detecting a foreign body in the vicinity of a means of input used for authentification

摘要

The device (1) has a directional coupler (2) supplying an oscillating signal (3) to two inputs (4, 5) of an antenna (6). The coupler supplies the signal at a preset level (7) to a detecting unit (8) and decouples a reflection signal (9) received by the antenna for the detecting unit. The coupler detects phase difference between the supplied signal at the preset level and the decoupled signal for detecting a foreign body (F). The antenna is formed as a circular polarized patch antenna with dispersion characteristic, which is constant in a monitoring area of the device within tolerance. An independent claim is also included for a method for detecting a foreign body applied in vicinity of an input unit utilized for identification and/or authentication.