同轴腔结构交叉耦合滤波器的设计

同轴腔结构交叉耦合滤波器的设计 摘要现代微波通讯的快速发展，对通道的选择性要求越来越高，不仅须要滤波器的过渡带尽可能窄，还可能须要产生非对称的频率响应，这就须要高性能的选频器件。传统滤波器如 Butterworth和Chebyshev滤波器只有依靠增加滤波器的阶数才能满意要求，加工出来的滤波器重量和体积都特别大，不适合现代通讯的需求。椭圆函数滤波器虽然具有很好的选择性，但不能产生非对称的频率响应。广义Chebyshev函数滤波器能通过引入交叉耦合在有限频率处产生传输零点而不用增加滤波器阶数来提高通道的选择性，并且它的随意零点特性能产生非对称的频率响应，相当于把滤波器的阻带抑制实力都集中在所须要的一侧，从而可以用较少阶数的滤波器来实现很高的选择性，因此与传统滤波器相比，体积小、成本低且通道选择性更好，从而可以减小系统的体积和重量，满意现代通信的需求。 同轴腔滤波器通过在谐振腔之间开窗口或加探针，实现电感或电容耦合，通过变更窗口的位置、大小或者探针的粗细、长短等来限制耦合电感或电容的强弱以实现窄带滤波器；而且很简洁实现谐振器之间的交叉耦合，通过限制交叉耦合的数量和强弱得以实现传输零点的位置和数目。在有电容加载的状况下，同轴腔滤波器具有小型化的优势，并且具有带宽窄、矩形系数高、功率容量高等优点，所以其应用前景特别广泛，是国内外广泛探讨的热点。 总之, 同轴腔广义Chebyshev滤波器具有体积小、带宽窄、矩形系数高、功率容量高等优点, 是国内外广泛探讨的热点。 本文主要论述运用广义切比雪夫滤波函数综合交叉耦合滤波器，并在HFSS中设计出了带有传输零点的四腔同轴腔滤波器。交叉耦合滤波器的综合设计从给定的滤波器参数中心频率，带宽，带内的回波损耗，归一化端口阻抗等起先，首先得出广义切比雪夫函数滤波器的反射系数和传输系数递推关系式，依据理论响应的表示关系式提取出描述各谐振腔耦合关系的耦合矩阵以及源与负载端的加载Q值;然后利用耦合谐振器电路理论在实际的微波电路结构中实现耦合矩阵中可实现的耦合系数和源与负载端的加载Q值。最终的仿真结果说明白这种方法的可行性和好用性。 关键词广义Chebyshev函数 交叉耦合 同轴腔滤波器 HFSS 耦合矩阵 Design Of Cross-coupled Coaxial Cavity Filter Abstract With rapid development of modern microwave communication, The high selectivity of channels have become more and more important. not only demand microwave Filters transitional zone is as narrow as possible, but also generate non-symmetric frequency response is necessary, therefore, we require high-frequency selection device. Conventional filter such as Butterworth and Chebyshev filters can meet the requirements only by increasing the filter order, so weight and size are very large when filters are processed, and not suitable for modern communication. Although elliptic function filter has good selectivity,But it can not produce non-symmetric frequency response. Generalized Chebyshev function filter can Produce transmission zeros in limited frequency by introducing Cross-coupling, without increasing filter order we also can improve the selectivity of the channel, and due to arbitrary zero point Characteristics make it can produce non-symmetric frequency response, stop-band rejection are concentrated to the required side, thus we can use smaller filter order to achieve high selectivity. Compared with the traditional filters, generalized Chebyshev filters have small size and low cost to meet the needs of modern communication. Coaxial cavity resonator filters realize inductive or capacitive coupling by opening windows or adding the probe between the open windows, changing the windows position, size or thickness and length of the probes, we can control the strength of the coupled inductor or capacitor to achieve narrow band filters, and it is easy to achieve cross coupling between resonators, the position and number of transmission zeros is definite by controlling the number and strength of cross-coupling. In the case of a capacitive load, coaxial cavity filters have the advantages of miniaturization, narrow bandwidth shape, factor and high power capacity are also its merits, Therefore, its applicat