HK1145366B - Combination eas and rfid label or tag using a hybrid rfid antenna - Google Patents

Description

Combination EAS and RFID tag or label using hybrid RFID antenna

Cross Reference to Related Applications

This application is a continuation-in-part application, U.S. national phase application serial No. 11/667,743 entitled "COMBINATION EASAND RFID LABEL OR" filed on 14/5/2007, based on PCT application No. PCT/US2005/041573 entitled "COMBINATION EAS AND RFID LABEL OR TAG" filed on 15/11/2005, which relates to and claims priority of U.S. provisional application serial No. 60/628,303 entitled "COMBINATION EAS/RFID LABEL OR TAG" filed on 15/11/2004, the entire contents of which are incorporated herein by reference.

Technical Field

The present disclosure relates to Electronic Article Surveillance (EAS) tags or markers for preventing or deterring unauthorized removal of articles from a controlled area. More particularly, the present disclosure relates to an EAS tag or label in combination with a Radio Frequency Identification (RFID) tag or label for recording data unique to an article and a new RFID tag or label, wherein the RFID label includes an RFID hybrid antenna inlay (inlay) having a helical antenna and a magnetic loop antenna.

Background

Electronic Article Surveillance (EAS) systems for preventing or deterring unauthorized removal of articles from a controlled area are generally known in the art. In a typical EAS system, an EAS marker (tag or label) is designed to interact with an electromagnetic field located at the exit of a controlled area, such as a retail store. 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 the article, the EAS marker may be deactivated, removed, or passed around the electromagnetic field to prevent detection by the EAS system.

EAS systems typically utilize reusable EAS tags or disposable EAS tags or labels to monitor articles to prevent theft and unauthorized removal of the articles from the store. Reusable EAS tags are typically removed from merchandise before the customer leaves the store. Disposable labels or tags are typically attached to the package by an adhesive and are located on the inside of the package. These markers are typically kept with the merchandise and must be deactivated before the customer removes them from the store. The deactivation device may use a coil that is energized to generate a magnetic field of sufficient magnitude to deactivate the EAS marker. The deactivated tags no longer respond to the incident energy of the EAS system such that an alarm is not triggered.

For the case where an article having an EAS tag is to be registered or returned to the control zone, the EAS tag must be activated or reattached to again provide theft protection. Because of the desirability of source tags, where the EAS marker is applied to merchandise at the point of manufacture or sale, it is generally preferred that the EAS marker be deactivatable and activatable rather than being removed from the merchandise. In addition, passing merchandise around the interrogation zone presents other problems because the EAS marker remains active and may interact with the EAS system in other control zones where these systems are inadvertently activated (activated).

Radio Frequency Identification (RFID) systems are also generally known in the art and may be used in many applications such as managing inventory, electronic access control, security systems, and automatic identification of cars on toll roads. RFID systems generally include 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 digital signal encoded with information stored by the RFID device.

Although the use of only helical antennas has its benefits, the coupling mechanism is primarily dependent on the electric field E rather than the magnetic field H. In some cases, the overall RFID read performance is optimized for the far field and the resulting near field read performance may be limited. That is, the antenna cannot be optimized for both the far field and the near field. The near field performance depends on how the antenna is designed for the far field. For combination EAS/RFID tag applications, the helical antenna may limit the various options for near field antennas used in detachers and other POS applications where close proximity reading performance is particularly important.

The open antenna structure of the spiral antenna allows a low frequency or electrostatic field E to develop a substantial voltage across the RFID chip, and this may cause malfunction of the device if the level is high enough. Such ESD (electrostatic discharge) can occur during label manufacturing or ultrasonic welding of hard tag frames (housing).

A market need to incorporate EAS and RFID functionality in a retail environment is rapidly emerging. Many retail stores that now have EAS for theft protection rely on inventory-controlled bar code information. RFID provides faster and more detailed inventory control of bar codes. The retail outlet has paid a considerable amount of money for the reusable hard tag. Adding RFID technology to EAS hard tags can easily afford increased costs due to increased productivity in inventory control and loss prevention.

What is needed, therefore, is an RFID antenna design for use in an EAS/RFID interrogation system that increases near field read performance without sacrificing far field read performance, while at the same time reducing the likelihood of chip failure due to the accumulation of electrostatic discharge.

Disclosure of Invention

The present invention advantageously provides a tag or label that combines the features of a separate EAS tag or label and a separate RFID tag or label in one tag or label.

More particularly, the present disclosure relates to a security tag that includes an EAS component having a defined surface area and an RFID component having a defined surface area. The defined surface area of the EAS component is configured to at least partially overlap the defined surface area of the RFID component.

The present disclosure provides a security tag that includes an EAS component having a defined surface area and an RFID component having a defined surface area. The surface area of the EAS component is configured to at least partially overlap the surface area of the RFID component. The RFID component includes an antenna that at least partially overlaps the first surface. A substantially planar spacer having a thickness is disposed at least partially between the defined surface areas of the EAS and RFID components. The RFID component read range is affected and controlled by the spacing between the RFID element and the EAS element. The RFID reader can activate the RFID component when the RFID component is within the read range. The antenna includes a magnetic loop antenna coupled to a helical antenna to increase the near-field read response.

The RFID component includes an antenna, and the antenna may at least partially overlap a defined surface area of the EAS component. A substantially planar spacer having a thickness is disposed at least partially between the defined surface area of the EAS component and the defined surface area of the RFID component. The thickness of the spacer determines a read range between the RFID reader and the RFID component, and the RFID reader is capable of activating the RFID component when the RFID component is within the read range. The antenna and the EAS component may form part of an impedance matching network of the antenna. The antenna impedance may include loading effects of the EAS component. The RFID component may include an antenna and an Application Specific Integrated Circuit (ASIC). The ASIC may have a complex impedance. The complex impedance of the ASIC may match a coupled complex conjugate impedance of the antenna including loading effects of the EAS component. The material of the bottom portion of the RFID component may be selected from the group consisting of: (a) base paper; (b) polyethylene; (c) a polyester; (d) polyethylene terephthalate (PET); and (e) Polyetherimide (PEI). The bottom portion material may be a plastic having a dielectric constant of about 3.3 and a loss tangent of less than about 0.01. The separator material may be selected from the group consisting of: (a) a low loss, low dielectric material and (b) air.

The present invention also relates to a method of operating a combination Electronic Article Surveillance (EAS) component and Radio Frequency Identification (RFID) component. The method includes the step of moving the RFID component to be overlapped by the EAS component to change the impedance of an antenna coupled to the RFID component. The impedance of the antenna includes loading effects of the EAS component. The antenna may include an antenna conductor and the antenna is tuned by severing the antenna conductor into at least two segments such that at least one segmentation point corresponds to an operating frequency of the antenna according to the length of the at least two antenna segments and isolating the severed antenna conductor from the remainder of the conductor.

The method may also include a combination of an Electronic Article Surveillance (EAS) component and a Radio Frequency Identification (RFID) component having a spacer disposed therebetween, the spacer having a thickness, and the method may include the step of varying the thickness of the spacer. The step of varying the thickness of the spacer may vary a read range between the RFID reader and the RFID component, and wherein the RFID reader is capable of activating the RFID component when the RFID component is within the read range.

In another embodiment, a security tag is provided, wherein the tag includes an Electronic Article Surveillance (EAS) component having a first defined surface area and a Radio Frequency (RFID) component having a second defined surface area. The RFID component includes a hybrid antenna inlay having an inward spiral antenna, a magnetic loop antenna in electrical contact with the spiral antenna, and an integrated circuit in electrical contact with the magnetic loop antenna.

In yet another embodiment, an RFID antenna inlay for use with a combination EAS/RFID security tag is provided. The antenna inlay includes an inward spiral antenna having a first portion and a second portion, a magnetic loop antenna in electrical contact with the spiral antenna and positioned between the first portion of the spiral antenna and the second portion of the spiral antenna, and an integrated circuit in electrical contact with the magnetic loop antenna.

In yet another embodiment, a method for providing an enhanced read response for a security tag is provided. The method includes providing an Electronic Article Surveillance (EAS) component having a first defined surface area, and positioning a Radio Frequency (RFID) component having a second defined surface area to at least partially overlap the EAS component. The RFID component includes a hybrid antenna inlay, where the antenna inlay includes an inward spiral antenna, a magnetic loop antenna in electrical contact with the spiral antenna, and an integrated circuit in electrical contact with the magnetic loop antenna.

Drawings

The subject matter regarded as the embodiments is particularly pointed out and distinctly claimed in the concluding portion of the specification. The embodiments, 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 disclosure;

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

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

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

FIG. 3B illustrates an RFID system using electric field coupling according to one embodiment of the present disclosure;

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

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

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

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

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

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

FIG. 8C illustrates an embodiment of the present disclosure of a combination EAS component with an RFID component mounted directly below the EAS component;

FIG. 8D illustrates an embodiment of the present disclosure of a portion of a security tag combination EAS component with an RFID component inserted;

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

FIG. 8F illustrates an embodiment of the present disclosure of a portion of a security tag combination EAS component with an RFID component inserted;

FIG. 8G is a front view of the embodiment of the present disclosure of FIG. 8F;

FIG. 9 illustrates an embodiment of the present disclosure of a combination EAS/RFID tag with a hybrid antenna inlay using a loop antenna between two inward spiral antennas;

FIG. 9A shows sample test data for the read range of a security tag having the hybrid antenna inlay of FIG. 9 as a function of the thickness of the spacer (spacer) between the EAS and RFID components of the security tag; and

fig. 9B illustrates the hybrid antenna inlay embodiment of fig. 9 with corresponding response regions for the loop and spiral antennas.

Detailed Description

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

Numerous specific details may be set forth herein to provide a thorough understanding of many possible embodiments of a combination EAS/RFID tag embodying the present disclosure. However, it will be understood by those skilled in the art 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 terms "coupled" and "connected," along with their derivatives. For example, some embodiments may be described using 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 be described using 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. The embodiments disclosed herein are not necessarily limited in this context.

It is worthy to note that any reference in the 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 disclosure, one way in which a combination EAS/RFID tag (or label) may be utilized is to place EAS-related components and REID-related components together and package them together. However, there may be some electronic or electromechanical interaction factors that may affect the performance of either the EAS functionality and/or the RFID functionality. Placing the RFID tag on top of the EAS tag is the most convenient method, but can result in considerable detuning and signal loss for the RFID tag. For example, in a typical RFID device, the performance of the RFID tag is typically very sensitive to impedance matching of the Application Specific Integrated Circuit (ASIC)/lead frame assembly of the RFID device to the effective impedance of the RFID antenna mounted on the substrate. A more detailed description of some possible embodiments of the RFID portion of the device is discussed further below. Other objects around the RFID tag may contribute to the effective impedance or absorption of electromagnetic energy for reading the RFID tag.

Some existing 2450MHz EAS/RFID combination tags use a configuration in which the RFID tag and the EAS tag are placed in an overlapping configuration. There may be considerable degradation in RFID tag detection using this particular application. While end-to-end or slight overlap works best in such systems, the mark size tends to become prohibitively large in these instances. In addition, it is known that the side-by-side arrangement produces an irregular RFID detection pattern. There are not many designs that can successfully implement a combination EAS/RFID tag in a store. Most applications using combinations of EAS and RFID for tagged items use separate EAS and RFID tags that are separately mounted so that they occupy a considerable amount of space on the tagged item compared to the space that would be occupied separately if mounted separately.

It is envisioned that a solution to this problem is to use the EAS tag portion of the combination marker as part of the impedance matching network of the RFID tag. For example, as RFID tags are placed closer and closer to EAS tags, the RFID tag antenna impedance is affected or adjusted by the EAS tags. To achieve RFID tag impedance matching, the RFID antenna geometry itself may be designed to account for any resulting electrical effect of the EAS tag on impedance. For example, an RFID antenna may be configured with a highly capacitive impedance, and it may be significantly mismatched to the impedance of the logic chip of the device (e.g., the ASIC/leadframe assembly mentioned above). When the RFID tag is placed in proximity to the EAS tag, e.g., directly underneath, the impedance of the RFID antenna nearly matches the ASIC impedance.

FIG. 1 generally illustrates an EAS component 1 and an RFID component 2. The EAS component 1 is an EAS tag or label. The EAS component 1 may include, for example but not limited to, a magnetic resonance element and a magnetic bias (or other EAS type resonant circuit) included within a housing of plastic or some other material. Other EAS tags or markers not specifically disclosed herein may perform the functions of the EAS component 1. The RFID component 2 is an RFID tag or label. For example and without limitation, and for purposes of the discussion of FIG. 1, RFID component 2 may include an antenna mounted on a substrate material to which an ASIC-based RFID logic circuit or processing chip is connected, as best shown in FIG. 4 discussed below. Other RFID tags or labels not specifically disclosed herein may perform the functions of RFID component 2. In one particularly useful embodiment, the RFID portion of the system, RFID unit 2, operates in the 868MHz and/or 915MHz ISM bands. However, one of ordinary skill in the art will readily recognize that the present invention is not so limited and may be used at any other available frequency.

When the EAS component 1 and the RFID component 2 are disposed adjacent to each other as shown in position "P1" of FIG. 1, there is only a small effect of the EAS component 1 on the antenna impedance of the RFID component 2. However, as shown at positions "P2", "P3", and "P4", the RFID antenna impedance is progressively affected when RFID component 2 is positioned beneath EAS component 1, i.e., by the degree of overlap shown by shaded region 3.

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

P1-EAS component 1 and RFID component 2 are disposed adjacent to each other;

P2-RFID component 2 is disposed at a distance 1/4 across EAS component 1 and below EAS component 1;

P3-RFID component 2 is disposed at a distance 1/2 across EAS component 1 and below EAS component 1; and

p4 ═ RFID component 2 is disposed directly beneath EAS component 1.

For example, fig. 2A and 2B show test results of real and imaginary components of RFID antenna impedance versus frequency over the 915mhz ish frequency band for a sample security tag including EAS component 1 and RFID component 2.

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

The RFID component 2 may be designed such that the antenna impedance is approximately the complex conjugate of the ASIC device. This results in resonance at the target frequency, e.g. 915 MHz. A typical test result for the impedance of an ASIC RFID device is 5-j 140 ohms for a chip manufactured by ST microelectronics of geneva, switzerland with a lead frame used in this example, and 20-j 270 ohms for a chip manufactured by Koninklikje Philips Electronics n.v. of amsterdam, the netherlands. For both RFID devices, the RFID tag antenna imaginary impedance Z must 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 using the impedance of the EAS component for matching purposes. In free space, the RFID component antenna may be designed with a negative imaginary impedance and obtain the proper imaginary impedance when placed directly under, on top of, or near the EAS component. As can be appreciated by the present disclosure, this configuration can be used with any type of EAS tag or label, such as various types of adhesive magnetostrictive labels and EAS hard labels, such as SuperTag manufactured by Sensormatic corporation-Tyco Fire and Security division of the BocaRaton LLC of FloridaEAThe type of S device is not limited to these specific examples.

The RFID component 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 embodiments may be particularly useful for Ultra High Frequency (UHF) spectrum. Depending on the application and the size of the area available for the antenna, the antenna may be tuned within a few hundred megahertz (MHz) or more, such as 868-950 MHz. For example, in one embodiment, the tunable antenna may be tuned to operate within an RFID operating frequency, such as the 868MHz band used in Europe, the 915MHz Industrial, scientific, and medical (ISM) band used in the United states, and the 950MHz band proposed for Japan. Note again that these operating frequencies are given as examples only, and the embodiments are not limited in this context.

For example, in one embodiment, the tunable antenna may have a unique antenna geometry with an inwardly spiral pattern useful for RFID applications or EAS applications. The inward spiral pattern may embed (nest) the antenna trace, bringing the trace back to the origin. This may result in an antenna that is functionally similar 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. In contrast, some embodiments may provide the same performance as a conventional half-wave dipole antenna at 915MHz operating frequency with a shorter length of about 3.81 cm. Further, the ends of the antenna traces may be modified to tune the antenna to a desired operating frequency. Because the ends of the antenna traces are inward from the perimeter of the antenna, this tuning can be accomplished without changing the geometry of the antenna.

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

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

Referring first to FIG. 4, FIG. 4 shows a side view of a security tag 200 in accordance with one particularly useful embodiment of the present disclosure. The RFID component 2 includes a base portion or substrate 202 having a first surface or surface area 202a and a second surface or surface area 202b generally on opposite sides of the base portion or substrate 202. An antenna 204 is disposed on the substrate 202. Antenna 204 has a first surface or surface area 204a and a second surface or surface area 204b that is generally on the opposite side of antenna 204. A lead frame 206 is disposed on the antenna 204, and an application specific semiconductor integrated circuit (ASIC)208 is disposed on the lead frame 206. The first and second surfaces or surface areas 202a and 202b, 204a and 204b are defined surface areas of the RFID component 2.

Security tag 200 includes a substantially planar covering material or spacer 210 disposed over RFID component 2 and an EAS component 1 disposed over spacer 210. The baffle 210 has surfaces or surface areas 210a and 210b disposed on opposite sides thereof.

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

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

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

In one embodiment, the defined surface or surface area of the RFID component 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 defined surfaces or surface areas 1a and 1b of the EAS component 1 and at least one of the defined surfaces or surface areas 202a, 202b, 204a, and 204b of the RFID component 2.

Although fig. 4 shows a limited number of elements, it may be appreciated that a greater or lesser number of elements may be used for security tag 200. For example, adhesive and release paper (release liner) may be added to the security tag 200 to facilitate attaching the security tag 200 to an object to be monitored. Those skilled in the art will recognize that semiconductor IC208 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 explained below with respect to fig. 4, security tag 200 is an RFID security tag, a tag or label that differs from the prior art by virtue of the inclusion of an EAS component, i.e., an EAS tag or label. The RFID component 2 comprises a resonant circuit 112. The resonant circuit 112 includes an inductive coil L2 with a resonant capacitor C2 connected across terminals T1 and T2 of the ASIC 208. The capacitance of ASIC 208 is typically negligible compared to C2. If additional capacitance has to be added to the resonant circuit 112 to be able to tune the antenna, i.e. the induction coil 112, to the correct frequency, a capacitor C2 is connected in parallel to the induction coil L2, so that the resonant circuit 112 becomes a parallel resonant circuit with terminals T1 and T2, an induced voltage Vi being formed across terminals T1 and T2. Terminals T1 and T2 are coupled to other portions of RFID component 2 as explained below with respect to FIG. 4. In addition, the inductance value of the induction coil or antenna L2 includes the inductance presented by the EAS tag or label.

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

RFID component 2 is a power conversion circuit that converts some of the coupled CW RF electromagnetic power of magnetic field 114 into direct current signal power used by the logic circuits of the semiconductor IC used to implement the RFID operation of RFID component 2.

RFID component 2 may also be an RFID security tag that includes memory to store RFID information and communicates the stored information in response to interrogation signals 104. The RFID information may include any type of information that can be stored in a memory used by RFID component 2. Examples of RFID information include 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 case.

The RFID component 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 volume of space bounded by a generally spherical surface having a radius R1, radius R1 generally originating from inductor L1. Radius R1 defines a detection distance or read range R1 such that if distance d1 is less than or equal to read range R1, RFID reader 102 induces a desired threshold voltage VT across terminals T1 and T2 to activate RFID component 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 component 2 may be activated by a dc voltage that is formed as a result of rectifying an incoming RF carrier signal, including interrogation signal 104. Once RFID component 2 is activated, it may then transmit the information stored in its memory register via response signal 110.

In a typical High Frequency (HF) operation, when the resonant circuit 112 of the RFID system 100 is in proximity to the tuned circuit 108 of the RFID reader 102, an Alternating Current (AC) voltage Vi is developed across terminals T1 and T2 of the parallel resonant circuit 112 of the RFID component 2. The AC voltage Vi across the resonant circuit 112 is rectified by the rectifier to a Direct Current (DC) voltage and the RFID component 2 is activated when the amplitude of the rectified voltage reaches a threshold VT. The rectifier is the aforementioned Application Specific Integrated Circuit (ASIC) 208. Once activated, RFID component 2 transmits the data stored in its storage 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 a detected serial data word bitstream of data representing information from RFID component 2.

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

Fig. 3B shows 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, by an electric field E. The UHF frequency band is considered herein to range from about 300MHz to about 3 GHz. The UHF range includes in particular frequencies within the 868MHz band, the 915MHz band and the 950MHz band.

For UHF applications, antenna 204 of RFID component 2 typically comprises a UHF open-ended dipole antenna, while RFID reader 152 typically comprises a patch antenna. The coaxial feed from reader 152 is connected to the patch antenna. The UHF antenna may be a simple half-wave dipole or patch antenna. Many popular designs use air-filled cavity-backed patch antennas that can be linearly 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 amplitude E-fields in certain vertical directions, which may be suitable for certain RFID tag orientations.

Thus, in UHF applications, antenna 204 of RFID component 2 comprises an open-ended dipole antenna, while in HF applications it is typically inductor L2.

In general, when operating in the UHF range, RFID component 2 need not include a capacitor, such as C2, in parallel with open-ended dipole antenna 204 to enable tuning to the frequency transmitted by the patch antenna of RFID reader 152.

Returning to fig. 4, as previously described, RFID component 2 may include a base portion or substrate 202 comprising any type of material suitable for mounting antenna 204, lead frame 206, and IC 208. For example, the material of the substrate 202 may include base paper (basepaper), polyethylene, polyester, polyethylene terephthalate (PET), and Polyetherimide (PEI) (e.g., ULTEM sold by General Electric Co of Verfeld, Connecticut)Amorphous thermoplastic PEI) and/or other materials. It is known that the particular material implemented for substrate 202 may affect the RF performance of security tag 200, and thus the dielectric constant and loss tangent may characterize an appropriate material for use as substrate 202The dielectric properties of the substrate material.

In general, a higher dielectric constant may cause a larger frequency shift of the antenna when compared to free space where no substrate is present. While it is possible to readjust the antenna to the original center frequency by physically changing the antenna pattern, it may be desirable to have a material with a high dielectric constant and with low dielectric losses, because the use of such a material results in smaller tag or label sizes. The term "read range" may refer to the communication operating distance between RFID reader 102 and security tag 200. Examples of the read range of security tag 200 may range from 1 to 3 meters, although embodiments are not limited in this context. The loss tangent may characterize the absorption of RF energy by a dielectric. 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 the read-out range may be reduced accordingly. Thus, it may be desirable to have the lowest possible loss tangent in substrate 202, since it cannot be "tuned out" by adjusting antenna 204. 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 substrate 202 may be configured using a base paper having a dielectric constant of about 3.3 and a loss tangent of about 0.135. The base paper may be relatively lossy at 900 MHz. The lossy material has a dielectric loss factor greater than about 0.01. In one embodiment, substrate 202 may be configured from a plastic having 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 IC208 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 for transmitting stored data to an RFID reader, a memory circuit that stores information, and logic circuits that control the overall function 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 semiconductor, Inc. of Amsterdam, Netherlands, or an XRA00RFID chip manufactured by ST microelectronics, Inc. of Geneva, Switzerland. However, the embodiment is not limited in this case.

A lead frame is a small connection that can connect an RFID chip, such as RFID chip 208, to an antenna, such as antenna 204. In one embodiment, RFID chip 208 may be bonded directly to antenna 204, without including lead frame 206. The leadframe 206 may also include a diemouting pad or flag and a plurality of lead finger feet. The wafer carrier plate is primarily used to mechanically support the wafer during package manufacturing. The lead fingers connect the die to circuitry external to the package. One end of each wire finger is typically connected to a bond pad on the die by wire bonding or tape automated bonding. The other end of each lead finger is a lead that is mechanically and electrically connected to a substrate or circuit board. The lead frame 206 may be constructed of sheet metal by stamping or etching, which is typically followed by finishing (finish), such as plating, downset (downset), and taping (taping). For example, in one embodiment, leadframe 206 may be implemented using, for example, the sensor EAS Microlabel manufactured by sensor corporation, TycoFire and Security division of Bocardon LLC of Florida^TMA lead frame. However, the embodiment is not limited in this case.

In one embodiment, antenna 204 includes an inductive coil L2 and, when desired, a capacitor C2 of resonant circuit 112 of RFID component 2. Terminals T1 and T2 are also included in antenna 204 to couple to RFID chip 208 to enable induced voltage Vi to activate RFID component 2 when threshold voltage VT is reached.

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

In one embodiment, the security tag 200 may also include a cover or spacer material 210 applied to the top of the completed security tag. As with substrate 202, covering or spacer material 210 may also affect the RF performance of RFID component 2. For example, the cover material 210 may be implemented using a cover stock 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 specifically, as previously described, the substantially flat spacer 210 has a thickness "t". The thickness "t" is typically about 1mm to 2mm when the security tag 200 is a hard combination tag, and significantly less than 1mm when the security tag 200 is a combination tag. As previously described, the baffle 210 has surfaces or surface regions 210a and 210b disposed on opposite sides thereof. In one embodiment, the spacer surfaces or surface areas 210a and 210b are parallel to each other. The EAS component 1 at least partially overlaps at least one of the spacer surfaces or surface areas 210a and 210 b.

An RFID interposer is a term commonly used in the art and may be defined herein as an RFID component 2 that includes a combination of a substrate 202, an antenna 204, a lead frame 206 if applicable, and an RFID chip 208. The RFID component 2 at least partially overlaps the other one of the spacer surfaces 210 b. Security tag 200 includes RFID insert or component 2 and spacer 210.

Security tag 200 may also include antenna 204. Antenna 204 may, for example, represent 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. Optionally, antenna 204 may also be a tunable antenna that is tuned to the carrier signal so that the voltage across the antenna circuit is maximized. As can be appreciated, this will increase the read range of antenna 204. The 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, one band of the RFID security tag spectrum is currently specified by the Federal Communications Commission (FCC) as 915 MHz. Thus, the transmitter 102 should transmit an interrogation signal 104 at approximately 915 MHz. To receive interrogation signals 104, antenna 204 should be closely tuned to the 915MHz signal. For 915MHz applications, RFID tag antenna 204 may be printed, etched, or plated.

The EAS tag 1 creates or presents a constant load impedance to the RFID component 2. As a result, the antenna 204 of the RFID tag 200 uses this constant load of the EAS tag 1 for impedance matching. More specifically, the antenna 204 has a complex impedance and the EAS component 1 forms part of the antenna's impedance matching network. Thus, the impedance of antenna 204 includes the loading effect of EAS component 1. That is, the loading effect of the EAS component 1 is the constant load impedance of the EAS component 1. The loading effect of the EAS component 1 may be varied by replacing or exchanging one material included in the EAS component 1 with another material having one dielectric constant and loss tangent.

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

Z_chip＝Z₁-jZ₂

where Z1 and Z2 are the real and imaginary components of the impedance of chip 208. The RFID device tag or label antenna 204 may be constructed from a complex impedance Z_antennaExpressed as:

Z_antenna＝Z₃+jZ₄(1)

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

In one embodiment, the thickness "t" of the spacer 210 may be varied to vary with respect to the RFID reader device 102 or the RFID reader device 152 to vary the read range R1, respectively. More specifically, thickness "t" determines the read range, i.e., the maximum distance R1 between security tag 200 and EAD/RFID reader 102 or EAS/RFID reader 152, at which distance R1 reader 102 or 152 can interrogate security tag 200. As the thickness "t" decreases, the read range R1 is adversely affected. In contrast, as the thickness "t" increases, the read range R1 increases. It should be noted that reader 102 for HF applications and reader 152 for UHF read only either EAS component 1 or RFID component 2, such that EAS component 1 is read by a dedicated EAS reader and RFID component 2 is read by a dedicated RFID reader. Alternatively, the reader 102 and the reader 152 may be combined in the same frame or their functions integrated to be performed by the same hardware. Because of the large difference between the range of read frequencies common to RFID components and the range of read frequencies common to EAS components, undesirable interference between the reading of EAS component 1 and the reading of RFID component 2 is prevented or minimized, EAS components are typically read at frequencies in the range of less than or equal to 8.2KHz, and RFID components are typically read at frequencies in the range of 13MHz or greater.

However, it is contemplated that because security tags 200 and 400 are stand-alone devices, security tags 200 and 400 provide EAS functionality and RFID functionality regardless of the type of reader or readers or the particular frequencies to which security tag 200 or 400 is subjected.

Use of low loss, low dielectric materials such as ECCOSTOCK manufactured by Emerson curing microwave products of Londoff, MassRH rigid foam or other similar material to make the spacer 210. The embodiments are not limited in this context. When fabricated from the foregoing materials, the read range is about 30.5 to 61.0cm (1 to 2 feet) when the thickness "t" of the baffle 902 is about 0.0762mm (0.003 inches). Similarly, when the thickness "t" of the baffle 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 component 1 directly overlaps RFID component 2.

In one embodiment, the spacer may be air, with the EAS tag 1 mechanically supported away from the RFID component 2.

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

In one embodiment, security tag 200 may use the induced voltage from the coil antenna for operation. The induced AC voltage may be rectified to produce a DC voltage. When the DC voltage reaches a certain level, the RFID component 2 starts to operate. By providing an energizing RF signal via transmitter 102, RFID reader 102 can communicate with remotely located security tag 200 without an external power source, such as a battery.

Because the excitation and communication between the RFID reader and RFID component 2 is accomplished through antenna 204, antenna 204 may be tuned for improved RFID applications. RF signals can be radiated or received efficiently if the linear dimensions of the antenna are comparable to the wavelength of the operating frequency. However, the linear dimension may be larger than the available surface area available for antenna 204. Thus, a truly full-size antenna utilized in a limited space may prove difficult, which is true for most RFID systems in HF applications. Thus, it is contemplated that RFID component 2 may use a smaller LC loop antenna circuit arranged 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 on a dielectric substrate from n turns of wire or n turns of printed or etched inductors.

For HF applications, the product of the loop area turns and the resonance frequency need to be optimized in order to achieve good RFID coupling. In one embodiment of the present disclosure shown in fig. 3A, the resonant frequency may be affected, including the impedance of the EAS tag 1 and RFID chip 208, by tuning the parallel capacitor C2 of the resonant circuit 112.

In HF or UHF applications, for a particular frequency of interest, the RFID chip complex impedance must be matched by the complex conjugate impedance of the antenna, including loading effects on the impedance of the EAS tag. In the HF case, a resonant capacitor is typically used to tune the frequency. This capacitor is typically larger than the RFID chip capacitance and will control the response. For the UHF case, the RFID chip complex impedance includes only the chip capacitance for tuning.

In another embodiment according to the present disclosure, antenna 204 may be designed such that the complex conjugate of the overall antenna matches the impedance to the complex impedance of leadframe 206 and IC208 at the desired operating frequency, e.g., 915 MHz. However, when RFID security tag 200 is placed on an object to be monitored, it has been observed that the resulting operating frequency may vary, i.e., each object may have a substrate material with dielectric properties that affect the RF performance of antenna 204. In other words, and as with substrate 202, the object substrate may cause a frequency shift and RF loss determined by the dielectric constant, loss tangent, and material thickness. Examples of different object substrates may include so-called "chip boards" (i.e., material for single-item (item-level) cartons, corrugated fiberboard as material for corrugated cartons), video tapes and Digital Video Disc (DVD) boxes, glass, metal, and the like. It is contemplated that each object substrate may have a significant effect on the read range R1 of the security tag 200.

Antenna 204 may be adjusted to compensate for such variations. In other words, because many materials have dielectric constants greater than 1, the operating frequency is generally reduced when the security tag 200 is attached to an object substrate. To establish the original frequency, the antenna 204 is typically changed in some way, otherwise the detection performance and read range may be reduced. Thus, antenna 204 can be altered by cutting the antenna inductor to trim the end of antenna 204 and isolate the resulting trimmed antenna segment from the cut-out end. The modified end portion does not necessarily have to be removed to allow for the tuning operation. Thus, it is possible to continuously tune antenna 204 to a desired operating frequency to allow operation of security tag 200 when security tag 200 is attached to a different object. Security tag 200 is generally described below in more detail with reference to fig. 5-7, and antenna 204 is particularly described.

Fig. 5 illustrates a top view of a portion of a security tag 200 having an antenna, the tag 200 being particularly suited for UHF applications, according to one embodiment of the present disclosure. Security tag 200 includes a substantially rectangular shaped antenna 204 disposed on a substrate 202. In one contemplated embodiment, the antenna 204 is disposed on the substrate 202 by die cutting the label antenna pattern onto the substrate 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 substrate material of substrate 202. The ends of lead frame 206 are mechanically and electrically bonded to the foil antenna (foilantenna) pattern of antenna 204. A covering material 210 (not shown) is applied over the entire top surface of the security tag 200 to protect the components and provide a surface for the printed indicia if desired. The use of anisotropic conductive heat set adhesives to bond RFID chip 208 to antenna 204 is known in the art. An example of such an adhesive is Loctite 383, manufactured by Henkel Loctite Inc. 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 below-the-day portion 308, first antenna portion 306 being connected to first side 206A of lead frame 206 and second antenna portion 308 being connected to second side 206B of lead frame 206. Thus, antenna 204 is an overall RFID tag antenna that is subdivided into a first antenna portion 306 and a 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 and as shown in fig. 5, first antenna end 306A of first antenna portion 306 is connected to lead frame 206A. The first antenna portion 306 is disposed on the substrate 202 to form an inwardly spiral pattern starting from the RFID chip 208 in a first direction, and the second antenna end 306B is positioned to terminate on the inner loop of the inwardly spiral pattern. Similarly, second antenna end 308A of second antenna portion 308 may be connected to lead frame 206B. Second antenna portion 308 is also disposed on substrate 202 to form an inwardly spiral pattern starting from RFID chip 208 in a second direction, with second antenna end 308B positioned to terminate on the inner loop of the inwardly spiral pattern.

In one embodiment, the antenna geometry of antenna 204 is configured to traverse around the perimeter of substrate 202 and spiral inward. It is envisioned that an inwardly directed spiral antenna pattern may provide several advantages:

(1) the ends of the antenna 204 may be placed completely inside the perimeter of the substrate 202. Placing the end of antenna 204 within the perimeter of substrate 202 may allow the end to be trimmed without changing the amount of area used by antenna 204.

(2) The Q factor of antenna 204 may be optimized so that the response of security tag 200, including the effects of spacer 210 and EAS tag 1, only changes by about-3 dB at the ISM band limit. Using Q1/(ka)³The Chu-Harrington limit of +1/(ka), where k is 2 pi/λ and "a" is the characteristic dimension of antenna 204, it can be seen that a sphere of radius "a" may just encompass security tag 200. For high Q factors, then "ka" should be < 1. Thus, by maximizing Q, "a" is minimized to fall within the operating frequency band limits. Tuning of an antenna 204 for UHF applications is disclosed in co-pending co-owned U.S. patent application serial No. 10/917,752 entitled "tuner antenna" filed on 8/13/2004.

Antenna 204 may also be tuned to a desired operating frequency, particularly for UHF applications, by altering the first length of first antenna portion 306 and the second length of second antenna portion 308 after these antenna locations are disposed on substrate 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 altered by electronically isolating at least the first antenna segment from the second antenna segment. The antenna length may be altered by cutting each antenna portion 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 results in a reduction in the length of each antenna portion, effectively changing the overall inductance of antenna 204. The antenna segments and segmentation points are described in more detail with reference to fig. 6.

Fig. 6 shows a diagram of a security tag 400 having an antenna with segmentation points, according to one embodiment. In particular, FIG. 6 shows a top view of a portion of security tag 400 having a plurality of segmentation points SP1, SP2, SP3, and SP 4. In a similar manner as shown in FIG. 4 with respect to security tag 200, security tag 400 may include EAS component 1, spacer 210, and RFID component 2. After these antenna locations are disposed on substrate 202, antenna 204 may also be tuned to a desired operating frequency by altering the first length of first antenna portion 306 and the 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 trimmed to be tuned to various objects. SP1 is the free space position where the length of the original free space antenna 204 was tuned to 868 MHz. SP2 is the free space position where the lengths of antenna portions 306 and 308 are tuned to 915 MHz. SP3 and SP4 are free space positions where the lengths of antenna portions 306 and 308 are tuned to various objects. Various objects include, for example, but not limited to, retail or wholesale merchandise.

The first and second antenna lengths may be altered by electronically isolating at least a first antenna segment from a second antenna segment. The antenna length may be altered by cutting each antenna portion at one of a plurality of segment points, each segment corresponding to the operating frequency of antenna 204. This severing may be accomplished in many different ways, such as cutting or perforating the antenna trace 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 should be noted that for HF applications, antenna 204 is tuned by changing the inductance or capacitance parameters instead of the length of the segments.

In one embodiment, and as shown in FIG. 6, each of the segmentation points SP1-SP4 corresponds to an operating frequency of antenna 204. In one example, SP1 tunable antenna 204 is used for an operating frequency of approximately 868MHz when security tag 400 is in free space and not attached to an object. The SP2 tunable antenna 204 is used for an operating frequency of approximately 915MHz when the security tag 400 is in free space and not attached to an object. The SP3 tunable antenna 204 is used for an operating frequency of approximately 915MHz when the security tag 400 is attached to the VHS box frame. The SP4 tunable antenna 204 was used for an operating frequency of approximately 915MHz when the security tag 400 was attached to a chip board. As can be appreciated, the number of segmentation points and the corresponding operating frequency of antenna 204 may vary depending on 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 described above, security tag 200 may be configured in many different ways. For example: 1) at block 502 an integrated circuit may be connected to a leadframe; 2) the antenna may be disposed on a substrate at block 504; 3) the lead frame may be connected to an antenna at block 506.

In one particular embodiment, the antenna is tuned for use with an operating frequency at block 508. The tuning may be performed by altering the length of the antenna by cutting the antenna into a plurality of antenna segments at segmented points corresponding to the operating frequency. The cut-off may electrically disconnect the first antenna segment from the second antenna segment, thereby effectively shortening the length of the antenna.

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

It is also contemplated that some embodiments of the present disclosure may be configured using an architecture that may vary in accordance with any number of factors, such as: 1) a desired computation rate; 2) a power level; 3) heat resistance; 4) a processing cycle budget; 5) an input data rate; 6) an output data rate; 7) a memory resource; 8) data bus speed and other performance limitations. For example, a software-configurable implementation is used which is 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 yet another example, an embodiment may be configured by programmed general-purpose computer components and custom hardware components. The embodiments are not limited in this context.

Examples of Security tags 200 and 400 are shown in fig. 8A through 8D, which are combination EAS and RFID tags/labels, and fig. 8A through 8D show various types of adhesive magnetostrictive tags and EAS hard labels, such as the SuperTag manufactured by sensomatic corporation, Tyco Fire and Security division of bocardon LLC, floridaFig. 8A shows an EAS tag 804 adjacent to an RFID tag 806 in a co-planar configuration. This configuration of adjacent tags 804 and 806 is known in the art. FIG. 8B illustrates 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 spacing 805 having a distance "g". This configuration of 804 and 806 separated by a space 805 is also known in the art.

In the configuration of fig. 8A and 8B, the EAS tag 804 and the RFID tag 806 function independently of each other with respect to matching of impedance values. 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 the total area occupied by the EAS tag 804 and the RFID tag 806 increases as the read range increases, necessitating more space or area on the object to be identified.

Fig. 8C illustrates an embodiment of the present disclosure showing a security tag 200 or 400 for an EAS component or tag 1. The RFID component or insert 2 is mounted directly beneath the EAS component or tag 1. The simulated barcode 802 is printed on the EAS component or tag 1 and is used for visual purposes only. The simulated barcode 802 has no EAS or RFID functionality. In contrast to the prior art, the configuration of security tag 200 or 400 as a combination EAS component or tag or label 1 provides minimal separation between the RFID component or insert 2 and the EAS label 1, with the RFID component or insert 2 mounted directly beneath the EAS component or label 1 (see FIG. 4).

Fig. 8D illustrates one embodiment of the present disclosure combining an EAS component or tag 1 with a portion 812 of the framework of an RFID component or insert 2. An RFID component or package 2 is defined to include an RFID chip 208 mounted on an antenna 204. However, the separator 210 or adhesive layer is not visible (see fig. 4).

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

Fig. 8F shows one embodiment of the present disclosure combining an EAS tag 816 with a portion 818 of the framework of an RFID insert 814, the EAS tag 816 being similar to an EAS component or tag 1 and the RFID insert 814 being similar to an RFID component or insert 2. The RFID interposer 814 is defined as another RFID chip 820 mounted on the antenna 204. Again, the separator 210 or adhesive layer is not visible (see fig. 4).

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

Fig. 9 shows another embodiment of the present invention. In FIG. 9, a combination EAS/RFID security tag includes a hybrid antenna inlay 900 having two inward spiral antennas 910 and 920 and a rectangular magnetic loop antenna 930 coupled to the inward spiral antennas 910 and 920. RFID chip 940 is electrically connected to magnetic loop antenna 930, and magnetic loop antenna 930 is then electrically connected to inward spiral antennas 910 and 920 as shown in FIG. 9. In a specific non-limiting example, an ImpinjGen.2Monza RFID chip is used. The overall geometry of the magnetic loop antenna 930 is such that the near field magnetic H performance is optimized. Helical antennas 910 and 920 control the far field response.

Magnetic loop antenna 930 also serves as a means of reducing ESD damage to RFID chip 940. For low frequency or electrostatic fields E generated by the manufacturing process of the hard tag frame or ultrasonic welding, the magnetic loop antenna 930 is essentially short circuited across the RFID chip 940. For example, if electrical discharge from one end of spiral antenna 910 to one end of spiral antenna 920 begins, loop antenna 930 diverts the discharge current away from RFID chip 940.

Physically, the helical antennas 910 and 920 are connected to the magnetic loop antenna 930 and not directly to the RFID chip 930. When an E-field is applied along the length of the hybrid spiral/loop antenna inlay shown in fig. 9, the current starts at the end of the spiral antenna 910 (left spiral in fig. 9) at a low level and gradually increases to the connection point of the magnetic loop antenna 930. The current sensing is counter-clockwise. The current through the magnetic loop antenna 930 is also sensed counterclockwise, but at a much larger value. The current from the magnetic loop connection point to the right spiral antenna 920 is sensed counterclockwise and gradually decreases toward the end of the antenna trace. Therefore, the direction of the current in each of the helical antennas 910 and 920 is the same.

The hybrid antenna inlay 900 shown in FIG. 9 is then placed inside the framework of a hybrid EAS/RFID tag that contains an EAS element, spacer and attachment clamp mechanism. The EAS/RFID security tag utilizing the hybrid antenna inlay 900 of fig. 9 may be read by any conventional RFID reader.

An example of a near field reader magnetic H-field loop antenna for use with the present invention is a 2cm diameter circular loop using a step-down transformer at the feed end (feed end) of the loop, two tuning capacitors at the halfway point, and termination resistors at the opposite ends of the loop. However, the present invention is not limited to a particular diameter or type of near field reader magnetic loop antenna. The near field magnetic loop antenna 930 may also comprise a cylindrical core of ferrite material.

Fig. 9A illustrates the RFID read performance characteristics of the hybrid antenna inlay 900 of fig. 9 and a prior art antenna inlay as a function of tag offset from the inlay center relative to the center of the reader near field magnetic loop antenna. As can be observed in fig. 9B, the use of the hybrid antenna inlay 900 provides a greater read-out distance than the prior art spiral antenna inlay on the antenna, and also provides an abrupt read-out region (degree of inlay offset from the center of the antenna).

The use of the hybrid antenna inlay 900 with a combination EAS/RFID tag not only provides the same far field read performance as a pure helical antenna, but also provides an improved near field magnetic response. For a given overall size of the hybrid antenna inlay 900, the ratio of the helical antenna area to the magnetic loop antenna area should be maintained. Fig. 9B shows these antenna zones.

In fig. 9B, region 1 represents the region of the magnetic loop antenna 930, while regions 2 and 3 represent the right-hand side inward spiral antenna 920 and the left-hand side inward spiral antenna 910, respectively. In one embodiment, to achieve the same near field response as a spiral antenna, the hybrid antenna inlay 900 has substantially similar areas for all three regions. For example, if the area of zone 1 is substantially smaller than zones 2 and 3, the far field response may be the same as that of the spiral, but the near field magnetic response may not be optimized. If zone 1 becomes substantially larger than zones 2 and 3, for a given overall size of inlay 900, there may not be enough room for the spiral antenna trace to operate in the UHF range when placed inside a combination EAS/RFID security tag.

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

The present disclosure advantageously provides a hybrid antenna inlay for use in an EAS/RFID security system, wherein the hybrid antenna inlay includes an RFID spiral antenna having two sections and a magnetic loop antenna positioned between the two spiral antenna sections. The hybrid antenna inlay design of the present disclosure maintains the far field response capability of the helical antenna due to the magnetic loop antenna while increasing the near field magnetic performance. Further, the hybrid antenna inlay reduces ESD damage to the RFID integrated circuit by diverting current from the IC.

While certain features of the 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.

It will be appreciated by persons skilled in the art that the present invention is not limited to what has been particularly shown and described hereinabove. Moreover, unless set forth to the contrary above, it should be noted that all of the accompanying drawings are not to scale. Various modifications and variations are possible in light of the above teachings without departing from the scope and spirit of the invention, which is limited only by the following claims.

Claims (14)

1. A security tag, comprising:

an Electronic Article Surveillance (EAS) component having a first defined surface area; and

a radio frequency RFID component having a second defined surface area, the RFID component including a hybrid antenna inlay configured to impedance match using characteristics of the EAS component,

the hybrid antenna inlay includes:

a far field antenna that is an inward spiral antenna having a first portion and a second portion;

a near field magnetic loop antenna in electrical contact with the inward spiral antenna, wherein the near field magnetic loop antenna is located between the first portion and the second portion, the near field magnetic loop antenna being rectangular with two ends of one long side of the rectangle in electrical contact with the first portion and the second portion of the inward spiral antenna; and

an integrated circuit in electrical contact with the near field magnetic loop antenna, the integrated circuit disposed on a long side opposite the one long side of the rectangle.

2. The security tag of claim 1, further comprising a substantially planar spacer disposed at least partially between the first defined surface area of the EAS component and the second defined surface area of the RFID component.

3. The security tag of claim 1, wherein the integrated circuit is an Application Specific Integrated Circuit (ASIC), the ASIC having a complex impedance.

4. The security tag of claim 1 wherein the first portion of the inward spiral antenna has a third defined surface area, the second portion of the inward spiral antenna has a fourth defined surface area, and the near field magnetic loop antenna has a fifth defined surface area, the fifth defined surface area of the near field magnetic loop antenna being no greater than the third and fourth defined surface areas of the inward spiral antenna.

5. The security tag of claim 1, wherein the RFID component is activatable when the RFID component is within a read range.

6. The security tag according to claim 1, wherein currents in the first and second portions of the inward spiral antenna flow in a same sensing orientation, the sensing orientation being one of clockwise and counterclockwise.

7. An RFID antenna inlay for use with a combination EAS/RFID security tag having an EAS component and an RFID component, the antenna inlay comprising:

a far-field antenna that is an inward spiral antenna having a first portion and a second portion, the inward spiral antenna configured to use characteristics of the EAS component for impedance matching;

a near field magnetic loop antenna in electrical contact with the inward spiral antenna and located between the first portion of the inward spiral antenna and the second portion of the inward spiral antenna, the near field magnetic loop antenna being oblong shaped with two ends of one long side of the oblong shape in electrical contact with the first portion and the second portion of the inward spiral antenna; and

an integrated circuit in electrical contact with the near field magnetic loop antenna, the integrated circuit disposed on a long side opposite the one long side of the rectangle.

8. The RFID antenna inlay of claim 7, wherein the integrated circuit is an application specific integrated circuit, ASIC, having a complex impedance.

9. The RFID antenna inlay of claim 7, wherein the first portion of the inward spiral antenna has a first defined area, the second portion of the inward spiral antenna has a second defined area, and the near field magnetic loop antenna has a third defined area, the third defined area of the near field magnetic loop antenna being no greater than the first and second defined areas.

10. The RFID antenna inlay of claim 7, wherein currents in the first and second portions of the inward spiral antenna flow in a same sense orientation, the sense orientation being one of clockwise and counterclockwise.

11. A method for providing an enhanced read response for a security tag, the method comprising:

providing an Electronic Article Surveillance (EAS) component having a first defined surface area;

positioning a radio frequency RFID component having a second defined surface area to at least partially overlap the EAS component, the RFID component including a hybrid antenna inlay, the antenna inlay including:

a far field antenna that is an inward spiral antenna having a first portion and a second portion;

a near field magnetic loop antenna in electrical contact with the inward spiral antenna, the near field magnetic loop antenna being disposed between and in electrical contact with the first portion of the inward spiral antenna and the second portion of the inward spiral antenna, the near field magnetic loop antenna being oblong shaped, two ends of one long side of the oblong shape being in electrical contact with the first portion and the second portion of the inward spiral antenna;

an integrated circuit in electrical contact with the near field magnetic loop antenna, the integrated circuit being disposed on a long side opposite the one long side of the rectangle; and

adjusting an impedance of the hybrid antenna inlay of the RFID component using the EAS component.

12. The method of claim 11, wherein the RFID component is activatable when the RFID component is within a read range.

13. The method of claim 11, wherein the first portion of the inward spiral antenna has a third defined surface area, the second portion of the inward spiral antenna has a fourth defined surface area, and the near field magnetic loop antenna has a fifth defined surface area, the fifth defined surface area of the near field magnetic loop antenna being no greater than the third and fourth defined surface areas of the inward spiral antenna.

14. The method of claim 11, wherein currents in the first and second portions of the inward spiral antenna flow in a same sense orientation, the sense orientation being one of clockwise and counterclockwise.