Analysis and simulation for broadening first-order sea clutter spectrum in high frequency hybrid sky-surface wave propagation mode

In high frequency (HF) hybrid sky-surface wave radar, the first-order sea clutter broadening is very severe under the influence of ionosphere and bistatic angle, which affects the detection of slow ship target. This study analyses and simulates the broadening first-order sea clutter spectrum based on a modified first-order ocean surface radar cross-section (RCS) model using wide beam. The authors first introduce the working principle, range equation and positioning principle based on the newly-developed integrated HF sky-surface experimental system; and derive an expression for the first-order Bragg frequency. Also presented is a modified RCS model of first-order sea clutter, in which the HF sea clutter spectrum distribution characteristics and broadening mechanism are fully considered. Finally, the proposed broadening first-order sea clutter spectrum model is examined by measured data. Simulation results indicate that the proposed first-order sea clutter spectrum model can well describe the characteristics of measured sea clutter.