Broadband circuit model for coupling between transmission lines and current probes in metallic enclosures of arbitrary shape

An equivalent circuit approach for the coupling between a transmission line and a current probe placed inside a metallic enclosure is presented. Within the limits of transmission line theory, we can use modal decomposition to derive the coupling. The convergence of this modal representation is accelerated by the extraction of quasiststic circuit elements. The resulting expression can be used together with transmission line theory to construct the impedance matrix of the system or cast into a broadband equivalent circuit, which is inherently stable and allows the simulation of arbitrary nonlinear loads with a commercial circuit simulator. The presented equivalent circuit model is validated in the frequency and time domain with an example computer casing of irregular shape.