| 摘要 |
A sensor for remote detection of objects (20), preferably for use in an article surveillance system, comprises a wireshaped element (22), which is arranged to be excited and detected electromagnetically. The wireshaped element (22) has a diameter less than 30 mum. The element is arranged to transmit an electromagnetic reply signal, the amplitude of which is modulated in response to an externally applied and time-varying magnetic field. According to a method of detecting the presence of an object (20) in a surveillance zone (10), the object is provided with at least one wireshaped element (22) of amorphous or nanocrystalline metal alloy with magnetic properties and with a diameter less than 30 mum. Electromagnetical signals are generated in the surveillance zone for exciting the wireshaped element. Furthermore, a time-varying magnetic modulating field is generated in the surveillance zone. Electromagnetic signals generated by the wireshaped element are received and analyzed with respect to a modulation in amplitude caused by the magnetic modulating field, so as to determine the presence of the element (and consequently the object) in the surveillance zone. |
