| The increasing speed and density of digital circuits are contributing to an increase in electromagnetic compatibility problems in the form of distortion of signals and crosstalk between signal lines. Previously, digital circuits were designed without regard to the previously mentioned problems. This approach is costly in terms of both time and money since the circuit must be redesigned only after problems are observed.; This thesis is an effort to create some computer-aided design (CAD) tools that were not previously available for simulating high-speed digital circuits from an electromagnetics point of view. These computer tools would allow the digital design engineer to pinpoint problems with crosstalk and distortion in a given circuit layout before the circuit is first physically realized.; Simulation of digital systems is a two-step process. In the first step, the various components of a digital circuit must be characterized by either distributed circuit elements or lumped circuit elements. The finite element method was used in this thesis to calculate the various lumped and distributed parameters. In the case of multiconductor transmission lines, the per unit parameters of inductance, capacitance, resistance, and conductance are calculated using a two-dimensional finite element analysis. For various discontinuities that may be present in a circuit, three-dimensional finite element analysis is used to solve for the lumped inductance and capacitance which characterized each of the discontinuities.; The second step of the simulation is a time-domain analysis of a given digital system whose components were previously characterized. The program developed for this simulation unites conventional nonlinear time-domain circuit analysis techniques with modal analysis of multiconductor transmission lines. A lumped model for nonlinear digital devices is also given which uses easily measured external parameters.; Results are given for the calculation of the various circuit parameters of both transmission-line systems as well as lumped circuits. Results for the time-domain analysis of some representative transmission-line systems are given as well, which compare some experimental data to the numerical data. |
