A novel substrate-embedded defected ground structure for differential-mode filter applications

A differential-mode bandpass filter (DM-BPF) using novel substrate-embedded defected ground structures (SE-DGSs) is demonstrated. With the proposed SE-DGS, the characteristics of the differential mode remain almost unchanged whereas the common-mode propagation is affected. The varied frequency response of the common mode leads to an avenue for broadening the common-mode suppression bandwidth of the DM-BPF. Indeed, the proposed SE-DGS is exploited for extending the 20-dB common-mode suppression bandwidth of the DM-BPF from 50% to 90%. The measured results show the demonstrated DM-BPF possesses a 84.5% 20-dB common-mode attenuation, which fully convers the 3-dB differential-mode bandwidth.