Miniaturized dual-band bandstop filter using defected microstrip structure and defected ground structure

A miniaturized dual-band bandstop filter (DBBSF) is proposed by using T-shaped defected microstrip structure (DMS) and U-shaped defected ground structure (DGS). To verify the design concept, the DBBSF is simulated and fabricated. Compared with other published filters, the proposed DBBSF occupies the minimal normalized area. Moreover, the center frequency of the first stopband and the second stopband can be controlled separately due to the negligible mutual coupling between the T-shaped DMS and U-shaped DGS. A two-stage DBBSF is also presented and simulated, which shows maximum stopband rejection up to 49 dB.