Doppler frequency

例句：

1. 1.The radar system uses Doppler frequency to detect moving objects.
   雷达系统使用多普勒频率来探测移动物体。
2. 2.In the field of radio science, Doppler frequency is used to measure the speed of sound waves.
   在无线电科学领域，多普勒频率被用来测量声波的速度。
3. 3.The scientists detected a sudden increase in Doppler frequency, indicating an approaching object.
   科学家检测到多普勒频率突然增加，表明有物体接近。