The use of a large number of passive devices in communication system makes passive intermodulation series connection problem becoming more and more common.In order to solve this problem

a simple model of two cascaded passive devices is established.In the mode of TE10

the nonlinear structure of metal-insulator-metal is characterized by Taylor series

where the effect of transmission line length on the input carrier signal phase is considered.We also analyze the variation of the passive intermodulation power with different length of transmission line and the input carrier phase differenceΔθ.The results show that the passive intermodulation power is different with the phase of input carrier signal in the two stage of the waveguide junction

and the cumulative value is between 0to 3dB.In addition

the transmission line phase length at the maximum and minimum cumulative value can be obtained by the phase differenceΔθ.Due to the interaction among the passive intermodulation frequency components

the intermodulation product types increase dramatically in waveguide.