Novel microstrip dual-band bandstop filter with controllable dual-stopband response

In this paper, a novel dual-band bandstop filter (DBBSF) is proposed by using composite shunt resonators, and an approximate design method is developed based on the lumped-element circuit of the filter. Both the midband frequencies and the stopband widths of the dual bands of the filter can be controlled separately. A dual-band BSF with center frequencies of 1.7 and 2.3 GHz is designed and fabricated using microstrip lines. The measured frequency response agrees excellently with theoretical predictions, validating well the proposed design theory and filter structure.