Wideband dual mode bandpass filters with wide suppress harmonics using notch rectangular slots and interdigital coupled line

This paper presents wideband dual mode bandpass filter with a wide suppress harmonics using a square ring resonator structure with a novel perturbation by notch rectangular slot and an interdigital coupled lines with open stubs. A rectangular slot shape perturbation is excited to degenerate a dual mode, which is made the two reject bands on each side of passband, resulting in high sharp cutoff frequency and low insertion loss. An interdigital coupled lines with open stubs are controlled the multi transmission zeros are appeared in out off band of the filter. This proves that the new design technique can improve the performances of the proposed filters.