An Ultra-Low-Cost Early Warning Sensor for Pedestrians

In this work, we present a low-cost wearable module that alerts pedestrian users of vehicles approaching from behind to avoid potential collision. It uses a custom IQ Doppler radar board at 10.5GHz on low-cost FR4 substrate to differentiate incoming vehicles' positive Doppler shift from the receding environment's negative shift. A second signal processing board with a microcontroller and accelerometer, also on FR4, performs Fourier analysis on the I and Q components to identify incoming vehicles. Using the onboard accelerometer, the module measures the user's gait and adjusts detection thresholds in real time to account for the complex movement of pedestrians. The module correctly detects approaching vehicles in the presence of other stationary and receding objects at an average distance of 27.6 and 28.2 meters for walking and jogging, respectively, and provides sufficient time to react.