Modalansätze für FIT

Modal approache for FIT

Modal approach:

The idea of the modal analysis is to take advantage of the weak point of the time-domain approach – the appearance of strong resonances. To this aim, the sought field solution is written as a series development of the structure's eigensolutions (see figure), and the problem is reduced to the determination of the weighting factors (series coefficients). Due to the problem's linear character and to the mode orthogonality, the weighting factors are easy to determine through the evaluation of an inner product. Once the eigensolutions are determined, this low-computational-complexity evaluation can be performed in as many frequency points as desired, yielding thus broad-band results.

An important feature is that, by using closed boundary conditions the eigenvalue problem remains real (for loss-free structures), and that typically only a small number of modes within the interesting frequency range needs to be determined.

The focus of the research is set on the extension of these methods to lossy problems, and to the coupling between the modal analysis and error estimation/correction approaches.

The method has many common features with approaches in the area of “Order Reduction”.

Publications on this theme:

  • M. Dohlus, R. Schuhmann, T. Weiland: Calculation of Frequency Domain Parameters Using 3D Eigensolutions. Int. Journal of Numerical Modelling, Special Issue, Vol.12, 1999 , pp. 1-68.
  • R. Schuhmann, P. Hammes, S. Setzer, B. Trapp, T. Weiland: A Modal Approach for the Calculation of Scattering Parameters in Lossfree and Lossy Structures Using the FI-Technique. Proc. of the 16th Annual Review of Progress in Applied Computational Electromagnetics (ACES 2000), Monterey, USA (2000), pp. 249-254.