In this article, a novel coupling structure is proposed. The surface voltage and current distribution on this structure can be tuned by changing the ratio of the two capacitances so that the central frequency and coupling coefficient can be tuned. The coupling structure can also be tuned to change the sign of coupling coefficient, which is utilized to control the transmission zero of cross coupled tunable bandpass filter. A second order bandpass filter with tunable central frequency and bandwidth is designed and measured. The measurement shows that the central frequency tuning range is 0.768 to 1.512 GHz and the fractional bandwidth tuning range is 0.052 to 0.18 at 1.14 GHz. It shows that the filter can also be tuned with constant fractional bandwidth or constant absolute bandwidth. A tunable cascaded triple bandpass filter with tunable central frequency and bandwidth is designed and measured, as well. The cross‐coupled transmission zero can be configured to locate at either high side or low side of the passband by changing the coupling type of the filter topology.

中文翻译：

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具有交叉耦合和可重新配置的零传输的完全可调滤波器

在本文中，提出了一种新颖的耦合结构。可以通过更改两个电容的比率来调整此结构上的表面电压和电流分布，以便可以调整中心频率和耦合系数。耦合结构也可以被调整以改变耦合系数的符号，这被用来控制交叉耦合可调带通滤波器的透射零。设计并测量了具有可调中心频率和带宽的二阶带通滤波器。测量显示，在1.14 GHz时，中心频率调谐范围为0.768至1.512 GHz，小数带宽调谐范围为0.052至0.18。它表明滤波器也可以用恒定的分数带宽或恒定的绝对带宽进行调谐。还设计并测量了具有可调中心频率和带宽的可调级联三重带通滤波器。通过更改滤波器拓扑的耦合类型，可以将交叉耦合的传输零点配置为位于通带的高端或低端。