A Dual-Mode Substrate Integrated Waveguide Filter With Controllable Transmission Zeros

In this letter, a circular dual-mode substrate integrated waveguide (SIW) filter with two controllable transmission zeros is proposed. Two vias situated on a diameter line are employed to perturb two modes in a circular substrate integrated waveguide resonator. Taking advantage of the modal orthogonality of multiple cavity modes, transmission zeros are created. By moving the vias along the diameter line, the transmission zeros can be adjusted. The coupling matrix is employed to analyze the design concept. A three-pole filter with the center frequency at 8 GHz and two transmission zeros at 8.6 and 9.2 GHz is designed and fabricated. Experimental and simulated results are presented which validate the design concept of the proposed filter.