Analysis of first-order sea clutter spectrum characteristics for HF sky-surface wave radar

HF OTH radar based on the hybrid operating mode of sky-wave transmitting and ground-wave receiving because of its special system layout and propagating characteristics, its first-order sea clutter spectrum characteristics are not just about oceanic dynamics and frequency, but also influenced by grazing angle, bistatic angle and ionospheric conditions, so it needs to consider these factors comprehensively. In this paper, according to the geometry configuration and characteristics of sky-surface OTH radar detection, the positioning principle were firstly analyzed. The formula of the Bragg frequency of first-order sea clutter is presented derived from the system configuration, the frequency shift and the broadening mechanism of first-order sea clutter is analyzed, and the effects of various factors like ionosphere, grazing angle and bistatic angle on the first-order sea clutter spectrum and the characteristics of frequency shift and broadening of sea clutter in detection ranges at different distances are analyzed through the simulation based on the system layout. Finally, the results of theoretic analysis are examined with the experimental results, and the dominant factor that cause sea clutter broadening is discussed. Simulation results show that the results of experiment consist with that of theoretic analysis.