Detection Of Low-Altitude Wind Shear Based On Multi-Channel LFMCW Radar

Low-altitude wind shear is an invisible,intangible,but real-life atmospheric phenomenon.It usually occurs suddenly,is strong and difficult to detect,and seriously affects flight safety,especially during the take-off and landing phases of the aircraft.Therefore,how to timely detection and avoidance of low-altitude wind shear has very important practical significance in the ensuring the flight safety of aircraft.At present,the pluse radar is the most commonly used low-altitude wind shear detection tool,and its detection accuracy is high,but the radar has complex structure,high cost,large size.However,the Linear Frequency Modulation Continuous Wave(LFMCW)radar has many advantages such as small size,light weight,simple structure and high resolution,using this radar for low-altitude wind shear detection can not only obtain good detection performance,but also meets the requirements of the airborne radar for miniaturization,lightweight,and low power consumption.Therefore,this thesis focuses on airborne multi-channel LFMCW radar,and carry out the detailed research work on detection technology of low-altitude wind shear.Firstly,the thesis briefly introduces the working principle of LFMCW radar,and combines the characteristics of LFMCW radar to establish the ground clutter echo signal model under airborne forward multi-channel LFMCW radar.Secondly,according to airborne forward-looking multi-channel LFMCW radar,this thesis proposes a detection method of low-altitude wind shear based on Space Time Adaptive Processing(STAP)algorithm.The method first needs to correct the clutter distance dependence,and then combines the characteristics of the low-altitude wind shear distributed target to construct a space-time optimal processor,solving the weight vector and realizing the wind speed estimation.Finally,the Dual-Pulse Repetition Frequency(D-PRF)resolve velocity ambiguity algorithm is used to correct the velocity ambiguity,and the real wind speed value is obtained.The simulation results show that the method can effectively filter ground clutter and retain relatively more complete wind shear signal.Thirdly,aiming at the problem of the huge amount of calculation and the high complexity in STAP algorithm,this dissertation proposes a detection method of low-altitude wind shear with multi-channel LFMCW radar based on modified Joint Domain Localized(JDL)algorithm.The method first selects part of the airspace beam and the Doppler channel in the Localized Processing Region(LPR)of the traditional JDL algorithm to design the dimension-reduced transform matrix,and utilizes this dimension-reduced transform matrix to reduce the dimension of the radar echo data of the measured range bin.Then the modified JDL dimension-reducing processor is constructed to filter adaptively the ground clutter and match wind shear signal.Finally,the D-PRF resolve velocity ambiguity algorithm is used to calculate the true wind speed value.The simulation results show that the method can obtain better wind speed estimation and further reduce the complexity and the computational load of the algorithm.