Static modeling of periodic structures with application to braided shields

Models for predicting the penetration of cable shields have a long history and have had considerable success. However, occasionally, modifications to cable topology call into question the use of these models. It would thus be useful to assemble a first principles model of the shield, not only to handle changes in topology from the standard geometry, but also to form a theoretical underpinning for the existing models. The paper discusses the progress on a first principles model of a braided shield. A planar approximation to the cylindrical braid is used to reduce the number of parameters involved in the braid description. The model uses Ewald summation techniques to sum efficiently over the periodicity of the braid. Connections between the electrostatic potential behind the planar braid shield and the transfer capacitance, and also between the magnetic flux behind the shield and transfer inductance, are derived to connect planar quantities with the transfer immittances of the cylindrical braid. The braid wires are taken to be perfect electrical conductors (i.e., losses are not considered at present). Moment methods are used to calculate the static potentials about the braid wires and match the boundary conditions on the wires. The field from the net current on the wire is represented by a vector potential.