ELECTROMAGNETIC SENSOR SYSTEM

A vehicle (160) such as a motor road vehicle is fitted with an electromagnetic sensor system comprising transmitting means (e.g. 4, 1) for transmitting a radio frequency signal, receiving means (e.g. 2, 6) for receiving reflections of said signal from remote objects, sampling means (20, 28) operable to sample the received reflected signal (or a signal derived therefrom), and processing means (e.g. 36) for processing the sampled signal, and operable to detect said reflections in the sampled signal, and to determine information on the presence, position and/or range of said object. The system includes filter means (e.g. 34) for preventing radio signals transmitted by other sources or noise spikes from causing interference which results in spurious detections or indications of range by the processing means.