Study For Scattering Of Rainfall And Near-field Target In Millimeter Wave Band

Millimeter wave system has many advantages, especially its military and civilianforeground which has great significance in the future. However, in the millimeter wavesystem, in most of time the target is in the near field region and the millimeter wavetransmission in atmosphere will be in the serious effect of troposphere material, inwhich the effect of rainfall is the most significant one. So the scattering of rainfall andnear-fieldtargetin millimeterwavehas always been the focusof researchers.This paper mainly presents the scattering of rainfall and near-field target inMillimeter Wave Band (MMW). Firstly, raindrop permittivity, raindrop geometric shape,raindrop-size distribution and raindrop scattering characteristics are introduced.Division methodof electromagnetic scattering region between near-field and far-fieldisdiscussed. The multiple scattering of electromagnetic wave from random discretemedium is analyzed. Using Monte Carlo method, rain attenuation which considersmultiple scattering is calculated. The influence of backscattering enhancement on rainscattering coefficient is studied according to the theory of backscattering enhancement.Secondly, the triangular faces information of target model is acquired by means ofmicrowave simulation software, and the near-field RCS characteristic of target isanalyzed by Physical Optics method and cell method. Finally, the composition andworking principle of millimeter-wave radar are introduced. The influence of rainbackscatteringenhancement on millimeter wave radar detection performance is studied.The results show that there are many effects in the millimeter wave band such asexistence of rainfall backscattering enhancement effect, many differences betweennear-fieldRCS characteristics and the far-fieldRCS characteristics of the target,and thebackscattering enhancement could cause the decrease in signal-to-clutter ratio and theincrease inclutter-to-noiseratio.The results of this paper have important practical significance for the millimeterwave systemboth inthe developmentapplication andtargetrecognition.