| High frequency(HF) hybrid sky-surface wave radar takes advantages of ionospheric reflection and ground wave diffraction. Due to the special combination of channels, this kind of radar is affected by the ionosphere,ground wave propagation lossing,sea clutters,sea state and enviromental noise drastically. Focusing on these problems, the characteristics of the broaden first-order sea clutter and its statistic characteristics are studied. Besides, sea clutters suppression and target parameters estimation are also studied. The main content is given as follows:(1)Sea clutters modeling and its characteristics analyzingFocused on the broadening first-order sea clutters, the model and characteristics of it are carried out. The result shows that when the total distance is fixed, the space distribution of sea clutters can be represented by an oval equation. Based on previous research, equation of the Bragg scattering frequency is given. Finally, simulations on how different factors, such as radar operation frequency, bistatic angle, wind direction and wind speed, will affect the RCS of sea clutter is carried out.(2)Study on sea clutter suppression algorithmFocusing on sea clutters suppression, different kind of algorithms are studied. First, the effect of traditional method is tested by simulation data, and its defects are analyzed. Second, improvements are made on traditional algorithm, simulation results show that the improved method is more adaptive than traditional one. Finally, a precise frequency estimation method is given. This new method can estimate the parameters of complex sinusoidal precisely, resulting in more effective sea clutter cancelling.(3)Target parameters estimationIn the target parameter estimation part, the motion of a target is represented by high order polynomial and a new ML estimator is given to estimate the initial position, velocity and acceleration of the target. The CRB of each parameter is derived and simulation result is given to show the efficiency of the ML estimator. |
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