Abstract: The significant reduction in manufacturing cost of 77GHz millimeter-wave radar sensors in automotive radar systems has laid the technological foundation for the widespread application of automotive radar networks. This paper briefly introduces the structural principles of developing millimeter-wave automotive radar networks, key technologies for multi-sensor networking, and the current research status of 77GHz automotive radar network systems. This paper provides a reference for the development and application of domestic automotive radar networks. Keywords: Millimeter-wave; Radar sensor; Automotive radar network 1 Introduction With the increasing demands for safety and comfort in automotive driving, automotive radar is widely used in adaptive cruise control systems, collision avoidance systems, and driver assistance systems. Among them , millimeter-wave radar is widely adopted due to its advantages such as high detection accuracy, small hardware size, and immunity to adverse weather conditions. However, traditional single radar sensors still have disadvantages such as small detection range and low reliability. Especially under complex driving conditions, lane changing, lane shifting, turning, going uphill and downhill, as well as static guardrails, signs and pedestrians on both sides of the road, make it very difficult for radar to identify the main target and the false alarm rate is very high. In order to completely solve the problem of radar false alarm, it is also necessary to adopt information fusion technology between multiple sensors. By integrating various radar sensors together to form a network system, the advantages of various sensors are combined, information analysis, synthesis and balance are realized, and the redundancy and complementarity between data are used for fault tolerance processing, overcoming the disadvantages of low reliability and small effective detection range of single sensors, and effectively reducing the false alarm rate of radar. The new, high-precision sensor network thus formed can greatly improve the performance of automotive radar network system [1]. 2 The principle of radar network construction The radar network shown in Figure 1 consists of four near distance sensors (NDS) distributed at equal distances on the bumper. Each radar sensor adopts the FMCW system. This sensor network can achieve a horizontal azimuth angle of 120° within a range of 35 meters. This kind of short-range, large-coverage radar sensor network can monitor targets in a large area in front of the car when the vehicle speed is not high and the road conditions are relatively complex (such as urban traffic). If long-range detection is required, a long-range radar sensor can be added in the middle of the bumper. With the maturity of 77 GHz automotive radar sensor technology, both short-range and long-range radar sensors tend to adopt 77 GHz MMIC (millimeter-wave integrated circuit) technology. Using this technology, it is easy to make an integrated design scheme, which greatly reduces the cost of the transceiver module. In the sensor network system block diagram shown in Figure 2 [2], the radar sensor based on 77 GHz MMIC technology is the key hardware of the front end of the automotive radar network. The back-end information processing needs to be completed by high-speed computing units such as digital signal processors. Data is transmitted between the sensor, digital signal processing unit and data fusion decision system via Ethernet and high-speed serial connection to meet the high data rate transmission requirements. The data fusion system adopts a distributed architecture, that is, each short-range sensor first performs local processing on the obtained echo signal, and then sends it to the fusion center for fusion to obtain the target's azimuth and speed information. The controller is the final decision-making body of the entire radar network system. It is responsible for identifying whether the distance and speed information of a target pose a threat to driving safety, and for alerting the driver through audio and visual means or directly influencing the vehicle's control system to make adjustments. For more details, please click: Research on Networking Technology of Millimeter-Wave Radar Sensors for Vehicles.