Abstract: Passive intermodulation often affects the normal operation of multicarrier communication satellites. Because of the complexity of passive intermodulation interference, it is impossible to analyze the passive intermodulation component directly. Therefore, it is necessary to establish models. According to the frequency distribution characteristics of passive intermodulation interference, double exponential function model and Volterrra series model were adopted to fit passive intermodulation interference, and the time series model of passive intermodulation interference of QPSK signals was established. By performing MATLAB simulation, the results show that the peak values appear at the theoretical frequency points. The ratio of the amplitude value at the center frequency of the input signals to the amplitude value at the passive intermodulation frequency components accords with the theoretical analysis.

Key words: passive intermodulation, satellite communication, nonlinearity, double exponential function, Volterra series