A stochastic finite-difference time domain (S-FDTD) combined with the piecewise linear recursive convolution method is applied to model wave propagation in unmagnetized plasma with random plasma frequency. The stretched-coordinate perfectly matched layer implementation of the S-FDTD method is also presented. The accuracy and efficiency of the proposed algorithm are validated by numerical examples.

In this study, the effect of random characteristics of the ionosphere on the enhanced Loran (eLoran) sky-wave signal was analyzed. First, the bilinear transform stochastic finite-difference time-domain (S-BT-FDTD) method in layered half-space isotropic plasma is derived, and the correctness of the calculation of the mean value and standard deviation of the field components of the eLoran sky-wave signal is verified. Second, the mean value and standard deviation of the amplitude and time delay of the eLoran sky-wave signal were analyzed by combining the International Reference Ionosphere, pseudo-1-D BT-FDTD method, and Monte Carlo method. The simulation results show that the mean value of the amplitude of the reflection coefficient amplitude (RA) in the eLoran signal bandwidth remains unchanged. The larger the standard deviation of the electron density, the larger is the standard deviation of RA. The standard deviation of RA during the day is greater than that at night. The mean value of the time delay remains unchanged, and the standard deviation of the time delay is related to the way the electron density varies randomly. When the incident angle increases, the RA increases, the standard deviation of RA decreases, the time delay decreases, the standard deviation of the time delay decreases, and the signal becomes more stable.

This study proposes a high‐precision algorithm used in enhanced Loran sky–ground wave separation based on the Levenberg–Marquart algorithm. The simulation results show that, compared with the existing algorithms, the algorithm proposed in this study has higher accuracy, especially in the case of a low signal‐to‐noise ratio. Furthermore, when the skywave of enhanced Loran has at least a 35 μs time delay compared with the groundwave, the performance of the algorithm is significantly better than that of other algorithms. Analysis of an actual signal showed that the average correlation coefficient was greater than 99% and that the signal was successfully separated.

The finite-different time-domain (FDTD) method is applied to solve wave propagation in anisotropic dispersive materials by means of bilinear transform (BT) technique. The frequency-dependent and anisotropic constitutive relation is translated into time-domain update equations with coupled x- and y-components of electric fields. The proposed algorithm has a simple formulation and is easy to apply to general dispersive anisotropic or isotropic material. The transmission and reflection coefficients of a 9-mm magnetized plasma slab are calculated and compared to analytical solutions for validation purpose. Very-good agreements are found in both amplitude and phase of these coefficients.

An efficient stochastic finite-difference time-domain (S-FDTD) with weighted Laguerre polynomials algorithm is presented for calculating the standard deviation of the electromagnetic fields caused by the variability or uncertainty of the isotropic cold plasma materials in a single run. Compared with the conventional S-FDTD method, the proposed algorithm uses an implicit marching-on-in-degree scheme, which improves the computational speed significantly. The perfectly matched layer with complex-frequency-shifted factor is implemented via formulation in the stretched-coordinate system. Numerical examples demonstrate the accuracy and effectiveness of the proposed algorithm.