mmWave Retroreflective Road Markers for Automotive Radar Vision

Road markings play a critical role in ensuring road safety and guiding drivers, particularly in adverse weather conditions where visibility is compromised. However, traditional detection methods using cameras and LiDARs often struggle to accurately detect road markings in such conditions. Factors like rain, fog, dust, and snow can obstruct camera views and interfere with the LiDAR's ability to capture thin or faded markings, compromising their effectiveness. In contrast, radar technology offers a promising potential in recognizing these markers even in severe weather conditions and at long ranges, provided they are engineered to retrodirect the radar signal effectively. In this work, a low-cost, low-profile mmWave retroreflective surface that is capable of retrodirecting the signals emanating from an automotive radar was designed and tested. The structure relies on a 78.5 GHz Yagi Uda Van Atta reflectarray that was demonstrated to achieve a measured median RCS of -30 dBsm over a wide angular coverage of 80°. The surface was also tested with respect to range, demonstrating a detection distance of 11 m. The proposed architecture was also simulated and measured in a stacked configuration showcasing its potential to achieve larger RCSs. Specifically, four Van Atta arrays were stacked vertically at a
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separation demonstrating an approximate 10 dB enhancement in measured RCS relative to the single array, theoretically leading to a 1.8x increase in detection range.