Ultra-wide stopband low-pass filter using multi-mode coupled defected ground structures

In this paper, a novel kind of DGS is proposed and its stopband characteristic is studied firstly. A new five-pole filter using this kind DGS is designed. Then the magnetic coupling characteristics of adjacent DGSs are studied. The stopand can be widened, if the multi-mode for both CDGS and strip section are coupled together. At last, the multi-modes coupled structures is used to suppress the spurious responses in the LPF, which makes the LPF has steep skirt attenuation and ultra-wide stopband. In short, the proposed multi-mode coupled structures can significantly improve the filters' performances and extend the scope of DGS applications.