调研报告

The Theory and Application of Radar
电子科技大学 格拉斯哥学院 2017级 汪青云
When it comes to radar, people think it has military implications. But radar technology can also be used in people’s lives. Radar can be divided into military radar and civil radar. In the military, radar is mainly used for ultra-long-range early warning, search and warning, control of fire weapons, guidance aircraft missiles, battlefield surveillance. For civil radar, the function is to observe weather, navigation, remote sensing equipment, objects or human motion detection.

The principle of radar. First, it reflects electromagnetic waves. Experience tells us that the echo is faster, the obstacle is nearer, the echo is slower, and the obstacle is farther. In other words, it judges the distance of the obstacle according to the echo velocity and the direction of the obstacle according to the echo direction. Ultrasonic wave belongs to mechanical wave, its inherent reflection characteristic can be used to measure distance. Similarly, in radar applications, mechanical wave sound waves, water waves and even electromagnetic waves (including radio waves, infrared waves, visible light, ultraviolet rays, X-ray, gamma rays) also have reflection characteristics under certain circumstances. It’s electromagnetic waves. Second, directional emission of electromagnetic waves. Directional emission is defined as the use of narrow beams to transmit pulsed electromagnetic energy at a specific instant. It has an important advantage, that is, it can save energy, the radar station can “see” the far small power, the effect is good. That’s how radar works. Because it concentrates energy in a small space, it is the best way to “shine” on a target. Beam narrowing has a reasonable limit, that is, it can meet the requirements of radar to a certain extent. For radar stations with different missions, the solution to this problem is completely different. Third, the velocity of electromagnetic waves is known. The speed of electromagnetic waves is many times that of sound waves. It’s going at 300,000 kilometres per second.

For life, reversing radar is a very close to life application. Reversing radar, also known as parking assistance system, is a kind of parking safety assistance device. It tells the driver to sweep out the dead Angle of sight through sound or more intuitive display, so as to realize fuzzy defects and improve safety. Generally by the ultrasonic sensor (commonly known as probe), controller and display part, reversing radar in the market now is mainly using the ultrasonic ranging principle, the driver when reversing, reversing radar, under the control of the controller, the equipment on the bumper to send ultrasonic probe, encounter problems, produce echo signal, the sensor receives the echo signal from the controller for data processing, determine the position of the obstacles, display shows distance and issued a warning signal, get timely warning, accomplish know fairly well when reversing, the driver makes it easier to reverse. Based on the principle that bats can fly at high speed in the dark without colliding with any obstacles, the detection principle reversing radar is designed and developed. The probe is mounted on the rear bumper. There are two probes, three probes, four probes and six probes, depending on the price and brand. The probe radiates at an Angle of 45 degrees. Its greatest advantage is that it can explore the obstacles under the bumper that drivers cannot see from the rear window and alarm. The back-up radar, which has a screen in the rereview mirror, constantly alerts the driver to how far the car is from the object behind it, and when it reaches a dangerous distance, the buzzer starts to sound and tells the driver to stop. When the gear lever enters reverse gear, the reversing radar automatically starts to work and the range reaches 1. About 5 meters, so the driver is very practical when parking. Reversing radar is equal to the ultrasonic probe, and the overall ultrasonic probe can be divided into two categories: one is to use electrical manufacture super living wave method, the second is using ultrasonic methods, considering the more commonly used is the piezoelectric ultrasonic generator, it has two chips and a punching bag, when the poles of the pulse signal, its frequency is equal to the natural oscillation frequency of piezoelectric chip, chip stress can produce resonance, and the driven plate vibration resonance, the process of mechanical energy into electrical signals, it becomes the working principle of ultrasonic probe. In order to study and make better use of ultrasound, many ultrasonic detectors have been designed and manufactured.