基于相邻-非相邻耦合的小型化微带带通滤波器

Miniaturized microstrip bandpass filter based on adjacent-nonadjacent coupling

提出了一种小型化微带带通滤波器,包含4个折叠阶梯阻抗谐振器。与传统均匀阻抗谐振器和阶梯阻抗谐振器相比,折叠阶梯阻抗谐振器充分利用其所占电路区域,可节约近50%的电路尺寸。由于同时存在相邻和非相邻耦合,该滤波器中可构建起3组不同的交叉耦合路径对,以产生3个不同的传输零点,从而有效提高滤波器的选择性和阻带宽度。滤波器样品的仿真与实测结果吻合良好,其过渡带滚降速度达100 dB/GHz,且抑制度优于33 dBc时的阻带达11.5 GHz。与一些同类工作相比,该滤波器的相对电尺寸缩减23%,满足微波电路的小型化需求。

A miniaturized microstrip bandpass filter is presented. The proposed filter consists of four folded stepped-impedance res-onators. As compared with its corresponding conventional uniform-impedance resonator or stepped-impedance resonator counterparts,the folded stepped-impedance resonator can save nearly 50 % circuit size since it takes full advantage of its occupied circuit area.Owing to the simultaneous existence of the adjacent and nonadjacent coupling in the proposed bandpass filter, three different cross-coupling path-pairs can be established to generate three different transmission zeros, which can improve the selectivity performance and width of stopband of the proposed filter effectively. Measured results of the prototyped filter agree with its simulations quite well. Meanwhile, the prototyped filter performs roll-off speed of 100 d B/GHz, and its upper stopband can be up to 11. 5 GHz with relative rejection over 33 d Bc. Compared with some similar works, the prototyped filter achieves electrical-size-reduction of 23 %,which can satisfy the requirements of miniaturization of microwave circuits.