The sky wave over the horizon radar (OTHR) is a new mechanism in which the ionosphere is used as a mirror to reflect the radar high frequency signal to detect the target.

高频天波超视距雷达所独有距离多跳现象，使得位于雷达威力覆盖范围以远的杂波通过地面与电离层的多次反射进入到雷达的接收阵列。

youdao

China has built several sky-wave based Over-the-Horizon radar stations that for the first time allow the PLA to monitor continuously U.S. Navy ship movements hundred miles out in the Western Pacific.

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