In the ever-evolving world of autonomous driving, I remember introducing you to LiDAR a while back. That "barrel" on top of the car has become one of the core technologies in the era of self-driving vehicles. Let’s take a closer look at this topic with our automotive electronics editor.
LiDAR is undeniably powerful. It offers high precision, a wide detection range, and 360° coverage. It can scan a 3D model of the environment around the vehicle and combine it with real-time global maps to significantly improve navigation accuracy. Plus, it's not affected by light conditions—whether it's pitch black or bright daylight, it remains reliable. It seems like with LiDAR, full autonomy is just a matter of time.
However, no technology is perfect. LiDAR can be easily impacted by bad weather, such as rain, snow, or fog, which can cause it to malfunction. More importantly, it's expensive. Early mechanical LiDAR systems could cost tens of thousands of dollars, and even the newer solid-state versions still run into the thousands. Companies like Velodyne and Quanegy are still working hard to reduce costs. Therefore, the "eyes" of autonomous vehicles can't rely solely on LiDAR; they need support from other sensors too.
Another popular option is millimeter-wave radar. Tesla, for example, uses it in its Autopilot 2.0 system. Alongside eight cameras and twelve ultrasonic sensors, a forward-facing millimeter-wave radar is also included. This technology isn’t new—it has been widely used in cars for years, even appearing in high-end models decades ago. For instance, many people use ACC (Adaptive Cruise Control), and the small black sensor at the front of the car is a millimeter-wave radar. Features like blind spot monitoring, lane change assistance, and automatic emergency braking also rely on this technology.
But don’t confuse this with a regular reversing radar. While the latter uses mechanical waves, millimeter-wave radar emits electromagnetic waves. The principle is similar: it sends out a signal and measures the time difference between transmission and reception to determine the position of an object. Millimeter waves operate in a frequency range between radio and visible light—roughly 10 GHz to 200 GHz. The most commonly used bands today are 24 GHz and 77 GHz. The 24 GHz band is typically used for short-range applications like blind spot monitoring, while 77 GHz is preferred for adaptive cruise control due to its longer range, higher resolution, and better interference resistance.
Compared to LiDAR, millimeter-wave radar can detect objects beyond 200 meters, whereas LiDAR usually doesn't exceed 150 meters. In high-speed driving scenarios, millimeter-wave radar is more suitable. It also performs well in rain and fog, making it more reliable in adverse weather. Most importantly, it's much cheaper. A single unit might cost just a few hundred dollars, far less than the tens of thousands needed for LiDAR. However, its accuracy is lower than that of LiDAR. It can detect obstacles and determine their distance, speed, and direction, but it can’t recognize their shape.
The technology is continuously evolving. Recently, many companies have started developing 79 GHz millimeter-wave radars. These advanced systems can produce images of the detected objects, addressing some of the limitations of traditional millimeter-wave radar. Since 77 GHz technology is currently dominated by large companies like Bosch and Delphi, Chinese tech firms are showing strong interest in 79 GHz radar, aiming to catch up and potentially overtake.
So, what's the best solution? LiDAR, cameras, or millimeter-wave radar? Actually, it's not a choice between them. The ideal approach is to combine these technologies. LiDAR provides high accuracy and detects the shape of obstacles, but it needs cameras to identify what those obstacles are. Cameras are intuitive but highly sensitive to lighting conditions and can be blocked by obstructions. They also struggle to create a 3D model of the environment. On the other hand, millimeter-wave radar is low-cost, works 24/7, and is unaffected by weather. Relying on just one sensor for such a complex task is impractical—more is definitely better.
This article was brought to you by Car Electronics, exploring the question: "Compared to LiDAR, is millimeter-wave radar becoming the 'new darling' of autonomous driving?" Stay tuned for more detailed and updated information from Electronic Engineering.
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