Implications of Noise Source Resolution on Detection Performance for Horizontal Directional Systems Operating in Ship-Induced Noise Fields

摘要

This report develops relationships between the probability of detection and the system and environmental factors governing the extent to which individual noise sources are angularly resolved by a linear array operating in a ship-induced noise field. The effect of noise source resolution is described both in terms of a 'detection opportunity probability' and a 'ship resolution gain' (SRG). The detection opportunity function describes the probability of detecting a constant level signal in a ship-induced noise field as a function of the mean signal excess. The SRG represents the change in the single-to-noise ratio required to achieve a specified detection probability for a ship-induced noise field over that required for a noise field with constant mean power. The results are obtained by using a model that relates the beam noise cumulative distribution function to the directivity and the side lobe level degradation of the system and to both the strength and the anisotropy of the shipping distribution. These results indicate that only a small increase in the directivity or a small decrease in the shipping strength can result in a large increase in the detection opportunity probability for a negative signal excess, and a large increase in the SRG for small detection probabilities. Furthermore, when the shipping is only weakly resolved, large degradations in the side lobe levels can be tolerated without an appreciable degradation in the SFG; when the shipping is highly resolved, any degradation in the side lobe level results in a corresponding degradation in the SRG.