Bumper sticker radar

Luxury cars often now come with ultrasonic proximity sensors to help drivers avoid collisions while parking. Now AB Automotive of Cardiff plans an add-on version that drivers can fit to older models (GB 2376075). The device is rather like an oversized bumper sticker, with a conductive strip stretching the length of the bumper. A control unit in the car feeds a low-voltage, high-frequency signal to the strip. Capacitance between the strip and the road below allows a certain amount of the signal to leak to earth. This capacitance changes as the strip on the bumper moves close to any solid…