The over-the-horizon radar is able to detect ships over very large oceanic areas. Detection performance is sometimes reduced because of smearing of the sea echo due to variations of the Doppler shift imposed by the ionosphere. In this paper we propose a alecontamination procedure, based upon maximum entropy spectral analysis of sea scatter Bragg lines, to correct the phase of the signal before performing classical fast Fourier transform processing. The improvement in quality of the signal after phase correction results in a sharpening of spectral peaks. In the example presented the signal was chosen to contain spectral lines of a transponder installed on board a ship, to be used as reference lines. The decrease in the spectral width is significant for the sea scatter Bragg lines and for the transponder lines. As the Bragg lines sharpen, the ship echo is more easily detected in the spectrum. The proposed decontamination procedure involves more computation load than the simpler frequency shift method used for sea state monitoring, but, on the other hand, it can handle Doppler shift variations during coherent integration time.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.