Improved Synthesis for the Design of Microwave Filters With a Minimum Insertion-Loss Configuration

This paper proposes a synthesis methodology for implementing microwave filters with a minimum insertion-loss configuration when several coupling topologies or coupling matrices are available with the selected technology. The methodology introduces, before dimensioning the distributed prototype, a careful characterization of losses due to individual distributed elements. The next step is to derive a precise equivalent circuit including losses for identifying the optimal configuration in terms of insertion-loss performance. The approach is applied to the synthesis of a dual-band bandpass filter. Best and worst configurations are identified among all the possibilities and the synthesis is validated by analyzing applicable electromagnetic models.