采用开路短路枝节加载开环谐振器,设计了一种新型的3个通带中心频率独立可调的三频带通滤波器.由于谐振器的结构对称,因此采用传统的奇偶模分析法.滤波器的第一和第三通带由偶模谐振频率产生,通过改变加载枝节的电长度和阻抗比可调节偶模谐振频率.滤波器的第二通带由奇模谐振频率产生,通过改变环的电长度和阻抗可调节奇模谐振频率.该滤波器的3个通带中心频率为1.57GHz(GPS),2.4GHz (WLAN)和3.5GHz (WIMAX), 3dB带宽分别为2.5%, 4.7%和2.0%,测量结果与电磁仿真结果基本吻合.
A tri-band bandpass filter has been designed using open-loop resonator with open and short stubs. The filter can control each center frequency independently. An odd-even mode analysis is performed on the resonator. The center frequencies of the first and third passbands are obtained with the even mode, and determined by the electrical length and impedance ratio of the stubs. The center frequency of the second passband is obtained with the odd mode and determined by the electrical length and impedance of the open-loop. The filter has triple passband center frequencies of 1.57 GHz for GPS, 2.4 GHz for WLAN, and 3.5GHz for WIMAX, with 3dB fractional bandwidths of 2.5%, 4.7%, and 2.0% , respectively. Measurement results are in general agreement with EM simulation results.
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