US 5,861,809 A · Deactivateable resonant circuit

Abstract

A resonant tag used with an electronic article surveillance system for detecting the presence of the tag within a surveilled area utilizing electromagnetic energy at a frequency within a predetermined detection frequency range includes a resonant circuit capable of resonating at a frequency within the predetermined detection frequency range. The resonant circuit includes an inductor formed at least in part on a surface of a dielectric substrate of the tag. The inductor is formed with a discontinuity or gap, causing an electrical open circuit. The open circuit is closed with a fuse secured proximate to the gap and wirebonded to the portions of the inductor proximate to the gap. The fuse is melted by a current greater than a predetermined level flowing therethrough. Such a high current may be induced in the inductor by an external electromagnetic field. Melting of the fuse causes an open circuit condition, which alters the frequency at which the tag resonates.

Claims33

Dependent claims

A resonant tag comprising:

a dielectric substrate having first and second opposite principal surfaces;
a resonant circuit which resonates when exposed to electromagnetic energy at a frequency within a predetermined detection frequency range, the resonant circuit comprising at least one conductive layer formed on one of the principal surfaces of the dielectric substrate, wherein the conductive layer includes a gap which forms an electrical open circuit;
a fuse structure including a fuse strip positioned proximate to the gap;
and
an electrical connector connecting the fuse structure to the conductive layer such that the connector and the fuse structure electrically close the gap, wherein a current above a predetermined level flowing through the fuse structure melts the fuse strip, thereby altering the resonant frequency of the resonant circuit such that the resonant circuit no longer resonates at a frequency within the predetermined detection frequency range.

2 more elements

An activateable/deactivateable resonant tag for use with an electronic security system having means for detecting the presence of a security tag within a surveilled area utilizing electromagnetic energy at a frequency within a predetermined detection frequency range, the tag comprising:

a dielectric substrate having first and second opposite principal surfaces;
at least one resonant circuit disposed on the substrate capable of resonating at a frequency within the predetermined detection frequency range, the resonant circuit including an inductor formed at least in part on one of the principal surfaces of the substrate, wherein the resonant circuit includes a gap forming an electrical open circuit condition;
a fuse structure including at least one fuse strip located on a surface of a carrier and connected to first and second bonding pads of the carrier by respective wedges of conductive material, the fuse structure positioned proximate to the gap;
and
first and second wires respectively connected to the first and second carrier bonding pads and to the resonant circuit, such that the first and second wires and the fuse structure electrically close the gap, wherein a current greater than a predetermined level flowing through the fuse structure melts the fuse strip, thereby altering the resonant frequency of the resonant circuit.

2 more elements

Dependencies are inferred from the claim text.

Deactivateable resonant circuit

Life of this patent

Deactivateable resonant circuit

Life of this patent

Abstract

Claims33