Synthesis of dielectric-loaded waveguide filters as an inverse problem

A design strategy is proposed for microwave devices built with dielectric-loaded waveguides having one- or two-dimensional discontinuity profiles. The problem is formulated as an inverse problem where the pre-defined scattering parameters are aimed to be the final response of the system. This goal is achieved by optimizing the dimensions of the filling materials. To increase the success of the optimization, the problem is reduced to the longitudinal and widthwise thickness determination of the unit cell, which constitutes the whole structure in a cascade form. To this aim, the frequency response of the unit cell is targeted and then that of the whole system, which is achieved by a two-level optimization procedure of the unit cell. The usefulness of the proposed design strategy is shown through numerical examples as well as the measurement results of two prototypes.