Zhaoyang Cai

A numerically efficient method for the FDTD analysis of the shielding effectiveness of large shielding enclosures with thin-slots

A numerically efficient method for the finite-difference time-domain (FDTD) analysis of shielding effectiveness (SE) of large shielding enclosures has been proposed in this paper. FDTD has been widely applied in the SE analysis, but it is difficult to analyze the SE using the standard FDTD method when large shielding enclosures with thin-slots are involved. To model the narrow apertures without involving too much memory occupation, the thin-slot formalism is adopted. The parallel implementation is induced into the simulation in order to overcome the limitation of a single processors memory. To decrease the simulating time, windowing technique is used in the SE analysis. By using these artifices, the FDTD analysis of large shielding enclosures can be carried out efficiently.

Improved Formalism for the FDTD Analysis of Thin-Slot Penetration by Equivalence Principle

An improved formalism by the equivalence principle has been verified to be an accurate model of the field distribution near a thin slot for the finite-difference time-domain analysis of the thin-slot penetration.

Study of Periodic Structures at Oblique Incidence by Radial Point Interpolation Meshless Method

This paper presents a novel split-field radial point interpolation meshless (RPIM) scheme for the study of periodic structures under oblique incidence condition. The time delay in the transverse plane is eliminated with the introduction of a set of auxiliary variables. With the application of split-field technique to the standard RPIM method, a leap-frog formulation is derived. Numerical experiment is implemented to demonstrate the effectiveness of the code and the obtained result is compared with result of split-field finite-difference time domain method.

A unified radiative magnetohydrodynamics code for lightning-like discharge simulations

A two-dimensional Eulerian finite difference code is developed for solving the non-ideal magnetohydrodynamic (MHD) equations including the effects of self-consistent magnetic field, thermal conduction, resistivity, gravity, and radiation transfer, which when combined with specified pulse current models and plasma equations of state, can be used as a unified lightning return stroke solver. The differential equations are written in the covariant form in the cylindrical geometry and kept in the conservative form which enables some high-accuracy shock capturing schemes to be equipped in the lightning channel configuration naturally. In this code, the 5-order weighted essentially non-oscillatory scheme combined with Lax-Friedrichs flux splitting method is introduced for computing the convection terms of the MHD equations. The 3-order total variation diminishing Runge-Kutta integral operator is also equipped to keep the time-space accuracy of consistency. The numerical algorithms for non-ideal terms, e.g., arti...

A Novel Weakly Conditionally Stable FDTD Method for Periodic Structures

In this letter, a novel weakly conditionally stable finite-difference time-domain (FDTD) method for solving periodic structures is presented, which is extremely useful for periodic problem with thin slots in one or two directions. To verify the validity of the proposed formulations, a numerical example of electromagnetic band-gap (EBG) structure with thin slots is given. Compared to the alternating-direction implicit FDTD (ADI-FDTD) method, the presented method has higher accuracy and efficiency. Results show the running time can be reduced to about 2/3 of the periodic ADI-FDTD method in the same simulation. To reduce the numerical dispersion error, the optimized procedure is applied.

Complex frequency shifted (CFS) PML for the WLP-FDTD method

This paper proposes a complex frequency shifted PML absorbing boundary condition for the unconditionally stable finite difference time-domain method based on weighted Laguerre polynomials (WLPs). The method offers a number of advantages over the traditional implementations of the PML in the WLP-FDTD method. Numerical results show the CFS PML is effective.

An Efficient Spectral WLP-FDTD Algorithm for Periodic Structures

An efficient weighted Laguerre polynomials based spectral finite-difference time-domain scheme for 2-D periodic structures is proposed in this communication. By replacing the conventional single-angle incident wave with a constant transverse wavenumber wave, the periodic boundary condition can be directly implemented in the time domain for both oblique and normal incident waves. The huge sparse matrix is transformed into one tridiagonal matrix and one untridiagonal matrix by adding a perturbation term. Then, an iterative procedure is introduced to eliminate the error. Results from the numerical example and HFSS have verified the accuracy and efficiency of the presented method.

A novel TF/SF boundary for cylindrical FDTD method with ground

The finite-difference time-domain (FDTD) method is proposed as a means of accurately computing electromagnetic scattering by an external plane wave. The total-field/scattered-field (TF/SF) formulation resulted from attempts to realize a plane-wave source that avoids the difficulties caused by using either hard sources or the initial-condition approach. It is very complicated to get the closed form of the incident fields with ground for a pulse plane wave. In this letter, we carry out the formulations of TF/SF boundary with the ground for the cylindrical FDTD. Numerical examples verify that the presented method can solve the incident wave with ground conveniently and accurately.

The stability analysis of the hybrid thin-slot algorithm

Sub-cellular FDTD algorithms for modeling thin slots in conductors have previously been developed. The integral-equation based hybrid thin-slot algorithm (HTSA) has been shown to agree well with results of other methods for thin slots in planes. The HTSA can not only model slots having zero thickness but that having depth. However, instability occurred for some cases when the method is used. In this work, the stability of the HTSA is analyzed with different slot width, depth, and length, and the source effect on the stability has also been studied. The analysis shows that the HTSA is best for short, narrow and thick apertures, and when long, wide, thin slots are involved, other ways should be occupied.

Study on the field cross-section distribution of the EMP propagation in crooked tunnel with parallel implementation

This paper presents the characteristic of the field cross-section distribution of the EMP propagation in crooked tunnel, which is significant for the electromagnetic protection of the engineering underground and the wireless communications in tunnel. The tunnel can be seen as a waveguide approximately, and is excited by propagation model such as TE10, TM11, etc. We use parallel FDTD algorithm to deal with the large-scale computational model of the crooked tunnel. The adopted parallel strategy has been proved to be feasible by comparing the result of the serial FDTD method.