提高天气雷达探测能力的互相关方法和中值滤波技术

应用双偏振天气雷达探测天气信号的方法备受国内外气象科技领域人员的关注。目前,双偏振天气雷达的双通道同时收发体制是由功分器将发射通道的能量等分为水平和垂直两路发射通道,其结果会使每个通道发射能量减半,又由于接收机产生的噪音能量是不变的,必然引起回波信噪比减弱,减弱值约为3 dB。为了避免3 dB损失带来的不利影响,需改进双偏振雷达的探测性能。将双偏振雷达回波信号中的双通道信号间的互相关信息、单通道信号自身的信相关信息及每个信号自身的能量信息求和,再将结果与预先设置好的阈值进行比较。如果结果大于这个阈值,就认为这个信号是有效信号,否则就认为它是噪声并被滤除。文中利用X波段双偏振天气雷达数据,对比了引入互相关算法前后的探测效果,证明利用双通道信号互相关、单通道自相关及信号能量自身求和判断信号是否存在的效果较好;介绍了中值滤波技术,并利用中值滤波技术去除了天气回波中的点杂波,提高了双偏振天气雷达的探测性能。

Cross Correlation Method and Median Filtering Technology for Enhancing Detection Capability in Weather Radar

The method using dual polarization weather radar to detect the signal has interested meteorological science and technology personnel at home and abroad . Dual channel transceiver system of dual polarization weather radar devides transmission channel into horizontal and vertical way by power divider. So energy of each channel will be cut in half and the echo signal energy will decrease about 3 dB. In order to avoid the negative influence of 3 dB loss, the dual polarization radar detection performance should be improved. The sum of the cross-correlation estimates as well as the power and autocorrelation from each of the dual-polarization returns should be gained. If the sum exceeds a predetermined threshold,the signal will be considered present. Otherwise,the data are considered to be noise and are censored. Based on the X-band dual polarization radar data, the detection effect with and without cross-correlation algorithm is constracted,and the sum of three portion is proved to be the best method for deciding signal present. In addition, median filtering technology is used to censor point clutter,and improve signal detection in dual polarization weather radars.