HK1111507B - Combination eas and rfid label or tag with controllable read range - Google Patents

Description

Combined EAS and RFID tag or label with controllable read range

Cross Reference to Related Applications

U.S. provisional patent application No.60/628,303, entitled "Combo EAS/RFID Label or Tag," filed 11/15/2004 as required by 35 u.s.c. § 119, entitled priority, the entire contents of which are incorporated herein by reference.

Technical Field

The present disclosure relates to an Electronic Article Surveillance (EAS) marker or tag for preventing or deterring unauthorized removal of an article from a controlled area. More particularly, the present disclosure relates to an EAS marker or tag in combination with a Radio Frequency Identification (RFID) marker or tag for recording data unique to the item, and a novel RFID marker or tag.

Background

Electronic Article Surveillance (EAS) systems are known in the art to prevent or deter unauthorized removal of articles from a controlled area. In a typical EAS system, EAS markers (tags or markers) are designed to interact with an electromagnetic field located at the exit of a controlled area. These EAS markers are attached to the article to be protected. If an EAS tag is brought into an electromagnetic field or "interrogation zone," the presence of the tag is detected and appropriate action is taken, such as generating an alarm. For authorized removal of an item, the EAS tag may be disabled (deactivated), removed, or passed around the electromagnetic field to avoid detection by the EAS system.

EAS systems typically employ reusable EAS tags or disposable tags or markers to monitor articles to prevent shoplifting and unauthorized removal of the articles from the store. Reusable EAS tags are typically removed from the item before the customer leaves the store. Disposable labels or tags are typically attached to or placed within the package with an adhesive. These tags are typically with the item and must be disabled before being removed from the store by the user. The disabling device may use a coil that, when energized, may generate a magnetic field of sufficient magnitude to deactivate the EAS tag. The disabled tags no longer respond to the incident energy of the EAS system and thus do not trigger an alarm.

For situations where items having EAS tags are to be registered or returned to the controlled area, the EAS tags must be activated or re-attached to again provide anti-theft functionality. Since it is desirable to make source tags in which EAS tags are attached to articles at the time of manufacture or distribution, it is typically desirable that EAS tags be disabled or activated rather than removed from the articles. In addition, other problems arise when items pass around the interrogation zone because the EAS tags remain active and can interact with EAS systems in other controlled areas, thereby inadvertently activating those systems.

Radio Frequency Identification (RFID) systems are also well known in the art and may be used in a number of applications, such as managing inventory (inventoriy), electronic access control, security systems, and automatic identification of vehicles on toll roads. An RFID system typically includes an RFID reader and an RFID device. The RFID reader may transmit a radio frequency carrier signal to the RFID device. The RFID device may respond to the carrier signal with a data signal encoded with information stored by the RFID device.

In the retail environment, market demand for a combination of EAS and RFID functionality is rapidly emerging. Many retail stores currently use EAS to prevent shoplifting, which relies on barcode information for inventory control. RFID provides faster and more detailed inventory control through bar coding. Retail stores have paid much for reusable hard tags. Adding RFID technology to EAS hard tags can easily pay for the added cost in inventory control and loss prevention due to yield improvement.

Additionally, to minimize interaction between the EAS and RFID units, prior art combination approaches place the two different units, i.e., the EAS unit and the RFID unit, far enough in an end-to-end or side-by-side manner to minimize interaction of the respective units. However, this requires increasing the size of the labels or tags being combined.

What is needed is a combination EAS and RFID tag or label in which a spacer, such as a low loss dielectric material or air, is used as a separation between the EAS and RFID units to vary and control the read range of the RFID units.

Disclosure of Invention

It is an object of the present invention to provide a tag or label in which the features of a stand-alone EAS tag or label and a stand-alone RFID tag or label are combined, wherein a spacer, such as a low loss dielectric material or air, is used as a spacer between the EAS and RFID units to vary and control the read range of the RFID units.

The present disclosure relates to a security tag that includes an Electronic Article Surveillance (EAS) element having a defined surface area, and a Radio Frequency Identification (RFID) element having a defined surface area. The prescribed surface area of the EAS element is configured to at least partially overlap the surface area of the RFID element. The security tag also includes a substantially planar spacer having a thickness, the spacer being positioned at least partially between the prescribed surface area of the EAS element and the prescribed surface area of the RFID element, wherein the thickness of the spacer is configurable to adjust a read range between the RFID reader and the RFID element. In one embodiment, the RFID reader is capable of activating the RFID element when the RFID element is within a read range.

The RFID element may include an antenna that at least partially overlaps the prescribed surface area of the EAS element. The antenna may have a complex impedance and the EAS element forms part of an impedance matching network of the antenna. The antenna impedance may include loading effects of the EAS element. In one embodiment, the RFID element includes an antenna and an Application Specific Integrated Circuit (ASIC), the ASIC having a complex impedance. The complex impedance of the ASIC may be matched to the coupled complex conjugate impedance of the antenna including the loading effect of the EAS element.

In one embodiment, the security tag comprises: an Electronic Article Surveillance (EAS) element having a defined surface area; a Radio Frequency Identification (RFID) element having a defined surface area, the surface area of the EAS element configured to at least partially overlap the surface area of the RFID element; and a substantially planar spacer having a thickness, the spacer being positioned at least partially between the prescribed surface area of the EAS element and the prescribed surface area of the RFID element, wherein the RFID element includes an antenna and an Application Specific Integrated Circuit (ASIC), the ASIC having a complex impedance, and the complex impedance of the ASIC matching a coupled complex conjugate impedance of the antenna including loading effects of the EAS element, and wherein the thickness of the spacer is configurable to adjust a read range between the RFID reader and the RFID element.

The RFID element may include a substrate portion, the material of which may be selected from the group consisting of (a) base paper, (b) polyethylene, (c) polyester, (d) polyethylene terephthalate (PET), and (e) polyetherimide (PEI, polyetherimide). The RFID element may include a substrate portion, the material of which may be plastic, having a dielectric constant of about 3.3 and a loss tangent of less than about 0.01. The material of the spacer may be selected from the group consisting of (a) a low loss, low dielectric material and (b) air.

The present disclosure also relates to a method of adjusting a read range of a combination of an Electronic Article Surveillance (EAS) element and a Radio Frequency Identification (RFID) element, the method comprising the steps of: providing a spacer positioned between the EAS element and the RFID element; the thickness of the spacer is varied to adjust the readable range of the RFID element. In one embodiment, the step of varying the thickness of the spacer varies a read range between the RFID reader and the RFID element, and the RFID reader is capable of activating the RFID element when the RFID element is within the read range.

Drawings

The subject matter regarded as the embodiments is particularly pointed out and distinctly claimed in the concluding portion of the specification. However, both as to organization and method of operation, together with objects, features, and advantages thereof, may best be understood by reference to the following detailed description when read with the accompanying drawings in which:

FIG. 1 illustrates a combination EAS/RFID security tag according to one embodiment of the present invention;

FIG. 2A illustrates a portion of sample test data for a combination EAS/RFID security tag in accordance with one embodiment of the present invention;

FIG. 2B illustrates another portion of sample test data for a combination EAS/RFID security tag in accordance with one embodiment of the present invention;

FIG. 3A illustrates an RFID system using magnetic field coupling according to one embodiment of the present invention;

FIG. 3B illustrates an RFID system using magnetic field coupling according to one embodiment of the invention;

FIG. 4 illustrates a perspective exploded view of a security tag according to one embodiment of the present invention;

FIG. 4A illustrates sample test data for the read range of the security tag of FIG. 4 as a function of spacer thickness between the EAS and RFID elements of the security tag;

FIG. 5 illustrates a top view of the security tag of FIG. 4;

FIG. 6 illustrates a top view of a security tag with an antenna having segmented points in accordance with an alternative embodiment of the present invention;

FIG. 7 shows a block flow diagram in accordance with one embodiment of the present invention;

FIG. 8A shows a prior art configuration of a coplanar EAS marker adjacent to an RFID marker;

FIG. 8B shows a prior art configuration of a coplanar EAS tag and RFID tag separated by a gap;

FIG. 8C shows an embodiment of the invention in which an EAS element and an RFID element mounted directly below the EAS element are combined;

FIG. 8D illustrates an embodiment of the invention in which a portion of a security tag combines an EAS element and an RFID element insert (insert);

FIG. 8E is a front view of the embodiment of the present invention in FIG. 8D;

FIG. 8F illustrates an embodiment of the invention in which a portion of the security tag combines an EAS element and an RFID element insert; and

fig. 8G is a front view of the embodiment of the invention in fig. 8F.

Detailed Description

A family of concurrently filed PCT applications commonly owned by r.copeland (attorney docket No. F-TP-00023) entitled "association EAS AND rfid system TAG" is hereby incorporated by reference in its entirety.

The present invention will become more fully understood from the detailed description given below and the accompanying drawings of specific embodiments of the present invention, which should not be taken to limit the present invention to the specific embodiments, but are for explanation purposes.

Numerous specific details may be set forth herein to provide a thorough understanding of several possible embodiments of a combination EAS/RFID tag incorporating the present invention. It will be understood by those skilled in the art, however, that the embodiments may be practiced without these specific details. In other instances, well-known methods, procedures, components and circuits have not been described in detail so as not to obscure the embodiments. It can be appreciated that the specific structural and functional details disclosed herein may be representative and do not necessarily limit the scope of the embodiments.

Some embodiments may be described using the expression "coupled" and "connected" along with their derivatives. For example, some embodiments may use the term "connected" to indicate that two or more elements are in direct physical or electrical contact with each other. In another example, some embodiments may use the term "coupled" to indicate that two or more elements are in direct physical or electrical contact. The term "coupled," however, may also mean that two or more elements are not in direct contact with each other, but yet still co-operate or interact with each other. Embodiments disclosed herein are not necessarily limited in this context.

It is worthy to note that any reference in this specification to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. The appearances of the phrase "in one embodiment" in various places in the specification are not necessarily all referring to the same embodiment.

Turning now to the details of the present invention, one way in which a combination EAS/RFID tag (or label) may be employed is to place both the EAS related elements and the RFID related elements together and package them together. However, there may be certain electrical or electromechanical interaction factors that affect the performance of the EAS function and/or the RFID function. Placing the RFID tag on top of the EAS tag is the most convenient way, but may result in actual de-tuning and signal loss of the RFID tag. For example, in a typical RFID device, the performance of the RFID tag is typically very sensitive to impedance matching of an Application Specific Integrated Circuit (ASIC)/lead frame assembly for the RFID device to the effective impedance of the RFID antenna mounted on the backplane. A more detailed description of some possible embodiments of the RFID portion of the device will be discussed further below. Other objects around the RFID tag may contribute to the effective impedance or electromagnetic energy absorption used to read the RFID tag.

Some existing 2450MHz EAS/RFID combination markers have used a configuration in which the RFID marker and the EAS marker are placed in a superimposed configuration. In this particular application, there may be a considerable degradation in the quality of the RFID tag detection. While end-to-end or slight overlap works best in such systems, the size of the tag tends to become quite large in these situations. Also, side-by-side configurations are known to produce irregular RFID detection patterns. There have not been many designs that successfully implement a combination EAS/RFID tag in the marketplace. Most applications of tagged items using a combination EAS and RFID use separate EAS and RFID tags that are separately installed, occupying a considerable amount of space on the tagged item compared to the space occupied by each tag in the case of a separate installation.

It is envisioned that a solution to this problem is to use the EAS tag portion of the combination tag as part of the impedance matching network of the RFID tag. For example, as the RFID tag is placed closer and closer to the EAS tag, the antenna impedance of the RFID tag may be affected by the EAS tag or tuned. To achieve impedance matching of the RFID tag, the geometry of the RFID antenna alone may be designed such that any resulting electrical effect of the EAS tag on impedance is taken into account. For example, the RFID antenna may be configured to have a high capacitive impedance and may be very mismatched to the impedance of the logic chip of the device (e.g., the ASIC/leadframe components described above). Since the RFID tag is placed close to, e.g., directly underneath, the EAS tag, the impedance of the RFID antenna nearly matches the ASIC impedance.

FIG. 1 generally shows an EAS element 1 and an RFID element 2. The EAS element 1 is an EAS marker or tag. The EAS element 1 may include, for example and without limitation, a magnetic resonator element (or other EAS type resonant circuit) with a magnetic bias housed in a housing made of plastic or other material. Other EAS markers or tags not specifically disclosed herein may also perform the functions of the EAS element 1. The RFID element 2 is an RFID tag or label. The RFID element 2 may include, for example, but not limited to, and for purposes discussed in FIG. 1, an antenna mounted on a substrate material with an ASIC based RFID logic circuit or processing chip connected to the antenna, as best shown in FIG. 4 discussed below. Other RFID labels or tags not specifically disclosed herein may also perform the function of RFID element 2. In one particularly useful embodiment, the RFID portion of the system, RFID element 2, operates in the 868MHz and/or 915MHz ISM bands. However, those skilled in the art will readily recognize that the present invention is not so limited and may be used at other available frequencies.

When the EAS element 1 and the RFID element 2 are placed adjacent to each other, as shown at location "P1" in fig. 1, the EAS element 1 has only a small effect on the antenna impedance of the RFID element 2. However, as RFID element 2 is placed beneath EAS element 1, as shown by positions "P2", "P3", and "P4", i.e., via the degree of overlap shown by shaded area 3, the antenna impedance of the RFID is increasingly affected.

More specifically, the flag positions P1-P4 of the RFID element 2 are configured as follows:

p1 — EAS element 1 and RFID element 2 are placed adjacent to each other;

p2 ═ RFID element 2 is placed under EAS element 1, with a partial crossover of 1/4;

p3 ═ RFID element 2 is placed under EAS element 1, with a partial crossover of 1/2;

P4-RFID element 2 is placed directly under EAS element 1.

For example, FIGS. 2A and 2B show the real and imaginary components of the antenna impedance of the RFID with respect to frequencies in the 915MHz ISM band for a sample security tag that includes an EAS element 1 and an RFID element 2.

As shown in fig. 2A, at the center frequency of 915MHz, the real impedance R varies from about 6 ohms R1 to about 13 ohms R4 when the RFID tag 2 moves from position P1 to position P4. A significant increase in the real impedance R represents an increase in the effective loss due to the EAS marker material. Accordingly, the imaginary impedance Z varies from-125 ohms Z1 to +195 ohms Z4 when the RFID tag 2 moves from position P1 to position P4. Therefore, the imaginary impedance Z changes from a capacitive characteristic to an inductive characteristic to some extent.

The RFID element 2 may be designed such that the antenna impedance is close to the complex conjugate of the ASIC device. This results in a resonance at the target frequency, e.g. 915 MHz. A typical test result for the impedance of an ASIC RFID device is 5-j140 ohms for a chip manufactured by ST Microelectronics, inc, of geneva, switzerland, and 20-j270 ohms for a chip manufactured by Koninklikje Philips Electronics n.v., inc, of amsterdam, netherlands. For both RFID devices, the virtual impedance Z of the antenna of the RFID tag is required to be in the range of + j (140 to 270) ohms to achieve resonance at the target frequency.

Thus, a combination RFID/EAS security tag may be designed for matching purposes using the impedance of the EAS element. In open space, the RFID element antenna may be designed to have a negative imaginary impedance and, when placed directly under, on top of, or near the EAS element, to get the correct positive imaginary impedance. As will be appreciated from the disclosure of the present application, this configuration may be used for any type of EAS tag or label, such as different types of adhesive magnetostrictive labels and EAS hard labels, such as those produced by Sensormatic corporationIt is a division of Tyco Fire and Security, Inc. of Boca Raton, Florida. The type of EAS device is not limited to these specific examples.

The RFID element may include, for example, a semiconductor Integrated Circuit (IC) and a tunable antenna. The tunable antenna may be tuned to a desired operating frequency by adjusting the length of the antenna. The range of operating frequencies may vary, although the embodiments may be particularly useful for the Ultra High Frequency (UHF) spectrum. Depending on the application and the size of the area available for the antenna, the antenna may be tuned in the range of a few hundred megahertz (MHz) or higher, such as 868-950 MHz. In one embodiment, for example, the tunable antenna may be tuned to operate within an RFID operating frequency, such as the 868MHz band for Europe, the 915MHz Industrial, scientific, and medical (ISM) band for the United states, and the 950MHz band for Japan. It is also noted that these operating frequencies are also given by way of example only, and the embodiments are not limited in this context.

In one embodiment, for example, the tunable antenna may have a unique antenna geometry in the form of an internal spiral, which is useful for RFID applications or EAS applications. The internal helical form may furl the antenna traces, bringing them back to the origin. This results in an antenna that functions similarly to a conventional half-wave dipole antenna, but with a smaller overall size. For example, the size of a conventional half-wave dipole antenna at 915MHz is approximately 16.4 centimeters (cm) long. By contrast, some embodiments may provide the same performance as a conventional half-wave dipole antenna at 915MHz operating frequency, but with a shorter length, about 3.81 cm. In addition, the ends of the antenna track may be adjusted to tune the antenna to a desired operating frequency. Since the ends of the antenna track are inward from the antenna perimeter, the tuning can be accomplished without changing the geometry of the antenna.

Fig. 3A shows a first system according to a particularly useful embodiment of the invention. Fig. 3A shows an RFID system 100 that may be configured to operate using an RFID element 2, the RFID element 2 having an operating frequency in the High Frequency (HF) band, which is considered to be up to and including 30MHz in frequency. In this frequency range, the main component of the electromagnetic field is magnetic. However, RFID system 100 may also be configured to operate RFID element 2 using other portions of the RF spectrum, as desired for a given implementation. The embodiments are not limited in this context. As depicted by way of example, RFID element 2 partially overlaps EAS element 1.

RFID system 100 may include a plurality of nodes. The term "node" as used herein may refer to a system, unit, module, component, circuit board, or device that may process signals representing information. The signal type may be, for example, but not limited to, electrical, optical, acoustical and/or chemical in nature. Although fig. 3A shows a limited number of nodes, it can be appreciated that any number of nodes may be used in RFID system 100. The embodiments are not limited in this context.

Referring initially to FIG. 4, FIG. 4 illustrates a side view of a security tag 200 in accordance with a particularly useful embodiment of the present invention. The RFID element 2 includes a base portion or panel 202 having a first surface or surface area 202a and a second surface or surface area 202b that are generally located on opposite sides of the base portion or panel 202. An antenna 204 is disposed on the backplane 202. Antenna 204 has a first surface or surface area 204a and a second surface or surface area 204b that are generally located on opposite sides of antenna 204. A lead frame 206 is placed on the antenna 204 and an Application Specific Integrated Circuit (ASIC)208 is placed on the lead frame 206. First and second surfaces or surface areas 202a and 202b, 204a and 204b are defined as surface areas of the RFID element 2.

The security tag 200 includes a substantially planar covering material or spacer 210 that is disposed over the RFID element 2, while the EAS element 1 is disposed over the spacer 210. The spacer 210 has surfaces or surface regions 202a and 202b on opposite sides thereof.

The EAS element 1 has a first surface or surface area 1a and a second surface or surface area 1b that are generally located on opposite sides of the EAS element 1. The first and second surfaces or surface areas 1a and 1b are defined as the surfaces or surface areas of the EAS element 1.

For reference purposes, the security tag 200 is illustrated as being placed directly beneath the EAS element 1, i.e., at position P4 of fig. 1. Security tag 200 is shown by way of example only at position P4 and may be placed at any location relative to EAS marker 1, as previously discussed with respect to fig. 1. Security tag 200 may also be used completely independently of EAS marker 1 or in combination therewith. The embodiments are not limited in this context.

More specifically, security tag 200 includes an EAS element 1 having one of defined surface areas 1a and 1b and an RFID element 2 having one of defined surfaces or surface areas 202a, 202b, 204a, and 204 b. At least one of the prescribed surfaces or surface areas 1a and 1b of the EAS element 1 is configured to at least partially overlap at least one of the prescribed surfaces or surface areas 202a, 202b, 204a and 204b of the RFID element 2. RFID element 2 may include an antenna 204 that at least partially overlaps at least one of the prescribed surfaces or surface areas 1a and 1b of the EAS element 1.

In one embodiment, the prescribed surface or surface area of the RFID element 2 is one of the surfaces or surface areas 202a and 202 b.

The substantially planar spacer 210 has a thickness "t" and is disposed at least partially between at least one of the prescribed surfaces or surface areas 1a and 1b of the EAS element 1 and at least one of the prescribed surfaces or surface areas 202a, 202b, 204a, and 204b of the RFID element 2.

Although fig. 4 shows a limited number of cells, it can be appreciated that a greater or lesser number of cells may be used for security tag 200. For example, an adhesive and release liner (release liner) may be added to security tag 200 to assist in attaching security tag 200 to an object to be monitored. Those skilled in the art will recognize that semiconductor IC 208 may be bonded directly to antenna 204 without lead frame 206.

Returning now to FIG. 3A, RFID system 100 may also include RFID reader 102 and security tag 200. Security tag 200 is physically separated from RFID reader 102 by a distance d 1. As described below with reference to fig. 4, the security tag 200 is an RFID security tag, label or label that differs from the prior art in that it includes an EAS element, i.e., an EAS label or tag. The RFID element 2 includes a resonant circuit 112. The resonant circuit 112 includes an inductor L2 and a resonant capacitor C2 connected across the terminals T1 and T2 of the ASIC 208. The capacitance of ASIC 208 is typically negligible compared to C2. If additional capacitance is required to be added to resonant circuit 112 to enable the antenna, i.e. inductor L2, to be tuned to the appropriate frequency, a capacitor C2 is connected in parallel with inductor L2 so that resonant circuit 112 becomes a parallel resonant circuit across which T1 and T2 develop an induced voltage V_i. Terminals T1 and T2 are coupled to other portions of RFID element 2 as described below with respect to FIG. 4. In addition, the inductance value of the inductor coil or antenna L2 includes the inductance exhibited by the EAS marker or tag.

RFID reader 102 may include a tuning circuit 108 having an inductance L1 that functions as an antenna for RFID reader 102. When additional capacitance needs to be added to the tuning circuit 108 to enable the inductor or antenna L1 to be tuned properly, a capacitor C1 is connected in series with the inductor or antenna L1. RFID reader 102 is configured to generate pulsed or Continuous Wave (CW) RF power across tuned circuit 108, which is electromagnetically coupled to parallel resonant circuit antenna 112 of RFID element 2 by alternating current action. The mutually coupled electromagnetic power from RFID element 2 is coupled to RFID reader 102 through magnetic field 114.

RFID element 2 is a power conversion circuit that converts some of the coupled CW RF electromagnetic power of magnetic field 114 into dc signal power for use by the logic circuits of the semiconductor IC to implement RFID operations on RFID element 2.

RFID element 2 may also be an RFID security tag that includes memory to store RFID information and transmits the stored information in response to an interrogation signal 104. The RFID information may include any type of information that can be stored in a memory used by the RFID element 2. For example, the RFID information includes a unique tag identifier, a unique system identifier, an identifier of the monitored object, and the like. The type and amount of RFID information is not limited in this context.

The RFID element 2 may also be a passive RFID security tag. Passive RFID security tags do not use an external power source, but rather use the interrogation signal 104 as a power source. Detection zone Z1 is defined as the imaginary area of space defined by a generally spherical surface, the radius of which R1 generally originates from inductor L1. Radius R1 defines a detection distance or read range R1 such that when distance d1 is less than or equal to read range R1, RFID reader 102 will induce a desired threshold voltage V at terminals T1 and T2_TTo activate the RFID element 2. The read range R1 depends on, among other factors, the strength of the EM field radiation and the magnetic field 114 from the tuned circuit 208. Thus, the intensity of the EM field radiation 114 determines the read range R1.

RFID element 2 may be activated by a dc voltage generated by rectifying an incoming RF carrier signal containing interrogation signal 104. An RFID element 2 is activated and can transmit the information stored in its memory register via a response signal 110.

In general High Frequency (HF) operation, when the resonant circuit 112 of the RFID system 100 approaches the tuned circuit 108 of the RFID reader 102, an Alternating Current (AC) voltage V1 and T2 is generated across the parallel resonant circuit 112 of the RFID element 2_i. AC voltage V across resonant circuit 112_iIs rectified to Direct Current (DC) voltage by a rectifier, and when the rectified voltage amplitude reaches a threshold value V_TAt this time, the RFID element 2 is activated. The rectifier is an Application Specific Integrated Circuit (ASIC)208 as described above. Once activated, RFID element 2 transmits the data stored in its memory register by modulating interrogation signals 104 of RFID reader 102 to form response signals 110. RFID device 106 then transmits response signal 110 to RFID reader 102. RFID reader 102 receives response signal 110 and converts it to serial data word bitstream data that is detected, representing information from RFID element 2.

RFID system 100 as shown in fig. 3A may be considered a High Frequency (HF) RFID system because RFID reader 102 is inductively coupled to RFID element 2 via magnetic field 114. In HF applications, antenna 204 is typically an inductive coil type antenna, as provided by inductive coil L2.

Fig. 3B illustrates an Ultra High Frequency (UHF) RFID system 150 in which an RFID reader 152 is coupled to an RFID device, tag or label 156 at a distance d2 via a magnetic field E. The UHF frequency band is considered herein to be in the range from about 300MHz to about 3 GHz. The UHF range specifically includes frequencies in the 868MHz band, 915MHz band, and 950MHz band.

For UHF applications, antenna 204 of RFID element 2 typically comprises an open-ended (open-ended) dipole antenna, while RFID reader 152 typically comprises a patch antenna. The coaxial feed line from the reader 152 is connected to the patch antenna. The UHF antenna may be a simple half-wave dipole antenna or a patch antenna. Many popular designs use air-filled cavity supported patch antennas that can be either linearly polarized or circularly polarized. For the case of circular polarization, the electric field vectors E1 and E2 rotate at equal magnitudes. Linearly polarized antennas have higher E-field amplitudes in specific orthogonal directions, which may be suitable for certain specific RFID tag orientations.

Thus, in UHF applications, antenna 204 of RFID element 2 comprises an UHF open-ended dipole antenna, while in HF applications, typically inductance L2.

In summary, when operating in the UHF range, RFID element 2 need not include a capacitor, such as capacitor C2, in parallel with open-ended dipole antenna 204, so that it can be tuned to the frequency transmitted by the patch antenna of RFID reader 152.

Returning to fig. 4, as previously mentioned, RFID element 2 may include a base portion or backplane 202 comprising any type of material suitable for mounting an antenna 204, a lead frame 206, and an IC 208. For example, the material of the base plate 202 may include base paper, polyethylene, polyester, polyethylene terephthalate (PET), Polyetherimide (PEI) (e.g., sold by general electric company of Fairfield, Connecticut)Amorphous thermoplastic PEI), and/or other materials. It is known that the particular material used to implement the substrate 202 may affect the RF performance of the security tag 200, as the dielectric constant and loss tangent may represent the dielectric properties of a suitable substrate material for the substrate 202.

In general, a higher dielectric constant may result in a greater frequency shift of the antenna when compared to an open space without a backplane. While it may be possible to retune the antenna to the original center frequency by physically changing the antenna pattern, a material with a high dielectric constant and low dielectric loss may be desirable because of the smaller tag or label size that results from using such a material. The term "read range" may refer to the communication working distance between RFID reader 102 and security tag 200. The read range of security tag 200 may be, for example, 1-3 meters, although the embodiments are not limited in this context. The loss tangent may represent the absorption characteristics of the dielectric for RF energy. The absorbed energy may be lost as heat and may not be usable by the ASIC 208. The lost energy may cause the same effect as reducing the transmitted power and may correspondingly reduce the read range. Therefore, it may be desirable to have as low a loss factor as possible in backplane 202 because antenna 204 cannot be "detuned" by adjusting. The total frequency shift and RF loss may also depend on the thickness of the substrate 202. As the thickness increases, the frequency shift and loss may also increase.

For example, in one embodiment, the backplane 202 may also be configured from base paper, which has a dielectric constant of about 3.3, and a loss tangent of about 0.135. The base paper may be relatively damaged at 900 MHz. The lossy material has a dielectric loss tangent greater than about 0.01. In one embodiment, the base plate 202 may also be configured from plastic, which has a dielectric constant of about 3.3, and a loss tangent of less than about 0.01. The embodiments are not limited in this context.

In one embodiment, security tag 200 may include an IC 208 having a semiconductor IC, such as an RFID chip or an Application Specific Integrated Circuit (ASIC) ("RFID chip"). RFID chip 208 may include, for example, an RF or Alternating Current (AC) rectifier that converts an RF or AC voltage to a DC voltage, a modulation circuit to transmit stored data to an RFID reader, a memory circuit to store information, and a logic circuit to control the overall functionality of the device. In one embodiment, RFID chip 208 may be configured to use an I-CODE high frequency Smart tag (HSL) RFID ASIC or a U-CODE ultra high frequency Smart tag (USL) RFID ASIC, both manufactured by Philips semiconductors, Amsterdam, the Netherlands, or an XRA00 RFID chip manufactured by ST Microelectronics, Inc. of Geneva, Switzerland. The embodiments, however, are not limited in this context.

The lead frame is a small connection that allows an RFID chip, such as RFID chip 208, to be attached to an antenna, such as antenna 204. In one embodiment, RFID chip 208 may be bonded directly to antenna 204 without the need to include lead frame 206. Leadframe 206 may also include a die mounting paddle (flag) or flag, and a plurality of leads (lead fingers). The die holder blades are primarily used to mechanically support the die holder during manufacture of the package. The pins connect the die holder to circuitry external to the package. One end of each pin is typically connected to a bond pad on the submount by wire bonding or tape automated bonding. The other end of each pin is a lead that is mechanically and electrically connected to a backplane or circuit board. Lead frame 206 may be made from sheet metal by stamping or etching, typically followed by final processing such as plating, drop forming (downset1), taping, and the like. In one embodiment, for example, leadframe 206 may be implemented using a Sensormatic EASMicrollabel leadframe, manufactured by Sensormatic, a division of Tyco Fire and Security, Inc. of Boca Raton, Florida. However, the embodiments are not limited in this context.

In one embodiment, antenna 204 includes an inductive coil L2 and, when desired, a capacitor C2 of resonant circuit 112 of RFID element 2. Terminals T1 and T2 are also included in antenna 204 to couple to RFID chip 208 such that once a threshold voltage V is reached_TInduced voltage V_iThe RFID element 2 can be activated.

In one embodiment, antenna 204 typically comprises an open-ended dipole antenna for RFID element 2 for UHF applications. Terminals T1 and T2 may also be included in antenna 204 to couple to RFID chip 208 such that electric field E excites the antenna of reader 152.

In one embodiment, security tag 200 may also include a cover or spacer material 210 that is applied to the top of the fabricated security tag. As with the backplane 202, the cover or spacer material 210 may also affect the RF performance of the RFID element 2. For example, the cover material 210 may be implemented using a surface material (cover stock material) having a dielectric constant of about 3.8 and a loss tangent of about 0.115. The embodiments are not limited in this context.

More particularly, as previously described, the substantially planar spacers 210 have a thickness "t". The thickness "t" is typically about 1mm to 2mm when security tag 200 is a hard combination tag, and is substantially less than 1mm when security tag 200 is a combination tag. As previously described, the spacer 210 has surfaces or surface regions 210a and 210b on opposite sides thereof. In one embodiment, the spacer surfaces or surface regions 210a and 210b are parallel to each other. The EAS element 1 at least partially overlaps at least one of the spacer surfaces or surface regions 210a and 210 b.

An RFID interposer is a common term in the art and is defined herein as an RFID element 2 that includes a combination of a backplane 202, an antenna 204, a lead frame 206 (if any), and an RFID chip 208. The RFID element 2 at least partially overlaps another one of the spacer surfaces 210 b. Security tag 200 includes an RFID insert or element 2 and a spacer 210.

Security tag 200 may also include antenna 204. Antenna 204 may represent, for example, antenna 112 of RFID device 106, or antenna 204 may be formed from a parallel resonant LC circuit, where L is inductance and C is capacitance. Alternatively, antenna 204 may be a tunable antenna that is tuned to the carrier signal such that the voltage across the antenna circuit is maximized. As can be appreciated, this will increase the read range of antenna 204. The degree of accuracy of the tuning circuit is known to be related to the spectral width of the carrier signal transmitted by the transmitter 102. For example, in the United states, the Federal Communications Commission (FCC) currently regulates one band of the RFID security tag spectrum to 915 MHz. Thus, the transmitter 102 should transmit the interrogation signal 104 at about 915 MHz. To receive interrogation signals 104, antenna 204 should be narrowly tuned to the 915MHz signal. For 915MHz applications, RFID tag antenna 204 may be printed, etched, or plated.

The EAS marker 1 creates or exhibits a constant load impedance to the RFID element 2. As a result, the antenna 204 of the RFID tag 200 uses the constant load of the EAS tag 1 for impedance matching. More particularly, the antenna 204 has a complex impedance and the EAS element 1 forms a portion of an impedance matching network of the antenna. Thus, the impedance of antenna 204 includes the loading effect of EAS element 1. That is, the loading effect of the EAS element 1 is a constant load impedance of the EAS element 1. The loading effect of the EAS element 1 may be altered by replacing or substituting one material with another having a dielectric constant and loss tangent with another material having a dielectric constant and loss tangent that is contained in the EAS element 1.

The RFID component chip 208 may be represented as an equivalent series RC circuit, where R represents a resistance and C represents a capacitance. The circuit consists of a complex impedance Z_chipExpressed as:

Z_chip＝Z₁-jZ₂，

wherein Z₁And Z₂The real and imaginary parts of the impedance of the chip 208. The RFID device tag or label antenna 204 may use a complex impedance Z_antennaIs represented as:

Z_antenna＝Z₃+jZ₄ (1)

where Z3 and Z4 are the real and imaginary parts of the impedance of antenna 204. When chip 208 is mounted on antenna 204, the complex impedance of chip 208 matches the coupling conjugate impedance of RFID antenna 204, including the impedance matching effect or loading effect of EAS component or marker 1. This allows maximum power to be coupled to RFID chip 208, which results in a maximum read range R1.

In one embodiment, the thickness "t" of spacer 210 may be varied relative to RFID reader device 102 or relative to RFID reader device 152 to vary the read range R1, respectively. More particularly, thickness "t" determines the read range, i.e., the maximum distance R1 between security tag 200 and EAS/RFID reader 102 or EAS/RFID reader 152 at which reader 102 or 152 can interrogate security tag 200. The read range R1 is adversely affected as the thickness "t" decreases. Conversely, the read range R1 increases with increasing thickness "t".

Referring to fig. 4 and 4A, fig. 4A shows actual data 41 and curve fit data 42, respectively, corresponding to a security tag, such as security tag 200, comprised of an EAS unit, such as EAS element 1, and an RFID unit, such as RFID element 2, within a hard tag housing (such as housing 812 in fig. 8D or housing 818 in fig. 8F, as described below). Spacer 210 is placed between EAS element 1 and RFID element 2 and may be formed of a low loss, low dielectric material or an air gap. In the particular case of the data shown in fig. 4A, the spacers 210 are air gaps. The y-axis shows the read range R1 in meters (m), while the x-axis shows the thickness "t" of a spacer, such as spacer 210, in millimeters (mm). Actual data 41 and curve fit data 42 show that the read range R1 is substantially constant, about 1.8 meters, as the thickness "t" of the spacer is increased to 20mm or greater. As the thickness "t" of the spacer is reduced to a value of about 3mm, the read range R1 is reduced to about 1 meter. The read range R1 continues to decrease as the spacer thickness "t" decreases because losses in the EAS element 1 become greater with decreasing spacer thickness "t".

As previously described with respect to fig. 4, in the combination EAS and RFID tag or label 200, the EAS element 1 and the RFID element 2 at least partially overlap, and the EAS element 1 is a portion of the impedance of the RFID antenna 204. In addition, referring to fig. 3A, 3B, and 4, spacer 210, corresponding to thickness "t", located between RFID element 2 and EAS element 1 may be used to determine a read range R1 of RFID element 2 from RFID reader 102. Further, the thickness "t" may be varied to establish a read range R1 at various preferred levels depending on the particular application. Thus, spacer 210 and corresponding thickness "t" define a read range R1 and function as a control unit for the combination EAS and RFID tag or label 200, or in other words, the thickness "t" of spacer 210 is configurable to adjust the read range R1 between RFID reader 102 and RFID element 2.

Since the data presented in fig. 4A is specific to the case where spacer 210 is an air gap, it can be appreciated that the relationship between read range R1 and spacer 210 thickness "t" may differ for the case of other low loss, low dielectric materials selected for spacer 210.

It should be noted that the reader 102 for HF applications and the reader 152 for UHF only read either the EAS element 1 or the RFID element 2 so that the EAS element 1 is read by a dedicated EAS reader and the RFID element 2 is read by a dedicated RFID reader. Alternatively, reader 102 and reader 152 may be combined into the same housing, or their functions integrated to be performed by the same hardware. Because of the large difference between the read frequency range common to EAS elements, which are typically read in a frequency range less than or equal to 8.2KHz, relative to the read frequency range common to RFID elements, which are typically read in a frequency range of 13KHz or greater, undesirable interference between the reading of EAS element 1 and the reading of RFID element 2 is avoided or minimized.

However, it can be seen that since security tags 200 and 400 are stand-alone devices, security tags 200 and 400 provide both EAS functionality and RFID functionality regardless of the type of reader or the reader or specific frequency at which security tag 200 or 400 is located.

The spacer 210 is manufactured by Emerson cutting Microwave Products of Randolph, MassLow loss, low dielectric material of rigid foam or any other similar material. The embodiments are not limited in this context. When made of one of the above materials, the read range is about 30.5 to 61.0cm (1 to 2 feet) when the thickness "t" of the spacer 902 is about 0.0762mm (0.003 inches). Similarly, when the thickness "t" of the spacer 210 is at least 1.02mm (0.040 inches), the read range is about 127cm (5 feet).

In one embodiment, spacer 210 may be a film having a thickness "t" of about 0.05mm, where EAS element 1 directly overlaps RFID element 2.

In one embodiment, the spacer may be air, with the EAS marker 1 mechanically supported, spaced from the RFID element 2.

As a result, security tag 200 provides significant advantages over the prior art by providing a combination EAS/RFID device having significantly lower space or volume and lower cost.

In one embodiment, security tag 200 may operate using an induced voltage from a coil antenna. This induced AC voltage may be rectified to a DC voltage. When the DC voltage reaches a certain level, the RFID element 2 starts operating. By providing an energizing RF signal via transmitter 102, RFID reader 102 may communicate with a remotely located security tag 200 that does not have an external power source, such as a power source.

Since the excitation and communication between the RFID reader and RFID element 2 is accomplished through antenna 204, antenna 204 may be tuned for improved RFID applications. RF signals can be efficiently transmitted or received if the wire size of the antenna is comparable to the wavelength of the operating frequency. However, the line size may be larger than the surface area available for antenna 204. Thus, it may be difficult to use a truly full-size antenna in a limited space, as is the case with RFID systems in most HF applications. Thus, it is contemplated that RFID element 2 may use a smaller LC loop antenna circuit configured to resonate at a given operating frequency. The LC loop antenna may include, for example, a spiral coil and a capacitor. Spiral coils are typically formed from n turns of wire or n turns of printed or etched inductor coils on a dielectric substrate.

For HF applications, loop area turn products and resonant frequencies need to be optimized in order to achieve good RFID coupling. In one embodiment of the present invention shown in FIG. 3A, the resonant frequency may be affected by tuning the parallel capacitance C2 of the resonant circuit 112, including the impedance of EAS tag 1 and RFID chip 208.

In HF or UHF applications, the RFID chip complex impedance must match the complex conjugate impedance of the antenna for the particular frequency of interest, including the loading effect on the EAS marker's impedance. In the case of HF, a resonant capacitor is typically used to tune the frequency. This capacitance is typically larger than the capacitance of the RFID chip and dominates the response. In the case of UHF, the complex impedance of the RFID chip contains only the chip capacitance for tuning.

In another embodiment in accordance with the invention, antenna 204 may be designed such that the complex conjugate impedance of the entire antenna matches the complex impedance of lead frame 206 and IC 208 at a desired operating frequency, e.g., a frequency of 915 MHz. However, when RFID security tag 200 is placed on an object being monitored, it has been found that the resulting operating frequency may change, i.e., the dielectric properties of the substrate material of each object may affect the RF performance of antenna 204. In other words, as with backplane 202, the target backplane may cause frequency shifts and RF losses that are determined by the dielectric constant, loss tangent, and material thickness. The different target base panels may for example comprise what is known as "chip board" (i.e. material for product-level cartons, corrugated cardboard as material for corrugated cartons), video tape and Digital Versatile Disc (DVD) boxes, glass, metal, etc. It is expected that each target substrate may have a significant impact on the read range R1 of security tag 200.

Antenna 204 may be tunable to compensate for such variations. In other words, since many materials have dielectric constants greater than 1, the operating frequency tends to decrease when the operating tag 200 is attached to a target substrate. To establish the original frequency, the antenna 204 is typically altered in some way, otherwise detection performance and read range may be degraded. Likewise, antenna 204 may be modified by trimming the ends of antenna 204, cutting the antenna wire, and separating the resulting trimmed antenna segments from the cut ends. The trimmed tip does not have to be removed to allow for the tuning operation. Thus, it is possible to continuously tune antenna 204 to a desired operating frequency, allowing security tag 200 to operate when security tag 200 is attached to a different target. Security tag 200 is described in greater detail below with reference to fig. 5-7, both in its entirety and specifically with respect to antenna 204.

FIG. 5 illustrates a top view of a portion of a security tag 200 with an antenna, which is particularly suited for UHF applications, in accordance with one embodiment of the present invention. Security tag 200 includes an antenna 204 disposed on a substantially rectangular substrate 202. In one contemplated embodiment, antenna 204 is disposed on backplane 202 by die cutting the logo antenna pattern onto backplane 202.

RFID chip 208 may be connected to lead frame 206 by ultrasonically bonding lead frame 206 to conductive pads on RFID chip 208. In the particular embodiment of fig. 5, RFID chip 208 and lead frame 206 are placed at the geometric center of the dielectric backplane material of backplane 202. The ends of lead frame 206 are mechanically and electrically bonded to the thin film antenna pattern of antenna 204. A cover material (not shown) may be applied to the entire top surface of security tag 200 to protect the components and provide a surface to print indicia when desired. It is known in the art to use an anisotropically electrically conductive thermal mount adhesive to adhere RFID chip 208 to antenna 204. An example of such an adhesive is Loctite manufactured by Henkel Loctite of Rocky Hill, Connecticut. Antenna 204 may also include multiple antenna portions. For example, antenna 204 may include a first antenna portion 306 and a second antenna portion 308, first antenna portion 306 being coupled to first side 206A of lead frame 206 and second antenna portion 308 being coupled to second side 206B of lead frame 206. Thus, antenna 204 is an entire RFID tag antenna that is divided to include first antenna portion 306 and second antenna portion 308.

The first antenna portion 306 may have a first antenna end 306A and a second antenna end 306B. Similarly, second antenna portion 308 may have a first antenna end 308A and a second antenna end 308B. In one embodiment, as shown in fig. 5, first antenna end 306A of first antenna portion 306 is connected to lead frame 206A. First antenna portion 306 is disposed on chassis 202 to form an inner spiral pattern in a first direction from RFID chip 208, and second antenna end 306B is positioned to terminate on an inner loop of the inner spiral pattern. Similarly, first antenna end 308A of second antenna portion 308 may be connected to lead frame 206B. Second antenna portion 308 is also disposed on backplane 202 to form an inner spiral pattern in a second direction from RFID chip 208, and second antenna end 306B is disposed to terminate on an inner loop of the inner spiral pattern.

In one embodiment, the antenna geometry of antenna 204 is configured to traverse the perimeter of backplane 202 and spiral inward. It can be seen that an inwardly spiraling antenna pattern can provide several advantages:

(1) the ends of antenna 204 may be well positioned within the perimeter of backplane 202. Placing the ends of antenna 204 within the perimeter of backplane 202 may allow the ends to be trimmed without changing the area occupied by antenna 204;

(2) the Q factor of antenna 204 may be optimized such that the response of security tag 200, including the effects of spacer 210 and EAS marker 1, only changes by about-3 dB at the ISM band limit. Using the Chu-Harrington constraint, Q1/(ka) 3+1/(ka), where k 2 pi/λ, "a" is the characteristic dimension of antenna 204, it can be seen that a sphere of radius "a" can just surround security tag 200. For high Q-factors, "ka" should be < 1. Thus, by maximizing Q, "a" is minimized to fall within the operating frequency band limits. For UHF applications, the tuning of ANTENNA 204 is disclosed in more detail in co-pending, co-owned U.S. patent application serial No. 10/917752 entitled "TUNABLE ANTENNA", filed on 13.8.2004 by r.copeland and g.m. shamer, the entire contents of which are incorporated herein by reference.

Particularly for UHF applications, antenna 204 may also be tuned to a desired operating frequency by changing the first length of first antenna portion 306 and the second length of second antenna portion 308 after these antenna portions are disposed on backplane 202. For example, each antenna portion may be divided into a plurality of antenna segments at a plurality of segmentation points. The first and second antenna lengths may be changed by electrically disconnecting at least the first antenna segment from the second antenna segment. The antenna length may be modified by cutting individual antenna portions at one of a plurality of segment points, each segment point corresponding to an operating frequency of antenna 204. Dividing first antenna portion 306 and second antenna portion 308 into multiple antenna segments may result in a reduction in the length of the respective antenna portions, effectively changing the overall inductance of antenna 204. The antenna segments and segments will be described in more detail with reference to fig. 6.

FIG. 6 illustrates a view of a security tag 400 with an antenna having segmented points, according to one embodiment. In particular, FIG. 6 shows a top view of portions of security tag 400 with a plurality of segmentation points SP1, SP2, SP3, and SP 4. In a similar manner as in fig. 4 with respect to security tag 200, security tag 400 may include an EAS element 1, a spacer 210, and an RFID element 2. Antenna 204 may also be tuned to a desired operating frequency after antenna portions 306 are disposed on backplane 202 by changing a first length of first antenna portion 306 and a second length of second antenna portion 308. For example, it is contemplated that each antenna portion may be divided into a plurality of antenna segments at a plurality of segmentation points SP1-SP 4. The plurality of segmentation points SP1 through SP4 represent end tuning positions where antenna 204 may be cut or clipped to tune various targets. SP1 is the open space position where the length of the original open space antenna 204 was tuned to 868 MHz. SP2 is the open space position where the lengths of antenna portions 306 and 308 are tuned to 915 MHz. SP3 and SP4 are open space positions where the lengths of antenna portions 306 and 308 tune to various targets. The various targets include, for example, but not limited to, retail and/or wholesale goods.

The lengths of the first and second antennas may be changed by electrically disconnecting at least the first antenna segment from the second antenna segment. The antenna length may be modified by cutting individual antenna portions at one of a plurality of segment points, each segment corresponding to an operating frequency of antenna 204. The severing may be achieved in several different ways, such as cutting or punching out the antenna track at a given segmentation point SP1-SP 4. The cutting may produce slots, such as slots 402, 404, 406, 408, 410, and 412, at the segmentation points.

It is noted that for HF applications, antenna 204 can be tuned by changing the inductance or capacitance parameters, rather than the length of the segments.

In one embodiment, as shown in FIG. 6, each of segmentation points SP1-SP4 corresponds to one operating frequency of antenna 204. In one example, SP1 may tune antenna 204 for an operating frequency of approximately 868MHz when security tag 400 is located in open space and not attached to a target. SP2 may tune antenna 204 for an operating frequency of approximately 915MHz when security tag 400 is located in open space and not attached to a target. SP3 may tune antenna 204 to an operating frequency of approximately 915MHz when security tag 400 is attached to a VHS cassette housing. SP4 may tune antenna 204 for an operating frequency of approximately 915MHz when security tag 400 is attached to chipboard. It will be appreciated that the number of segmentation points and the corresponding operating frequency of antenna 204 may vary according to a given implementation. The embodiments are not limited in this context.

Fig. 7 shows a block flow diagram 500 according to another embodiment of the invention. As previously described, security tag 200 may be configured in several ways. For example: 1) the integrated circuit may be connected to a leadframe at block 502; 2) the antenna may be placed on the backplane at block 504; 3) the lead frame may be connected to an antenna at block 506.

In a particular embodiment, the antenna is tuned to be used at the operating frequency at block 508. The tuning may be achieved by cutting the antenna into a plurality of antenna segments at segmented points corresponding to the operating frequencies, thereby changing the length of the antenna. The cut may electrically separate the first antenna segment from the second antenna segment, thereby effectively shortening the antenna length.

As described above, the unique antenna geometry of the inner spiral pattern may be useful for RFID applications when connected to an RFID chip. However, as previously mentioned, the unique antenna geometries shown in fig. 5 and 6 may also be useful for EAS systems where the security tag 200 and security tag 400 include an EAS element 1 and spacer 210, respectively. In one embodiment, RFID chip 208 may be replaced with a diode or other non-linear passive device whose voltage and current characteristics are non-linear. The antenna for the diode or other passive nonlinear EAS device may have the same geometry as shown in fig. 5 and 6 and may be tailored to tune the antenna to the operating frequency of the transmitter for transmitting interrogation signals for the EAS system. Similar to RFID system 100, the range of operating frequencies may vary, although the described embodiments may be particularly useful for the UHF spectrum, such as 868-950 MHz. The embodiments are not limited in this context.

As previously described with respect to fig. 3A, 3B, 4 and 4A, the read range R1 of the combination EAS and RFID tag or label 200 may be measured, controlled and varied by varying the thickness "t" of the spacer 210. In a similar manner, the read range R1 of security tag 400 may also be measured, controlled, and varied by varying the thickness "t" of spacer 210.

It is also contemplated that some embodiments of the invention may be configured using architectures that differ according to any number of factors, such as: 1) a desired calculation rate; 2) a power level; 3) heat resistance; 4) a processing cycle budget; 5) a data input rate; 6) a data output rate; 7) a storage resource; 8) data bus speed and other performance constraints. For example, embodiments may be configured using software executed by a general-purpose or special-purpose processor. In another example, an embodiment may be configured as dedicated hardware, such as a circuit, an ASIC, a Programmable Logic Device (PLD), or a Digital Signal Processor (DSP). In another example, an embodiment may be configured by any combination of programmed general-purpose computer components and custom hardware components. The embodiments are not limited in this context.

Examples of security tags 200 and 400, i.e., combination EAS and RFID tags/labels, are shown in FIGS. 8A through 8D, which illustrate various types of adhesive magnetostrictive labels and tagsEAS hard tags, e.g. produced by Sensormatic corporationIt is a division of Tyco Fire and Security, Inc. of Boca Raton, Florida. FIG. 8A shows EAS marker 804 adjacent to RFID marker 806 in a co-planar configuration. The adjacent flag 804 and 806 configurations are known in the art. FIG. 8B shows a variation of the co-planar configuration of the EAS tag 804 and the RFID tag 806 of FIG. 8A, wherein the EAS tag 804 and the RFID tag 806 are separated from each other by a gap 805 having a distance "g". Such a configuration where 804 and 806 are separated by a gap 805 is also known in the art.

In the configuration of fig. 8A and 8B, the EAS marker 804 and the RFID marker 806 operate independently of each other in impedance value matching. As "g" increases, the read range increases. As a result, the size of the gap "g" controls the impedance load. However, this is not a desirable effect because although the read range is increased, the total area occupied by the EAS marker 804 and the RFID marker 806 is also increased, requiring more space or area to be occupied on the object to be identified.

Fig. 8C illustrates one embodiment of a security tag 200 or 400 of the present invention showing an EAS element or marker 1. An RFID element or insert 2 is mounted directly beneath the EAS element or marker 1. A dummy (dummy) barcode 802 is printed on the EAS element or marker 1 and is used for visual purposes only. The virtual barcode 802 does not have EAS or RFID functionality. In contrast to the prior art, the configuration of security tag 200 or 400 as an EAS element or marker or combination of tag 1 and RFID element or insert 2, mounted directly beneath EAS element or marker 1 (as shown in fig. 4), provides minimal isolation between the RFID element or insert 2 and the EAS marker 1.

FIG. 8D shows a portion 812 of the housing of one embodiment of the present invention, namely the combination of the EAS element or marker 1 and the RFID element or insert 2. An RFID element or package 2 is defined to include an RFID chip 208 mounted on an antenna 204. However, the spacers 210 or adhesive layer are not visible (see fig. 4).

Fig. 8E is a front view of the combination EAS element or marker 1 and RFID element or insert 2 disclosed in fig. 8D, but showing spacer 210 placed between the EAS element or marker 1 and the RFID element or insert 2.

FIG. 8E shows a portion 818 of a housing of one embodiment of the invention, namely an EAS tag 816 similar to EAS element or tag 1 in combination with an RFID insert 814 similar to RFID element or insert 2. The RFID interposer 814 is defined as another RFID chip 820 mounted on the antenna 204. Also, the spacers 210 or adhesive layer are not visible (see fig. 4).

Fig. 8G is a front view of the combination EAS marker 816 and RFID insert 814 disclosed in fig. 8F, but showing spacer 210 positioned between EAS marker 816 and RFID insert 814.

The type of EAS device and RFID combination is not limited to the EAS and RFID devices described herein.

It is also envisioned that not only is the thickness of the spacer configurable to vary the effective read range of the RFID element of the combination EAS/RFID tag, but it is also envisioned that varying the thickness or shape of the spacer may affect the read range of the RFID element. In addition, it is also contemplated that the spacer disposed between the EAS and RFID elements may be made of a variety of different low loss, low dielectric materials that may be aligned on the surface to affect the read range of one or both of the EAS and RFID elements. It is also contemplated that the type of spacer material may vary the read range of the EAS element and the RFID element. Still further, it is contemplated that the spacer(s) may be configured in different geometric configurations or patterns, with different or varying dimensions (i.e., length, width, thickness, etc.), to affect the read range, or to further adjust the read range of one or both of the EAS and RFID elements, depending on the particular purpose.

While certain features of the described embodiments have been illustrated as described herein, many modifications, substitutions, changes and equivalents will now occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the embodiments.

Claims (8)

1. A security tag, comprising:

an Electronic Article Surveillance (EAS) element having a defined surface area;

a radio frequency RFID element having a defined surface area, the defined surface area of the EAS element configured to at least partially overlap the defined surface area of the RFID element; and

a substantially planar spacer having a thickness, the thickness of the spacer defining a read range between an RFID reader and an RFID element, the spacer being at least partially disposed between a defined surface area of the EAS element and a defined surface area of the RFID element;

wherein the RFID reader is capable of activating the RFID element when the RFID element is within the read range;

wherein the RFID element includes an antenna at least partially overlapping a prescribed surface area of the EAS element, the antenna has a complex impedance, and the EAS element forms part of an impedance matching network of the antenna;

wherein the RFID element comprises an Application Specific Integrated Circuit (ASIC); and is

Wherein a complex impedance of the ASIC matches a coupled complex conjugate impedance of the antenna that includes loading effects of the EAS element.

2. The security tag according to claim 1, wherein said RFID element comprises a substrate portion, and wherein the material of said substrate portion is selected from the group consisting of (a) base paper, (b) polyethylene, (c) polyester, (d) polyethylene terephthalate PET, and (e) polyetherimide PEI.

3. The security tag of claim 1, wherein said RFID element comprises a substrate portion, and wherein the material of said substrate portion is a plastic having a dielectric constant of about 3.3 and a loss tangent of less than 0.01.

4. The security tag according to claim 1, wherein the material of said spacer is selected from the group consisting of (a) low loss, low dielectric materials; and (b) air.

5. A method of adjusting the read range of a combination Electronic Article Surveillance (EAS) element and Radio Frequency Identification (RFID) element, the method comprising the steps of:

providing a spacer positioned between the EAS element and the RFID element; and

adjusting a read range of the RFID element by varying a thickness of the spacer;

wherein the RFID reader is capable of activating the RFID element when the RFID element is within the read range;

wherein the RFID element includes an antenna at least partially overlapping a prescribed surface area of the EAS element, the antenna has a complex impedance, and the EAS element forms part of an impedance matching network of the antenna;

wherein the RFID element comprises an Application Specific Integrated Circuit (ASIC); and is

Wherein a complex impedance of the ASIC matches a coupled complex conjugate impedance of the antenna that includes loading effects of the EAS element.

6. The method of claim 5, wherein adjusting the read range of the RFID element comprises changing the read range between an RFID reader and the RFID element by changing a thickness of the spacer.

7. The method according to claim 5, wherein adjusting the read range of the RFID element includes varying an amount of overlap of a surface area of the EAS element and a surface area of the RFID element.

8. The method of claim 5, further comprising tuning an antenna of the RFID element.