Numerical dispersion and stability condition of the nonstandard FDTD method

In order to reduce the phase error in the FDTD analysis, Cole proposed the NS-FDTD method. However, in the paper by Cole, numerical dispersion characteristics and accurate stability condition were not presented. Also, definition was given only for cubic lattices. In this paper, the NS-FDTD method is extended to the rectangular lattices and the numerical dispersion characteristic and the stability condition are derived. From the analysis for the stability condition, it is found that the stability condition in the present method is larger than those for the FDTD method and the FDTD(2, 4) method. From the analysis of the dispersion characteristic, it is shown that the present method has much higher accuracy than the FDTD method whether the lattices are cubic or rectangular. An analysis of a waveguide model is carried out in which the NS-FDTD method and the FDTD method are mixed. (C) 2001 Scripta Technica.