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FDTD propagator using the moving window concept.
Source publication
This work introduces a finite-difference time-domain (FDTD) propagation model based on a moving window algorithm. The FDTD is evaluated by an unconditionally stable (US) method combined with a material independent (MI) perfectly matched layer (PML) formulation. Thus, the time step used in simulation is no longer restricted by the Courant-Friedrich-...
Contexts in source publication
Context 1
... moving window concept is illustrated by Figure 1, where a typical radio propagation scenario shows a transmitter (TX) and a receiver (RX) in the presence of an irregular terrain. The FDTD mesh needs to be long enough to contain the dispersed pulse and all of the FDTD computation space outside of this virtual window is not considered. ...
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Citations
The long-range propagation of a charged particle beam has important research value in the fields of active space exploration and astrophysics. In geostationary orbits and other quasi-vacuum environments, relativistic electron beams are affected by the initial emittance and space charge effects during the propagation process. The dispersion in all directions causes the beam quality to decrease; however, this description cannot reflect further on the detailed physical processes. The axial energy distribution change of the beam and the axial transient electromagnetic effect caused by current changes in the head and tail regions of the beam also cause the beam to expand and affect its quality. In this study, the particle-in-cell (PIC) method was used to construct a long-range propagation model of the relativistic electron beam in a vacuum environment. By calculating and simulating the axial energy distribution of the beam and the changes in the transient electromagnetic field, the axial effect during the propagation process was analysed, and the parameter change law of the effective propagation of the beam was explored. This provided a theoretical reference for a more accurate assessment of the beam quality during propagation.
In recent years, it has been proposed to use satellite-mounted radio-frequency (RF) accelerators to produce high-current relativistic electron beams to complete debris removal tasks. However, when simulating the long-range propagation (km-range) process of the electron beam, it is difficult to directly use the particle-in-cell method to simultaneously consider the space charge effect of beam and the influence of the geomagnetic field. Owing to these limitations, in this paper, we proposed a simplified method. The ps-range electronic micropulses emitted by the RF accelerator were transmitted and fused to form a ns-range electron beam; then, combined with the improved moving window technology, the model was constructed to simulate the long-range propagation process of the relativistic electron beam in near-Earth environment. Finally, by setting the direction of movement of the beam to be parallel, perpendicular and at an inclination of 3° to the magnetic field, we analyzed and compared the effects of the applied magnetic fields in different directions on the quality of the beam during long-range propagation. The simulation results showed that the parallel state of the beam motion and magnetic fields should be achieved as much as possible to ensure the feasibility of the space debris removal. © 2021 Hefei Institutes of Physical Science, Chinese Academy of Sciences and IOP Publishing.
This letter introduces a finite-difference time-domain (FDTD) propagation method employing a moving window algorithm and a new formulation based on three features: high-order and unconditionally stable method with a material independent perfect matched layer (PML) formulation. The achievement is an efficient and accurate time-domain (multiband) propagation method. The formulation is validated through an analytic problem. Finally, we analyze two measurement campaigns with HF and VHF signals to evaluate the performance of method.
