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THE LIMIT TO ANGULAR RESOLUTION OF AN ARRAY DUE TO ACOUSTIC FLUCTUATIONS

机译：由于声波波动导致阵列的角度分辨率的限制

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Features of the underwater environment include internal waves, stratification and turbulence, and in shallow continental shelf waters such effects can be represented by a one-dimensional wavenumber spectrum dominated by a buoyancy range with a -3 power law and a turbulence range with a -5/3 power law. The effect of these medium fluctuations on acoustic propagation can be modelled using various techniques, leading either to a spatial coherence function, or separate phase and (log-) amplitude correlation functions for acoustic fluctuations at the receiving array. These results may then be used to calculate the resulting effect on the array directivity pattern. A number of visits to Cambridge during the early eighties when this research was beginning led to many discussions, firstly with Tony Hewish at the Cavendish Lab., who then introduced the author to Barry Uscinski at the Department of Applied Mathematics and Theoretical Physics (DAMTP). This led to a more direct approach, suggested by Barry, which is to consider the propagating wavefront as an angular plane wave spectrum representing the fluctuations [1]. The receiving array observes this field with an angular resolution determined by its directivity pattern, and the array output is the convolution of the plane wave spectrum and the array directivity pattern. In the limit, when the array pattern becomes narrower than the plane wave spectrum, the shape of the convolution converges on that of the plane wave spectrum. Thus, the angular resolution cannot be less than the width of the plane wave spectrum. This limit is independent of the array and is determined entirely by the medium and its effect on acoustic propagation [2, 3].
机译：水下环境的特征包括内部波，分层和湍流，并且在浅大陆架水域中，这种效果可以由一个由浮力范围主导的一维波浪光谱来表示，其中一个电力法和湍流范围与-5 / 3电力法。这些介质波动对声学传播的影响可以使用各种技术进行建模，其用于空间相干函数，或分离相位和（对数）幅度相关函数，用于接收阵列处的声波波动。然后可以使用这些结果来计算对阵列方向性模式的产生效果。在八十年代初期开始，剑桥在八十年代初期导致了许多讨论，首先是托尼·韦氏素在Cavendish实验室。然后将作者介绍了在应用数学和理论物理系（DAMTP）的Barry Uscinski 。这导致了一种更直接的方法，由Barry建议，这是考虑传播波前作为表示波动的角度平面波谱[1]。接收阵列以由其方向模式确定的角度分辨率观察该字段，并且阵列输出是平面波谱和阵列方向性模式的卷积。在极限中，当阵列模式变得比平面波谱窄时，卷积的形状会收敛于平面波谱的形状。因此，角度分辨率不能小于平面波谱的宽度。该限制与阵列无关，并且完全由介质确定及其对声学传播的影响[2,3]。

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