Ground Clutter Suppression Of Airborne Polarized Weather Radar

Airborne weather radar,as an indispensable electronic equipment on civil aviation aircraft,can detect and display the weather information of the route in real time,help pilots to avoid dangerous weather in time,so as to ensure the safe operation of civil aviation aircraft.With the continuous improvement of flight safety requirements,the detection capability of airborne weather radar needs to be improved urgently.Compared with traditional airborne weather radar,dual-polarization weather radar can transmit horizontal and vertical electromagnetic wave signals alternately or simultaneously,and can obtain not only radar echo intensity information of different polarization channels,but also phase state,shape and spatial distribution information of weather targets.So the dual polarization weather radar has better ability of detecting and classifying weather targets.In addition,when airborne weather radar is working in downview mode,ground clutter must be included in the radar echo received,because of its large intensity and wide distribution,it will seriously affect the detection of weather targets.Therefore,it is necessary to study the ground clutter suppression of airborne polarized weather radar.Based on airborne polarized weather radar,this thesis studies the ground clutter suppression of airborne polarized weather radar.The main contents are as follows:Firstly,the simulation principle of airborne polarized weather radar echo is described.The ground clutter data of airborne polarized weather radar are obtained by combining the backscattering coefficient empirical model and polarized SAR data simulation,and the meteorological target data of different polarized channels are simulated.The characteristics of ground clutter of airborne polarized weather radar are analyzed,which lays a foundation for ground clutter suppression of airborne polarized weather radar.Secondly,a ground clutter suppression method based on improved Gaussian Model Adaptive processing(GMAP)is proposed for single antenna airborne polarized weather radar.This method combines the polarization information of different polarization channels,changes the radar echo signal of different polarization channels to the frequency domain,obtains the spectral power and spectral reflectance factor of echo signal,then obtains the spectral differential reflectance of each range unit polarized radar echo signal.The GMAP method is implemented for spectral differential reflectance of polarized radar echo signal of each range unit,successively,the echo signal of each range unit is windowed,the noise power level is determined,and the clutter points of spectrum power of polarization radar echo signal are eliminate.The power spectrum of meteorological target signal is fitted to replace the removed clutter points to restore the power spectrum of meteorological target signal.Finally,ground clutter suppression is realized by using polarization information.Finally,a ground clutter suppression method based on Space-time Adaptive Processing(STAP)of dual-polarization and multi-channel data fusion is proposed for airborne polarized phased array radar.This method can combine the space-time information and polarization information of different polarization channels to improve clutter suppression performance.The method first calculates the average power of ground clutter data of polarization channel and cross-polarization channel,then obtains the weighted coefficient of clutter covariance matrix of different polarization channels in the fusion matrix according to the average power.Moreover,the weighted coefficient and covariance matrix of different polarization channels are combined to obtain the clutter covariance matrix after data fusion of dual polarization channel;Finally,STAP processor is constructed to suppress ground clutter.