Police RADAR警察雷达
RADAR speed detectors bounce microwave radiation off of moving vehicles and detect the reflected waves. These waves are shifted in frequency by the Doppler effect, and the beat frequency between the directed and reflected waves provides a measure of the vehicle speed. 雷达速度检测器通过将微波辐射反射自移动车辆来检测车辆速度。这些波的频率因多普勒效应而发生改变，而定向波与反射波之间的拍频则可作为车辆速度的度量。
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Index Traveling wave concepts 行波概念索引 | ||
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Doppler Shift, Moving Target多普勒频移，移动目标
The Doppler shift for relatively low velocity sources such as those encountered by police RADAR is given by 对于如警察雷达所遇到的相对低速源而言，多普勒频移由以下公式给出
 where c is the speed of light (and all electromagnetic waves in a vacuum). But in this case there are two shifts: one because the wave incident on the moving car is Doppler shifted and an additional shift because the reflection is from a moving object. The frequency shift of the reflected wave received at the source of the wave is 其中 c 是光（以及真空中的所有电磁波）的速率。但在此情况下有两个频移：一个是由于波撞击运动的汽车而产生的多普勒频移，还有一个是由于反射来自运动物体的频移。接收到的反射波的频率偏移为
 This shift is detected by measuring the beat frequency with the transmitted wave. 这种位移通过测量传输波的拍频来检测。
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Index Traveling wave concepts Doppler concepts 索引 波动概念 多普勒概念 | ||||
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Beat Frequency and Speed拍频与速度
The beat frequency between a microwave transmitted signal and a reflected signal off a moving object is 微波传输信号与反射自运动物体的反射信号之间的拍频是
 where the target velocity is taken as positive if the target if approaching the transmitter. Police RADAR uses this method for measurement of auto speed. 其中，若目标是接近发射器，则目标速度取正。警察雷达使用这种方法来测量汽车的速率。
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Index Traveling wave concepts Doppler concepts 索引 波动概念 多普勒概念 | ||
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Beat Frequency and Speed拍频与速度
 Note: If not entered as data, the transmitted frequency will default to 10.6 GHz, a typical X-band radar frequency. K-band units with frequencies on the order of 30 GHz are also used. Any parameters can be changed. 注意：如果未输入数据，发射频率将默认为10.6 GHz，这是典型的X波段雷达频率。也常用30 GHz量级的K波段单位。任何参数都可以更改。
并且拍频将是赫兹 中文译文中的待填/计算数值依次对应：1：fbeat。实际数值以上方原输入框为准。 |
Index Traveling wave concepts Doppler concepts 索引 波动概念 多普勒概念 | |||
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