Coupling Analysis of Non-Parallel Transmission Lines Excited by Ambient Wave Using a Time Domain Hybrid Method

A time domain hybrid method is presented to solve the coupling problem of non-parallel transmission lines (NPTLs) excited by ambient wave efficiently, which consists of transmission line (TL) equations, finite-difference time-domain (FDTD) method, and interpolation techniques. In this method, NPTLs are firstly divided into multiple independent transmission line segments according to the FDTD grids. Then TL equations are applied to build the coupling models of these TL segments, which rely on the calculation precisions of per unit length (p.u.l) distribution parameters of NPTLs and equivalent sources of TL equations. Thus, the p.u.l parameters of NPTLs are derived from empirical formulas, and the equivalent sources are obtained by some linear interpolation schemes of electric fields on the edges of FDTD grids. Finally, the difference scheme of FDTD is utilized to discretize the TL equations to obtain the voltages and currents on NPTLs and terminal loads. The significant feature of this hybrid method is embodied by its synchronous calculations of space electromagnetic fields and transient responses on NPTLs in time domain. The accuracy of this presented method is testified by the numerical simulations of plane wave coupling to NPTLs on the ground and in the shielded cavity by comparing with FDTD-SPICE method and CST software.