This program will research the physics of electromagnetic interactions that Ultra-Wide Band (UWB) signals can induce on cables and printed circuit boards in complex electronic systems. It will find efficient algorithms for computing these interactions and simulating system behavior in time domain. The connecting backbones of multi-component systems are multi-component transmission lines (MTL). Most of the computational models for representing them are set in the frequency domain, and are approximate. A promising computational approach that is in time domain has already been formulated and partially developed. Based on a form of Green function, it is intrinsically three-dimensional and non-approximate. It will be further developed and evaluated for modeling MTLs and becoming one of the algorithmic tools in the planned simulation code. To make the complex system being simulated tractable, it must first be separated into individual components - computational modules - that interact with each other via distinct connections. The technique of splitting a system into modules according to its EM topology has been developed primarily in the frequency domain. This technique will be adapted for use in the time domain simulation code, whose development is the ultimate goal of the whole project.