Efficient Design Procedure for Combline Bandpass Filters With Advanced Electrical Responses

In this paper, a very efficient procedure for designing waveguide combline bandpass filters with an advanced electrical response is presented. The proposed technique is based on a segmentation strategy, which reduces the number of variables to be optimized by dividing the design process into simpler stages. The electrical response of an appropriate equivalent circuit model of the waveguide structure considered in each stage is used to generate the target curve needed in the optimization process. Moreover, the well-known Aggressive Space Mapping technique has been also implemented to improve the computational efficiency of the whole method. In order to validate the proposed design procedure, two high-order combline bandpass filters, with symmetric and asymmetric electrical responses including transmission zeros, have been successfully designed and simulated with full-wave analysis tools. Furthermore, as an experimental validation, a prototype of the symmetric filter has been manufactured, showing a good agreement between simulated and experimental data.