基于工字型双模谐振器的双阶带通滤波器设计

Two-order bandpass filter based on I-shaped dual-mode resonator

为了提高滤波器的带外抑制度和选择性,首次提出了一种双阶拓扑结构的带通滤波器。采用奇偶模方法对工字型双模谐振器的特性进行了分析,通带内具有四个谐振模式。滤波器有效尺寸为13.7 mm×5.35 mm,等于0.56λ_g×0.22λ_g(λ_g为中心频率处的波导波长)。该滤波器的中心频率为7.34 GHz,相对带宽为20.9%,通带内最小插损为1.9 d B,阻带的三个传输零点分别位于3.17,8.36和9.61 GHz,上下阻带抑制度分别大于30 d B和46 d B,一次杂散抑制度大于18 d B。该滤波器具有结构紧凑,带外抑制度与选择性较高的优点。

In order to achieve higher stopband rejection and selectivity, a two-order bandpass filter was designed based on I-shaped dual-mode resonator. The odd- and even-mode method was adopted to analyze the characteristics of dual-mode resonator.There are four resonant modes in the passband. The effective overall size is 13. 7 mm×5. 35 mm, about 0. 56λg ×0. 22λg（λg is theguided wavelength at the central frequency）. The center frequency is 7. 34 GHz, with the 3dB fractional bandwidths of 20. 9%. Theminimum insertion loss is 1. 9 dB. These transmission zeros in stopband are located at 3. 17, 8. 36 and 9. 61 GHz. The maximumstopband rejections are better than 30 dB and 46 dB in the upper stopband and lower stopband respectively. The rejection in firstspurious is better than 18 dB. The filter has the advantages of compact size, high stopband rejection and high selectivity.