Rolf Schuhmann

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In this paper, a generalized derivation of the alternating direction implicit finite-difference time-domain algorithm based on operator splitting is proposed. The formulation follows the notation of the finite integration technique. A straightforward proof of stability is given and the numerical dispersion formula is presented and verified by numerical(More)
We propose a comparison of two approaches to analyze the periodic arrays of left-handed metamaterials by field simulations in a single unit cell. First, a scattering matrix analysis in time domain is able to produce broadband results. The set of transfer functions between a small number of input and output ports of the unit cell is able to describe its(More)
This paper presents a numerical procedure applied to the modeling of double negative metamaterial (MTM) structures. At the unit-cell level, the properties of the MTM are described by the extracted isotropic constitutive parameters, dispersion diagrams, and higher order modes analysis. The information gathered at the unit-cell level is used to characterize(More)
The novel idea of waveguide miniaturization presented in this work relies on the insertion of spiral resonators and dipole arrays in the symmetry plane of the waveguide. Waveguide miniaturization in this context means moving the first transmission band of a waveguide below its cutoff frequency. The design, fabrication and measurement of miniaturized(More)
Whispering gallery modes of a flat dielectric disk are studied by means of analytical and numerical computational methods based on the finite integration technique. The results are compared to a high accuracy measurement. The frequently used semi-analytical method of effective refractive index has certain weaknesses in finding accurate eigenfrequencies and(More)
A method to overcome unfavorably small time steps in FDTD simulations on cylindrical meshes is proposed in this paper. A three dimensional cylindrical grid for azimuthally inhomogeneous regions apart from the z-axis is coupled to a multi modal two dimensional grid in the vicinity of the origin. This leads to a diminished ammount of mesh cells and,(More)
For the numerical solution of complex eigenvalue problems, arising with gyrotropic materials in resonators, the Jacobi-Davidson method is considered. In this paper the correction equation, which has to be solved within the Jacobi-Davidson method, is simplified and several preconditioning strategies, including also a multigrid scheme, are compared for the(More)
We present a hybrid formulation which combines the finite integration technique (FIT) with a ray tracing technique. Ray tracing allows the treatment of complicated structures with very large objects. A typical application of ray tracing techniques is the simulation of indoor propagation. The presented hybrid technique has therefore a rather broad field of(More)