Novel dual-band bandstop filter with controllable stopband frequencies

This article presents a novel dual-band bandstop filter (BSF) with controllable stopband frequencies and sharp skirt selectivity.The proposed filter consists of a main transmission line and stub-loaded resonators coupled to the main line. The stub-loaded resonator has the advantage that the even-mode resonant frequencies can be flexibly controlled by changing the stub length without affecting the odd-mode resonant frequencies. Using this configuration, the stopband frequencies can be easily tuned to desired values. Based on the proposed idea, a third-order dual-band BSF is implemented operating at 2.4 and 3.5 GHz. Comparisons of experimental and simulated results are presented and good performance is observed. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:1203–1206, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26786