Frequency part end of the transponder with an amorphous wire for use in a system for the presence of determining.

摘要

A transponder (18) for detecting electromagnetic radiation at a first predetermined frequency includes an amorphous, magnetostrictive, ferromagnetic wire (19), which, when excited by electromagnetic radiation at a first predetermined frequency while in the presence of a DC magnetic bias field, transmits electromagnetic radiation at a lesser second predetermined frequency that is a frequency-divided quotient of the first predetermined frequency. The frequency dividing-wire (19) is produced by flash annealing an amorphous ferromagnetic alloy wire that has been cast by first melting and then quenching the alloy. A useful article (20) containing a transponder (18) including a frequency-dividing wire (19) may be verified as to its authenticity with a presence detection system, in which: electromagnetic radiation (28) at the first predetermined frequency is transmitted into a surveillance zone (30); the frequency-dividing wire (19) detects the transmitted radiation (28) at the first predetermined frequency and responds thereto by transmitting electromagnetic radiation (32) at a lesser second predetermined frequency that is a frequency-divided quotient of the first predetermined frequency; and a detector (24) detects the transmitted radiation at the second predetermined frequency. The transponder (18) also includes a tube (21), which encloses the wire (19) within the article (20) in such a manner as to enable the wire (19) to mechanically vibrate when excited by an electromagnetic field at the characteristic first predetermined frequency of the wire.