1. 4D millimeter-wave radar product features and application prospect analysis
1.1 Functions and features of 4D millimeter-wave radar
The 4D millimeter-wave radar increases the estimation of the target height (vertical angle) on the basis of the 3D information of the target detected by the 3D millimeter-wave radar (the distance between the radar and the target, the relative radial velocity, and the data of the horizontal angle). Wave radar has characteristic points such as a large number of antennas and high density, and the output point cloud image density is higher.
4D millimeter-wave radar has improved in terms of distance resolution, distance accuracy, angle resolution, angle accuracy, velocity resolution, and velocity accuracy, especially in terms of angle resolution. At present, the angle super-resolution algorithm has become a 4D millimeter-wave radar. One of the core competitiveness of imaging radar!
The advantages of 4D millimeter wave radar compared with 3D millimeter wave radar are as follows:
(1) High degree of recognition: more effectively "draw" the outline of the target, and identify the category and behavior of the target. Going a step further, small or partially occluded objects as well as stationary objects or objects moving laterally can be identified.
(2) High sensitivity: The increase of height information can filter out some false alarms of false braking, which can avoid missing or false braking.
(3) High dynamic range: It can distinguish strong and weak targets in the same direction, at the same distance, and at the same speed.
(4) Longer detection distance: The detection distance will be increased to more than 300 meters.
1.2 Comparative Analysis of 4D MMW Radar and Other Sensors
Vertically, compared with 3D millimeter-wave radar, 4D millimeter-wave radar has better performance in many aspects, but the cost is higher, and the current mass production verification is less, and only a small number of leading radar companies are mass-produced. Horizontally, compared with other sensors, 4D millimeter-wave radar not only has the traditional advantages and disadvantages of millimeter-wave radar, but also enhances the ability to recognize objects and pedestrians.
4D millimeter-wave radar can perform higher-performance detection of target information in ordinary scenes, and the coverage and processing capacity of ordinary scenes are improved compared with 3D millimeter-wave radar; at the same time, 4D millimeter-wave radar brakes in front It can maintain good performance in corner case scenarios such as preventing continuous rear-end collision and high light ratio and bad weather.
1.3 Analysis of Application Prospects of 4D MMW Radar
1.3.1 Comparison with 3D millimeter-wave radar
1.3.2 Comparison with lidar
2. Analysis on the development trend of 4D millimeter-wave radar technology
2.1 Overview of 4D millimeter-wave radar technology trends
The figure below shows the detailed classification of technologies involved in the research and development of 4D millimeter-wave radar. It is mainly divided into four modules: front-end radio frequency module, digital signal processing module, control circuit, test and verification. Each module is subdivided into many sub-modules, which jointly build the technology stack of automotive radar.
2.2 4D millimeter-wave radar waveform design and comparative analysis
According to the different ways of radiating electromagnetic waves, millimeter wave radar is mainly divided into two working systems: pulse system and continuous wave system.
For the measurement of a single static object, the sawtooth wave can meet the requirements, and for the moving object, the triangular wave modulation method is often used. Before, when measuring the transmission waveform of the Continental 548 radar in the anechoic chamber, it was found that the FM waveform was up and down, and the slope was positive or negative. I guessed that it might be the triangular wave modulation (just a guess, no evidence).
PMCW (phase modulated continuous wave scheme) detects the distance and speed of the target by transmitting quadrature phase coded signals at the same time through multiple antennas. Mutual interference between radar and radar, in the design of 4D millimeter-wave radar, PMCW (Phase Modulation Continuous Wave Solution) has gradually emerged, and its representative radar chip company is Uhnder in the United States.
2.3 Trend Analysis of 4D MMW Radar Antenna Element Design
Multi-chip cascaded radar transceiver antennas have increased significantly. If the microstrip design idea is still adopted and the feed-away and complexity-variable arrays can only be laid out in the xy direction, the radar area will be too large. The area used by Rogers boards will also increase, and the cost will increase significantly. ; Using a waveguide cavity antenna, the array layout can extend along the z direction, which can significantly reduce the area and volume of the radar compared to the microstrip antenna.
Therefore, in the multi-chip cascading technology solution, the waveguide cavity antenna will become the trend of antenna element design, which is very worthy of attention.
Compared with 3D millimeter-wave radar, 4D millimeter-wave radar adds pitch angle information, and the antenna array design is more complicated. Usually, the indicators are mutually restricted (such as angular resolution and angular ambiguity), and are closely related to waveform design, hardware design, and manufacturing process.
2.4 Trend Analysis of 4D MMW Radar Signal Processing Framework
The core work of radar signal processing: complete the estimation of radial distance, radial velocity, and azimuth in turn (under certain conditions, they can be equivalent to the estimation of their independent frequencies, that is, linear operation). The common processing architecture is range-Doppler-Angle or range-Angle-Doppler. However, 4D millimeter-wave radar introduces height information, chip cascading → signal processing framework is more abundant (FFT increase), and the appropriate processing framework needs to be selected based on the application scenario. As shown below:
The design of the 4D millimeter-wave radar signal processing scheme takes the extended target as the final result, while the detection and angle measurement modules in the traditional radar signal processing process are designed with the assumption that the target is a point target. The traditional process cannot achieve a single-frame high-density point cloud. Adopting a new radar signal processing algorithm flow, the algorithms of coherent/non-coherent accumulation, target detection, angle measurement and other modules are different from traditional algorithms.
The content of this part comes from the compilation of the [Nine Chapters Smart Driving] report. The content is very valuable. Due to the large space, the follow-up content will not be expanded for the time being. For the high-definition version without watermark, please download it in the [Official Account Sharing Information List ] .
All the information shared by the official account is in this list, please know!
https://docs.qq.com/sheet/DT0RrZGJ6ZlRRc2tm?tab=BB08J2