Advanced higher-order FDTD concepts for the absorption enhancement of Grote-Keller boundary conditions in electromagnetic scattering analysis using 3D spherical co-ordinates

A novel generalised FDTD methodology in 3D curvilinear co-ordinates is pres ented in this paper) for the absorption enhancement of the Grote-Keller bou ndary conditions truncating complex open-region electromagnetic problems. T he technique, which introduces both conventional and nonstandard schemes, i ncorporates a higher-order rendition of the covariant and contravariant vec tor component theory. In the temporal variable, the Jour-stage Runge-Kutta integrator is invoked, whereas the wider spatial increments near absorbing walls are effectively limited through the use of properly modified compact operators. Moreover, an efficient curvilinear lattice expansion algorithm l eads to a significant size reduction of the entire discretised domain. Nume rical verification, addressing extensive comparisons with various spherical PML absorbers, (demonstrates that the proposed higher-order FDTD Grote-Kel ler ABCs offer a remarkable decrease in dispersion, dissipation or anisotro py errors and can be imposed very close to the scatterer, thus attaining no table savings in computational resources.