According to this, this paper focuses on the study of bearings-only passive tracking system in the aspects of the target location, time alignment and nonlinear filtering algorithm.

基于这样的背景，本文从目标定位、时间配准和非线性滤波算法三个方面对多站纯方位被动跟踪系统进行了研究和算法改进。

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So, the detection and extraction of signals reflected by the target are difficulties and the key technology of passive tracking location.

因此，目标反射信号的检测和提取是个难点，也是无源探测定位的关键技术之一。

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The sensor nodes must be aware its position to explain 'what happens and where ', to implement the target of the location and tracking.

传感器节点必须准确定位才能说明“在什么位置或区域发生了特定事件”，实现对外部目标的定位和追踪。

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