Transmission characteristic control of dual-mode filter using spurline technique

A new type of microstrip dual-mode microstrip filter using spurlines is proposed in this letter. It is found interestingly that the embedded spurlines can excite, couple and split the degenerate modes. Moreover, the transmission characteristics of the loop resonator can be controlled by adjusting the relative length of the embedded spurlines appropriately. Parameter study of the transmission characteristics using spurline technique are discussed also. Details of the filter design are presented and experimental results are given to demonstrate the performance of the proposed filter.