Absolute speed measurement of vehicles

The authors describe a novel absolute speedometer using radio waves propagated by a broadcasting station. The method estimates speed by calculating the delay time between spatial patterns detected by front and rear sensors that are separately positioned on a vehicle and aligned in the direction of movement. It is known that the electric field intensity of radio waves in the VHF/UHF range exhibits spatial periodic patterns due to the multipass fading phenomenon. The proposed method uses this pattern as the spatial scale for speed measurement. The authors examined from various viewpoints whether the patterns could be used for speed measurement, and it was found that they could