Sea Clutter Processing for Target Detection in Skywave Over-the-Horizon Radar

摘要

In order to intuitively understand sea clutter, its Doppler spectrum was simulated through Barrick's second-order cross section equation of HF radar. The imitated sea clutter echo was closely related to the normalized cutoff wave number of radar. Simulated results are consistent with the measured data. This paper presents "CFAR-three-step-test" to deal with the sea clutter of measured data for target detection: (1) detect all the distance units that passing detection threshold G; (2) judge whether the detected units being next to each other, isolated unit getting through; (3) decide whether the peak of the isolated unit being in these three special positions of positive or negative Bragg peak or "zero frequency", if not, determining it a moving target. When skywave OTH radar monitored large area of sea surface, it received a large number of sea echoes. Contraposing these echoes, after analog-to-digital conversion, producing two orthogonal data, using fast Fourier transform and "CFAR-three-step-test", after exclusion of all false alarms, a object was detected finally. This proves that "CFAR-three-step-test" can effectively reduce the sea clutter, and greatly lessen the echo broadening and ghosting caused by ionosphere contamination.