Study On Passive Intermodulation Of Microwave Waveguide Connector

In recent years,with the rapidly development of communicat ion industry,the number of users is increasing,the large-scale construction of the communication link,make use of passive devices is very common;at the same time,Passive Intermodulation(PIM)caused by nonlinear of passive devices is becoming more and more seriously.Once the Passive Intermodulation product fall into the frequency band of receiver,will seriously affect the quality of communication system,therefore,the problem of how to reduce passive intermodulation interference has attracted more a nd more attention of the communications industry,so it has certain theoretical and practical significance for the study of passive intermodulation.To reduce the passive intermodulation interference in the communication system,it is necessary to study the mechanism of passive intermodulation.The paper is based on the rectangular microwave waveguide connector,to analyze the mechanism of passive intermodulation and establish passive device two-stage model.The generating mechanism of passive intermodulation are: material nonlinear and contact nonlinear,one of the common reasons of passive intermodulation generation is contact nonlinear of waveguide junction,it is include the contact mechanism and the mechanism of semiconductor.The contact mechanism is believed that the closely contact waveguide flanges,from the microscopic perspective,the actual contact occurs only in a small number of asperities of the rough surface.The current of flowing through the waveguide junction gather to contact asperities produce nonlinear because of sudden contraction,resulting in passive intermodulation.The semiconductor mechanism mainly originates from the waveguide junction of the Metal-Insulator-Metal(MIM)structure,because the air oxidation,contamination and other reasons in the surface of flanges formed a layer of insulator,formation of MIM structure.This paper focuses on the study of quantum tunneling effect and thermal electron emission effect of the semiconductor mechanism,analyzed the main influencing factors of two intermodulation interference effect,the change trend of passive current density with various factors;and discussed the leading role who plays between the intermodulation generation mechanism under the same conditions,it has guidance meaning for reducing the intermodulation interference.The extensive use of passive devices makes there are more than one passive device in a communication link,aiming at the common phenomenon of passive devices cascade,this paper established two cascaded model with the passive device is simplified as waveguide junction.Analysis of the passive intermodulation power changes when the input carrier signal continuously through two waveguide junctions,and account for the phase changes of the input signal effected by the transmission line connecting the two waveguide junction,the passive intermodulation power varies with the length of the transmission line phase and the phase relationship between two input signal and difference the length of the transmission line phase can be obtained,which can effectively avoid the passive intermodulation power cumulative maximum value,achieve the purpose of reducing passive intermodulation interference.