Radar parameters influence on the clutter in maritime forward scatter radar

Abstract

Th e development of Forward Scatter Radar (FSR) for use in maritime applications requires a fundamental understanding of the operating environment. Presently, there is insufficiency of published experimental FSR sea clutter data at near zero grazing angle over the sea. Such data is fundamental for the development of FSR systems for maritime applications. Therefore clutter experiments have been undertaken and data has been recorded at frequencies of 7.5 GHz and 24 GHz with static, medium gain antennas for low sea state 1-3 on the Douglas scale. Analysis of forward scatter propagation phenomena is presented, and spectral and statistical analysis of forward scatter clutter is performed. This paper is continuation of previous published work (5- 10) and it presents the results of clutter studies of an FSR. Essentially this type of radar does not have range/angular resolution (3, 5), clutter is picked up from the large surface area illuminated by Tx/Rx antennas. FSR is clutter, rather than noise, limited (11) and therefore, for estimation of FSR performance, the characteristics of sea clutter in the forward scattering direction at near zero grazing angles must be understood. For this reason, intensive measurements have been conducted in sea conditions, over a range of frequencies and radar parameters of the FSR system. The results discussed here are obtained at frequencies of 7.5 GHz and 24 GHz with grazing angles between 0.05° and 0.7° at different FSR system ranges (800-3300m) and sea states 1-3 by Douglas scale (15). Spectral and statistical analysis of the sea clutter data have been made and will be presented in the paper. Sea clutter has been discussed previously in (8-10) where it was shown that the clutter statistics obey mainly Rayleigh distribution while the spectra been demonstrated to be limited from above by 1Hz and the slopes were of 20 - 35 dB per decade. These results are in good agreement with numerical simulation of near-zero grazing angle FS performed in (13) where spectral and statistical properties of clutter were discussed. In this paper distribution of clutter will be considered as a function of antenna beamwidth, polarization and antenna height.