The numerical superiority of the unconditionally stable fundamental locally one-dimensional finite-difference time-domain (FLOD-FDTD) method has been proved in some studies. In this paper, the FLOD-FDTD method is extended to simulate general dispersive media in combination with the auxiliary differential equation (ADE) scheme with formulation based on the electric field ( E ) and electric polarization ( P ). The relative permittivity of dispersive media is described by the arbitrary multi-term modified Lorentz model which can also represents Debye and Drude models. Thus, this method is able to include different types of dispersion in a unified formulation. The correctness and efficiency of the proposed method is demonstrated by some numerical cases.

Mid‐infrared absorption spectroscopy is a powerful tool to identify analytes by detecting their material fingerprint in a label‐free way, but it faces barriers on trace‐amount analysis due to the difficulties in enhancing the broadband spectral signals. Here, we propose a sensing scheme based on the angular scanning of polarized light on a dielectric metagrating, and demonstrate it by numerical simulation. This approach not only indicates a series of significant signal enhancement factors over 30 times in an ultra‐wide mid‐infrared band, but also enables the explicit identification for various analytes, including 2D materials and trace‐amount thin film samples. Our method would facilitate mid‐infrared sensing for 2D materials and trace‐amount analysis, and enable many new applications on non‐destructive molecular identification.

In this paper, a new architecture for the emergency healthcare system based on mobile cloud computation (MCC) and fifth-generation (5G) wireless link is proposed. Based on the processing speed of MCC and the communication rate of 5G scheme, this system can monitor and locate patients in real time. Multiple base stations of the massive multiple input multiple output cooperate with each other to locate the patients using cross-location method. Then, a new direction-of-arrival (DOA) estimation algorithm is proposed in the presence of unknown mutual coupling. The uncorrelated signals are first estimated using the estimation of signal parameters via rotational invariance technique algorithm. Then, these estimators construct the manifold matrix of uncorrelated signals to estimate the mutual coupling coefficients. The information about uncorrelated signals and mutual coupling is eliminated based on oblique projection technique in order to estimate the DOAs of coherent signals using the original array. Finally, the DOAs of coherent signals are achieved based on sparse representation theory. Simulation results demonstrate the effectiveness and performance of the proposed algorithm.

The preceding works introduced the leapfrog complying divergence implicit finite-difference time-domain (CDI-FDTD) method, which exhibits high accuracy and unconditional stability. In this study, the method is reformulated to simulate general electrically anisotropic and dispersive media. The auxiliary differential equation (ADE) method is employed to solve the equivalent polarization currents, which are then integrated into the CDI-FDTD method. The iterative formulae are presented, and the calculation method is similar to that of the traditional CDI-FDTD method. Additionally, the Von Neumann method is utilized to analyze the unconditional stability of the proposed method. To evaluate the performance of the proposed method, three numerical cases are conducted. These include calculating the transmission and reflection coefficients of a monolayer graphene sheet and a monolayer magnetized plasma, as well as the scattering properties of a cubic block plasma. The numerical results obtained by the proposed method demonstrate its accuracy and efficiency in simulating general anisotropic dispersive media, compared to both the analytical method and the traditional FDTD method.

A finite-difference time-domain (FDTD) method is developed to analyze electromagnetic scattering from threedimensional (3-D) fully anisotropic periodic structures impinged by obliquely incident plane waves. Starting from Maxwell’s curl equations, we employ material transformation matrices to link the update of the electric and magnetic fields in the FDTD method. The problem under consideration is Bloch-Floquet periodic in the horizontal directions but finite in the vertical direction. At the FDTD truncation boundaries in the horizontal directions, the Bloch-Floquet periodic boundary conditions (BPBCs) are applied, while the perfectly matched layer (PML) absorbing boundary condition is implemented for the vertical direction. We design three different anisotropic models in 3-D simulations to validate our method with a commercial software package COMSOL. These examples show the accuracy and efficiency of the FDTD method for analyzing the propagation characteristics, including reflectance, transmittance, absorptance, and complex reflection and transmission coefficients for the fully anisotropic periodic structures.

Efficient and unsplit-field-based stretched coordinate perfectly matched layer (PML) formulations with the complex frequency-shifted (CFS) scheme that combine the memory-minimized method (Tri-M) and the direct Z-transform (DZT) method are proposed to truncate the finite-difference time-domain lattices. The proposed algorithm takes advantage of the minimized memory of the Tri-M method, the optimal accuracy of the DZT method, and the capacity of the PML for attenuating evanescent waves and reducing late-time reflections. Three 3-D numerical simulations have been carried out to validate the proposed formulations.