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An efficient discontinuous Galerkin time-domain (DGTD) method with an implementation of generalized periodic boundary conditions (PBCs) is proposed to analyze the electromagnetic scattering from arbitrary skewed periodic structures. The transformed field variable approach and the discontinuous Galerkin technique with nonconformal mesh are presented to implement the generalized PBCs for arbitrary skewed periodic structures under both normally and obliquely incident illuminations. The arbitrary high-order time-stepping scheme, which retains the DGTD feature of high-order accuracy and breaks the Butcher barrier, is extended to a transformed version of Maxwell’s equations introduced by the generalized PBCs implementation. The proposed method enables an efficient modeling of arbitrary skewed arrays with a fixed unit-cell mesh. Numerical examples for skewed periodic structures, such as an infinite gold film, 1-D and 2-D staggered dipole frequency-selective surfaces (FSSs), mechanically reconfigurable FSSs, and skewed nanohole arrays, are presented to demonstrate the accuracy and applicability of the proposed method. [ABSTRACT FROM AUTHOR]

Dynamic characteristics of streamer discharge in a parallel-plane electrode system are described within the framework of a drift-diffusion model coupled with Poisson’s equation at atmospheric pressure. The spectral-element time-domain (SETD) method is applied to the solution of streamer discharge problems, and the flux-corrected-transport (FCT) algorithm is also applied to suppress possible numerical divergence or numerical oscillation. The performance of the proposed method is examined in a number of numerical tests. Then the tempo-spatial evolutions of the streamer are obtained in detail under the different situations. Numerical results show that after the initial stage of adjustment, the streamers propagate in a steady-state mode, where the characteristics of the steady state are decided by background ionization frequency which is determined by pressure and background electric field together. And space charge effect is a dominant factor for the distortion of spatial electric field, making the discharge channel expand toward both electrodes faster. These works presented here are instructive for high-voltage insulating device protection and plasma application. [ABSTRACT FROM AUTHOR]

In this article, an efficient transient analysis method with arbitrary high-order accuracy for nonlinear field-circuit cosimulation problems is proposed. The proposed method combines a local time-stepping (LTS) technique with the discontinuous Galerkin time-domain (DGTD) method based on an arbitrary high-order derivatives (ADER) time integration scheme. The stability of the proposed method is not limited by the global time step size, allowing nonlinear and linear elements to update themselves with individual and optimal time intervals in accordance with the local stability condition. It is shown that the efficiency of the proposed method can be significantly improved when the nonlinear effects increase, which requires a smaller time interval to ensure system convergence. Several field-circuit coupling structures are simulated to demonstrate the accuracy and efficiency of the proposed method, confirming that it represents an effective tool for transient analysis of nonlinear field-circuit structures. [ABSTRACT FROM AUTHOR]

In this communication, a paralleled interior penalty discontinuous Galerkin time-domain method based on the vector wave equation (IPDG-WE) combining with a generalized dispersive material (GDM) model is introduced. In addition, the auxiliary differential equation (ADE) technique is employed to establish a universal solution for scattering analysis of dispersive structures in a wide frequency range. The proposed method presents great characteristics of energy conservation and the optimal convergence rate even in low-order bases and exhibits promising competitiveness in CPU time and memory usage compared with the traditional Maxwell’s equations-based discontinuous Galerkin time-domain (DGTD-ME) method. Numerical simulations are executed to demonstrate the accuracy and efficiency of the proposed method, which realize twice the memory and triple the CPU time reductions. [ABSTRACT FROM AUTHOR]

In this paper, the multi-carrier microwave breakdown in air-SF6 mixtures is analyzed with the spectral-element time-domain method. In this process, a three-dimensional multi-physics model coupling Maxwell's equations with electron fluid equations is established. The tail-erosion and frequency shift phenomenon caused by multi-carrier microwave breakdown in different proportions of air-SF6 mixtures can be observed. Numerical results demonstrate that multi-carriers will make the wireless communication system sensitive to microwave breakdown. On the other hand, the different proportions of air-SF6 mixtures can obviously improve the breakdown threshold to inhibit the multi-carrier microwave breakdown, which is favorable to the propagation of multi-carrier microwaves in air. Meanwhile, increasing the pressure can suppress the frequency shift phenomenon, and the proportion of different SF6 in the mixed gas has little effect on the frequency shift of the transmitted wave. Our research provides theoretical guidance for comprehensively exploring the characteristics and physical mechanism of multi-carrier microwave breakdown in air-SF6 mixtures and is helpful for protection of microwave devices and plasma application. [ABSTRACT FROM AUTHOR]

In this paper, a modified multi-physics method for transient analysis of high-power microwaves (HPM) gas breakdown is proposed. Distinguished from previous works, the proposed method couples the plasma fluid equations with Maxwell's equations to fully consider the interaction between plasma and electromagnetic waves. To perform the numerical simulation, the spectral-element time-domain method is employed, which has the advantages of spectral accuracy and block diagonal mass matrix. Numerical simulations are conducted to demonstrate the accuracy of the proposed method. Moreover, with an external DC magnetic field, HPM breakdown can be effectively delayed by increasing its breakdown threshold. Simultaneously, the phase shift of electromagnetic waves during the HPM breakdown can also be controlled by the external DC magnetic field, which can improve the quality of the phase-modulated signal in HPM illumination. This proposed framework is expected to provide an effective numerical tool for analyzing the microwave propagation characteristics and suppressing the HPM breakdown in gas-filled microwave devices. [ABSTRACT FROM AUTHOR]

A three-dimensional (3D) multi-physics model is developed to describe the characteristics of light emitted from high power microwave nitrogen breakdown. This model consists of electromagnetic (EM) fields and plasma physics in which plasma physics and EM fields are controlled by plasma fluid equations and Maxwell's equations. A continuity equation of excited molecule (ion) is introduced into the fluid model to describe the light brightness produced in the breakdown system. The resulting multi-physics system is analyzed and described with the spectral-element time-domain method. The external dc magnetic field applied in breakdown volume is used to prolong the breakdown time. The light brightness is weakened by the dc magnetic field before the occurrence of breakdown, and the variation in light brightness with different wavelengths produced by breakdown is discussed. The position of the maximum light brightness spot can be changed by the influence of the dc magnetic field on the electron concentration. Our research provides theoretical guidance for further understanding the physical process and physical phenomena in microwave nitrogen breakdown. [ABSTRACT FROM AUTHOR]

A nonconforming mixed-element (tetrahedral/hexahedral) discontinuous Galerkin time-domain (DGTD) method with a perfectly matched layer (PML) absorber is proposed to analyze the electromagnetic scattering from doubly periodic structures. An efficient auxiliary differential equation (ADE)-based PML implementation is presented with transformed field variables introduced by the time-domain periodic boundary conditions (PBCs). The proposed PML implementation performs well in absorbing the waves with high-order Floquet modes. Additionally, a mixed-order DGTD method is introduced to improve the proposed PML implementation’s long-term stability and reduce the total computational cost. Based on the mixed tetrahedral and hexahedral grids, the nonconforming DGTD method can provide accurate field distribution near complex scattering geometries while simultaneously reducing the degrees of freedom (DoF) in the rest of the computational domain, including the open space and PML regions. Finally, electromagnetic simulations are presented to demonstrate the applicability, accuracy, and efficiency of the proposed method. [ABSTRACT FROM AUTHOR]

A flexible and universal domain decomposition parallel scheme is proposed for the unconditionally stable finite-difference time-domain (FDTD) method. The leapfrog alternating direction implicit FDTD (ADI-FDTD) method is employed to eliminate the restriction of the Courant–Friedrichs–Lewy stability condition. The proposed domain decomposition parallel implementation of the leapfrog ADI-FDTD method is more flexible with process allocation and requires fewer data communications. A buffer region is introduced to decouple the interactions between neighboring subdomains at each time step. Electromagnetic simulations are presented to demonstrate the applicability, accuracy, and efficiency of the proposed method. [ABSTRACT FROM AUTHOR]

An efficient polynomial chaos expansion (PCE)-based discontinuous Galerkin time-domain (DGTD) method is proposed to analyze microwave components with interval-valued electromagnetic (EM) parameters. The proposed method retains the flexibility of the conventional DGTD method in the element-level domain decomposition and parallel computing. Numerical examples with the interval-valued electron density of plasma and permittivity of a dielectric block are presented to demonstrate the accuracy and capability of the proposed method. The scattering from a dielectric sphere with an interval-valued permittivity is evaluated to verify the applicability of the proposed method in unbounded scattering analysis. Numerical results illustrate that the proposed PCE-based DGTD method has great superiority in computational accuracy and efficiency over the Gaussian process (GP) technique and the Monte Carlo (MC) method in both deterministic and stochastic analyses with the interval-valued parameters, and it requires only a single simulation to obtain all results in the high-dimensional interval domains. [ABSTRACT FROM AUTHOR]

In this paper, mechanic–electric–circuit coupling algorithm based on the finite‐difference time‐domain (FDTD) method is proposed to analyze a one‐order microwave bulk acoustic wave (BAW) filter. FDTD method is used to solve the coupled mechanic–electric–circuit system equations to obtain the voltage and current at port position of the BAW filter in the time domain. Then S parameters of the BAW filter in the frequency domain are calculated using the Fourier transform. In our work, a one‐order BAW filter consists of two film bulk acoustic resonators (FBARs) by means of series and parallel. These two FBARs in the BAW filter are coupled together through an equivalent electrical connection. Similarly, multiphysical mechanic–electric–circuit analysis of the BAW filter is implemented in the commercial software COMSOL, which is realized by the time‐domain finite element method. The accuracy of the proposed method is verified by comparison with simulation results in COMSOL. In addition, the computational time and memory of the proposed method have obvious advantages over those of COMSOL. [ABSTRACT FROM AUTHOR]

This paper designs a mesa‐structured monolithic microwave integrated circuit (MMIC) limiter working in C‐band. The quasi‐vertical Si‐based PIN diodes are heterogeneously integrated on the SiC substrate with high thermal conductivity, such that the parasitic parameters are greatly reduced and the power capacity is enhanced. According to the measured results, a maximum insertion loss of 1.1 dB and a minimum return loss of 17.69 dB for both input and output terminals are realized to cover the 5–6 GHz frequency range. The flat leakage of 23 dBm is achieved for a 150 W continuous wave and 370 W pulse input signal level. We believe the proposed MMIC limiter provides an effective tool that can be used in the transmit‐receive modules working in C‐band. [ABSTRACT FROM AUTHOR]