双基地多普勒天气雷达探测能力分析

双基地多普勒天气雷达系统是由一个常规多普勒天气雷达和一个或多个远程被动低增益接收机共同组成,是大气风场探测领域的新技术之一。文中首先在瑞利散射假设的前提下,考虑了雷达波的偏振方向、散射体的空间位置等条件,推导了小球形粒子散射函数在双基地雷达系统中的表达形式,建立了双基地雷达气象方程,并将该方程应用于双基地雷达的探测能力、有效探测范围等方面分析,模拟计算了侧向散射能力和被动雷达回波功率在空间的分布变化,为探讨去除旁瓣影响提供了依据。通过分析证明了双基地雷达系统工作状态垂直偏振优于水平偏振的结论。在入射波为水平偏振情况下,高空探测好于低空,而垂直偏振情况则是低空的散射能力强。如果采用双线偏振发射体制,根据需要采用不同的偏振波组合,能够有效扩大双基地探测的范围和信息量。在水平偏振情况下较强回波区域在基线附近和被动雷达一侧的基线延长线周围。由于侧向散射强度低于后向散射强度,双基地雷达对于弱天气回波不太敏感,它的探测范围小于单基地雷达的探测范围。在双基地雷达探测中旁瓣污染是一个不容忽视的问题。文中对双基地雷达参数进行了模拟回波强度计算,并与实测回波资料进行了比较,两者较一致,存在差别的重要原因可能是被动接收天线的垂直变化影响。

DETECTING CAPABILITY ANALYSIS ON A BISTATIC DOPPLER RADAR NETWORK

A bistatic Doppler weather radar system consists of one conventional Doppler weather radar and one or more remote passive receiver(s) with low-gain antenna(s).It is one of among the new techniques in the atmospheric wind field probing aspect.In the paper bistatic scattering function and radar equation were derived based on Rayleigh-scattering condition and the considerations of radar transmitting wave polarization directions and space location of scatter volume firstly.The radar equation was used in the analyzing probing capability and range.A series of simulative calculation of meteorological target scattering ability in all-directions and the distributions in space of passive radar received power have been done,providing basis for eliminating sidelobe contamination.The results show that radar transmitting with vertical polarization is better than that with horizontal polarization in bistatic radar technique.An agile transmitting with vertical/horizontal polarizations is useful for exploiting information,because the received power level is higher at upper altitude than that at lower altitude in horizontal polarization transmitting case and reverse in vertical polarization transmitting case.The stronger echo zone is around the baseline and its extension in receiver side.Because the intensity of obliquely echo is less than monostatic echo,bistatic site is less sensitive to weak weather echoes and the probing range of bistatic radar is smaller than monostatic.Sidelobe contamination is an important problem in the bistatic radar network.Comparison between simulations and actual data according to the Anhui Sun-create Ltd.showed a good reproduction of observed effect,with difference explained by receiver antenna pattern in vertical.