Study of Passive Intermodulation of Microwave Waveguide Connection Based on Rough Surface Model

A novel model for calculation of Passive Intermodulation（PIM） induced by waveguide connection is presented.Considering asperity heights of real engineering surfaces may follow asymmetric distribution,the more adaptable Weibull distribution is used to describe the surfaces topography of the waveguides.Based on the model of contact rough surfaces the effect on its equivalent circuit,dependances of the 3rd PIM of rectangular waveguide connection MIM on the factors such as surface roughness,thickness of insulator,contact load and so on are studied with Taylor series method in this paper.The results show that the rougher the surface,the thicker the insulator,the less the contact load is,the lower will be the PIM.It is also predicted by this theoretical model that when the applied contact load increased from 104Pa to 106Pa the PIM level has a mitigation about 50dB.