Tracking target by using anti-helicopter mine (AHM) is actually the bearing-only measurement because precision of range detected by passive acoustic measurement cant satisfy the need of tracking.

目前被动声探测距离精度还不能满足跟踪的需要，因此，反直升机智能雷对目标的跟踪问题归结为仅有角测量的跟踪问题。

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For underwater acoustic positioning system based on measurement of time_delay, range ambiguity appears when pulse's propagating time is longer than its repetition period.

基于时延测量的水声跟踪定位系统，当信号传播时延大于脉冲重复周期时，就会出现距离模糊。

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