微波滤波器腔体Q值研究与分析

Research and Analysis of Q-Factor of Microwave Filter Cavity

针对微波滤波器的某些特殊设计要求或加工制造缺陷造成滤波器中某一或某些腔体Q值降低的情况,分析了其对滤波器性能可能造成的影响并提出了工程中可实现的解决办法。首先研究了传输模式以及调谐螺钉深度对谐振器Q值的影响;然后通过理论推导得到滤波器某一或某些谐振腔体Q值下降对频率变量矩阵的影响公式,进一步通过MATLAB实现对5阶带通滤波器某一腔体Q值下降的情况进行综合与结果分析,并据此提出通过调节调谐螺钉适当增加滤波器输入输出与腔间耦合的方法来有效的减小Q值变化带来的不利影响;最后采用Designer进行电路级仿真,验证理论推导结果的正确性。研究结果表明:谐振腔体Q值的降低会造成滤波器驻波带宽增加、整体性能变差,并且越靠近拓扑结构中心腔体Q值的改变对整个滤波器性能造成的影响越大。当滤波器中某些单腔Q值的降低在一定范围之内,则可以通过调节耦合螺钉来提高滤波器输入输出与腔间耦合,以有效的减小其带来的不利影响。文章结论可为研究与解决微波滤波器Q值降低造成性能变差问题提供一定理论指导价值与实际工程意义。

Aiming at some special design requirements or manufacturing defects of microwave filters,the Q-factor of one or some cavities in the filter is reduced.The influence on the performance of the filter is analyzed and the achievable solution in engineering is proposed.Firstly,the influence of the transmission mode and the depth of the tuning screw on the Q-factor of the resonator is studied.Then,the influence formula of the Q-factor of one or some resonators on the frequency variable matrix is obtained by theoretical derivation,and the fifth order is further realized by MATLAB.The integration and result analysis of the Q-factor of a cavity of a band-pass filter is carried out.Based on this,the method of adjusting the input and output of the filter and the cavity is adjusted by adjusting the tuning screw to effectively reduce the variation of Q-factor.Adverse effects;finally,using Designer to perform circuit level simulation to verify the correctness of the theoretical derivation results.The results show that the decrease of the Q-factor of the resonant cavity will increase the bandwidth of the filter standing wave and the overall performance will be worse,and the closer to the Q-factor of the central cavity of the topology,the greater the impact on the performance of the whole filter.When the reduction of some single-cavity Q-factor in the filter is within a certain range,the coupling between the filter input and output and the cavity can be improved by adjusting the coupling screw to effectively reduce the adverse effects.The conclusions of the paper can provide theoretical guidance and practical engineering significance for the study and solution of the performance degradation caused by the decrease of the Q-factor of the microwave filter.