基于半导体可变电容的高温超导可调滤波器研究

Microwave tunable filters are attracting more and more attention because of their potential applications in the future wireless communications systems and modern military equipment systems. How to achieve high performance tunable filters with compact size, reduced weight and low insertion loss is challenging at present. The unloaded quality factor of high temperature superconducting (HTS) microstrip resonator with semiconductor varactor is one to two orders of magnitude higher than that of normal metal microstrip resonator. Thus, research on HTS tunable filter is of great significance. This project plans to attack on the scientific problems and key technologies in HTS tunable filters with constant fractional bandwidth (BW) and constant absolute BW. Aiming at the problem of the grounding of the HTS resonator, the physical model and the electromagnetic simulation optimization method are used to solve the influence of the superconducting stub on the resonator frequency and coupling between resonators; For solving the mismatch problem between the inter-resonator coupling coefficients, the coupling mechanism is analyzed, and the new coupling structure is introduced to realize the accurate control of the coupling coefficient and good matching. Systemic independent intellectual property rights in the design, fabrication, and packaging of HTS superconducting tunable filters will be acquired with the implementation of this study. It would be helpful for the better performance of wireless communication systems and modern military equipment systems, and expand the application field of superconductors.

微波可调滤波器由于其在未来无线通信系统和现代武器装备系统中潜在的应用价值而受到日益广泛的关注。如何实现尺寸小、重量轻、插损小的高性能可调滤波器是当前的研究热点和难点。用高温超导材料和变容二极管设计的谐振器的Q值比常规可调谐振器高一到两个数量级，因此高温超导可调滤波器的研究具有重要意义。本项目拟研究相对带宽恒定、绝对带宽恒定的超导可调滤波器的相关科学问题和关键技术。针对超导情形下谐振器的接地问题，通过物理建模分析、电磁仿真优化途径解决超导接地块对谐振器频率、谐振器间耦合的影响问题；针对耦合系数不能实现良好匹配的难题，深入分析耦合机理、引入新型可控耦合结构，实现耦合系数精准调控和良好匹配。本项目的实施，将在高温超导可调滤波器的设计方法、制备与封装工艺等方面取得系统的自主知识产权，为提升无线通信系统和现代武器装备系统的性能，拓展超导的应用领域作出贡献。

现代通信系统往往要在多标准和多频率下工作，电子可调谐滤波器在现代无线系统中发挥着越来越重要的作用。因为它们可以有效地降低复杂性和成本，充分利用频谱资源。尺寸紧凑的双模谐振器对于可调滤波器的设计很有吸引力。此外，半导体变容二极管由于其高调谐速度和低成本的优点，已成为制造可调滤波器的普遍选择。. 课题组通过研究可调谐滤波器的基本原理，提出了两种奇、偶模频率分别可控的双模谐振器，采用砷化镓变容二极管作为调谐元器件，实现了高温超导带通滤波器的连续可调谐。基于全波电磁仿真分析方法，在YBCO/MgO基片上成功设计、制作了两款四节高温超导带通滤波器。仿真结果与实验测量结果高度一致，验证了该设计方法的有效性。课题组还提出了一种具有可调带阻特性的超宽带超导滤波器，可有效抑制通带内的干扰信号。该滤波器的3.1-10.6 GHz超宽带带通特性是由改进的多模谐振器实现。超宽带通带内的可调带阻特性是通过一端加载2比特叉指电容阵列的二分之一波长L型可重构谐振器与多模谐振器耦合作用产生的。该可调阻带可以有效抑制来自其他通讯设备的干扰信号。阻带的中心频率通过点焊线改变叉指电容的接地状态，进而改变其电容值的大小实现的。最终设计、制作完成后的滤波器的尺寸为20.0 mm × 6.9 mm。未经调谐的测试结果和仿真结果吻合得很好，并且显示出了优异的性能。. 此外，本课题组还提出了一种基于多模谐振器的四通带高温超导滤波器。所提出的滤波器中心频率和四个通带的带宽可以灵活控制，从而大大增强了设计可行性。测试结果与仿真结果吻合较好，验证了所提方法的有效性和可行性。