Radar by emitting sound waves or electromagnetic waves on the target object irradiation and receive its echo, thus obtaining the target object distance, distance rate of change (radial velocity), size, orientation and other information. Radar was first used in the military, and later gradually civilized. With the development trend of intelligent vehicle, radar began to appear in the car, mainly for ranging, speed and other functions. Car radar can Sensor be divided into ultrasonic radar, millimeter-wave radar, laser radar, different radar principles are different, performance characteristics are also advantages, can be used to achieve different functions.

  Ultrasonic radar is the use of ultrasonic sensors within the sensor to produce 40KHz ultrasonic, and then received by the receiver to recover the ultrasound back through the obstacles, according to the ultrasonic reflection of the time difference between the calculation and the distance between the obstacles. Ultrasonic radar cost is low, the detection distance is very high precision, and is not affected by light conditions, so it is commonly used in parking system. Automatic parking can not be separated from ultrasonic radar. BMW's latest i-series and 7-series series already support Suction Control Valve the use of car keys remote control car automatic parking, during the operation of the user only need to issue forward or backward two instructions, the car will continue to use the ultrasonic sensor to detect parking spaces and obstacles, automatic steering wheel And brakes, to achieve automatic parking. Volkswagen third-generation ultrasonic semi-automatic parking system, parking assist system usually use 6-12 ultrasonic radar, the rear of the four short-range ultrasonic radar is responsible for detecting the distance between the reversal and the obstacles, Ultrasonic radar is responsible for detecting parking spaces.
  Millimeter wave radar: ADAS core sensor, millimeter wave refers to the wavelength of 1mm to 10mm between the electromagnetic wave, converted into frequency, the frequency of millimeter wave between 30GHz to 300GHz. The wavelength of the millimeter wave is between the centimeter wave and the light wave, so the millimeter wave has both the advantages of microwave guidance and photoelectric guidance. Millimeter-wave radar Fuel Rail Pressure Sensor in the missile guidance, target monitoring and intercept, fire control and tracking, high-speed communications, satellite remote sensing and other fields have a wide range of applications. In recent years, with the millimeter-wave radar technology level and cost reduction, millimeter-wave radar began to apply to the automotive field.
  Millimeter-wave radar has many advantages, is the ADAS core sensor. The wavelength of the millimeter wave is between the centimeter wave and the light wave, so the millimeter wave has both the advantages of microwave guidance and photoelectric guidance: 1) Compared with the centimeter waveguide, the millimeter waveguide has the advantages of small volume, light weight and spatial resolution High-frequency features, 2) and infrared, laser and other optical seeker compared to the millimeter wave leader through the fog, smoke, dust, strong ability to transport distance, with all-weather all day characteristics; 3) stable performance, Not subject to the target object shape, color and other interference. Millimeter-wave radar is a good way Temperature Sensor to make up for such as infrared, laser, ultrasound, camera and other sensors in the car application does not have the use of the scene. Millimeter-wave radar detection distance, high precision, is the ACC, AEB preferred sensor. Millimeter-wave radar detection distance is generally between 150m-250m, and some high-performance millimeter-wave radar detection range can even reach 300m, to meet the car in high-speed movement to detect a wide range of needs. In addition, millimeter wave due to shorter wavelength, low dispersion, good focus, so the detection accuracy of millimeter-wave radar is high. These features enable the millimeter-wave radar to monitor the operation of a wide range of vehicles, while the front of the vehicle speed, acceleration, distance and other information detection is more accurate, it is ACC, AEB preferred sensor. Millimeter-wave radar available frequency band has 24GHz, 60 ~ 61GHz, 76 ~ 79GHz, the current mainstream is 24GHz and 76 ~ 77GHz, 60 ~ 61GHz only use in Japan. Millimeter-wave radar key technology is dominated by foreign electronics companies. Millimeter-wave radar system mainly includes antenna, transceiver module, signal processing module, and MMIC (Monolithic Microwave Integrated Circuit) chip and antenna PCB board (Printed Circuit Board) is the millimeter-wave radar hardware core.
  Low-cost CMOS solutions are expected to speed up market opening. The current 77GHz millimeter-wave radar system unit price of about 250 euros, high prices limit the millimeter-wave radar car-based applications. Millimeter-wave radar transceiver chips generally use SiGe bipolar transistors and other special semiconductors, but with the advances in semiconductor technology, is widely used in digital circuits and relatively low cost CMOS, can also be used for millimeter-wave circuit. CMOS can be run at low voltage compared Speed Sensor to conventional SiGe bipolar transistors, thus reducing power consumption. Although there is a problem of low noise in the low frequency region of the CMOS, both of them have roughly the same performance in the millimeter wave region (76-81 GHz). The future mainstream of the vehicle-mounted millimeter-wave radar is 77-79 GHz, so the CMOS low- Not too prominent. As the current global CMOS industry chain has been more mature, can be mass production, the future if the CMOS can replace the SiGe bipolar transistor, millimeter-wave radar is expected to significantly reduce the cost of the market is expected to speed up the opening.

 Comparison of Two Millimeter - wave Radar Transceiver Chip Technology

  Fujitsu Research Institute has been successfully developed using CMOS technology 4-channel receiver chip. Fujitsu developed this product not only with the existing SiGe products have the same high-frequency function, but also successfully solved the low-frequency area noise problem. The new CMOS chip than the traditional SiGe chip reduced by about half of the power consumption, but also can achieve mass production and low cost. Fujitsu is expected to be around 2018, the product can be mass production, the use of the technology of the millimeter-wave radar cost is expected to significantly reduce. Low cost is expected to speed up the detonation of millimeter-wave radar market. Car millimeter-wave radar localization soon, 24GHz product technology has been a breakthrough, 77GHz products are stepping up research and development. Front-end monolithic microwave integrated circuit (MMIC) is a Throttle Position Sensor key component of millimeter-wave radar, MMIC technology is mainly monopoly of foreign parts giants, domestic in this area is still in its infancy. However, some domestic companies after several years of research and development, 24GHz car radar technology has been a breakthrough, the product is coming soon. 77GHz product development due to foreign technology blockade, most of the current research and development is still in the experimental stage. With the rapid development of the smart car industry, will open a large number of demand for millimeter-wave radar, domestic companies will accelerate research and development, 77GHz products are expected to achieve localization within the next three years.