具有高共模抑制特性的微带差分带通滤波器

Microstrip Differential Bandpass Filter with High Common Mode Suppression Characteristics

该文提出了一款中心频率可调的三阶差分带通滤波器,该滤波器主要由1个折叠的枝节加载谐振器(FSLR)和1对折叠的平行耦合线结构来实现滤波特性,同时使用微带-缝隙线转换结构激励差模和抑制共模。与传统的微带滤波器相比,该结构的共模响应和差模响应无关,所以在不降低差模特性情况下实现了良好的共模抑制,使设计更灵活。该差分滤波器整体尺寸为26 mm×49.2 mm,中心频率为3 GHz,相对带宽可达28.67%,共模抑制水平优于37 dB。结果表明,实际测量结果与仿真结果基本吻合。

In this paper,a third order differential bandpass filter with adjustable center frequency is presented.The filter uses the structure mainly consisting of a folded stub loaded resonator(FSLR)and a pair of folded parallel coupled lines to achieve filtering characteristics,at the same time,the microstrip-slotline conversion structure is used to excite the differential mode and suppress the common mode.Compared with the traditional microstrip filter,the common mode response of the proposed structure is independent of the differential mode response,so the good common mode suppression can be realized without reducing the differential mode performance,which makes the design more flexible.The overall size of the differential filter is 26 mm×49.2 mm,the center frequency is 3 GHz,and fractional bandwidth(FBW)is up to 28.67%,the level of common mode suppression is better than 37 dB.The results show that the measured results are in good agreement with the simulation ones.