インターデジタル型共振器を用いた広帯域通過フィルタの一設計法

摘要

本稿では，インターデジタル型共振器と平行結合線路を用いた小型広帯域フィルタの一設計法について検討した.　まず，本共振器の回路解析を行うことで，偶奇モードインピーダンス比に基づいた通過帯域幅の制御法を示した.次に，フィンガー数および接地面の加工に着目した帯域幅の広帯域化について検討を行うことで，本共振器が比帯域幅100%以上の通過帯域を確保できることを確認した．さらに，平行結合線路についても同様に検討し，それらを組み合わせたBPFの解析および測定を行った．その結果，提案のBPFは3.5-10.3GHzの通過域，急峻なスカート特性に加え，20dB程度の阻止減衰量を実現した．%A new type of the compact UWB BPF made up of a shunt inter-digital finger resonator and parallel-coupled lines was proposed. The bandwidth of the inter-digital finger resonator is determined by the ratio of the even and odd impedances and thus becomes wider by increasing the number of fingers and shaving the ground plane. The design of the parallel-coupled line was made by optimizing the structural parameters so that the bandwidth is the same as that of the inter-digital resonator. The measured results of the combination of above elements for the BPF agreed well with the simulated ones such that the insertion loss is less than 0.67 dB and that the sharp skirt characteristics are realized by attenuation poles near the edges of the passband.