Abstract: The present invention replaces the conventional bias magnets for EAS markers with a paintable or printable bias magnet material, which is either directly painted onto the EAS marker or first placed onto a substrate material, which is then placed into the EAS marker. The material includes a magnetic powder mixed with resin and solvent. This “bias paint” is then applied onto the EAS marker. The magnetic powder, resin, and solvent provide a very dense layer after drying, which has a magnetic material density that is usually lower than a rolled product, but is higher than that of the injection-molded magnet material. Printing the bias magnet allows nondeactivatable magnetomechanical EAS markers to be made using web-based mass production methods.

Abstract: The present invention replaces the conventional bias magnets for EAS markers with a paintable or printable bias magnet material, which is either directly painted onto the EAS marker or first placed onto a substrate material, which is then placed into the EAS marker. The material includes a magnetic powder mixed with resin and solvent. This “bias paint” is then applied onto the EAS marker. The magnetic powder, resin, and solvent provide a very dense layer after drying, which has a magnetic material density that is usually lower than a rolled product, but is higher than that of the injection-molded magnet material. Printing the bias magnet allows nondeactivatable magnetomechanical EAS markers to be made using web-based mass productions methods.

Abstract: A method of making a magnetomechanical electronic article surveillance marker is provided that, in one embodiment, includes deposition or placing of at least one elongated bias magnet onto a substrate, depositing a cavity layer onto the substrate where the cavity layer defines an elongated cavity adjacent the bias magnet. Placing a magnetomechanical resonator into the cavity and sealing a cover onto the cavity layer wherein the resonator is captured in the cavity and free to mechanically vibrate substantially unencumbered. The substrate itself may be magnetic thereby eliminating a separate bias magnet. In an alternate embodiment, a cavity is molded in a plastic substrate sized to fit a resonator, and a cover is sealed to the substrate to capture a resonator in the cavity. At least one bias magnet is placed onto the cover adjacent the cavity and a second cover is sealed to the substrate, to the first cover, and to the bias fixing the bias in place adjacent the cavity.

Abstract: A flat magnetomechanical electronic article surveillance marker is provided having a magnetostrictive resonator and a pair of bias magnets disposed on opposite sides and adjacent the resonator to bias the resonator with a magnetic field of a preselected field strength. The pair of bias magnets and the resonator are maintained substantially parallel and coplanar with each other to form a thin, flat EAS marker. During assembly of the marker, the bias magnets can be laterally adjustable to fine-tune the resonant frequency of the marker, and to compensate for material variability. Alternately, during assembly of the marker, the bias magnets can be adjustable in length to fine-tune the resonant frequency of the marker, and to compensate for material variability.

Abstract: An electronic article surveillance and identification tag and system is provided. The tag couples energy from a radiated energy source, which comprises first and second radiated signals. A mixing member in the tag mixes the first and second signals to produce a sideband of the first signal, which is re-radiated by the tag. The mixing member is activated by a controller that switches the mixing member into and out of the circuit according to a code stored within the controller that is associated with an article to be identified. As the mixing member is activated and deactivated, the sideband is radiated in a sequential manner according to the stored code. A receiver detects the sideband, and a decoder recovers the stored code according to the sequence of received sideband emissions from the tag.

Abstract: An electronic article surveillance (EAS) system and method utilizing two transmitted signals to generate and detect a marker signal is provided. The first signal is set at or near the resonance of the marker so its energy can be transmitted and stored in the marker. The second signal is a low frequency magnetic field that changes the resonant frequency of the marker. Because the marker's resonant frequency is constantly varying in response to the low frequency magnetic field, the marker's response to the first transmitted signal also changes. As a result, the marker performs a modulation on the first transmitted signal. Detection of a sideband of the modulated signal indicates the presence of the marker within an interrogation zone formed by the two transmitted signals. Multiple interrogation zones can be implemented by transmitting multiple low frequency signals, one low frequency signal for each interrogation zone.

Abstract: A resonant RF electronic article surveillance marker includes a substrate, a coil formed on the substrate, and a capacitor formed on the substrate. The coil includes a magnetic element which exhibits a GMI effect. Two signals are employed to interrogate the marker—an RF carrier signal and a low-frequency alternating magnetic field. Because of the presence of the GMI element, the marker mixes the low frequency signal with the carrier signal to generate a sideband of the carrier signal. The sideband signal is very unique and can be detected with a high degree of reliability. The marker may also include magnetic control elements which can be magnetized to disable the marker and de-magnetized to reactivate the marker.

Abstract: An EAS marker for use in a microwave-GMI article surveillance system includes a length of wire which exhibits a giant magneto-impedance effect, and deactivation elements installed along the length of the wire. The deactivation elements exhibit semi-hard ferromagnetic properties and have a triangular profile, or alternatively exhibit acute-angle corners or have edges that cross the wire at acute angles. The deactivation elements can be magnetized to disable the marker.

Abstract: A single antenna transmits and receives signals. The single antenna has first and second antenna loops substantially lying in a common plane and partially overlapping. First and second transceiver circuits are coupled to the first and second antenna loops respectively, for respectively generating in a first mode of operation first and second pulsed magnetic fields together defining an interrogation zone for a marker generating a characteristic response to the magnetic fields in the interrogation zone, and for receiving signals from the interrogation zone in a second mode of operation. The first and second transceiver circuits alternately generate the first and second magnetic fields substantially in phase with one another and substantially out of phase with one another. The partially overlapping antenna loops prevent detuning of the transceivers otherwise resulting from the phase alternating.

Abstract: A magnetomechanical EAS marker includes a housing, a magnetostrictive active element in the housing, and a bias magnet mounted on the housing adjacent to the active element. Both the active element and the bias magnet are substantially planar metal strips. The length and/or surface area of the bias magnet is substantially less than the length and/or surface area of the active element. The reduction in the size of the bias magnet relative to the active element enhances reliable deactivation of the marker by increasing the resonant frequency shift obtained by degaussing the bias magnet. The increased reliability of deactivation is obtained without increasing the sensitivity of the marker, when in an active state, to variations in applied bias magnetic field.

Abstract: A magnetostrictive element for use in a magneto-mechanical marker has a resonant frequency characteristic that is at a minimum at a bias field level corresponding to the operating point of the magnetomechanical marker. The magnetostrictive element has a magnetomechanical coupling factor k in the range 0.28 to 0.4 at the operating point. The magnetostrictive element is formed by applying cross-field annealing to an iron-rich amorphous metal alloy ribbon (45 to 82 percent iron) which includes a total of from 2 to 17 percent of one or more of Mn, Mo, Nb, Cr, Hf, Zr, Ta, V. Cobalt, nickel, boron, silicon and/or carbon may also be included. The metal alloy may include one early transition element selected from the group consisting of Zr, Hf and Ta, and also a second early transition element selected from the group consisting of Mn, Mo, Nb, Cr, and V.

Abstract: A bias element for use in a magnetomechanical EAS marker is magnetized to saturation. Then the magnetic charge in the bias element is redistributed by applying to the bias element a magnetic field having an AC ringdown characteristic. The redistribution of magnetic charge improves the stability of the bias element, so that the marker incorporating the bias element is less likely to have its resonant frequency shifted by exposure to a stray magnetic field.

Abstract: A magnetomechanical EAS marker is formed of a housing, a magnetostrictive active element in the housing and a bias element fixedly mounted on the housing. A central portion of the active element is secured to the housing to keep the active element from shifting in a longitudinal direction relative to the bias element and to keep ends of the active element spaced from the housing. The active element remains free to mechanically resonate in response to an EAS interrogation signal. The stable positioning of the active element prevents variations in the bias magnetic field due to shifting relative to the bias element, while keeping ends of the active element free from frictional damping due to mechanical loading from contact with the housing.

Abstract: An antenna system for an electronic article surveillance system, comprising: a first, tunable transmitting loop; a second, tunable transmitting loop, the first and second transmitting loops being arranged for first and second modes of operation, the transmitting loops being field-coupled to one another such that tuning the antenna system for one of the modes of operation detunes the antenna system for the other mode of operation; a tunable compensation coil field-coupled to each of the first and second transmitting loops, the tunable compensation coil enabling the antenna system to be tuned for operation in one of the modes at a first resonant frequency, and despite the detuning, enabling the antenna system to be tuned for operation in the other of the modes at a second resonant frequency independently of the tuning for the first mode of operation. The first and second resonant frequencies can be the same as or different from one another.

Abstract: A magnetostrictive element for use in a magnetomechanical marker has a resonant frequency characteristic that is at a minimum at a bias field level corresponding to the operating point of the magnetomechanical marker. The magnetostrictive element has a magnetomechanical coupling factor k in the range 0.28 to 0.4 at the operating point. The magnetostrictive element is formed by applying current-annealing to an iron-nickel-cobalt based amorphous metal ribbon, or by cross-field annealing an iron-nickel-cobalt alloy that includes a few percent chromium and/or niobium.

Abstract: A self-biasing magnetostrictive element for use in a magnetomechanical EAS marker is a strip of amorphous alloy with crystalline particles of semi-hard or hard magnetic material distributed throughout the bulk of the amorphous alloy strip. The crystalline particles are magnetized to bias the amorphous alloy strip to resonate in response to an interrogation signal. The crystalline particles are formed by heat-treating the amorphous alloy strip at a temperature above the Curie temperature of the amorphous alloy in the presence of a longitudinal magnetic field. The alloy strip is then cross-field annealed at a temperature below the Curie temperature of the amorphous alloy to form a transverse anisotropy in the amorphous bulk of the alloy strip. A preferred alloy composition includes iron, cobalt, niobium, copper, boron and silicon.

Abstract: A marker for use in a magnetomechanical electronic article surveillance (EAS) system is made by mounting a magnetostrictive element in a housing adjacent to a biasing element that is magnetized to a degree of magnetization that is less than saturation. The resonant frequency of the marker is detected. If the detected resonant frequency does not match a predetermined operating frequency of the EAS system, the degree of magnetization of the biasing element is adjusted so as to tune the resonant frequency of the marker to the predetermined operating frequency.

Abstract: A ribbon-shaped strip of an amorphous magnetic alloy is heat treated, while applying a transverse saturating magnetic field. The treated strip is used in a marker for a pulsed-interrogation electronic article surveillance system. A preferred material for the strip is formed of iron, cobalt, silicon and boron with the proportion of cobalt exceeding 30% by atomic percent.