| X-parameters, the nonlinear extension of scattering parameters, have been shown to have a wide array of applications in the modeling of nonlinear devices and systems. In this dissertation, the use of X-parameters is extended to signal integrity applications, particularly to the modeling of input/output buffers. These input/output buffers are the nonlinear terminations of the high-speed links that the signal integrity engineer is tasked with designing and optimizing. Brief treatments of the X-parameter formalism, the harmonic balance simulation method, the latency insertion method, and the Input/Output Buffer Information Specification (IBIS) are provided as background information along with some examples of how X-parameters are generated via simulation and measurement and used in simulation. Two processes for using X-parameters for signal integrity purposes, lim2x and x2ibis, are described and analyzed in detail.;The process lim2x uses the latency insertion method to perform a transient simulation of a given circuit with specific port stimuli and terminations. It then uses Fourier analysis to extract X-parameters from the simulation results. This process leverages the linear numerical complexity of the latency insertion method to provide a viable X-parameter generation platform that is well-suited for very large, high-frequency circuits, particularly those which are seen in input/output buffers. The lim2x process is demonstrated on a simple buffer circuit. The X-parameters generated from it are compared to those generated with harmonic balance and are shown to be in excellent agreement.;IBIS models are the current standard for modeling input/output buffer circuits. The process x2ibis uses X-parameter models to generate the current-voltage and voltage-time tables used in an IBIS file. This process shows that properly generated X-parameter models contain the information needed to describe the behavior of an input/output buffer. Results are compared with those of another method of IBIS model generation. |
