| 摘要 |
Radar apparatus is mounted in a vehicle so as to transmit a radar signal in a rearward direction with respect to the direction of travel of the vehicle. The signal is reflected from objects behind the vehicle, and a detection is given when the relative speed between vehicle and object is a closing speed, in other words a detection is provided when a following vehicle is closing the distance between it and the radar-equipped vehicle. When the closing speed exceeds a threshold value, an alarm device, such as a rearwardly aimed flashing light, is activated thereby warning the driver of the following vehicle; as an alternative or an addition, a suitably equipped following vehicle might have its automatic braking system activated. Doppler radar apparatus provides a particularly simple implementation, since differences in the frequency characteristics of the received signal when compared with the transmitted signal can be readily used to detect whether any relative speed is a closing speed or not, thereby avoiding detection of receding background objects. <IMAGE> |
