On the calculation of stripline filter scattering parameters: spatial vs. spectral domain approach

The authors consider a stripline geometry in which a metallized filter structure shielded by a top and a bottom ground plane is located between two dielectric layers. Located on plane z=0 the metallized structure consists of an input, an output transmission-line, and a finite number of coupling strips with arbitrary width, length, and spacing. The authors present a spatial and a spectral domain approach developed to determine the scattering parameters of the class of problems sketched above. Both concepts implemented are well-posed and lead, up to discretization errors, to identical numerical results. However, the spatial domain analysis is faster by an order of magnitude. The reason for this is twofold: (a) the associated Green´s function in the spatial domain can be constructed in series form containing only tabulated functions; and (b) one can show that the convergence rate of this series can be improved significantly. As an example, a passband filter structure is analyzed by the spatial domain method.<>