Dual-band bandstop filter using stub-loaded resonators with sharp rejection characteristic

Dual-band bandstop filters using open-circuited stub-loaded resonators are presented. The first and second resonant frequencies of the open-circuited stub-loaded resonator can be flexibly controlled by tuning the length and position of the open-circuited stub. To illustrate the concept, a dual-band bandstop filter has been designed, fabricated and measured. The prototype of the dual-band bandstop filter achieved attenuation of 42 and 44 dB at 2.4 and 5.2 GHz.