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This letter focuses on the propagation characteristics of the electromagnetic wave in the plasma under high-power microwave (HPM) illumination. A multi-physical method coupling the electromagnetic field and plasma fluid field is proposed as the dynamic Drude model. The differences between the method based on dynamic Drude model and traditional static Drude model are discussed theoretically for the first time. Unlike the static Drude model, the dynamic Drude model fully considers the motion of electrons in plasma driven by electromagnetic field. Numerical examples demonstrate that both the dynamic Drude model-based and static Drude model-based method are consistent with each other under low power microwave illumination, where the plasma can be considered as a static media. While under HPM illumination, electrons gradually gather together to hinder the propagation of electromagnetic waves. Hence, the proposed dynamic Drude model is more logical to analyze the characteristics of electromagnetic wave in plasma than the traditional static Drude model under HPM illumination.

In order to evaluate scattering from hypersonic vehicles covered with the plasma efficiently, time domain volume shooting and bouncing rays (TDVSBR) is first introduced in this paper. The new method is applied to solve the transient electromagnetic scattering from complex targets, which combines with non-homogeneous dielectric and perfect electric conducting (PEC) bodies. To simplify the problem, objects are discretized into tetrahedrons with different electromagnetic parameters. Then the reflection and transmission coefficients can be obtained by using theory of electromagnetic waves propagation in lossy medium. After that, we simulate the reflection and transmission of rays in different media. At last, the scattered fields or radiation are solved by the last exiting ray from the target. Compared with frequency-domain methods, time-domain methods can obtain the wideband RCS efficiently. Several numerical results are given to demonstrate the high efficiency and accuracy of this proposed scheme.

To effectively analyze the electro-thermal characteristics of a semiconductor p-i-n diode in the microwave limiter circuit, a cosimulation algorithm of the time-domain impulse response technique and physical-model-based semiconductor solver is proposed in this article. The physical-model-based semiconductor solver algorithm is based on the drift diffusion model (DDM). First, the multiphysical field coupling equations of the drift diffusion model and heat conduction model are used to analyze the electro-thermal behavior of a semiconductor p-i-n diode. Second, the time-domain impulse response technique based on the field–circuit coupling algorithm is used to extract the time-domain impulse response at each port of the electromagnetic field structure. Finally, the time-domain impulse response is combined with the volt–ampere characteristic relationship of the physical-model-based p-i-n diode. As a result, an efficient computation of the time-domain electro-thermal coupling characteristics of p-i-n diode in the microwave limiter can be obtained. The simulation results are in good agreement with those by the commercial software (COMSOL). The computation time and the memory requirement of the proposed algorithm are significantly reduced when compared with COMSOL.

This article concentrates on the high-power microwave (HPM) breakdown process and behaviors in air-filled rectangular waveguide under the external dc magnetic field. To solve the persuasive issue, a three-dimensional (3-D) multiphysics model coupling full-wave Maxwell’s equations with plasma fluid equations is established and solved by the spectral-element time-domain (SETD) method. In our simulation, the Galerkin’s method is employed for the space discretization and the central difference scheme is used for the temporal discretization during the SETD process. The numerical results reveal that the external dc magnetic field applied in breakdown volume can significantly enhance the breakdown threshold to suppress the HPM breakdown, which is beneficial for the propagation of HPM pulse in air-filled waveguide. Our research provides theoretical guidance for suppressing the impact of HPM breakdown for HPM devices protection.

An ultra-wideband(UWB) conformal circuit analog absorber (CAA) using resistive ink is presented. According to the equivalent circuit model, a two-segment transmission line cascade structure are designed in ADS, which obtained a reflection coefficient bandwidth from 1.9 GHz to 16.9 GHz with fractional bandwidth (FBW) of 159.6%, and then the srtucture are designed in HFSS by using the conversion formula between the equivalent circuit model and the actual srtucture, simulation results and the ADS results made a good fit. The overall dimensions of the unitcell is $0.089\ \lambda_{L}\times 0.089\ \lambda_{L}\times 0.092\ \lambda_{L}$ . Finally a $10 \times 10$ planar array and two conformal arrays are simulated. A 10-dB RCS reduction is achieved from 2.1 GHz to 16.5 GHz with FBW of 154.8% at the central angle of 90°, and the absorber exhibits the stable response for both TE and TM polarizations.

We propose an effective finite difference time domain (FDTD) simulations of two-dimensional metasurface with an effective surface impedance boundary condition (SIBC) model. The physical structures of the modulated metasurface are substituted by homogeneous surface impedances in the simulation. The number of unknowns both in transverse and longitudinal directions is reduced significantly with respect to the standard FDTD. Numerical simulations of the metasurface for electromagnetic fields manipulations with realistic meta-atoms demonstrate the validity of the proposed FDTD-SIBC method.

In this paper, an innovative multi-physics DGTD solution is proposed for field-circuit co-simulation, which combines the drift-diffusion equations and Maxwell's equations. The bat algorithm is adopted to match the date sheet of semiconductor to obtain the extracted parameters of physical model. Moreover, with the high-efficiency DGTD solution, the electromagnetic characteristics of field-circuit coupled systems can be analyzed accurately.

The analysis for large-scale antenna arrays is a hot topic for design and optimization. In this paper, an efficient method for analyzing antenna arrays by using characteristic mode (CM) is proposed. In order to analyze common antennas composing of conductor and dielectric, the theory of CM is first introduced into the volume-surface integral equation. An auxiliary general eigen-equation is established to make the modes orthogonal. Furthermore, a source mode (SM) is constructed to modify the accuracy when using CMs to expand the currents excited by a delta gap source for antenna problems. To demonstrate the influence of antenna structures and excitations on the CM and SM, three antennas are analyzed and only a few modes are required to achieve a good accuracy. Due to the periodicity of antenna arrays, CMs can be served as entire-domain basis functions defined on one antenna element and reused to reduce the unknowns in the method of moments (MoM). Numerical results have shown that the proposed method can have a good agreement with the traditional MoM. Meanwhile, both the memory requirements and computational time of the proposed method can be significantly reduced.

Electromagnetic waves carrying orbital angular momentum (OAM) have drawn much attention in the fields of radar detection and wireless communication. In such applications, vortex beams with multiple OAM modes need to be transmitted and received at the same time. This communication introduces the shared-aperture concept into metasurfaces for generating OAM vortex beams with different modes. Two independent geometry phase profiles on the same aperture are utilized to modulate the phase of two orthogonal linear-polarization waves. The alliance of polarization and orbit provides a routine to generate two different OAM modes simultaneously and achieves higher aperture efficiency than the conventional shared-aperture schemes. In this manner, different OAM modes can be separated easily by hardware. The simulated results validate the proposed method and structure.

In this paper, a paralleled interior penalty discontinuous Galerkin time domain method based on the second order vector wave equation (IPDG-WE) is proposed for electromagnetic scattering analysis of dispersive targets. Compared with the Maxwell's equation-based discontinuous Galerkin time domain (DGTD-ME) method, this proposed method enables efficient scattering analysis in terms of CPU time and memory consumption. Numerical results show the accuracy and efficiency of the IPDG-WE method.

In this paper, the finite-difference time-domain method based on the Runge-Kutta exponential time differencing formulation (RKETD-FDTD) is used to analyze the radiation characteristics of the plasma-covered Beidou antenna. Simulation results show that the plasma sheath will seriously hinder the propagation of electromagnetic waves, which may cause communication interruption. Specially, adding a “magnetic window”, the influence of plasma on electromagnetic waves can be weakened, which is expected to alleviate the problem of communication interruption. Therefore, our research has an extensive application prospect.

Three dimensional high-order discontinuous Galerkin time domain (DGTD) method is proposed to solve electromagnetic problems of dispersive media, which utilizes hierarchical basis function in space domain and Rung-Kutta iteration in time domain. The presented method is applied into the analysis of scattering problems of hypersonic aircraft which is coated with plasma. The hypersonic aircraft includes blunt cone model, missile model and metal warhead model. It is observed that high-order DGTD method reduces the number of unknowns greatly and accelerates the convergence against low-order DGTD. Numerical results are given to demonstrate the accuracy, efficiency, and compatibility of the presented method.

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.

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.

In this letter, the time-domain impulse response with the time-domain volume–surface integral equation field-circuit coupling algorithm is presented. This method uses the time-domain impulse response technique to separate the calculation of the linear electromagnetic field structure from the nonlinear equivalent circuit in the microwave circuit. First, the time-domain impulse response sources of the linear microwave structure are extracted at the location of ports. Then, the nonlinear system equations are built by the time-domain impulse response sources and the equivalent circuit equations. Meanwhile, the Newton–Raphson iteration algorithm is utilized to solve the nonlinear system equations. Finally, the simulation results illustrate that the proposed method is more accurate and effective than the conventional method.

This paper introduces the simulation of the MOSFET common-source amplifier circuit, and provides a method to jointly solve the physical model of the device and the external circuit to simulate the transient electro-thermal characteristics of a single device in the actual operation of the circuit. The spectral element time-domain (SETD) method is used to solve the coupling drift-diffusion model equation by using the electronic quasi-fee potential, the hole quasi-Fei potential and the potential as variables. The corresponding current density and electrical strength distributed in the device can be used to couple the heat transfer equation. Furthermore, the Kirchhoff laws should be satisfied when the MOSFET device is inserted in the circuit. The numerical results demonstrate the validity of the proposed method.

A field-circuit coupling algorithm combined with time domain impulse response based on conformal FDTD is presented in this paper. First, the time domain pulse response source are extracted at the port position of the linear microwave structure. Then the nonlinear system equation is established by using time domain impulse response source and equivalent circuit equation. At the same time, Newton-Raphson iterative algorithm is used to solve the nonlinear system equations. The cascaded nonlinear circuit is analyzed to demonstrate the efficiency and accuracy of the proposed method.

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.

This paper presents an effective electromagnetic analysis method for simulating infinite nanoarray. Instead of the infinite nanoarray, only a unit needs to be calculated by the Volume Integral Equation (VIE) Method with the periodic Green's functions (PGF). A numerical result validates the accuracy and efficiency of the method.

A hybrid method based on quantum mechanics and electromagnetics is used for simulation of the real time dynamics. The scalar and vector potentials are used to integrate Maxwell's equations in the time domain. The TDDFT-NEGF-EOM method is employed to simulate the electronic dynamics in the quantum mechanical region. When a classical electromagnetic wave penetrates into the quantum mechanical region, the entire system can be solved with Maxwell's equations.

For terahertz wave, we only need to know rough surface profiles to calculate RCS of simple target. But for the complex and electrically large target, this paper uses a semi deterministic and semi statistical idea, which divides the scattering of targets into coherent and incoherent scattering. Coherent scattering is based on high frequency approximation, and incoherent scattering is calculated by rough surface scattering theory. Thus, the terahertz scattering characteristics of complex targets can be analyzed.

In this paper, a new method based on SBR method is proposed to calculate the electromagnetic scattering problem of electrically large target. In traditional SBR method, the split size is usually less than 0.4 wavelength to ensure the accuracy. In this paper, the split size which could describe the shape of the target is enough. So the calculating memory and time can be reduced greatly. And the parallel technology is utilized to further accelerate the speed of the program.

This paper analyzes the scattering characteristics of the hypervelocity models with the shooting and bouncing rays (SBR). The algorithm provides a reliable treatment to measure the object with electrically large size covered by inhomogeneous plasma sheath. The numerical results indicate that covering with plasma sheath will change the value of RCS of the hypervelocity. And the inhomogeneous plasma sheath also has great influence on the RCS result.

This letter proposes a fast method that combines the complex-source beam (CSB) and multilevel fast multipole algorithm (MLFMA) for electromagnetic (EM) scattering problems. The CSB for the MLFMA is obtained by introducing an imaginary part for the independent variable of the spherical Hankel function in the translation operator, which makes the translation operator directional. Furthermore, a window function is introduced in the translation operator to make it more directional. A large part of the angular translation operators are then discarded with an angle threshold. Numerical examples demonstrate that the translation operator memory cost can be reduced significantly compared to the MLFMA, and more accurate results can be obtained compared to the ray-propagation multilevel fast multipole algorithm (RP-MLFMA).

In this paper, the spectral-element time-domain (SETD) method based on Gauss-Lobatto-Legendre (GLL) polynomials is applied to the solution of Maxwell’s Equations coupled to fluid model in 3-D microwave gas breakdown simulation of high-power microwave (HPM) propagation problems. The Galekin’s method is employed for the space discretization and the central difference scheme is used for time stepping. Numerical examples, compared with reported results demonstrate the ability and effectiveness of the SETD method for the analysis of microwave gas breakdown phenomena.

For electromagnetic analysis using Method of Moments (MoM), three-dimensional (3-D) arbitrary conducting surfaces are often discretized in RWG basis functions. The contribution of the Green's function to the scattered magnetic field is not well expressed in the traditionally used magnetic field integral equation (MFIE) when the source and field points lie on the same plane. This leads to the inaccuracy of MFIE for objects with flat surfaces. To solve this problem, some researchers proposed a normal magnetic field equation using the magnetic normal boundary condition. It is then combined with the traditional MFIE to form a new MFIE formulation, named the combined magnetic field integral equation (CMFIE). Through the use of an appropriate combination parameter, the lost contribution of the Green's function to the scattered magnetic fields in the MFIE can be recovered in this new CMFIE and can mitigate the discrepancy in RCS.

When the hypersonic vehicle is cruise in the near space, it will produce a plasma sheath with inhomogeneous material properties aroundthe vehicle. The Electromagnetic waves will be blocked or attenuated, which leads to communications blackout. Compared with experiments, numerical simulation is much efficient, time saving, and low cost. In this contribution, we propose an efficient multiphysics analysis framework of the rotationally symmetric hypersonic cruise object. The computational fluid dynamics tool is first employed to the complex dielectric constant of plasma sheath, when the flight height and speed are determined. When the hypersonic cruise object is flight with a null attack angle, the plasma sheath is also axial symmetry. As a result, it can be simulated with an efficient body of revolution method of moments (BoR). The number of unknowns can be defined on a surface that is generated by rotating a planar curve about the axis of symmetry, which reduces the 3D volume discretization unknowns into 2D case. Numerical simulations compared with finite-difference time-domain (FDTD) and volume surface integral equation (VSIE) show the proposed method is much more efficient than the volume surface integral equation.

The characteristic mode (CM) theory has been widely used for solving the resonant behaviors of radiation problems, since it can get the resonance frequency and orthogonal modal field. However, most previous works focus on the perfect conducting bodies. Now we propose a systematic method to analyze the dielectric resonator antennas (DRA) by using CM theory. The calculation of the CMs bases on the PMCHWT formulation. Moreover, the feeding location is optimized by studying the modal field distribution inside the dielectrics. A DRA with multiple dielectrics is analyzed in this paper. Numerical results present a good agreement with HFSS simulations. It validates the accuracy of the proposed method to analyze the radiating properties of DRA.

In this paper, the time domain volume surface integral equation method is used to analyze PIN diode Limiter under high voltage with a field-circuit coupling algorithm. Besides, the mathematical equations of lumped charge model are also combined here. The electromagnetic field-circuit coupled system matrix of microwave nonlinear element loaded circuit problem is established. With Newton iteration method, nonlinear equation is solved in a rigorously synchronous and seamless way. Finally, a modified solution process of time domain nonlinear coupled system matrix is introduced, the results of simulation shows the process of solution can be accelerated obviously.

Electromagnetic scattering by conducting bodies of revolution (BOR) coated with homogeneous chiral media above a lossy half-space is formulated in terms of the Poggio-Miller-ChangHarrington-Wu surface integral equation combined with combined field integral equation. A field decomposition scheme is utilized to split a chiral media into two equivalent homogeneous media. The spatial domain half-space Green’s functions are obtained via the discrete complex image method. Due to the rotational symmetry property of BOR, the method of moment for BOR (BORMoM) is applied to the linear system solved by the multifrontal direct solver. Numerical results are presented to demonstrate the accuracy and efficiency of the proposed method.

In this paper, a simplified plasma limiter is modeled and simulated based on spectral-element time-domain (SETD) method. Maxwell Equations coupled to fluid model are proposed to describe the physics procession of the gas discharge and the mechanism of the plasma limiter. In order to solve the proposed PDEs, the Galekin's method is employed for the space discretization and the central difference scheme is used for time stepping. Numerical examples demonstrate the ability and effectiveness of the SETD method for the design and analysis of these structures.

It is proposed that the radar cross section (RCS) of a microstrip antenna can be effectively reduced over a broad frequency band by utilizing a well-designed meshed ground plane. The radiation characteristic of the microstrip antenna is only slightly influenced by cutting slots on the ground plane. The calculated results suggest that the meshed microstrip ground antenna has much lower RCS than the solid ground one over a band 1–18GHz, with a maximum reduction of 15dB, while the radiation performance of the microstrip antenna, such as gain, impedance bandwidth and so on, remains almost the same as that of the solid antenna.

A millimeter wave (MMW) pseudo random code continuous wave (PRC-CW) radar utilizing Doppler compensation is introduced. The novel hybrid transmitted waveform used in this radar combining single frequency pulse with pseudo random binary phase-coded signal is presented which makes consequent target detection through pulse compression independent of Doppler frequency. Doppler frequencies of targets are firstly estimated based on interpolated FFT in the time span of single frequency pulse and the Doppler compensated signal can be constructed. The effect of Doppler mismatch on the correlation detection can be eliminated by processing the compensated signal using conventional pulse compression-FFT, which makes the radar capable of short-range high-speed target detection. The theoretical analysis and simulation result demonstrate the validity of this technique.

A simplified plasma limiter prototype is proposed and the fluid model coupled with Maxwell's equations is established to describe the operating mechanism of plasma limiter. A three-dimensional (3-D) simplified sandwich structure plasma limiter model is analyzed with the spectral-element time-domain (SETD) method. The field breakdown threshold of air and argon at different frequency is predicted and compared with the experimental data and there is a good agreement between them for gas microwave breakdown discharge problems. Numerical results demonstrate that the two-layer plasma limiter (plasma-slab-plasma) has better protective characteristics than a one-layer plasma limiter (slab-plasma-slab) with the same length of gas chamber.