With the development of automotive safety standards, automotive electronics and people's driving safety requirements, in recent years, ADAS systems with active safety technology have shown a rapid development trend, which requires a large number of sensors. According to IHS Research, a market research organization, with the wide application of the ADAS system, the average annual growth rate of the automotive radar sensor market will be as high as 23% in the next few years. Among them, the millimeter wave radar is the best choice.
Different types of radars used in cars
Automobile radar can be divided into ultrasonic radar, millimeter wave radar, laser radar, etc. The principle of different radars is different, and the performance characteristics also have their own advantages, which can be used to achieve different functions.
Ultrasonic radar uses the ultrasonic generator in the sensor to generate 40KHz ultrasonic waves, and then the receiving probe receives the ultrasonic waves reflected by the obstacles, and calculates the distance from the obstacle according to the time difference of the ultrasonic reflection receiving. Ultrasonic radar has a low cost, but the detection distance is only a few meters, so it is often used in parking systems, and ultrasonic radar will limit weather conditions.
Lidar has the advantages of high resolution, high precision and strong resistance to active interference. It is a high-precision radar technology for military transfer. The application in the automotive field is mainly used for unmanned systems, such as Google Unmanned Vehicles and Baidu Unmanned Vehicles, which use laser radar. Lidars are also affected by the weather, and their functions are limited in heavy snow and haze, and they are expensive.
The millimeter wave radar is the main sensor of the ADAS system. The millimeter wave radar has a frequency range of 30 GHz to 300 GHz, the wavelength is from 1 cm to 1 mm, and the millimeter wave radar has a long detection distance of more than 200 meters. It can detect, measure, and measure the target. And azimuth measurements. It has good angular resolution and can detect smaller objects. At the same time, the millimeter-wave radar has a strong penetration rate, which can accurately detect objects through illumination, rainfall, dust, fog or frost. It can work in an all-black environment and can work around the clock.
As can be seen from the above comparison, the millimeter wave radar still has a strong advantage over the laser radar. The wavelength of the laser is much smaller than the millimeter wave (nm vs mm), so the haze may cause the laser radar to fail. For the same reason, the detection range of millimeter-wave radar can easily exceed 200 meters, while the lidar is generally no more than 150 meters, so for highway follow-up scenes, millimeter-wave radar can do better.
In addition, the main reason is that the millimeter wave radar is cheap. As a mature product, the current price of the millimeter wave radar is about 1.5 thousand, and the price of the laser radar is still calculated in units of 10,000.
Although the eyes of the laser radar, known as the unmanned vehicle, have been sought after in recent years, at the current stage, the mainstream of ADAS and autonomous driving options is still the millimeter wave radar.
Millimeter wave radar market is hot
Before the era of unmanned driving, the most popular is the ADAS driver assisted driving system. Therefore, the millimeter wave radar will be the mainstream of vehicle radar in recent years. At the same time, the main component cost of the millimeter-wave radar has been greatly reduced in recent years, which has also enabled it to be rapidly applied in the automotive field.
It is understood that many car companies, such as Volkswagen, Mercedes-Benz, Audi, Toyota, etc., have been equipped with millimeter-wave radars on high-end models. It is believed that with the development of intelligent driving and driverless driving, millimeter-wave radar will become a car. Standard. According to the data, in 2015, China's vehicle-mounted millimeter-wave radar sold 1.8 million units, with an average of 1 vehicle per 12 vehicles. The growth rate in these two years is rapid, and the Chinese market has great potential.
According to the “2016-2022 China Millimeter Wave Radar Industry Market Supply and Demand Forecast and Investment Strategy Research Report†released by Zhiyan Consulting, it is estimated that by 2020, the global shipment of vehicle-mounted millimeter-wave radars will reach 72 million. According to the domestic ADAS penetration rate reached 30% in 2020, each set of ADAS requires 4 short-range millimeter-wave radars + 1 long-range millimeter-wave radar, and domestic shipments can reach 45 million, and the market size will exceed 20 billion. .
Application mode of millimeter wave radar in automobiles
In the 1990s, millimeter-wave radars began to be used in the automotive field. At that time, the application was the adaptive cruise control (ACC) function, which relied on the distance detection function with a millimeter wavelength of more than 200 meters. Other means are difficult to do. Arrived. Later, many other functions such as anti-collision and blind spot detection were developed, but the technical threshold has been high and the price has been very expensive. Until 2012, chip-level millimeter-wave RF chips appeared, and the technical threshold was reduced. The cost has also dropped, opening the window for a wide range of applications in the automotive field.
At present, in the millimeter wave band, the band that is open to civilian use is 24 GHz\60 GHz\77 GHz\120 GHz. Among them, 24 GHz and 77 GHz are used in automobiles, and 24 GHz is the earliest open, and is currently widely used. 24GHz is mainly for medium-short-range detection of 5-70m, and the main applications are BSD\LDW\LKA \LCA\PA. The 77GHz is mainly for medium to long range detection of 100-250 meters, such as ACC \ FCW \AEB. However, with the improvement of the accuracy requirements of the vehicle radar system, 77GHz will be the mainstream in the future.
Single chip high precision is the development trend
With the increase in the degree of intelligence and active safety of automobiles, the demand for automotive millimeter-wave radars has developed to high precision, and radar systems for some high-end models are upgrading from 24 GHz to 77 GHz.
Taking ACC adaptive cruise as an example, after the radar used is upgraded to 77 GHz millimeter wave radar, the working speed of ACC adaptive cruise is from 25 km, compared with the 24 GHz radar system, the recognition rate is three times, the speed and the measurement. The accuracy of the distance is increased by three to five times, so that the distance to the preceding vehicle can be monitored more accurately and quickly, and the acceleration, deceleration, braking and starting with the speed of the preceding vehicle can be performed while maintaining the distance. And because of the characteristics of the radar, accurate detection results can be obtained even in bad weather conditions such as fog, smoke, and dust.
Millimeter wave radar system structure
The millimeter wave radar system mainly includes an antenna, a transceiver system, a signal processing system, a transceiver system chip and an antenna PCB are hardware cores of the millimeter wave radar.
Among them, transceiver chips generally use special semiconductors such as SiGe bipolar transistors. These silicon germanium-based chips cannot achieve higher integration. Therefore, a radar system often requires multiple chips and peripheral devices. Although the 77GHz automotive radar system based on SiGe technology can meet the needs of automobiles, they are too large, too bulky, occupy a lot of board space, and are more expensive.
With advances in semiconductor technology, CMOS, which is widely used in digital circuits and relatively low in cost, can also be used in millimeter wave circuits. Compared to traditional SiGe bipolar transistors, CMOS can operate at low voltages, reducing power consumption. Although CMOS has a problem of high noise in the low frequency region, the two have roughly the same performance in the millimeter wave region (76-81 GHz). For the 77-79 GHz vehicle millimeter wave radar application, the problem of large noise in the CMOS low frequency region is not prominent. . At the same time, the global CMOS industry chain is very mature, can be mass-produced, based on CMOS technology to achieve the key components of the millimeter wave radar, the cost of the entire radar system can be significantly reduced.
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