一种基于互补谐振结构的宽带共模噪声滤波器

提出了一种用于高速差分信号传输的宽带共模噪声滤波器,采用在差分线正下方参考地平面上刻蚀内外互补的共面波导1/4波长谐振器和Z字形短路枝节线来实现。滤波器采用内外互补耦合λ/4开路枝节线谐振器结构,有效减小了横向尺寸,利用Z字形枝节线增大互感以改善滤波器的带内增益平坦度,最后用级联实现了共模噪声抑制阻带的展宽。仿真和测试结果表明,该滤波器在4.1~12.5 GHz频率范围内实现了20 dB的共模噪声抑制,共模阻带相对带宽(FBW)为101%,尺寸仅为0.78λ_g×0.18λ_g(15.8 mm×3.6 mm),其中λ_g为阻带中心频率处对应的波长。且该结构在实现共模噪声宽带抑制的同时,还可有效保证差分信号传输特性良好。

A Wideband Common-mode Noise Filter Based on Complementary Resonant Structure

A novel wideband common-mode noise(CMN)filter is proposed for high-speed differential signal transmission.It is realized by etching the inner and outer complementary coplanar waveguide(CPW)quarter wavelength resonators and the Z-shaped short circuit branch line on the reference ground plane beneath the center of differential lines.The filter adoptsλ/4 open circuit branch line resonators structure with complementary coupling inside and outside,which effectively reduces the lateral size of the filter,and increases the mutual inductance by using Z-shaped short circuit branch lines to improve the in-band gain flatness of the filter.By cascading two units,the proposed CMN filter can achieve a wide bandwidth for practical applications.The simulated and measured results show that the CMN can be suppressed within 4.1-12.5 GHz,and the fractional bandwidth(FBW)is 101%with a noise suppression level of 20 dB,while the size of the filter is only 0.78λ_g×0.18λ_g(15.8 mm×3.6 mm),whereλ_g is the wavelength of the stopband central frequency.Besides,the filter maintains good transmission characteristics for the differential signals.