Abstract: The blanketed zone of support jamming is computed by the pattern propagation factor (PPF) with different reflection coefficient and carrier frequency. The signal jamming noise ratio is concluded with the different reflectance on different propagation path. The antenna model is built with rectangular aperture, and a cosine-squared-on-a-pedestal is adopted to suppress the back lobe. The PPF calculation model is formed according to reflection coefficient definition and the wave path difference between the direct path and reflected path. The simulation results show that the jamming blanketed zone is extended for the multipath effect, and the zone is divided into parts. In addition, the exposed zone decrease with the decrease of reflection coefficient, but the shape of exposed zone does not change. And the higher the radar carrier frequency is, the greater the PPF fluctuation is. Analysis results indicate that the multipath effect can be lightened or utilized in virtue of the diversity of carrier frequency for the broad band radar.