Massachusetts Institute of Technology, Mechanical Engineering, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA.
J Acoust Soc Am. 2011 Jul;130(1):84-101. doi: 10.1121/1.3557039.
Doppler analysis has been extensively used in active radar and sonar sensing to estimate the speed and direction of a single target within an imaging system resolution cell following deterministic theory. For target swarms, such as fish and plankton in the ocean, and raindrops, birds and bats in the atmosphere, multiple randomly moving targets typically occupy a single resolution cell, making single-target theory inadequate. Here, a method is developed for simultaneously estimating the instantaneous mean velocity and position of a group of randomly moving targets within a resolution cell, as well as the respective standard deviations across the group by Doppler analysis in free-space and in a stratified ocean waveguide. While the variance of the field scattered from the swarm is shown to typically dominate over the mean in the range-velocity ambiguity function, cross-spectral coherence remains and maintains high Doppler velocity and position resolution even for coherent signal processing algorithms such as the matched filter. For pseudo-random signals, the mean and variance of the swarms' velocity and position can be expressed in terms of the first two moments of the measured range-velocity ambiguity function. This is shown analytically for free-space and with Monte-Carlo simulations for an ocean waveguide.
多普 勒分析在主动雷达和声纳感测中得到了广泛应用，可根据确定性理论，在成像系统分辨率单元内估计单个目标的速度和方向。对于目标群，例如海洋中的鱼类和浮游生物，以及大气中的雨滴、鸟类和蝙蝠，多个随机移动的目标通常会占据单个分辨率单元，这使得单目标理论不够充分。在这里，我们开发了一种方法，可通过自由空间和分层海洋波导中的多普勒分析，同时估计单个分辨率单元内一组随机移动目标的瞬时平均速度和位置，以及整个目标群的速度和位置的标准差。虽然从群中散射的场的方差通常在距离-速度模糊函数中超过平均值，但交叉谱相干性仍然存在，即使对于相干信号处理算法（如匹配滤波器），也能保持高的多普勒速度和位置分辨率。对于伪随机信号，群的速度和位置的均值和方差可以用所测量的距离-速度模糊函数的前两个矩来表示。这在自由空间中进行了分析，并通过海洋波导的蒙特卡罗模拟进行了验证。
