S频段低无源互调同轴滤波器设计

A Design of Low-Passive Intermodulation Coaxial Filter in S-band

介绍了无源互调产生的机理,分析了同轴滤波器无源互调产生的位置,提出了减小无源互调的措施。针对同轴滤波器的无源互调问题,单独突出一个无源互调源,即同轴谐振杆和腔体连接处。比较了两种同轴滤波器的无源互调,并采用表面氧化和传统镀银工艺对谐振杆进行表面处理,测试了两种工艺对无源互调的影响。结果表明,接触点和接触点处的氧化层对无源互调有较大影响,因此在设计低无源互调滤波器时应尽量避免这两个因素,在工程设计上具有一定的参考意义。

The mechanism of passive intermodulation is described and the position of passive intermodulation in coaxial filters is analysed. Then some advices to reduce passive intermodulation are proposed. And as one of the passive intermodulation sources in coaxial filters,conjunction between rod and coaxial resonator cavity is analysed. During the designing,resonant rods are treated by traditional silver-plated method and surface-oxidized method. And then the passive intermodulation level of the two types of S-band coaxial filters are compared. Meanwhile the influence of the two surface treatments is also analysed. It is proved that the states of the contact point and the oxide layer on contact point surface have stronger effect on passive intermodulation level. Therefore,it is helpful to design coaxial filters with low passive intermodulation level.