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。

youdao

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