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Abstract
In this paper, a novel defected ground structure (DGS) is proposed for lowpass filter (LPF) applications. The proposed structure exhibits wideband attenuation without increasing the circuit size, as compared with the conventional DGS. An equivalent circuit for the proposed DGS is described, and its equivalent-circuit parameters are analyzed and extracted. Benefitting from the quasi-elliptic function of the DGS, a demonstration LPF using one DGS unit and a compensated microstrip line is designed, and an attenuation pole near to the passband edge is realized to enhance roll-off of the stopband. To improve rejection level of the stopband, three cascaded DGS units are utilized for the LPF design. The fabricated LPF shows more than 20 dB attenuation from 2.1 GHz to over 8.0 GHz, as well as sharp rolloff. The simulated and measured results are presented, showing good agreement.