HK1144126A - Rfid antenna system and method - Google Patents

Description

RFID antenna system and method

Technical Field

The present invention relates to the field of radio frequency identification ("RFID") communications, and in particular to RFID transceiver (RFID transponder) constructions.

Background

Radio Frequency Identification (RFID) devices are becoming increasingly popular in a wide variety of industrial, retail, transportation, and other applications. RFID technology provides active identification of any object, person or the like carrying an RFID transceiver by using passive radio frequency signals. In a typical application, an RFID transceiver includes an antenna and an integrated circuit. When a separate RFID reading device broadcasts a radio frequency signal, the signal interacts with the RFID transceiver antenna. The transceiver antenna converts a portion of the received RF signal energy into an electrical current. This current powers the integrated circuit. The integrated circuit then adjusts its impedance to produce a return RF signal. The return RF signal is then detected by an antenna in the RFID reading device. The conditioned RF return signal carries encoded data about the transceiver based on data previously stored in the integrated circuit. For example, a serial number of the transceiver may be returned to the RFID reading device via the adjusted RF signal. Finally, the RFID reading device decodes the signal returned from the transceiver to complete the identification.

RFID transceivers are being integrated into an increasing number of applications. Employee identification tags, animal identification devices, retail pricing and inventory devices, retail security devices, product manufacturing and material tracking devices, vehicle identification devices, and the like are just a few examples of expanded areas of application for RFID technology. RFID transceivers are ideally suited for integration with a wide variety of products and in a wide variety of environments. The RFID transceiver may be a purely passive device in which all of the energy used to operate the integrated circuit is from a broadcast RF signal. Alternatively, an active RFID system may include an on-board battery (on-board) to power the identification tag and/or to power the return RF signal of the transceiver. In fixed systems, such as motor vehicle transceivers for automatic toll collection systems, the additional cost of on-board batteries is readily justified by the improved performance devices. In contrast, in cost sensitive applications, such as retail pricing and security tags, the RFID transceiver devices must be as inexpensive as possible and are therefore typically passive devices.

On-board antennas (on-board antennas) are key to the technology of implementing RFID transceiver devices. The broadcast RF energy may be in the form of a magnetic, electric or mixed field as in typical radio signal broadcasts. The shape and size of the transceiver antenna is designed based on the characteristics of the broadcast RF energy, such as the type of field and the signal frequency. Furthermore, the design of RFID tags typically requires matching the antenna impedance and the load impedance, usually by matching circuits, to maximize the RF energy from the interrogation of the reader or command signals received by the tag antenna to be passed to the RFIC with minimal loss, thereby achieving optimal tag sensitivity. Theoretically, maximum energy transfer is achieved by conjugating the impedance match, which requires that the impedance from the antenna be as close as possible to the mathematical conjugate value of the RFID input impedance. This represents an ideal impedance match.

In many applications, it is desirable to reduce the overall size or "footprint" of a particular RFID device. Including on or in retail goods having small dimensions may require reduced dimensions. Alternatively, it may be simply desirable to make the RFID device as unobtrusive as possible. While techniques exist to greatly reduce the size of the IC components of an RFID device, similar miniaturization of the antenna of an RFID device can result in significant performance degradation. As described above, the particular IC and antenna of the RFID device ideally have matching impedance characteristics. By reducing the overall size of the RFID device, and thus the overall size of the antenna, it may prove difficult to adequately provide impedance characteristics for efficient functioning of the device. Thus, RFID can suffer from: inefficient energy transfer to the IC, reduced operating range relative to the interrogator, and weak return signals in response.

In addition, antennas connected to RFID tags are generally designed to operate over a specific or narrow range of substrates to which the antennas may be attached. Other substrates may cause the radiation efficiency of the antenna to deteriorate from the optimally designed mounting substrate. Thus, the antenna, and thus the RFID device, will no longer operate as desired. This loss in antenna efficiency may be due to many variable packaging factors. For example, each substrate has its own dielectric and conductive properties that typically affect the impedance matching between the wireless communication device and its antenna. Impedance matching ensures the most efficient transfer of energy between the antenna and the wireless communication device, as discussed above, and placing the RFID device near a surface having dielectric and conductive properties outside of a particular range may degrade the performance of the RFID device. These adverse effects on the performance of RFID devices may also be placed on electronic article surveillance ("EAS") tags or devices that are included or integrated. Such EAS devices typically include a magneto-acoustic mechanism (magneto-acoustic mechanism) having one or more metallic elements that may subsequently interfere with or degrade the performance characteristics of a particular RFID device.

In view of the above, it would be desirable to provide an RFID device having a reduced footprint while providing efficient operation on various surfaces and/or in conjunction with EAS tags.

Disclosure of Invention

The present invention advantageously provides a method and system for an RFID/EAS device. According to a first aspect of the invention, an RFID device is provided having a dielectric substrate body (dielectric substrate body), an antenna disposed on the substrate body, and a first spacer element, wherein at least a portion of the substrate is wrapped around a portion of the spacer element.

The substrate may be made of a material including at least one of polyimide, polyester, fiberglass, ceramic, plastic, and paper, and the antenna may be made of a material including at least one of copper, aluminum, and conductive ink (conductive ink). The antenna may include a conductive material patterned onto a surface of the substrate body. In particular, the pattern comprises a plurality of polygons, for example one or more polygons having a substantially rectangular shape with square or rounded corners. The pattern may also include meanderline (meander pattern) segments. The multiple polygonal antennas may be non-continuous and/or include non-conductive openings or breaks therein to thereby provide a single conductive path. In addition, one or more capacitors may be disposed on the substrate and in electrical communication with the antenna.

In another aspect of the invention, an RFID/EAS device is provided. The RFID/EAS device may generally include a dielectric substrate body, an antenna disposed on the substrate body, a first spacing element, and a second spacing element. In addition, an EAS element may be disposed between the first and second spacing elements, and at least a portion of the substrate body may be positioned to surround a portion of the first and second spacing elements. The EAS element may include an acousto-optic-magnetic device (acousto-magnetic device) and/or a microwave device.

In another aspect of the invention, a method of assembling an RFID/EAS device is provided, where the method includes the steps of: an RFID device is provided having a dielectric substrate body and an antenna disposed on the substrate body. The method further comprises the following steps: positioning the EAS element between the first spacer element and the second spacer element, and then wrapping at least a portion of the RFID device around at least a portion of the first spacer element and the second spacer element.

Drawings

A more complete understanding of the present invention, and the attendant advantages and features thereof, will be more readily understood by reference to the following detailed description when considered in conjunction with the accompanying drawings wherein:

FIG. 1 illustrates an embodiment of an RFID device constructed in accordance with the present invention;

FIG. 2 illustrates an alternative embodiment of an antenna pattern for an RFID device constructed in accordance with the present invention;

FIG. 3 illustrates another embodiment of an antenna pattern for an RFID device constructed in accordance with the present invention;

FIG. 4 illustrates the use of one or more capacitors electrically connected to an antenna constructed in accordance with the present invention;

FIG. 5 illustrates the ability of an antenna according to the present invention to be wrapped around a spacer element (spacer element); and

figure 6 illustrates an alternative configuration of spacer elements for use in accordance with the present invention.

Detailed Description

Referring now to the drawings in which like reference designators refer to like elements, there is shown in FIG. 1 a diagram of an exemplary apparatus constructed in accordance with the principles of the present invention and designated generally as "10". The device 10 is an RFID device that may generally include a substrate body 12 to which an integrated circuit ("IC") component 14 is attached, and an antenna 16 disposed on the substrate body 12 in electrical communication with the IC component 14. The antenna 16 may generally include a pattern of conductive material. In particular, the antenna 16 may include a plurality of substantially square or rectangular shaped polygons 18 having square or rounded corners, wherein a portion of the polygons 18 is hollowed out, i.e., contains no conductive material. The plurality of polygons 18 may be electrically connected to one another by strips or portions of conductive material 20 that connect each polygon 18 and further connect the plurality of polygons 18 to IC component 14. Although not shown, it is also contemplated that the pattern of the antenna 16 may take the form of a meander line segment such that the overall length of the antenna 16 is greater than the distance from the end of the antenna connected to the IC component 14 to the outer edge of the substrate body 12. This may be accomplished, for example, by allowing the antenna 16 to "meander" back and forth along the substrate body 12 as the antenna 16 extends from the IC component 14 to the outer edge of the substrate body 12. The meander line segments may be used independently or in combination with one or more polygons. The antenna 16 may also include a conductive coupling (not shown) located between the first and second portions of the antenna 16 on either side of the IC component 14. The coupler may provide a current loop to augment or otherwise optimize the performance characteristics of the antenna 16.

The apparatus 10 may further include a spacer element 22, wherein at least a portion of the substrate body 12 surrounds at least a portion of the spacer element 22. As described in detail below, the RFID device 10 may also include an EAS element, such as an acousto-optic-magnetic device (not shown in FIG. 1), that is attached to at least one of the substrate body 12 and/or the spacing element 22.

In particular, the substrate body 12 may generally define a first surface 13a and a second surface 13b opposite the first surface 13a, wherein the first surface 13a may receive the IC component 14 and at least a portion of the antenna 16. The first surface 13a may include dielectric properties in order to reduce or eliminate the possibility of interference with the antenna 16 or otherwise prevent shorting of the antenna 16 and/or the IC component 14. The second surface 13b may be adapted to be secured or otherwise attached to a particular article, package, or the like. For example, the second surface 13b may include adhesive properties or the like to facilitate placement of the RFID device 10. Further, the second surface 13b may have dielectric properties similar to those of the first surface. The substrate body 12 may comprise one or more layers of substrate made of a flexible material, such as an organic material like, for example, polyimide or polyester. The substrate body 12 may have an elongated rectangular shape of dimensions appropriately designed for a given application, but an infinite number of shapes and sizes may be used for different environments.

The IC component 14 of the RFID device 10 may be attached or otherwise positioned on the first surface 13a of the substrate body 12. The IC component 14 may generally comprise an integrated circuit device capable of storing multiple bits of data, and may further be capable of adjusting the current in the antenna of the RFID device 10 to thereby encode data onto the RF signal. In particular, IC components 14 may include semiconductor-based devices, such as silicon chips, and may also include active and/or passive components integrated thereon, such as transistors, resistors, capacitors, and the like. For example, IC components 14 may include a passive network of resistors, capacitors, and/or inductors that exhibit a resonant response to an incoming RF signal. Further, the IC component 14 may include a diode device to simply rectify the incoming RF signal. The IC component 14 may also include a fixed response frequency and/or identification data pattern (identification datapattern), and optionally may include a programmable and/or pre-programmable response frequency and/or identification data pattern.

The RFID device 10 of the present invention further includes an antenna 16 disposed on the first surface 13a of the substrate body 12, wherein the antenna 16 is capable of conducting RF signals. Antenna 16 may include a patterned configuration of conductive material in electrical communication with IC component 14 to communicate signals to and from IC component 14. The pattern of the antenna 16 may be varied and/or selected to provide desired impedance characteristics to conform to the electrical characteristics of the IC component 14 for optimal use and performance of the RFID device 10. The antenna 16 may include a material having sufficiently high conductivity, such as a metal material including copper (Cu) or aluminum (Al), or a microwave conductive carbon fiber. The antenna 16 may be patterned onto the first surface 13a of the substrate body 12 using any conventional patterning method, such as, but not limited to, photolithography, ion etching, chemical etching, or vapor deposition. The antenna 16 may generally comprise a dipole configuration with the IC component 14, although the invention is equally applicable to a monopole configuration.

Further, the antenna 16 may be patterned to provide a single conductive path or, alternatively, a plurality of series-connected electrical paths. For example, the antenna pattern may include a plurality of connected polygons 18 that provide a path for conducting a desired signal. Each polygon 18 may have a substantially continuous shape, with multiple polygons 18 connected to one another to define a series of conductive vias therethrough. The polygons of a particular antenna pattern may be "hollowed out" or have different diameters or thicknesses of conductive material in order to provide a desired impedance for a particular application.

Alternatively, as shown in FIG. 2, the antenna 16 may include a pattern of "open" polygons 18 that provide a single conductive flow path. The pattern of polygons 18 in fig. 2 is non-continuous, i.e., one side or portion of each polygon 18 is non-conductive, thereby providing a single conductive flow path through the length of the antenna 12. In fig. 2, the polygons 18 are configured in an alternating pattern. Similar to the antenna arrangement described above depicted in fig. 1, the plurality of non-continuous polygons 18 may be in electrical communication with one another by connecting the plurality of polygons 18 together and connecting the antenna pattern to a connection or deposit of conductive material of the IC element 14. Furthermore, if the antenna 16 includes a dipole configuration extending on either side of the IC component 14, there may be conductive strips or portions 23 that connect the two sides of the antenna to one another to form a current loop or path external to the IC component 14 or independent of the IC component 14, as shown in fig. 2.

Fig. 3 illustrates another antenna configuration in which each polygon 18 is non-continuous, as in the embodiment shown in fig. 2. However, in this configuration, the orientation of each polygon 18 is repeated. The present invention is not limited to any particular orientation of the polygon 18 and may include combinations of patterns and is not limited to only the orientations depicted in fig. 2 and 3. By varying the pattern (or meander line) of the polygons 18, different total impedances can be obtained.

Note that although the embodiments shown in fig. 2 and 3 show symmetrical antenna segments on each side of IC chip 14, the invention is not limited thereto. It is contemplated that asymmetric antenna segments may be implemented, for example, by taking a different number of polygons 18 on each side of IC chip 14.

Similarly, as shown in the exemplary embodiments of fig. 1-3, the capacitive and inductive portions of the impedance used to match the antenna to IC chip 14 may originate from antenna 16 itself, without the need for external discrete devices. By varying the length of the conductive path of the antenna 16, the capacitive and inductive portions of the impedance can be varied. By way of non-limiting example, extending the length of the antenna 16 results in an increase in the capacitive and inductive portions of the impedance. In situations such as that shown in fig. 1, where the resulting length of the antenna 16 exceeds the length of the spacer 22 (or EAS element), the substrate body 12 (along with the antenna 16) may be wrapped around the spacer to minimize the overall package size, as described in detail below.

In fig. 4, one or more discrete capacitors 26 may be electrically connected to either or both ends of the antenna 16 to provide the desired electrical capacitance characteristics of the RFID device. As used herein, the term "capacitor" is intended to include any element or structure that exhibits capacitive properties. For example, it may comprise an elongate portion of the antenna 16 or the like, and is not limited to the configuration of a separate "capacitor" element consisting of two charged conducting surfaces (charged conducting surfaces) having opposite polarities separated by a dielectric. Although it is not necessary to create a matching impedance based on the use of the conductive path length of the antenna 16 itself, a discrete capacitor 26 and/or a discrete inductor (not shown) may be implemented in any of the antenna arrangements described herein.

As described above, the RFID device 10 of the present invention may also include one or more spacer elements 22, the one or more spacer elements 22 being coupled to the substrate body 12 to bias or otherwise manipulate the position of the substrate body 12, or any portion thereof relative to one another. Each spacing element 22 may define a substantially planar body having non-conductive and/or dielectric properties, and may be made of a non-conductive plastic, polymer, or other suitable insulating material. For example, the spacing element 22 may constitute a substantially rectangular shaped portion of the insulating foam, wherein the thickness of the spacing element is less than about 3 mm.

Fig. 5 illustrates an exemplary configuration of the RFID device 10 of the present invention using any of the foregoing antenna configurations. As discussed above, the IC component 14 is attached to the non-conductive surface of the substrate body 12. The antenna 16 extends from the IC component 14 on the substrate body 12 and is in electrical communication with the IC component 14 to provide the desired impedance characteristics, as described above. At least a portion of the substrate body 12 of the RFID device 10 may then be positioned around a peripheral or outer portion of the spacer element 22. The substrate body 12 may then be substantially wrapped, folded, or otherwise disposed about the spacer element 22 such that the IC component 14 and the antenna 16 face or otherwise approach the spacer element 22. Note that although fig. 5 shows spacer elements 22 separate from substrate body 12, it is contemplated that a cover stock (not shown) may be positioned over substrate body 12 such that the cover stock functions as spacer elements 22 when substrate body 12 is wrapped around itself. The thickness of the cover stock, e.g., paperboard, paper, plastic, etc., may be varied to establish the desired resulting spacing when the substrate body 12 is wrapped over itself.

When the substrate 12 is wrapped substantially around the spacer element 22 and over the spacer element 22, the resulting RFID device 10 has substantially the same physical dimensions as the spacer element without compromising or reducing the actual length of the antenna 16. The spacing element 22 prevents the antenna 16 from shorting out as it provides a buffer between opposing portions of the antenna 16. As a result, when the antenna 16 is wrapped over the spacer element 22, the overall impedance of the antenna 16 matches the impedance of the IC component 14, and the size of the RFID device 10 is significantly reduced due to the ability of the substrate 12 to be folded over the spacer element 22. Thus, with the substrate 12 "wrapped" over the spacing element 22, the RFID device 10 achieves impedance matching between the IC component 14 and the appropriate antenna pattern while greatly reducing its overall size, while at the same time preventing short circuits in the antenna or circuitry on the device 10 due to the spacing element 22.

The apparatus of the present invention may also include an electronic article surveillance ("EAS") element 24 attached to the substrate body 12. The EAS element 24 may comprise an acousto-optic-magnetic device having amorphous ferromagnetic metal strips, wherein the strips are free to mechanically oscillate and are identified by their resonant response to an induced magnetic field.

Alternatively, the EAS element may comprise a microwave device having a nonlinear element (e.g., a diode) coupled to a microwave and electrostatic antenna. One antenna emits a low frequency (about 100kHz) field and the other emits a microwave field, where the device acts as a mixer that re-emits the combined signal from the two fields to trigger an alarm. Additional suitable EAS devices and/or tags known in the art may be equally suitable for use with the present invention.

Referring now to fig. 6, the EAS element 24 may be embedded or otherwise disposed between one or more spacer elements 22 while the substrate body 12 remains disposed about the periphery of the one or more spacer elements 22. In particular, the EAS element 24 may be disposed between a first spacing element 22a and a second spacing element 22b (collectively referred to herein as "spacing elements 22"), wherein the substrate body 12 with the IC element 14 and antenna 16 is disposed around a portion of the perimeter of the first and second spacing elements 22, resulting in the folded configuration shown in fig. 5. Because the substrate body 12 and the EAS element 24 are not in electrical communication with each other, the desired impedance characteristics of the antenna/IC element pair remain intact while allowing the RFID device 10 to provide identification and article surveillance functionality.

In an exemplary use of the RFID device 10, the RFID device 10 may be attached to or otherwise positioned on an article or item. The RFID device 10 may include an EAS element 24 embedded within one or more spacing elements. Furthermore, the overall footprint of the RFID device is greatly reduced by wrapping at least a portion of the device around one or more spacer elements.

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, it should be noted that, unless stated to the contrary above, 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 (20)

1. An RFID device, comprising:

a dielectric substrate body;

an antenna disposed on the substrate body; and

a first spacer element, wherein at least a portion of the substrate is wrapped around a portion of the spacer element.

2. The RFID device of claim 1, wherein the antenna comprises a conductive material patterned onto a surface of the substrate body.

3. The RFID device of claim 2, wherein the pattern includes at least one of a plurality of polygons and a meander line.

4. The RFID device of claim 3, wherein each polygon of the plurality of polygons has a substantially rectangular shape.

5. The RFID device of claim 4, wherein each polygon of the plurality of polygons is non-continuous, thereby providing a single conductive path.

6. The RFID device of claim 1, wherein the first spacing element is substantially non-conductive.

7. The RFID device of claim 1, further comprising an EAS element coupled to at least one of the substrate body and the first spacing element.

8. The RFID device of claim 1, further comprising a second spacer element, and wherein the EAS element is disposed between the first spacer element and the second spacer element.

9. The RFID device of claim 7, wherein the EAS element is an acousto-optic-magnetic device.

10. The RFID device of claim 7, wherein the EAS element is a microwave device.

11. The RFID device of claim 1 wherein the substrate is made of a material comprising at least one of polyimide, polyester, fiberglass, ceramic, plastic, and paper.

12. The RFID device of claim 1, wherein the antenna is made of a material comprising at least one of copper, aluminum, and conductive ink.

13. An RFID/EAS device, comprising:

a dielectric substrate body;

an antenna disposed on the substrate body;

the first spacer element is arranged to be spaced from the first spacer element,

a second spacing element; and

an EAS element disposed between the first and second spacing elements, at least a portion of the substrate body surrounding a portion of the first and second spacing elements.

14. The RFID/EAS device according to claim 13, wherein the antenna includes a conductive material patterned onto a surface of the substrate body.

15. The RFID/EAS device according to claim 14, wherein the pattern includes at least one of a plurality of polygons and a meander line.

16. The RFID/EAS device according to claim 15, wherein each polygon of the plurality of polygons has a substantially rectangular shape.

17. The RFID/EAS device according to claim 15, wherein each polygon of the plurality of polygons is non-continuous, thereby providing a single conductive path.

18. The RFID/EAS device according to claim 13, wherein the antenna is in contact with at least one of the first spacer element and the second spacer element.

19. The RFID/EAS device according to claim 13, further comprising an RFID integrated circuit disposed on the substrate body, wherein the antenna includes a first antenna portion and a second antenna portion, both the first antenna portion and the second antenna portion in electrical communication with the RFID integrated circuit and in electrical communication with each other in a current loop.

20. A method of assembling an RFID/EAS device, comprising the steps of:

providing an RFID device comprising a dielectric substrate body and an antenna disposed on the substrate body;

positioning an EAS element between a first spacer element and a second spacer element; and

wrapping at least a portion of the RFID device around at least a portion of the first and second spacing elements.