Study On Short-range Heterogeneous Clutter Suppression Algorithms For Airborne Radar Based On Elevation Map

In the airborne radar clutter suppression, conventional STAP algorithms assume that the clutter environment is homogeneous and the sample data is independently and identically distributed, thus, they can achieve good performance under ideal condition. Because the actual terrain environment exists topographic relief, the clutter model under homogeneous environment is no longer applicable and STAP has an obvious performance degradation. Therefore, under the background of phased-array airborne radar, this paper focuses on two aspects. On the one hand, we establish the general clutter model based on the digital elevation map(DEM) by creating elevation map, judging the shelter points, and calculating the echo signal. On the other hand, we utilise the idea of two-dimensional-pulse-to-pulse canceller(TDPC) and direct data domain to suppress the short-range heterogeneous clutter. These two algorithms can avoid the performance degradation caused by the estimation deviation of the covariance matrix.The main work and content of this paper are as follows:1. Chapter 2 introduces the homogeneous clutter model for airborne radar and the corresponding clutter suppression method. Firstly, the geometry model of the clutter is presented. Secondly, the principle of the optimal STAP is discussed. Thirdly, some classical reduced-dimension STAP algorithms are described, such as joint domain localization(JDL), factored approach(FA), and extended factored approach(EFA). The performance of EFA is better than that of FA, because EFA has more system degrees of freedom(DOFs).2. In chapter 3, we establish and analyze the general clutter model for airborne radar based on elevation map. The elevation map is set up firstly. Then, the method to judge the shelter points is put forward, and the clutter echo signal is calculated. Finally, some simulation experiments and analysis are illustrated. Through the simulation, we can observe the different distribution of the clutter power spectrum under the condition of long-range, medium-range, short-range, respectively. Moreover, the clutter power spectrum shows "spectrum shifting" phenomenon. In this paper, the clutter model which we build is general. Once the height information is input through a matrix, the corresponding power spectrum is obtained.3. In chapter 4, in order to suppress the short-range heterogeneous clutter, we propose two algorithms. One is TDPC based on elevation map. This method makes use of the priori information of aircraft speed and radar parameters. The error function is then constructed by adjacent pulse subtraction, and the filter coefficient matrix is calculated by minimizing the error function. Thus, the clutter DOFs decreases. The other is the direct data domain which is non-statistical. This method processes the sample data directly, and can be applied in non-homogeneous environment. Meanwhile, for practical engineering need, we propose two disciplines on plane route planning theoretically. Simulation results prove that these two algorithms can achieve better performance than the conventional reduced-dimension STAP in the suppression of short-range heterogeneous clutter.