Time response of a network containing field-excited multiconductor lossy lines with nonlinear loads

A combined frequency- and time-domain method is proposed for the analysis of a network containing field-excited multiconductor lines with nonlinear loads above a lossy ground. The incident electric field in free space is due to the primary EMP (electromagnetic pulse) wave and the wave reflected from the ground plane. Each excited line-section is represented by a PI-type equivalent circuit with induced shunt current sources in the frequency domain. The nonlinear loads are replaced by unknown current sources. The transient voltages and currents at each port of the network are determined by defining the Thevenin or Norton time-domain equations. The transient open-ended voltages or short-circuit currents are computed by the inverse Fourier transform of the corresponding quantities by the nodal approach in the frequency domain. The defined time-domain model at each port is constituted by the second type Volterra equation and the nonlinear known boundary expressions. The proposed method is applied to compute the transient response of a tree-type network including three line-sections above a lossy ground, with terminal nonlinear protection devices, excited by an EMP plane wave