直接馈电的小型化微带双模带通滤波器

Compact Microstrip Dual-Mode Bandpass Filter With Direct Feeding Scheme

采用直接接触馈电的方法设计制作了一款微带结构的双模带通滤波器。该滤波器采用了分布式电容加载的双模环形谐振器,馈电时不需额外的耦合结构或阻抗变换器,在实现较大耦合量的同时,可保持谐振器的小型化。所制作的单级和两级的滤波器样品分别获得了0.6dB(在22.0%的相对带宽下)和1.1dB的最小插入损耗(在16.7%的相对带宽下)、40.0dB的带外抑制并在通带的两侧各有两个传输零点的较好测试结果,测试值与仿真值相当吻合。测试结果还表明,在得到相对较小的插入损耗的同时,也得到了优于-15.0dB的带内匹配。

A microstrip dual-mode bandpass filter by direct feeding scheme is presented.Loaded with four distributed capacitors,a dual-mode ring resonator is fed directly by the feed-line instead of additional coupling structure or impedance transformer.Therefore,tight coupling could be realized remaining compact size.The experimental data show that fabricated filters using one and two resonators achieve 0.6 dB（22% relative bandwidth） and 1.1 dB（16.7% relative bandwidth） minimal insertion losses respectively and obtain sharp out-band rejection（-40.0 dB） with two transmission zeroes at its each stopband,which agree well with the simulated results.Moreover,the in-band matching is better than-15.0 dB whereas keeping relatively low insertion loss.