A low-cost defected ground structure (DGS) wideband stopband filter adopting complementary structure is pro-posed, which is designed for common-mode noise suppression in high-speed differential signals. The filter is etched below the low cost FR4 printed circuit board. To avoid stimulating the common-mode noise, the DGS cells on ground planes are kept symmetrical to the central line of the two differential signal lines. Both sides of the filter adopt a symmetric cup-shape DGS structure and the middle of the filter adopts a symmetric umbrella-type structure. All of the DGS struc-tures are complementary, which makes the filter compact and miniaturized. What is more, because the spaces among the three DGS are closer, there exist the mutual inductances among them, which are utilized to achieve a wide stopband filter. The simulated result demonstrates the proposed filter has a wideband bandwidth of 6.8 GHz over 20 dB. In order to analyze the effect of compact structure of the filter, a filter having the same DGS patterns but large spaces among them is compared with it. The simulated result demonstrates that the stopband bandwidth of the compared filter has a wideband bandwidth of 4.4 GHz over 20 dB, of which the bandwidth is about 2.4 GHz less than that of the proposed filter. It is obvious that there exists a mutual inductance in the compact DGS structure common-mode filter, which plays an important role in broadening the bandwidth of the proposed filter. In order to facilitate analysis, an equivalent model of LC circuit is also given. The equivalent parameters of LC can be deduced from the definition of 3 dB cut-off frequency and resonant frequency, of which the values can be obtained by the HFSS simulation. The simulated and measured results show that the differential signal under the DGS filter is nearly intact, and the common-mode noise can be reduced over 20 dB from 4.6 GHz to 11.4 GHz and over 15 dB from 4.3 GHz to 12 GHz, while the area of the filter is only 10 mm by 10 mm. Compared with the periodic DGS at the same suppression depth of common-mode noise over 20 dB, the method has the advantages that surface area is reduced to no more than 30%, and the stopband width is increased by over 50%.%为了抑制高速差分信号传输中的共模噪声,提出了一种基于低成本FR4材料制作的互补型缺陷地结构(defected ground structure, DGS)共模阻带滤波器.滤波器两边采用对称性酒杯形DGS结构,中间采用对称伞形DGS结构.由于这两种DGS 结构互补,整个滤波器结构紧凑,可以实现小面积设计目的；另外,由于三个DGS结构相邻较近,相互之间存在互感,可以通过改变相互之间的距离来调节相互之间的互感,从而实现宽阻带滤波的目的.仿真和测试结果表明,该DGS滤波器的差模信号损耗小,在抑制共模噪声20 dB条件下其阻带范围为4.8—11.4 GHz,而且面积仅为10 mm ×10 mm.与周期性DGS结构相比,本方法在相同共模噪声抑制深度下,具有占用面积不到30%、阻带宽度增加约50%等优点.
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