A 2.5-D PSTD algorithm in cylindrical coordinates

The finite-difference time-domain (FDTD) method has been playing an important role in the simulations of transient electromagnetic wave propagation and scattering. However, when dealing with a large-scale problem the FDTD method starts to show its limitations. It requires significant computer memory because of the required high grid density (number of nodes per minimum wavelength) of 10-20 even for a moderate size problem. For large scale problems the required grid density increases, greatly limiting the size of solvable problems. The PSTD (pseudospectral time-domain) method is promising in that it requires only a grid density close to the Nyquist sampling density. Compared with the second-order accuracy of the FDTD method, the PSTD method has an infinite order of accuracy. Previously, the PSTD method has been applied to Cartesian and 3-D cylindrical coordinates. In this work, a 2.5-D PSTD algorithm is developed for the medium which possesses an axial symmetry, i.e., the material properties are only functions of /spl rho/ and z. The azimuthal dependence of the fields is accounted for analytically through a Fourier series. The perfectly matched layer is used as the absorbing boundary condition to truncate the computational domain. Compared with the 3-D PSTD method it saves significant computer memory and computational time.