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In this paper, the hybrid microstrip T-stub/defected ground structure (HMT/DGS) cell is presented, which is composed of a microstrip T-stub and an interdigital DGS with the broadside-coupled (BC) transition. Finely adjusted resonance can be achieved by the proposed cell. Meanwhile, strong slow-wave effect is employed by the structure, which leads to wide stopband responses. Based on these HMT/DGS cells, the interdigital-coupled scheme is employed to implement the electromagnetic interference (EMI) bandpass filter with high performance. To verify the aforementioned mechanism, two filters are designed and fabricated. Specifically, the second-order bandpass filter with a fractional bandwidth (FBW) of 14.3% has a 29.1-dB stopband rejection up to 15 f0 (where f0 stands for the passband center frequency). The fourth-order bandpass filter with an FBW of 10.8% demonstrates a 30.1-dB stopband rejection up to 12.1f0. Both types of filters show compact sizes with low insertion losses less than 1.1 dB.
Electromagnetic Compatibility, IEEE Transactions on (Volume:53 , Issue: 3 )
Date of Publication: Aug. 2011