Omnidirectional Imaging FMCW Radar System for Rescue Robotics

A compact real aperture omnidirectional imaging radar system for use in robotic search and rescue operations is presented. This system uses an ultrawideband frequency-modulated continuous wave (FMCW) radar sensor operating at 80 GHz and a mechanically steered lens-mirror antenna configuration to capture images comparable to 360° photographs. The antenna configuration is optimized for a compact footprint on a mobile robot and a small moment of inertia for fast scans. The directivity of the lens-mirror arrangement is characterized, and the influence of the mirror dimensions on sidelobes is investigated. This reveals spillover effects that are inversely proportional to mirror size. Key factors that influence the scan time are investigated, including the chirp repetition rate of the radar sensor and the time required to change the direction of the radar beam. The investigation shows a compromise between FMCW bandwidth and scan time. A signal processing method that addresses the processing steps from input samples to output images is presented, with a focus on the detection process. This process uses range and image data to determine the detection threshold. The imaging system is applied in a rescue robotics scenario to demonstrate its ability to visualize human shapes and complex indoor environments with scan times of up to 2 min.