Patent ID: 7456740
Filing Date: 2008-11-25
Classification: G01S,G08B

Abstract:
1. A detector device for detecting an object in a detecting zone by emitting an electromagnetic signal using a generated signal into the detecting zone and receiving an electromagnetic signal therefrom through a first conductor, the detector device comprising: a second conductor for carrying a portion of the generated signal; a field-distorter comprising a semi-conductor device disposed adjacent to one of the first conductor and the second conductor, the field distorter being responsive to an input signal to shift a phase of the electro-magnetic signal conducted in the one of the first conductor and the second conductor to produce a phase shifted signal in the conductor; and a phase-comparator configured to receive and mix signals of the first and second conductors and to produce a combined signal having a characteristic determined by the input signal, the combined signal indicative of the correct operation or otherwise of the detector device, wherein the characteristic of the combined signal corresponds to a change in a dc voltage component of the combined signal; the change being responsive to the input signal.