Hybrid Computational Methods For Investigating On Electromagnetic Pulse Effects And Mechanism In Communication Systems

With the rapid development of electronic information technology, electromagnetic compatibility (EMC) and electromagnetic interference (EMI) issues are more and more important for the realization of various communication systems with high realiability. Under such circumstances, to develop accurate and fast computational electromagnetic methods to handle practical EMC/EMI problems of complex 3-D structures is very challenging and much effort needs to be further devoted.This dissertation is focused on the development of various hybrid numerical methods with high efficiency to study electromagnetic pulse effects and interaction mechanism in some typical communication systems illuminated by an external electromagnetic pulse (EMP). Its academic contribution is briefly summarized as follows.(1) In Chapter 2, hybrid FDTD-based method is proposed at first, in which several sub-grid algorithms are proposed to accurately predict shielding effectivenesses (SE) of various metallic enclosures with thin slots, thin wires, with one software package developed. The improved hybrid FDTD code is computationally efficient; and it is able to capture all information during the interaction process of one or several EMPs with metallic enclosures for different geometries and physical parameters, respectively.(2) In Chapter 3, further numerical studies are carried out to investigate inner field characteristics of various metallic enclosures. In particular, thin-wire antenna loading case and common frequency interference problem caused by multiple EMP incidences simultaneous are treated appropriately. Further, some useful techniques used to enhance the SE of metallic enclosures are suggested; based on sufficient numerical information obtained using the developed hybrid FDTD algorithms.(3) In Chapter 4, an improved theoretical transfer impedance model of shield cable together with a set of coupling field equations of shielded cables is proposed. The modified nodal approach (MNA) is integrated with FDTD to predict EMP response and interaction mechanism in transmission lines (MTL)networks even with nonlinear devices loaded. (4) In Chapter5, hybrid field-circuit FDTD algorithm is developed to handle lumped-element microwave devices under the impact of an EMP-induced signal, with the techniques of linear one- and two-port networks implemented. Further, the technique of multi-port lumped-element networks is implemented into the development of hybrid FDTD algorithm. The EMP responses of several microwave devices, such as filters and amplifiers are examined and discussed.(5) In Chapter 6, transient thermal responses of active semiconductor devices are investigated in the presence of an EMP using nonlinear time-domain finite element method (TD-FEM), and the maximum channel temperature is captured and discussed. This information is useful for further electromagnetic protection of on-chip devices form electro-thermal breakdown.(6) In Chapter 7, in order to improve the simulation efficiency of ADI-FDTD method, one new arbitrary order implicit FDTD method, based on locally one dimension, is proposed. Further, various theoretical and numerical verifications of its unconditionally stability and numerical dispersion are performed, and in particular, the effect of some parameters related to numerical dispersion error is investigated comprehensively. It is found that the second-order one presents the numerical dispersion errors similar to those of the ADI-FDTD method, but with much improved computational efficiency achieved.(7) In Chapter 7, in order to further reduce the dispersion errors, a parameter optimized LOD-FDTD method is proposed. By setting different optimization objectives, such method can satisfy different requirements of computational accuracy. The performance variation of the (2, 4) parameter-optimized LOD-FDTD method, with different frequencies and time steps, is also examined in detail. Various numerical results show that the PO-LOD-FDTD method can dramatically reduce the dispersion errors to the level of the conventional (2, 4) stencil FDTD, but with larger time steps and without introducing any additional computational cost. Finally, it is verified by dealing with typical EMC/EMI problem.(8) In Chapter 8, the EMP effects on some high-performance miniaturized filters and active modules are investigated experimentally through an EMP injecting test system, and these experiments can provide some beneficial guidelines for electromagnetic protection of the passive devices and active modules in various communicational systems.