Weak Target Detection In The Sea Background Based On Fractal Theory

By emitting electromagnetic wave and receiving the echo, radar detects and locates the target. The sea clutter among the received echo has a great impact on radar target detection. So. it is significant to study sea clutter for radar system design, radar signal processing and target detection. At present, the detection of weak sea target is a great challenge for marine radar, and with the development of science and technology, weak target detection in the sea background has a broad prospect for development in the field of military and civilian areas. Therefore, the research of weak sea target detection has very important theoretical significance and application value.To detect weak sea target, the traditional method studies the statistical characteristic of sea clutter and then sets up a corresponding model, but the statistical model cannot reflect the physical mechanism of sea clutter well, so the weak target among sea clutter is difficult to be detected. With the development of nonlinear theory, many new methods have been applied to the detection of weak sea target. Fractal is an important branch of nonlinear science, which studies the irregularity of object on structure. In this paper, how to apply the fractal theory to sea clutter processing and weak target detection is researched. Theoretical and experiment researches are combined in this dissertation. On the one hand, the latest fractal theories are used to analyze the sea clutter. On the other hand. IPIX real-life datas are used to verify the effectiveness of the theories and methods.This paper mainly studies the different fractal parameters between sea clutter and target echo, analyzes the quality of several fractal parameters based on IPIX real-life datas. and detects the weak sea target by the method based on wavelet leaders multifractal (WL-MF). The main contains of this paper include the study of the fractal characteristic for sea clutter, analysis of the different characters between sea clutter and target echo by box-counting dimension in time domain. Hurst index in fractional brownian motion and comparison of the detection performance of two methods. Then this paper verifies the multifractal characteristic of sea clutter, and presents a method of using the multifractal detrended fluctuation analysis(MF-DFA). compares the difference of sea clutter and target echo and compares the qualities with the former two methods. At last, according to the theoretical advantage of wavelet analysis, a method based on WL-MF is studied in this paper, and by comparison with several methods mentioned before, this method has good qualities.