Research On Spectrum Of Sea Clutter Detected By Sky-wave Over-the-Horizon Radar

The Over-the-Horizon Radar(OTHR) operates in shortwave band(3-30MHz).It using sky-wave propagation via refraction by the ionosphere is capable of detecting targets at distances an order of magnitude greater than conventional microwave radar limited by the line of sight. The target above sea can be detected and information of sea state can be got by employing OTHR in illuminating sea and analyzing Doppler spectrum of sea echo.In this dissertation, the simulation of sea clutter, effect that ionosphere imposed on sea clutter and decontaminant of ionospheric distortion are studied detail. The summary of the research work is as follows:1) Based on the ocean scattering intensity formula proposed by Barrick, the ocean clutter spectrum is simulated. The characteristics of sea clutter distribution and its dependence on parameter of sea state are deduced. According as T.M.Georges's theory on the effects of space and time resolution on the quality of sea echo Doppler spectra, A relevant emulator is made.2) The Doppler shift brought by radar wave propagation through ionosphere is calculated by using ray tracing equation and combining the F2 layer critical frequency and M(3000)F2 described in CCIR-340 report.3) Decontamination of ionospheric distortion and ship echo detection in sea clutter background are studied. First, that enhanced OTHR ship detection via dual frequency operation is investigated. Then, the compensation for ionospheric layer movement and ship echo detection in sea clutter background by using the Wigner-Ville distribution and Modified Prony arithmetic are researched.Finally, the whole dissertation is concluded. And the future work is pointed out.