新型Koch岛分形耦合微带线带通滤波器

A Novel Microstrip Coupled-Line Bandpass Filter Based on Koch Island

为抑制平面带通滤波器的二次谐波,实现高选择性和低插入损耗,提出了一种新型Koch岛分形结构,并将其应用到平面耦合微带线带通滤波器的设计中。仿真及测试结果表明:所设计的新型Koch岛分形耦合微带线带通滤波器的中心频率为3 GHz,3 dB通带宽度为10%;与传统的耦合微带线带通滤波器相比,该新型滤波器的二次谐波降低了11.5 dB,选择特性提高了5 dB/GHz,通带内最大回波损耗降低了4.7 dB,尺寸缩小了近5%。该新型滤波器具有尺寸小、重量轻、成本低且性能好等优点。

To suppress the second harmonic and realize high selectivity and low insertion loss, a novel microstrip coupled- line bandpass filter（BPF） operating at 3 GHz is presented by introducing Koch-island-fractal-shaped structure. Simulation and measurement results indicate that the proposed filter is with significant superiority in terms of 1 i. 5 dB of deeper suppression of second harmonic, steeper selectivity of 5 dB/GHz, better insertion loss of 4.7 dB as well as 5 % of size reduction with respect to its conventional counterpart. The 3 dB bandwidth （insertion loss） is up to 10%. What＇s more, the designed filter has such advantages as small size, light weight, low cost, and good capability.