In the second part, for the interconnection between complex metallic/dielectric EM structures and circuits, a simultaneous simulation scheme of EM section and linear/ nonlinear lumped circuit section is developed through combining TDIE used in EM simulation and MNA used in circuit simulation. The scheme is based on thought of "coupling current" serving as the bridge to connect the circuit section and EM section. Following the "coupling current", the "modified" continuity equation and "generalized" Kirchoff's Law are used to analyzing the coupling between the EM section and circuit section.Finally, a microstrip power splitter and a microstrip filter are analyzed using TD-E-PMCHW algorithm. In addition, a miniature dielectric resonator loaded patch antenna and a printed circular disc monopole Antenna for UWB systems are computed, and the performance of impedance match and radiation of the two antennas is analyzed. Through analysis effect of the antennas' structure parameters on resonant frequency and return loss bandwith is gained. For nonlinear elements in circuits, a diode applied in a mixer is computed. All these examples demonstrate the better stability in analysis of complex structure of TD-E-PMCHW algorithm compared with other TDIEs and the advantages of computation in time domain.