基于双边平行带线的新型微波差分低通滤波器

A Novel Microwave Differential Lowpass Filter Based on Double-sided Parallel-strip Line

该文介绍了一种基于双边平行带线的新型微波频段低通滤波器。由于双边平行带线其本身固有差分传输特性,其中一条金属带条可作为另一条的地或者是信号线。通过相反的端口结构实现了滤波器差模响应的低通特性。提出了差模和共模不同的L-C等效电路,并用来分析这两种模式的频率响应。为了该验证理论,设计了一个3 d B截止频率为1 GHz的低通滤波器滤波器,制造并进行了测试。所设计的滤波器具有低插入损耗和宽带的共模抑制能力等优点。仿真和测试结果吻合良好,验证了所提出的结构和设计方法。

In this letter,a novel microwave differential lowpass filter(LPF)is firstly proposed based on the double-sidedparallel-strip line(DSPSL).As the DSPSL is with the inherent differential transmission property,one of identical metal stripsin DSPSL can be either signal line or ground for the other strip.The lowpass characteristic for the differential-mode operationis achieved when port1'(2')possess opposite signal lines as compared with port1(2).L-C equivalent circuits for bothdifferential-mode and common-mode are given to illustrate the frequency responses of the two modes.A demonstrated filterwith3dB cut-off frequency at1GHz has been designed,fabricated and measured for the purpose of verification.The designedLPF features advantages of low in-band insertion loss and wide-band common-mode suppression.Good matching between thesimulated and measured results has been observed,which verifies the proposed structure and its design concept.