高选择性的紧凑型WLAN微带带通滤波器设计

Design of Compact WLAN Microstrip Band-Pass Filter with High Selectivity

为了满足现代无线通信系统对紧凑型带通滤波器的需求,提出一种基于左右手传输线原理的新型微带带通滤波器。该滤波器采用了具有两个左手级和一个右手级的三级结构。左手级由螺旋互补裂环谐振器和交指电容构成,右手级由传统传输线和螺旋互补裂环谐振器构成,螺旋互补裂环谐振器在接地层中蚀刻实现。提出的右手级与两个左手级串联,以便改善频率选择性和带外抑制。给出了等效电路模型和全波仿真结果,并对设计的滤波器进行了制作和性能测试。实验结果表明,仿真结果与测量结果吻合良好,相比现有同类滤波器,该滤波器在尺寸减小和选择性方面都有明显的改善,通带覆盖2.3 GHz~2.45 GHz,测量的3 dB分数带宽约为7.5%,总尺寸为0.18λ_(g)×0.15λ_(g)。

In order to meet the needs of modern wireless communication systems for compact bandpass filters,a novel microstrip bandpass filter based on the principle of right-handed and left-handed transmission lines is proposed.The filter adopts a three-stage structure with two left-handed stages and one right-handed stage.The left-handed stage is composed of spiral complementary split-ring resonator and interdigital capacitor,and the right-handed stage is composed of traditional transmission line and spiral complementary split-ring resonator,which is etched in the ground plane.The proposed right-handed stage is connected with two left-handed stages in series to improve frequency selectivity and out-of-band rejection.The equivalent circuit model and full-wave simulation results are given,and the designed filter is fabricated and tested.The experimental results show that the simulation results are in good agreement with the measured results.Compared with the existing similar filter,the filter has obvious improvement in size reduction and selectivity,the pass band covers 2.3 GHz-2.45 GHz,the measured 3 dB fractional bandwidth is about 7.5%,and the total size is 0.18λ_(g)×0.15λ_(g).