Analysis and Measurement of Passive Intermodulation in Coaxial Cavity Filter

In this paper, passive intermodulation (PIM) in a third order coaxial cavity filter is studied. Firstly, the filter is designed and the current density around resonant rods are obtained using software ansoft HFSS. Secondly, we compare the current density around resonant rods and sequence them according to the values of the current density. Thirdly, several coaxial cavity filters are manufactured according to the same design model. These filers are same in structure, but only different in assembling form. Lastly, the third order PIM level of these filters is measured at different input powers. The result shows that the filter in which the current density around the resonant rod is largest will have high PIM level if the resonant rod is just connected with screws during assembling at the same input power.