An advantage of time-domain electromagnetic simulation tools is that an entire spectrum can be obtained in a single simulation run by using a broadband initial condition and Fourier transformation of the ensuing time sequences. However, when the simulation involves time-varying materials, the system is no longer time-invariant, and Fourier techniques must be reconsidered to obtain desired results. Most theoretical and many experimental conditions assume a single-frequency or narrowband source excitation, which minimizes the unintended effects of frequency mixing. However, performing many single-frequency time-domain simulations would be needed to construct an entire spectrum in this way, which would become computationally impractical. This work shows how a few finite-difference time-domain (FDTD) simulations can be used with broadband initial conditions to obtain scattering spectra in time-modulated resonator systems that effectively correspond to a single-frequency source spectrum. The approach involves running FDTD simulations in which the phase between the modulating signal and the source signal is deliberately changed and then averaging the spectra from the simulations. Using only six simulations, the source frequencies up to (plus or minus) five times the modulating frequency can be canceled out, which provides good agreement with theoretical predictions over a broad range of parameter values.

中文翻译：

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时变材料宽带时域电磁仿真中的有效单频源谱

时域电磁仿真工具的一个优点是，通过使用宽带初始条件和随后的时间序列的傅立叶变换，可以在单个仿真运行中获得整个频谱。然而，当模拟涉及时变材料时，系统不再是时不变的，必须重新考虑傅立叶技术以获得所需的结果。大多数理论和许多实验条件都假设单频或窄带源激励，这可以最大限度地减少混频的意外影响。然而，以这种方式构建整个频谱需要执行许多单频时域模拟，这在计算上变得不切实际。这项工作展示了如何将一些有限差分时域 (FDTD) 模拟与宽带初始条件结合使用，以获得有效对应于单频源频谱的时间调制谐振器系统中的散射频谱。该方法涉及运行 FDTD 模拟，其中调制信号和源信号之间的相位被故意改变，然后对模拟的频谱进行平均。仅使用六次模拟，就可以抵消高达（正或负）调制频率五倍的源频率，这在广泛的参数值范围内与理论预测非常吻合。该方法涉及运行 FDTD 模拟，其中调制信号和源信号之间的相位被故意改变，然后对模拟的频谱进行平均。仅使用六次模拟，就可以抵消高达（正或负）调制频率五倍的源频率，这在广泛的参数值范围内与理论预测非常吻合。该方法涉及运行 FDTD 模拟，其中调制信号和源信号之间的相位被故意改变，然后对模拟的频谱进行平均。仅使用六次模拟，就可以抵消高达（正或负）调制频率五倍的源频率，这在广泛的参数值范围内与理论预测非常吻合。