Detection Of Low-altitude Wind Shear With Airborne Weather Radar Under Complex Trajectories

When airborne weather radar detects the low-altitude wind shear,it faces a lot of clutter due to its looking-down working mode,which causes the wind shear signal to be submerged in the clutter environment.Therefore,the ground clutter must first be suppressed to detect the low-altitude wind shear.In the actual complex flight environment,when the aircraft is affected by strong airflow in the air and maneuvering(such as turning),it may have yaw,dive,roll,acceleration,pitch and other motion states,resulting in complex aircraft trajectories,which will make the clutter spectrum more complex,thus increasing the difficulty of ground clutter suppression and seriously affect the detection of low-altitude wind shear.Therefore,it is of great significance to research the detection of the low-altitude wind shear under complex trajectories.Based on this,the special cases of yaw and dive of the aircraft are selected to research the detection of low-altitude wind shear under complex trajectories.Firstly,the low-altitude wind shear,ground clutter echo signal models and radar echo data model of airborne forward-looking weather radar under complex trajectories are introduced in the thesis.Then the ground clutter characteristics of airborne forward-looking weather radar under complex trajectories are analyzed.The low-altitude wind shear and ground clutter echo signals are also simulated.Secondly,when the yawing angle and the dive angle of the aircraft are relatively small,the complex trajectories of the aircraft cause the clutter echo characteristics to become complex,which affects the inaccurate detection of low-altitude wind shear.A method of low-altitude wind shear speed estimation based on Generalized adjacent Multi-Beam(GMB)Adaptive Processing is proposed.The clutter range-dependence compensation method based on echo data is first used to correct the range dependence of clutter for estimating the clutter covariance matrix.Then the dimension-reduced transform matrix is calculated by using this method,and the radar echo data of the measured range bin is reduced in dimension.Finally,the optimal weight vector of the method is constructed to filter adaptively and complete the wind speed estimation of low-altitude wind shear.Finally,when the yawing and dive angles of the aircraft become larger and the number of reference range bin that can be used to estimate the clutter covariance matrix of the range bin to be measured,a low-altitude wind shear wind speed estimation method based on Cascading three Doppler Transform after Direct Data Domain joint adaptive processing(DDD-3DT)without reference range bin is proposed.The method firstly uses the direct data domain algorithm to filter out the wind shear signal of the range bin to be measured,and obtains a plurality of training samples through the sliding window.Then the joint dimension-reduced transform matrix of the DDD-3DT method is obtained,and the training samples are subjected to dimension reduction processing.Finally,the optimal weight vector of the method is constructed to filter adaptively and match the wind shear signal for each Doppler channel of the range bin to achieve wind speed estimation of low-altitude wind shear.