First, let's talk about the principle of radar velocity measurement. The radar velocimeter is based on the calculation of the frequency shift from * * to the reflected wave to obtain the moving speed of the object. The radar beam has a large illuminating area, so the radar velocity measurement is easy to capture the target without accurate aiming. The radar equipment can be fixed on the road or installed on patrol vehicles. It can detect the speed in motion, which is an important part of the "mobile electronic police". Secondly, the error of radar fixed speed measurement is ± 1Km/h, and the error of moving time measurement is ± 2Km/h, which fully meets the requirements of traffic violations investigation. The international use of radar speed measurement has a history of more than 20 years, and the technology is mature. From the current situation, Backward speed measurement is the main method on the road nationwide, but there are also a few forward speed detectors. Most of them are positive speed measuring devices on expressways. The back direction means that the direction of the radar wave and camera is the same as that of the car. When the car exceeds the speed limit, the camera captures the rear license plate of the car. The forward direction means that the direction of the radar wave and camera is opposite to that of the car. When the car exceeds the speed limit, the camera captures the front license plate of the car. The principle of the radar detector is very simple, that is, when the radar signal is received, it will alarm the car owner to slow down.

　　Most of the radar detectors are imported, and the price is generally between 800 yuan and 5000 yuan. The performance level is also very different. The most different is that the frequency bands of the radar waves that can be sensed are different, because the radar speed measuring equipment for roads in different cities in China are produced in different countries and our own countries, and the frequency of the radar waves used is different. Some of the same cities have three or four radar speed measuring devices with different frequency bands, low-end radar detectors, Usually, only one band of radar waves can be sensed, while high-end radar detectors can sense multiple radar waves of different bands, even with light sensors, and can also prevent laser speed detectors.

　　In addition, the distance of sensing also reflects the performance of the radar detector. If the sensing distance is too close, the car owner has been photographed before he can slow down; If the deceleration is too fast, it is also easy to cause a rear end collision. The high-end radar detector can sense the radar wave for about one kilometer in the positive direction, while the poor one can only sense it at about 200 meters.

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