Automotive Semiconductors and Functional Safety
Which correctly describes a feature of millimeter-wave radar used in ADAS (advanced driver assistance systems)?
- AIt uses radio waves in the 76–81 GHz band, its performance degrades little in rain, fog or at night, and it can directly measure relative velocity via the Doppler effect
- BIt excels at distinguishing color and shape and is best suited for reading the text on road signs and the colors of traffic lights
- CIt scans the surroundings finely with laser light and can measure object shapes as fine 3D point clouds with the highest resolution of any automotive sensor
Show answer and explanation
Answer: A. It uses radio waves in the 76–81 GHz band, its performance degrades little in rain, fog or at night, and it can directly measure relative velocity via the Doppler effect
Millimeter-wave radar uses reflections of radio waves to measure the distance and direction to objects, and can also directly obtain relative velocity from the frequency shift of the reflected wave (Doppler effect). Radio waves are little affected by rain, fog or darkness, so radar is widely used for functions such as maintaining the gap to the vehicle ahead. On the other hand, its angular resolution is low, and it is poor at classifying object types. Recognizing colors and text is the strength of cameras, and high-resolution 3D point clouds are the strength of LiDAR; sensor fusion combines them so each compensates for the others' weaknesses.
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