Abstract:
A cordless handheld EAS tag deactivator is provided. The deactivator is housed in a portable handheld housing. An antenna is attached to the housing. The antenna is adapted for transmission of an electromagnetic field, which deactivates EAS tags within the field. An electronic circuit is connected to the antenna to generate the electromagnetic field. A battery contained within the housing is connected to the electronic circuit to power the generation and transmission of the electromagnetic field.

Description:
CROSS REFERENCES TO RELATED APPLICATIONS 
     Not Applicable 
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not Applicable 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to electronic article surveillance (EAS) and more particularly to handheld deactivators for deactivation of EAS tags. 
     2. Description of the Related Art 
     EAS systems are well known for the prevention or deterrence of unauthorized removal of articles from a controlled area. In a typical EAS system, tags designed to interact with an electromagnetic field located at the exits of the controlled area are attached to articles to be protected. If a tag is brought into the electromagnetic field or “interrogation zone”, the presence of the tag is detected and appropriate action is taken. For a controlled area such as retail store, the appropriate action taken for detection of an EAS tag may be the generation of an alarm. Some types of EAS tags remain attached to the articles to be protected, but are deactivated prior to authorized removal from the controlled area by a deactivation device that changes a characteristic of the tag so that the tag will no longer be detectable in the interrogation zone. 
     The majority of EAS tag deactivation devices are fixed at a specific location, such as adjacent a point-of-sale (POS) station in a retail environment. If an article is purchased, and for whatever reason the attached EAS tag is not deactivated at the deactivator adjacent the POS station, the EAS tag will set off an alarm at the store exit. To then deactivate the EAS tag, the article must be brought back to the deactivator adjacent the POS station, which causes confusion and customer embarrassment. Handheld deactivators for RF type EAS tags, which are part of a handheld bar-code scanner, are known, but still require the EAS tag to be brought near the POS station, within range of the handheld scanner/deactivator cord, for deactivation. 
     There is presently a need for a cordless, handheld deactivator that can deactivate EAS tags when they are away from or “remote” from the hardwired deactivator near the POS station. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention is a cordless handheld EAS tag deactivator. The deactivator is housed in a portable handheld housing. An antenna is attached to the housing. The antenna is adapted for transmission of an electromagnetic field, which deactivates EAS tags within the field. An electronic circuit is connected to the antenna to generate the electromagnetic field. A battery contained within the housing is connected to the electronic circuit to power the ageneration and transmission of the electromagnetic field. 
     The invention can be adapted for use for various types of EAS tags including but not limited to RF, microwave, harmonic, and magnetomechanical EAS tags. For example, the antenna can be an RF antenna for transmitting an electric field for deactivation of RF EAS tags. The antenna can be a coil for transmitting a magnetic field for deactivation of magnetomechanical EAS tags. In addition, the invention can be configured to detect EAS tags. 
     The invention can include a method for entry of data and control instructions, and a display for displaying information to an operator. A battery charger is adapted to receive the housing with the battery electrically connected to an exterior of the housing for connection to the charger. A releasable lock secures the housing to the charger until released by entry of a user identification code. 
     Objectives, advantages, and applications of the present invention will be made apparent by the following detailed description of embodiments of the invention. 
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
     FIG. 1 is a perspective view of one embodiment of the present invention. 
     FIG. 2 is a plot of energy requirements and weight per various coil configurations. 
     FIG. 3 is a plot of battery life calculations for various deactivation rates. 
     FIG. 4 is plot of the magnetic field in the x-axis, at a constant field level, for one embodiment of the present invention. 
     FIG. 5 is plot of the magnetic field in the z-axis, at a constant field level, for one embodiment of the present invention. 
     FIG. 6 is a schematic diagram of one embodiment for the electronic circuit of the present invention. 
     FIG. 7 is a schematic diagram of a transmit module of the circuit shown in FIG.  6 . 
     FIG. 8 is a schematic diagram of a receive module of the circuit shown in FIG.  6 . 
     FIG. 9 is a schematic diagram of a deactivation module of the circuit shown in FIG.  6 . 
     FIG. 10 is a perspective view of an alternate embodiment of the present invention. 
     FIG. 11 is a front plan view of the embodiment shown in FIG. 10 while plugged into a battery charging base unit. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention can be adapted for use with a plurality of different EAS tag types. The most challenging embodiment will be used as an example herein, and is the embodiment used for deactivation of magnetomechanical EAS tags, which requires generation of a magnetic field for deactivation. The problem of generating a magnetic field of a particular strength and shape is equivalent to that of driving a coil (inductor) with an electric current of the necessary amplitude and shape as that of the desired magnetic field. The necessary field shape for deactivation is alternating in polarity with a decaying envelope. The major problem for a handheld cordless EAS tag deactivator, however, is to find a way to implement the electrical requirements in a hardware package that has low enough weight and energy requirements. The low weight requirement is necessary to minimize operator fatigue and the low energy requirement is necessary to make battery operation feasible. A deactivation range of at least about 3 inches, a weight of less than about 2 pound, and a battery life of at least about 12 hours with a deactivation rate of 200 per hours is desired. 
     Referring to FIG. 1, one embodiment of the present invention  1 , includes a substantially circular air-core coil  2 , an electronic circuit  4 , a handheld housing  6 , and a battery  8 . The selection of coil size and amp-turns to achieve the required field level for deactivation of magnetomechanical EAS tags out to at least about 3 inches from coil  2 , while minimizing weight and battery energy, is determined using computer simulation as further explained below. Battery  8  can be contained fully within housing  6 , or plugged into a mating connector and attached to housing  6  in a flush manner. 
     Referring to FIG. 2, a plot of deactivation energy requirements verses weight for a number of different sample combinations of coils, cores, and shields is illustrated, each normalized to the same field strength. 
     Sample  10  is a circular air-core coil, 13 cm in diameter driven at 3500 amp-turns (AT). 
     Sample  11  is a circular iron-core coil, 13 cm in diameter driven at 3500 AT, with a 12 cm×2 cm core. 
     Sample  12  is a circular iron-core coil, 13 cm in diameter driven at 2000 AT, with a 12 cm×2 cm core and a 1 cm shield. 
     Sample  13  is a circular iron-core coil, 13 cm in diameter driven at 2000 AT, with a 12 cm×2 cm core and a 1 cm shield with a 1 cm skirt. 
     Sample  14  is a circular iron-core coil, 13 cm in diameter driven at 2200 AT, with a 12 cm×0.5 cm core and a 0.5 cm shield. 
     Sample  15  is a circular air-core coil, 13 cm in diameter driven at 2200 AT, with a 0.5 cm shield. 
     Sample  16  is a dual U iron-core coil, 2 cm×2 cm cross-section driven at 2500 AT in each of 4 legs. 
     Referring to FIG. 3, a second plot of samples  10  through  16  illustrates battery life verses deactivation rate per hour for each sample. The plots use the following equation to calculate battery life per deactivation rate:            T   B          (       R   D     ,     E   D       )            :          =       E   B         P   s     +     P   t     +         R   D     3600     ·     (       E   D     +     E   tx     +     E   rc       )           ·     (     1   3600     )                              
     where; 
     E B =AH·V B  ·3600 (battery energy (J))=2.592×10 4 , where 
     AH=1.0 (battery amp-hours) and V B =7.2 (battery voltage), 
     E tX =4 (bias and transmit (T x ) energy during deactivation (D x )), 
     E rc =1.5 (dissipation in current limiting charging resister (J)), 
     P s =0.06 (bias power during idle for D x ), 
     P t =0.05 (bias power for detection), 
     R D =10→1000 (D x  rate per hour), 
     with both D x  and T x  idle between deactivations and during deactivations, bias power and transmit power are both about 4J. 
     As is apparent from FIGS. 2 and 3, sample  10  provides the best selection of coil parameters of the sample coils investigated. Sample  10 , which is a circular air-core coil, 13 cm in diameter driven at 3500 AT, weighs less than 0.5 lbs., requires just below 1.2 J of power, and has a battery life of about 15 hours at a deactivation rate of 200 deactivations per hour. An analogous analysis method can be performed for coil selection for deactivation of other types of EAS tags. 
     Referring to FIGS. 4 and 5, magnetic field plots in the x and z direction, respectively, are illustrated for sample coil  10  with a constant 35 Oersted magnetic field surface. The orientation of the x, y, and z reference axes in relation to the coil are shown at  9  in FIG.  1 . The plots have a 1 cm grid and illustrate that the selected coil configuration of sample  10  provides the desired field level for deactivation of magnetomechanical EAS tags at about 3 inches away from the coil. 
     Referring to FIG. 6, one embodiment of electronic circuit  4  is illustrated, and includes battery  8 , 125 V boost inverter  20 , deactivation (D x ) module  22 , receive (R x ) module  24 , digital signal processor  26 , A/D converter  28 , coil  2 , microprocessor  30 , transmit (T x ) module  32 , programmable array logic (PAL) unit  34 , keypad and LCD display module  36 , and battery charging station (BCS) communication unit  38 . Several modes of operation of the present invention are possible, and include manual and automatic, or “hands-free”, deactivation and detection only. As well known in the art, when an EAS tag receives the correct transmitted interrogation frequency, the tag resonates and can be detected. Operator input through keypad and LCD display module  36 , which communicates with microprocessor  30  and DSP  26 , initiates mode selection and operation. Approximately a 1.6 ms burst of the desired interrogation frequency is transmitted by T x  module  32  and coil  2  at a repetition rate of about 36 Hz. PAL  34  ensures proper timing control for the transmitted signal. A typical interrogation frequency for magnetomechanical EAS tags is about 58 kHz, which will be used herein as an example. Depending upon the selected mode of operation, the 58 kHz bursts will continue for 3-4 minutes, or for a preselected period of time for hands-free operation. determines if the return signal is a valid EAS tag signal by examining the returned signal for selected attributes. For example, the returned signal must have proper spectral content and must be received in successive windows as expected. If DSP  26  determines that the returned signal is a valid EAS tag signal, the DSP  26  signals the microprocessor  30  to initiate deactivation, or to indicate the detection of an EAS tag, depending on the particular mode of operation. Indication of an EAS tag detection can take the form of an audio and/or visual alert to the user. 
     For deactivation, microprocessor  30  signals D x  module  22  to generate an EAS tag deactivation pulse. Dx module  22  utilizes 125 V boost inverter  20  to convert the DC battery voltage of battery  8 , to a high current, 125 V alternating pulse having a decaying envelope to deactivate the detected EAS tag. Microprocessor  30  can send commands to a battery charger (fully described hereinbelow) and receive battery  8  and charger status indications through BCS  38 . 
     Referring to FIG. 7, an example of a circuit to implement T x  module  32  is illustrated for generation of a 58 kHz burst  39 . Microprocessor  30 , shown as a Motorola 68HC908GP32, and PAL  34  shown as a Lattice PALLV16V8Z, as well as other part numbers shown on the schematics herein, are examples of possible component selections only and are not to be limiting. Microprocessor  30  signals PAL  34  to generate the proper transmit frequency and burst rate, which is sent by driver  40 , through resister  42  and capacitor  44  to coil  2 . 
     Referring FIG. 8, an example of a circuit to implement the Rx module  24  is illustrated for detecting a return signal  45  from an EAS tag with a resonant frequency of about 58 kHz. The return signal  45  from coil  2  passes through capacitor  46 , passes through amplifier  48  and low pass filter  50  stages, and is detected by DSP  26 . After verification of valid return signal attributes, DSP  26  signals microprocessor  30  of a valid return signal, which indicates an active EAS tag has been found. 
     Referring FIG. 9, an example of a circuit to implement the D x  module  22  is illustrated for generating the EAS tag deactivation pulse. Pulse width modulator  52 , in conjunction with capacitor  54  and inductor  56 , form boost inverter  20 , shown in FIG. 6, and converts the nominal DC battery voltage from battery 8 to 125 V DC. When switch  58  is closed on command from microprocessor  30 , the fully charged capacitor  54  is connected to main coil  2 . This initiates a natural resonant discharge producing a decaying alternating sinusoidal current waveform in the main coil  2 . The deactivation frequency is approximately 800 Hz with a 25% decay rate. The inductance value, capacitance value and the initial voltage of the capacitor determine the strength of the current waveform. These parameters are sized to produce the magnetic field level of sufficient strength to deactivate an EAS tag out to the desired range of 3 inches. As shown in FIGS. 4 and 5, 35 Oersted is used herein as the desired field strength at 3 inches, however, a field as low as 25 Oersted will deactivate magnetomechanical EAS tags. 
     All of the components used in the invention have been optimized for both size and energy requirements. Battery  8  can be a pair of high energy density rectangular lithium ion cells tightly packaged together to fit in the allotted space within the handheld housing. PWM  52  can be a Texas Instruments UUC39421, specifically designed for low power battery driven applications, and includes a unique sleep mode, which conserves energy when demand is low. Capacitor  54  can be a high technology, metalized polyester 2 μM film to enhance energy density, recently made available from NWL, and includes a customized shape to fit within the allotted space within the handheld housing. The complete set of deactivation parameters: field strength, capacitance &amp; charge voltage, coil inductance &amp; resistance, coil size &amp; wire gauge, discharge frequency &amp; decay rate and energy available for each deactivation comprise a unique mathematical solution that is determined according to the specifications of the EAS tag that is to be deactivated and the weight, battery, and component size constraints. 
     Referring to FIG. 10, an alternate embodiment of the handheld deactivator  60  is illustrated including handheld housing  62 , keypad and LCD display module  36 , battery  8  contained within housing  62 , and a coil (not shown) contained within coil end  64  of housing  62 . The primary difference between embodiment  1  described above and embodiment  60  is the coil. The coil in embodiment  60  is substantially elliptical in shape rather then circular, and can be comprised of  26  turns of flat copper magnet wire (1.02 mm×2.59 mm), which is equivalent to approximately #13 AWG round wire. This results in an impedance that, to achieve the necessary magnetic field, requires about 3900 amp-turns. Flat wire minimizes eddy current losses in the coil, which tend to degrade the decay rate, as describe above, beyond an acceptable range. Keypad and LCD display module  36  includes pushbutton switch  66 , keys  67 , display  68 , and LEDs  69 . Pushbutton switch  66  can be analogous to a trigger or an “enter” key on a computer keyboard to input various operational modes, as fully described herein, which are selected by a user via keys  67 . Display  68  can be an LCD, plasma or other suitable display to display information to the user. LEDs  69  can be used to indicate selected information to a user. Cart hook  70  can be used to hang handheld deactivator  60  from a suitable device such as a shopping card, which can be positioned in a desired location, for hands-free operation of the invention. Lock aperture  72  can be used to secure the handheld deactivator for prevention of unauthorized removal. 
     Referring to FIG. 11, a battery charging base unit  80  is adapted to receive handheld deactivator  60  as illustrated. Battery  8  within housing  62  can be charged through external connector  74  (shown in FIG.  10 ). A retractable rod (not shown) can extend from base unit  80  through lock aperture  72  to secure handheld deactivator to base unit  80 . To retract the locking  10  rod and release handheld deactivator  80 , a suitable identification number must be entered via keys  67 . Handheld deactivator  60  communicates with base unit  80 , via BCS  38  shown in FIG. 6, to control release of the rod. Similarly, an identification number can be required to be entered prior to operation of the handheld deactivator  60  to prevent unauthorized use. In addition to security features, many operational modes, diagnostic and test routines, and informational requests can be programmed into the handheld deactivator to provide a customized and flexible device. Operational modes can include, but are not limited to, manual detection and deactivation, manual detection and automatic deactivation, manual detection only, automatic detection and deactivation, and sleep. Once a mode is selected via entry by keys  67 , the user to initiate the mode can simply use pushbutton switch  66 . 
     It is to be understood that variations and modifications of the present invention can be made without departing from the scope of the invention. It is also to be understood that the scope of the invention is not to be interpreted as limited to the specific embodiments disclosed herein, but only in accordance with the appended claims when read in light of the forgoing disclosure.