Design and synthesis of microwave dual mode filter

The design and synthesis of dual mode and quasi-elliptic dual-mode filters are presented in this paper. The transmission and reflection polynomials of the filters are generated to get the even- and odd-mode admittances. The admittances give the network prototype, routing structure and finally the coupling matrix of the filters. In order to suite the proposed filter topology which will later be used as the experimental prototypes, the matrix rotation technique is applied. As a result, the inter-resonator coupling of each filters matrix is eliminated and with the mentioned rotation, the new coupling matrices and routing structures are obtained. The prototypes of dual mode and quasi-elliptic dual mode filters have been designed and fabricated to prove the feasibility of this approach. The results show the excellent agreement with the theories.