Research On Wind Turbine Clutter Mitigation Method Of Airborne Array Radar

As a clean energy source,wind energy has attracted attention from various nations,however,the large-scale construction of wind farms has severely affected the electromagnetic environment.When the moving target is detected by airborne radar in the background of wind turbine clutter,due to such characteristics of wind turbine as long blade,high rotation speed,and the metal material,false alarm rate of target detection is enhanced,and the detection threshold of nearby distance units is increased,causing problems such as increased target missed detection rate.Hence,this article conducts a research based on these problems.Modeling of wind turbine echo signal and analysis of echo characteristics.Firstly,the mathematical model of wind turbine echo is established with the idea of finite element segmentation,and the radar echo signal of the wind turbine is obtained via pulse compression;further,the echo characteristics of wind turbine clutter are analyzed.The short-time Fourier transform is adopted in this article to analyze the time-frequency domain echo characteristics of wind turbine echo,and obtain the time and frequency domain characteristics by deducing from its time-frequency domain characteristics,which is verified by typical experiments.Experimental results show that the Doppler frequency of each blade due to rotation changes sinusoidally with time,and frequency flicker occurs when the blade is perpendicular to the line of sight.During long-term observation,the period of echo power in time domain is 1/2 of that of echo signal.In the case where the dwell time is short,the sum of the Doppler frequencies corresponding to the three-blade clutter is zero.Finally,the single-channel echo is expanded to multiple-channel echo,and its space-time two-dimensional echo characteristics are analyzed by experiment.The results indicate that the space-time two-dimensional power spectrum of wind turbine clutter has larger spectral width in corresponding spatial domain.Classical wind turbine clutter mitigation algorithm and simulation analysis.Aiming at problems in target detection under the background of wind turbine clutter,the applicability of existing algorithms and IAA-Capon-based clutter covariance matrix reconstruction algorithm are studied comparatively and analyzed via simulation experiments.According to the frequency domain characteristics of wind turbine clutter,the frequency unit where the target is located by searching for the frequency corresponding to the peak point in the frequency domain is obtained via the algorithm.And the wind turbine clutter mitigation problem is converted into a searching the optimal solution with linear constraint.Results show that,the airborne primary radar wind turbine clutter mitigation algorithm can effectively achieve the detection of target when clutter and target are at different range units;The time-frequency domain periodic target detection and matching pursuit algorithm has better clutter mitigation performance when there is long dwell time,and target and clutter are in the same range unit;The proposed algorithm is suitable for target detection when clutter and target are in the same range unit with a short dwell time.Whereas,when the target and wind turbine clutter are in same frequency unit,the proposed algorithm can mitigate target signal while mitigating clutter.When the target and the wind turbine clutter are in the same frequency unit,the IAA-Capon-based clutter covariance matrix reconstruction algorithm suppresses the wind turbine clutter,the target signal is also suppressed.To solve this problem,this paper proposes a multi-dimensional joint wind turbine clutter mitigation algorithm.For airborne side-looking multi-channel radar,the Doppler frequency of the blade clutter changes sinusoidally with time during long-term observation.According to this characteristic,filtering is performed in the time-frequency domain to achieve the suppression of the rotating blade clutter.The mast clutter and the target signal are in different directions,The clutter ridges of the rotating blades of different channels are extracted to complete the estimation of the direction of the mast clutter,and it is filtered in the space to suppress the static mast clutter.Experimental results show that when the target and wind turbine clutter are in the same frequency unit,the algorithm can retain the target signal while suppressing the wind turbine clutter.