Compact multiband bandstop filters based on symmetric split structure multimode resonators

In this paper, a design method of multiband bandstop filters with symmetric split structure multimode resonators is proposed. Because of the established degree of freedom, the suggested bandstop filters' center frequencies may be modified based on the design approach. Meanwhile, the suggested BSFs have small dimensions and abrupt roll-off skirts for transition bands. A technology demonstration filter with six stopbands placed at 1.91/2.37/3.43/4.35/5.16/6.81 GHz was constructed to verify the design and analyses. It is found that the measurement of filter is consistent with the comparison of simulation data, which indicates that the proposed structure is an optional approach for BSF design. The filter proposed can be applied in the field of communication, information and coal mine automation.