CalTag: Robust calibration of mmWave Radar and LiDAR using backscatter tags

The rise of automation in robotics necessitates the use of high-quality perception systems, often through the use of multiple sensors. A crucial aspect of a successfully deployed multi-sensor systems is the calibration with a known object typically named fiducial. In this work, we propose a novel fiducial system for millimeter wave radars, termed as \name. \name addresses the limitations of traditional corner reflector-based calibration methods in extremely cluttered environments. \name leverages millimeter wave backscatter technology to achieve more reliable calibration than corner reflectors, enhancing the overall performance of multi-sensor perception systems. We compare the performance in several real-world environments and show the improvement achieved by using \name as the radar fiducial over a corner reflector.