| With the continuous development of electronic technology,the feature size of modern electronic equipment is continuously reduced,its internal complexity is constantly increasing,and the demand for its operating frequency and power is constantly increasing.This makes it be affected by multiple physical fields such as electromagnetic fields and thermal fields during its operation.Therefore,its design method not only needs to ensure the main electromagnetic performance,but also needs to evaluate factors that affect reliability such as heat dissipation performance.What’s more,it is necessary to consider the electromagnetic-thermal and other multi-physics coupling problems of its interaction,so as to optimize its comprehensive performance.Among the research methods for analyzing these problems,the theoretical analysis method is only suitable for simple structures,which is no longer suitable for the increasingly complex structures of modern electronic equipment;the test period of the experimental test method is long and its cost is high,and the test site,surrounding environment and human factors will interfere with the experimental results,which may cause large errors;and with the development of computer technology,it is an economical and efficient means to simulate and analyze the coupling problems of electromagnetic-thermal and other multi-physics fields through numerical analysis methods and CAE technology.Therefore,it is of great significance to study efficient numerical analysis methods and CAE technology,and develop electromagnetic-thermal coupling simulation CAE software for electronic equipment.This dissertation mainly focuses on a series of research work on electromagneticthermal coupling simulation and CAE technology based on the finite element method(FEM).Aiming at the electromagnetic analysis problems,thermal analysis problems and electromagnetic-thermal coupling problems involved in electronic equipment,the corresponding efficient simulation technology research was carried out,and on this basis,the electromagnetic-thermal coupling simulation CAE software was developed.The main work and innovations of this dissertation can be summarized in the following five aspects:1.An efficient electromagnetic simulation technology based on the FEM is proposed.Firstly,the finite element formulation of the electromagnetic boundary value problem is derived.Then,since the solution of a large finite element linear sparse matrix consumes most of the computing resources,it is necessary to use a suitable matrix solution method to improve the efficiency of finite element analysis.Therefore,a hybrid PMG-MFBICF preconditioning technology combining p-type multigrid preprocessing and multi-front block incomplete Cholesky factorization based on the generalized conjugate residual iteration method is proposed to improve the efficiency in solving matrices.Then,for the infinite periodic structure problem,by introducing the periodic boundary conditions,the intractable infinite periodic structure problem is transformed into a finite area analysis of the periodic unit,thereby saving the consumption of computing resources.Finally,a three-dimensional electromagnetic simulation solver EMS based on the FEM is developed,and the efficiency and accuracy of the solver are proved by numerical simulation examples.2.A high-speed interconnection system simulation technology based on transfinite element method is proposed.Firstly,based on the finite element electromagnetic simulation research in Chapter 2,the Helmholtz equation is combined with the mode function expansion on waveguide ports to derive the finite element formula.Finally,the finite element matrix based on the transfinite element method is obtained,which can directly obtain the mode network parameters of multiple waveguide ports and provide the basis for the acquisition of terminal network parameters of multi-conductor ports.Then,aiming at the problem of multi-conductor ports in high-speed interconnection systems,the transfinite element method is further combined with the terminal theory.The conversion formulas from mode scattering parameters to terminal network parameters and the conversion formulas from terminal network parameters to differential network parameters can be derived.The simulation analysis research on terminal network parameters of multi-conductor ports is completed accurately and conveniently.Finally,a three-dimensional simulation solver TFES based on the transfinite element method is developed,and the solver is verified numerically through numerical simulation examples.3.An efficient thermal simulation technology based on the FEM is proposed.Firstly,the finite element formula of the three-dimensional heat conduction boundary value problem is deduced.Then,for nonlinear thermal problems,the p-type scalar multigrid preconditioning technology and inexact Newton-Raphson method are used to conduct accurate and efficient simulation analysis of radiation boundary thermal problems,and the nonlinear contact boundary method and energy functional minimization technology are used to conduct accurate and efficient simulation analysis of nonlinear contact thermal problems with temperature variation.Then,a non-overlapping domain decomposition method based on the internal penalty is used for the thermal analysis of large-scale complex structures,and the block Jacobi and MFBICF preconditioning techniques are used to improve the efficiency of solving large-scale matrices.Finally,a threedimensional thermal simulation solver TCS based on the FEM is developed,and the efficiency and accuracy of the solver are demonstrated by numerical simulation examples.4.An electromagnetic-thermal coupling simulation technology for the traveling wave tubes is proposed.Firstly,aiming at the temperature change properties of material parameters,a variable material parameter simulation technology is proposed,and the nonlinear temperature change curve is fitted by using the interpolation method.Then,aiming at the coupling problem of results of multiple fields in the electromagnetic-thermal coupling simulation,the weak coupling mode is adopted.An accurate grid-level coupling solution technology is proposed,which realizes the joint generation of grids of electromagnetic solution domain and thermal solution domain,calculation of highfrequency dielectric loss powers and accurate loading of electron bombardment heat sources.The electromagnetic-thermal coupling simulation analysis can be realized accurately and automatically through the grid mapping relationship and based on the solution process control.5.Based on the above simulation technology,an electromagnetic-thermal coupling simulation CAE software ETCS with completely independent intellectual property rights has been developed.The software has complete pre-processing model setting,simulation analysis and post-processing display modules,which can realize efficient and accurate simulation analysis of high-frequency electromagnetic problems,heat conduction problems,electromagnetic-thermal coupling problems,and can help users improve the simulation design capabilities of related issues,reduce design costs,shorten the design and analysis cycle,so that better production design can be carried out. |
