Calculation of Electromagnetic Eigenmodes in Complex Structures Using Coupled S-Parameter Calculation

Abstract

Eigenmode calculations are usually carried out with dedicated solvers as e.g. [1]. If eigenmodes of large and complex structures have to be calculated, the application of these solvers is limited even on the most powerful workstations by the available computational resources in terms of memory and computation time. This paper will present a technique based on scattering parameters that allows to split the complete geometry into subsections which can be modeled individually. The broadband S-parameters of each section have to be calculated externally using appropriate solvers. Such runs are significantly smaller problems and may be performed in parallel on different machines. In the paper we present a description which is well suited to calculate the eigenfrequencies of an entire structure and the wave amplitudes needed to determine the internal fields once the S-parameter of the segments are known. This approach is of special advantage if the structure contains segments of identical shape, parts that can be described analytically or components of local complexity, which enforce enhanced grid resolution. Further it establish a mean for frequency selective eigenmode analysis, which is difficult for most eigenmode solvers. We illustrate the procedure with a test example that was calculated both with Coupled S-Parameter Calculation and a direct eigenmode solver. Results of the comparison are presented.