Tunable bandpass filter with low insertion loss based on electrically controlled liquid crystal

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• 作者：Zhaosheng He^a ; ^{he.zhsheng@gmail.com} ; Di Jiang^a ; ^b ; Changjiang You^a ; ^b ; Xiang Li^a
• 关键词：Liquid crystal ; Low loss ; Tunable bandpass filter ; Tunable dielectrics
• 刊名：Optik - International Journal for Light and Electron Optics
• 出版年：2017
• 出版时间：February 2017
• 年：2017
• 卷：130
• 期：Complete
• 页码：505-510
• 全文大小：1512 K
• 卷排序：130

文摘

This paper presents a low loss electrically tunable bandpass filter based on liquid crystal. By utilizing structure of transmission line and direct-connected feeding lines without coupling gaps which eliminate mismatch and radiation losses, then the proposed filter gets a low insertion loss. And the tunability of the filter is realized by utilizing electrically controlled liquid crystal (LC) material as the substrate. In order to verify the design concept, a liquid crystal tunable prototype filter is designed, fabricated and measured. Measured results agree well with the simulated results. With no bias voltage applied, the filter operates at center frequency of 11.5 GHz with fractional bandwidth of 11.3%. And with voltage tuning from 0 V to 10 V, the filter gets a tuning range of 500 MHz and the insertion losses are 2–3.1 dB, respectively.