Direct Matrix Synthesis Approach for Narrowband Mixed Topology Filters

In this letter, a novel direct coupling matrix synthesis approach is proposed for the narrowband mixed topology filter (i.e., the filter structure part with extracted-pole and part with cross-coupled configurations). First, canonical coupling matrix for the filter is constructed based on a set of new characteristic polynomials with complex coefficients to generate extracted-pole sections at the source and load directly. Then, a specific matrix rotation sequence is introduced to reduce the filter to a more practical N-tuplets & extracted-pole mixed topology. For validation purposes, two illustrative examples are given. As the synthesis is done by a simpler coupling matrix process, the presented approach provides a more convenient solution for synthesizing mixed topology filters with terminal extracted-pole sections.