Physically Based Modeling of Hand-Assembled Wire Bundles for Accurate EMC Prediction

In this paper, a new modeling approach to generate wire bundles with geometry accurately mimicking the random displacements of the wires in real, hand-assembled bundles is proposed. To this end, the wire trajectories are modeled by three-dimensional (3-D) curves that retain continuity of the wire path and its first derivative, allow enforcing random fluctuations of wire position in the bundle cross section and controlling bundle density. An iterative algorithm involving both local and global perturbations of initially generated trajectories is used to prevent wire overlapping. As a whole, the proposed modeling approach is able to reproduce (through the use of a limited number of parameters) the main physical properties of real hand-assembled wire bundles. In order to get either deterministic or statistical estimates of the electromagnetic compatibility performance, the obtained bundle geometry can be easily imported into 3-D electromagnetic solvers or modeled as a multiconductor transmission line by approximating the nonuniform wire paths as a sequence of uniform cascaded sections. Application examples aimed at the prediction of crosstalk and field-to-wire coupling are used to prove the importance of accurate modeling of the bundle geometry and proper digitization of the bundle along its length for prediction at high frequencies of the electromagnetic noise induced in the terminal units.