Aiming at the fault of silent sentry radar system in war field, a kind of method based on portable passive radar is introduced in this paper.

针对静默哨兵系统等隐身雷达的战场机动能力不足，提出了一种便携式无源侦察系统的设计方法。

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The SENTRY GUNS are silent, and the GATES are open to the forest.

哨戒炮沉默了，地狱之门向森林敞开。

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Silent Sentry, as the Lockheed system is known, will be tested by the American government in a few weeks time, according to Sam Crow, the project's leader.

ECONOMIST: Remote sensing

And since a moving object causes a tiny change (known as a Doppler shift) in the frequency of the reflected signal, Silent Sentry can also calculate how fast it is moving.

ECONOMIST: Remote sensing