Moving-window propagation model based on an unconditionally stable FDTD method

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-Levy (CFL) stability condition and the formulation can be efficiently applied to any real propagation scenario without any modification. The US-IPML formulation is tested through an analytic problem. The proposed propagation model is applied to two idealized terrain profiles involving HF and VHF signals.