Patent ID: 8201745
Filing Date: 2012-06-19
Classification: G06K

Abstract:
1. A reader device for detecting the presence of a transponder within an operating distance of the reader device, the reader device comprising a resonant circuit configured to generate an electromagnetic field having a frequency distribution around a resonance frequency; a transponder detection unit configured to detect the presence of the transponder within the operating distance of the reader device both by a downward shift of the resonance frequency of the resonant circuit, and by a damping of a resonance curve of the resonant circuit, in the presence of the transponder within the operating distance of the reader device; and wherein the transponder detection unit is configured to determine the absence of a transponder within the operating distance of the reader device by an upward shift of the resonance frequency of the resonant circuit in the presence of a metal object within the operating distance of the reader device.