A broad beam Doppler speed sensor for automotive applications

On‐board absolute speed sensors would be very useful in automotive applications in order to perform the measurement of the speed independently of the wheel rotation. Narrow beam Doppler sensors give a good accuracy but only operate if there is a reflecting obstacle in the antenna footprint on the road. Broad beam Doppler sensors have the advantage of offering a higher probability of getting a reflected wave, but they require multiple frequencies. A novel sensor is presented. It uses a single frequency emission, which leads to low cost devices. Simulations and measurements have been carried out which show that it is particularly well adapted to high‐risk situations, for instance icy or very wet road surfaces, when only a few reflecting obstacles are present. In such situations, the accuracy of the measurement is typically of the order of 0.5 per cent.