Due to the numerical methods used for the coupling analysis of the shielded cavity with penetrated wire excited by ambient wave are lack, an efficient time domain hybrid method is presented in this article, which consists of thin wire finite difference time domain (FDTD) method and hybrid FDTD and transmission line equations method (called FDTD‐TL method). In this method, the penetrated wire is decomposed into external and internal transmission lines according to the enclosure structure of the shielded cavity firstly. Then the thin wire FDTD method is applied to calculate the currents on the external transmission line, which are enforced as the boundary of the internal transmission line naturally. Meanwhile the FDTD‐TL method is used to build the coupling model of ambient wave to the internal transmission line to obtain the voltage and current responses on the terminal load of internal line. This method has one prominent advantage is that it can realize the cooperative calculations of electromagnetic field radiation and the coupling responses on the penetrated wire. Finally, two numerical simulations of ambient wave to one shielded cavity with penetrated wire in the free space and shielded cavity are utilized to verify the accuracy and efficiency of this presented method by comparing with the electromagnetic software CST.

At present, numerical methods applied to the coupling analysis of transmission lines on the lossy dielectric layer excited by ambient wave are still rare in the literature. As a temptation to fill this gap, a novel time domain hybrid method is proposed, in which the modified transmission line (TL) equations, finite-difference time-domain (FDTD) method, and some interpolation schemes are organically combined together. It can overcome the difficulty in building the coupling model of ambient wave to transmission lines on the lossy dielectric layer greatly. In this method, the modified transmission line (TL) equations suitable for the coupling analysis of multi-conductor transmission lines (MTLs) on the lossy dielectric layer are derived from the traditional TL equations firstly. Compared with the traditional TL equations, the electromagnetic fields in the lossy dielectric layer are introduced into the equivalent distribution sources of modified TL equations. Generally, the precision of TL equations is dependent on the accuracy of equivalent distribution sources, which are obtained from the incident electric fields parallel and perpendicular to the MTLs. Therefore, the FDTD method is utilized to model the structure of lossy dielectric layer to calculate the electromagnetic field distribution surrounding the MTLs and in the dielectric layer. Since the heights and distances of MTLs can be arbitrary values, the electric fields parallel and perpendicular to the MTLs cannot be obtained from the electric fields on the edges of FDTD grids directly, which should be computed via some interpolation schemes. Then the modified TL equations are established, which should be solved by the central difference scheme of FDTD method to obtain the voltages and currents on the MTLs and terminal loads. The significant feature of this proposed method is that it can realize the synchronous calculations of electromagnetic field radiation and transient responses on the MTLs. Finally, numerical simulations of single and multiconductor transmission lines on the lossy dielectric layer excited by ambient wave at different incident angles are employed to exhibit the accuracy and efficiency of the proposed method by comparing with the simulation software CST. Because the structures of MTLs do not need to be meshed, the proposed method outperforms the simulation software CST in both memory usage and computation time.

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This paper presents a hybrid method consisting of thin wire FDTD method and transmission line (TL) equations to be used for the coupling analysis of multiconductor transmission lines (MTLs) excited by a dipole antenna. In this method, the thin wire FDTD method is used to build the structure of the dipole antenna and obtain the radiation electromagnetic fields surrounding the MTLs, which are introduced into the TL equations as the distribution sources. The TL equations are utilized to model the coupling of the radiation electromagnetic fields to the MTLs, which are discrete by the scheme of the FDTD method to obtain the transient voltage and current responses on the lines and terminal loads. The accuracy and efficiency of this method have been verified by comparing with the commercial simulation software CST via one case. Moreover, the influences of the frequencies and polarization of the dipole antenna and the heights of the MTLs on the coupling of MTLs are analyzed.