Dual-band bandstop filter using open and short stub-loaded resonators

Novel dual-band bandstop filters (BSF) using open and short stub-loaded resonators are presented in this paper. The even-mode resonant frequencies are utilized to generate the stopbands, while the odd-mode frequencies of the open and short stub-loaded resonators are suppressed. For open stub-loaded BSF, its second harmonic of even-mode is used as the second stopband. For short stub-loaded BSF, its third harmonic of evenmode is used as the second stopband. Both the open and short stub-loaded resonator bandstop filters have been implemented with two parallel transmission paths, which help improve the stop response. For demonstration, two dual-band bandstop filters using open and short stub-loaded resonators are implemented. Comparisons of the measured and simulated results are presented to verify the proposed design.