This letter introduces two continuously tunable bandpass filters with substrate integrated coaxial line (SICL) and liquid crystal (LC) technologies. The tunability of the filters is a kind of electric tuning, achieved by the permittivity changing of the LC material filled in the SICL cavities. The SICL resonator and the electric and magnetic coupling between the resonators are investigated. Then, fourth‐order direct‐coupled and cross‐coupled tunable filters (Filter I and II) with center frequency of 6.5 GHz are designed, fabricated, and measured. The experimental results show that the continuous tuning ranges are 220 and 280 MHz for Filter I and II, respectively. Furthermore, the insertion losses of the Filter I and II are 3.93–4.78 dB and 3.65–4.3 dB over the whole tuning range.

中文翻译：

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采用液晶技术的可连续可调基板集成同轴线带通滤波器

这封信介绍了两个具有衬底集成同轴线（SICL）和液晶（LC）技术的连续可调带通滤波器。滤波器的可调性是一种电调谐，它是通过改变填充在SICL腔中的LC材料的介电常数来实现的。研究了SICL谐振器以及谐振器之间的电磁耦合。然后，设计，制造和测量中心频率为6.5 GHz的四阶直接耦合和交叉耦合可调滤波器（滤波器I和II）。实验结果表明，滤波器I和II的连续调谐范围分别为220 MHz和280 MHz。此外，在整个调谐范围内，滤波器I和II的插入损耗分别为3.93–4.78 dB和3.65–4.3 dB。