Two unconditionally stable implementations of the higher‐order perfectly matched layer are proposed for the modeling of magnetized ferrite in the finite‐difference time‐domain lattice. By incorporating the approximate Crank–Nicolson (CN) algorithm and the modified auxiliary differential equation (ADE) approach, the proposed implementations take full advantage of the CN methods in terms of reducing the computational time and improving the computational efficiency. Approximate CN algorithms including the Crank–Nicolson–Douglas–Gunn and the Crank–Nicolson Approximate‐Decoupling schemes are implemented in 2D simulation. Furthermore, based on the ADE method, an alternative method at the integer time step is proposed to analyze the anisotropic magnetized ferrite structures. Its computational efficiency can be further enhanced compared to the shift operator method from the previous works. A full‐filled ferrite model and a ridge waveguide structure are introduced to illustrate the effectiveness and efficiency of the proposed algorithms. The results show that the proposed algorithms can improve the computational efficiency, overcome the Courant–Friedrich–Levy limit, and obtain considerable absorbing performance.
To deal with EM simulations with the low‐frequency evanescent and propagation waves, multi‐order nearly perfectly matched layers (NPML) with complex frequency shifted factor are presented to terminate finite‐difference time‐domain (FDTD) domains. By incorporating the digital signal processing techniques including the bilinear Z‐transform, matched Z‐transform, and direct Z‐transform methods, the proposals can not only obtain better performance compared with the original NPMLs but also have considerable efficiency compared with other multi‐order PMLs. Meanwhile, these implementations can terminate arbitrary mediums without changing the field‐updated equations in the PML regions. Based upon the multi‐order concept, the proposals can be switched flexibly between the first order and multi‐order according to different EM simulations by changing the optimized parameters. Numerical results indicate that our proposals can not only enjoy higher computational efficiency but also easier to implement according to different mediums in the EM modeling and simulations.
In order to analyze the scattering properties in multi-radiator problems, the active radar cross section (ARCS) concept is proposed under complex electromagnetic (EM) environments. The corresponding calculation methods and formulation are proposed by incorporating the monostatic radar cross section (RCS) concept with external disturbances. By introducing the phase characteristics into the ARCS concept, the coherent problems can be accurately solved. Through analyzing the external disturbance and the radar waves by employing the finite element method, the coherent and the incoherent characteristics of the external disturbance can be simulated in complex structures. Numerical examples and an experiment are carried out to further demonstrate the effectiveness of the proposed ARCS concept. The results demonstrate that the proposed ARCS concept obtains better universality compared with the existing incoherent multi-radiator formulation. Meanwhile, the ARCS can be identical with the solution which is obtained by the single radar wave. Compared with the existing incoherent methods for external disturbances calculations, the proposed ARCS concept is more rational. Through the experiment, the effectiveness of the calculation method and formulation is further demonstrated and validated.
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