Cross-correlation function simulation of the signal scattered by sea surface under glancing radiation

Abstract

Simulation is accomplished for ship navigation radar with mechanical scanning and probing signal, with horizontal polarization and linear frequency modulation. The sea surface was treated  as a linear parametric circuit. Spectrum of the signal scattered by sea surface is defined as product of the probing signal spectrum and complex scattering coefficient. Dependence calculation of the complex scattering coefficient on the frequency is done via integral equation method for a 10 m long section of the sea surface. Linear model of sea waves interaction combined with Elfouhaily wave spectrum is applied to generate sea surface implementations. It is demonstrated that achieving the cross-correlation function shape close to possible in theory can be done by averaging the scattered signal spectrum. The cross-correlation function of a broadband signal with zero Doppler frequency shift depending on the averaging coefficient is examined for wind speed values as 3 m/s and 3.38 m/s over sea surface. The averaging ratio is regarded as the number of progressive implementations of the averaged-value signal spectrum. The maximum duration of time lapse for signal analysis used for averaging was 10 s. It is found that peak sidelobe of the cross-correlation function decreases with an increase of the averaging ratio and its width increases as the wind speed raises compared with expected theoretical value. These transformations of cross-correlation function shape of the scattered signal occur with wind speed gain due to phase fluctuations’ increase of the complex scattering coefficient of the sea surface. It is likely that to ensure the defined shape of the signal cross-correlation function with further wind speed gain there will be needed the averaging ratio raise due to mean variation range expansion and root-mean-square deviation of the sea surface z-axis.