A new systematic design method based on coupling matrix and non-resonant structure for HTS filters with multiple transmission zeros

Paper proposes a new systematic design method based on coupling matrix theory and non-resonant structure for high-temperature superconducting (HTS) filters, which can introduce more transmission zeros (n + X) than the conventional coupling matrix theory. The proposed approach not only introduces transmission zeros at the near end of the passband through a coupling matrix, but also introduces transmission zeros at the far end of the passband through a new non-resonant structure. The non-resonant structure is realized by a grounded microstrip line structure, and the exact expression of the non-resonant structure is derived through the equivalent circuit. To demonstrate the proposed method, two-order, four-order and six-order filters are designed. The effectiveness of the methods is verified through simulations and experiments, with results that closely match theoretical calculations.