When the radio waves pass through the area of rain, the rain not only absorbs the energy of the radio waves, but also scatters the radio waves. This absorption and scattering together form the attenuation of radio waves. Scattering can also lead to large-scale radio interference and has a depolarizing effect on the radio waves. We call these attenuation and interference rain attenuation. This attenuation presents non-selective performance and slow time-varying characteristics, which are the main factors that lead to signal degradation and affect system availability. Therefore, the problem of rain attenuation has become an important issue that must be considered in the system design process. The size of the rain attenuation is closely related to the ratio of the diameter of the raindrop to the wavelength. When the wavelength of the signal is larger than that of the raindrop, the scattering attenuation plays a decisive role. When the wavelength of the electromagnetic wave is smaller than the raindrop, the absorption loss plays a decisive role, whether it is absorption or scattering. The effect is that the radio wave is attenuated in the direction of propagation; when the wavelength of the electromagnetic wave and the diameter of the raindrop are closer, the attenuation is greater. In general (such as medium and short waves) the wavelength of the electromagnetic wave is much larger than the diameter of the raindrop, so the attenuation is very small, and the C band The influence of the signal by rain attenuation can also be ignored. For electromagnetic waves above 10GHz, the influence of rain attenuation is very obvious, and the influence of rain attenuation must be considered in the link calculation. The higher the frequency, the greater the influence of rain attenuation, and the attenuation of electromagnetic waves by heavy rain and torrential rain is much greater than that of light rain.

Theoretical analysis and practical research show that the attenuation of the Ku-band wireless signal passing through the rainfall area above the moderate rain will be very obvious. When the passing degree is 10Km, the attenuation can reach 2 dB. When the rainfall area is heavy rain, the rain attenuation of the Ku-band wireless signal can reach 10 dB, and the rainfall intensity is proportional to the rain attenuation amplitude.