Coupling Matrix Extraction and Reconfiguration Using a Generalized Isospectral Flow Method

Abstract

The coupling matrix model is a helpful tool during synthesis and analysis of coupled resonator filters. Application of the coupling matrix for filter synthesis often requires the designer to reconfigure the coupling matrix to yield a specific matrix structure matching the topology of the filter. Currently, there is no closed-form solution known to this matrix reconfiguration problem. This paper proposes a new approach to solve this problem for coupling matrix representations of general lossy filters. The method is based on infinitesimal matrix rotations and can be considered as a continuous analog to the well-known coupling matrix similarity transforms. The results shown indicate good convergence behavior of the reconfiguration algorithm, as well as the ability of the method to always keep the desired scattering parameter goal. Based on this algorithm, a method for coupling matrix extraction of lossy filters is presented and successfully evaluated using simulated and measured scattering parameter data.