Adaptive nulling of skywave interference using horizontal dipole antennas in a coastal surveillance HF surface wave radar system

This paper presents the results of a preliminary study of an adaptive system using horizontal antennas for the suppression of skywave interference in HF surface wave radar (HFSWR). Four horizontal dipoles, configured as two separate crosses, were added to a HFSWR system that normally uses vertically polarized antennas (VPAs). The data received from the dipoles were correlated with the data received from the VPAs to estimate and cancel the interference adaptively in the VPAs. The results of the study show that the technique worked well against the observed interference. The interference-plus-noise power was reduced by up to 13 dB, and the Bragg-to-interference-plus-noise-ratio (BINR) was enhanced by up to 21 dB. The study also compared the effectiveness of the adaptive technique using one, two (different combinations) or four horizontal dipole antennas. This comparison indicates that the technique was more effective when all four horizontal dipoles were used