Matrix Synthesis of Cascaded K-Tuplets Filters with Frequency-Variant Couplings

This paper presents for the first time the direct synthesis of filter prototypes containing cascaded K-tuplets with frequency-variant couplings. Compared with traditional K-tuplets where only constant couplings are involved, it is shown that the number of couplings can be considerably reduced by applying the proposed method. Based on a general admittance matrix transformation, both coupling and capacitance elements are manipulated here, which brings in more possibility for the topology determination. In consequence, a specific transformation sequence is introduced, resulting in the proposed novel K-tuplets serially cascaded. Without any optimization process during the synthesis, this work expands the direct approach for synthesizing filters with frequency-variant couplings, and provides favorable topologies for filter implementation at the same time.