Beyond the mesh handling Maxwell's curl equations with an unconditionally leapfrog stable scheme
Numerical solution of equations governing time domain simulations in computational electromagnetics, is usually based on grid methods in space and on explicit schemes for the time evolution. A predefined grid in the problem domain and a stability step size restriction must be accepted. Evidence is given that efforts need for overcoming these heavy constraints. Recently, the authors developed a meshless method to avoid the connective laws among the points scattered in the problem domain. Despite the good spatial properties, the numerical explicit integration used in the original formulation of the method provides,also in a meshless context, spatial and time discretization strictly interleaved and mutually conditioned. Afterwards, in this paper the stability condition is firstly addressed in a general way by allowing the time step increment get away from the minimum points spacing. Meanwhile, a formulation of the alternating direction implicit scheme for the evolution in time is combined with the meshless solver. The formulation preserves the leapfrog marching on in time of the explicit integration scheme. The new method, not constrained by a gridding in space and unconditionally stable in time, is numerical assessed by different numerical simulations. Perfect matching layer technique is used in simulating open spatial problems; otherwise, a consistency restoring approach is introduced in treating truncation at finite boundary and irregular points distribution. Three case studies are investigated by achieving a satisfactory agreement comparing both numerical and analytical results.