双/多基地天气雷达探测小椭球粒子群的雷达气象方程

Radar meteorological equations for bistatic/multistatic weather radar systems detecting small spheroid raindrops

首先导出小椭球散射的方向函数及侧向散射截面的表达式。然后,考虑发射水平偏振波与垂直偏振波这两种情况下,当小椭球粒子群旋转轴作一致铅直取向和在空间作均匀随机取向时,分别建立适用于双/多基地雷达接收子站的雷达气象方程。主要结果为:(1)当入射波以不同的仰角及方位角射到旋转轴任意取向的椭球上时,会在椭球的3个轴上产生不同的极化电偶极矩分量,使小椭球散射方向函数不仅与散射方向有关,还与天线和粒子两个直角坐标之间的配置情况有关。(2)无论入射波偏振方式是水平还是垂直,小椭球粒子的总侧向散射截面恒是散射波在该方向上造成的侧向散射截面之和。(3)双基地雷达气象方程与单基地雷达气象方程比较,其差别在于侧向散射截面与后向散射截面的不同,另外,有效照射体积不同,子站与单基地站天线方向性函数不同,使双基地雷达气象方程中多出与双基地角有关的一个因子。(4)主站天线辐射在半功率点内不论均匀与否,双基地雷达气象方程中的侧向散射截面均代表总的侧向散射截面且依赖入射波偏振方式。(5)给出了小椭球群旋转轴一致铅直取向情况下的双基地雷达气象方程,这些方程与入射波偏振方式、主站发射天线辐射在半功率点内均匀与否有关。入射波为垂直偏振时一致铅直取向的椭球群的侧向散射截面可能由包含铅直分量在内的3个正交分量组成。这具体依赖于主站天线仰角。但入射波为水平偏振时到达子站天线处的回波功率与主站天线仰角无关。(6)给出了小椭球群旋转轴在空间无规则取向时的双基地雷达气象方程,这些方程与主站天线仰角、入射波偏振方式等无关,但与主站发射天线辐射在半功率点内均匀与否有关。

Expressions for the directivity function of a small spheroid particle and its side-scattering cross-section are obtained and then sets of radar meteorological equations for bistatic and multistatic weather radar systems are given for the cases that the orientation of the detected small spheroid particle is uniquely upward and omnidirection-distributed,respectively,as well as the polarization of the transmitted radar wave is horizontal and vertical,respectively.The main results include that（1） the 3 components of dipole moment can be generated because of the radar waves incident from arbitrary azimuth and elevation,which leads the directional function of particle scattering to depending on not only the scattering direction but also the relationship between the two respective coordinates of the radar antenna and the particle;（2） the side-scattering cross-section of the particle is the sum of the side-scattering cross-sections for all the 3 components of the scattering waves;（3） the difference in radar meteorological equations between the bi-static radar system and the mono-based radar system are caused by the difference between the side-scattering cross-section and the back-scattering cross-section in addition to the difference between their effective volumes and the difference between their antenna directional functions;（4） the side-scattering cross-section in radar meteorological equations is the sum of the side-scattering cross-sections for all the 3 components of the scattering waves and is sensitive to the polarization manner of the incident wave;（5） the obtained bistatic radar meteorological equations for the case in which the orientation of all the spheroids is uniquely vertical are classified according to both the polarization manner of the incident wave and the directional feature of the transmitting antenna;the elevation of the incident wave may make the side-scattering cross-section of the spheroids consist of 3 orthogonal components,one of which must be vertical in case the incident wave is vertical polarized,but the scattered power is independent of the transmitting antenna elevation if the incident wave is horizontal polarized;（6） the obtained bistatic radar meteorological equations for the case in which the orientation of all the spheroids is omnidirection-distributed depend on the directional feature of the transmitting antenna but independent of the elevation and polarization manner of the incident wave.