Abstract: Based on the transmission function of an electromagnetic wave in the random rain medium by the random system method, the expressions for the double-frequency correlation function and the intensity of a pulse wave are derived. The pulse fluctuation characteristic and the pulse broadening effect are investigated. The function relation of pulse group velocity with frequency and rain rate is obtained. The effects induced by the EM wave frequency and bandwidth on the pulse broadening velocity is studied and the simulated results are given in the mm band. The results show, based on the calculation in this paper, that the pulse broadening velocity of horizontal polarization wave is greater than that of the vertical polarization wave and that the pulse broadening velocity increases with an increase in bandwidth and rain rate.

Key words: rain medium, pulse wave, double-frequency correlation function, broadening