HK1149121A - Combination electronic article surveillance/radio frequency identification antenna - Google Patents

Description

Combined electronic article monitoring/radio frequency identification antenna

Technical Field

The present invention relates generally to electronic security systems and, more particularly, to antenna designs that combine electronic article surveillance ("EAS") and radio frequency identification ("RFID") features such that the overall size of the antenna is reduced.

Background

Electronic article surveillance ("EAS") systems are detection systems that allow identification of a marker or tag within a given detection area. EAS systems have many applications, but they are most commonly used as security systems for preventing shoplifting in malls or assets in mobile office buildings. EAS systems come in many different forms and use many different technologies.

A typical EAS system includes an electronic detection device, a tag and/or label, and a detacher or deactivator. For example, the detection device may be formed as a pedestal device (pedestal unit) buried under the floor, mounted on a wall, or suspended from the ceiling. Detection devices are often placed in high flow areas such as entrances and exits of malls or office buildings. The tags and/or identifications have specific characteristics and are specifically designed to be attached to or embedded in merchandise or other objects sought to be protected. When an active tag passes through the tag detection zone, the EAS system issues an alarm, a light is activated and/or some other suitable alarm device is activated to indicate that the tag has moved outside of the prescribed zone.

Common EAS systems operate using these same general principles using either a transceiver or separate transmitter and receiver each capable of transmitting and receiving. Typically, the transmitter is placed on one side of the detection area and the receiver is placed on the opposite side of the detection area. The transmitter generates a predetermined excitation signal in the tag detection area. In the case of retail stores, this detection zone is typically formed at an exit. When an EAS tag enters the detection zone, the tag has a unique response to the excitation signal that can be detected. For example, the tag may respond to the signal sent by the transmitter by using a simple semiconductor junction, a tuned circuit including an inductor and a capacitor, a soft magnetic strip or wire, or a vibrating magneto-acoustic resonator (magneto). The receiver then detects this unique response. By design, the tag-specific response is unique and cannot be produced by natural environments.

Radio frequency identification ("RFID") systems are also commonly known in the art and may be used in many applications, such as managing inventory, electronic access control (electronic access control), security systems, and automatic identification of cars on toll roads. An RFID system generally includes an RFID reader and an RFID device. The RFID reader may transmit a radio frequency ("RF") carrier signal to the RFID device. The RFID device may be responsive to a carrier signal with a data signal that is interpreted into an electronic code by information stored by the RFID device.

Market demand for combining EAS and RFID functionality in a retail environment is rapidly emerging. Many retail stores today that have EAS for shoplifting protection rely on bar code information for inventory control. RFID provides faster and more detailed inventory control over bar codes. Retail stores have spent a considerable amount of money on reusable hard tags (hard tags). Adding RFID technology to EAS systems can easily incur the additional expense incurred due to improved productivity in inventory control and loss prevention.

Additionally, to minimize the interaction between the EAS and RFID elements, the prior art combination method places the two different elements, i.e., the EAS element and the RFID element, end-to-end, side-by-side, or stacked far enough to minimize the interaction of the individual elements. However, this requires a significant increase in the overall size and footprint of the combined antenna.

Recent attempts to reduce the overall size and footprint of combined EAS and RFID elements and to manufacture antennas with EAS and RFID capabilities have met with further difficulties. For example, it is difficult to attempt to have EAS and UHF RFID antennas work together in the same space, because RFID antennas are typically designed as patch antennas (patchantenna) that require a large ground plane.

EAS antennas are typically designed as loop antennas. It may be advantageous to place the RFID patch antenna inside the EAS loop antenna. However, a problem arises when this is done because the EAS transmission field is significantly attenuated by eddy currents generated in the RFID ground plane that oppose the EAS field. If the RFID antenna is a dipole or helical coil type antenna, this alternative design does not allow for a patch antenna, although the alternative antenna design does not suffer from the problems described above.

What is needed is a combination EAS and RFID antenna design that will allow EAS and RFID elements to be placed in close proximity to each other in order to reduce the overall size of the antenna while reducing the attenuation effects of eddy currents.

Disclosure of Invention

The present invention advantageously provides a combination EAS/RFID antenna design that includes both EAS and RFID elements such that the overall size of the antenna is reduced. The EAS loop antenna is incorporated in an EAS/RFID system along with an RFID patch antenna. A hatch pattern (hashing pattern) is applied to the RFID ground plane and/or patch antenna. A hatched RFID antenna (hatched RFID antenna) is located proximate to the EAS loop antenna. The RFID ground plane may be located in an interior region of the EAS loop antenna to further reduce the space occupied by the combined antenna.

In one aspect of the present invention, a combination electronic article surveillance/radio frequency identification antenna is provided, wherein the antenna includes an EAS loop antenna defining an interior portion and an RFID antenna element having an RFID patch antenna, wherein the RFID patch antenna has a hatched conductor pattern. The RFID antenna element is positioned proximate to the EAS antenna element.

In another aspect, the present invention provides a combination electronic article surveillance/radio frequency identification antenna wherein the EAS loop antenna has an interior portion. The RFID antenna element has an RFID patch antenna, a ground plane, and a dielectric element disposed between the RFID patch antenna and the ground plane. The RFID patch antenna has a hatched conductor pattern. The RFID antenna elements are disposed substantially coplanar and in an interior portion of the EAS loop antenna.

In another embodiment, the present invention provides a combination electronic article surveillance/radio frequency identification reader wherein the transmission line is configured to output an interrogation signal. The interrogation signal includes at least one of an EAS signal and an RFID signal. The receive line is configured to receive a response signal in response to the interrogation signal. The EAS loop antenna transmits an EAS signal and has an internal portion. The RFID antenna element includes an RFID patch antenna to transmit an RFID signal. The RFID patch antenna has a hatched conductor pattern. The RFID antenna element is positioned proximate to the EAS loop antenna.

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 is a block diagram of a combination electronic article surveillance/radio frequency identification detection system constructed in accordance with the principles of the present invention;

FIG. 2 is a front view of an EAS loop antenna used in the combined electronic article surveillance/radio frequency identification detection system of FIG. 1;

FIG. 3 is a front view of an RFID patch antenna for use in the combination electronic article surveillance/radio frequency identification detection system of FIG. 1;

FIG. 4 is a side view of the RFID patch antenna of FIG. 3;

FIG. 5 is a front view of an RFID patch antenna having a hatch pattern and used in the combination electronic article surveillance/radio frequency identification detection system of FIG. 1;

FIG. 6 is a front view of a combination EAS/RFID antenna used in the combination electronic article surveillance/radio frequency identification detection system of FIG. 1;

FIG. 7 is a front view of a handheld reader having the combination EAS/RFID antenna of FIG. 6; and

FIG. 8 is a perspective view of a handheld reader having the combination EAS/RFID antenna of FIG. 6.

Detailed Description

The present invention relates to antenna designs with EAS and RFID elements. The antenna combines an EAS loop antenna and an RFID patch antenna and may be used in EAS/RFID systems such as a combination handheld reader, table deactivator and pedestal. The hatch pattern is applied to the RFID ground plane and patch antenna. The RFID antenna includes a ground plane, a dielectric element, and a patch. A hatched RFID antenna is located proximate to the EAS loop antenna. In one embodiment, the RFID patch antenna is located inside the EAS loop antenna. In this embodiment, the RFID ground plane is substantially coplanar with the EAS loop antenna and is located within an interior region of the EAS loop antenna. In another embodiment, the RFID antenna is substantially non-coplanar with respect to the EAS loop antenna and is located in front of or behind the EAS loop antenna. In another embodiment, one or both of the RFID patch and the ground plane are etched in one of various hatched conductor patterns.

In another embodiment, the RFID patch and ground plane are created in one of various hatch patterns. 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 system constructed in accordance with the principles of the present invention and designated generally as "100". FIG. 1 depicts a system that includes a combination EAS/RFID reader 102 and one or more remote communication devices (tags) 104 attached to one or more items. Although only one reader 102 and one tag 104 are shown in fig. 1, the invention is not so limited and may include any number of these devices.

System 100 represents a monitoring system that combines the anti-theft features of an EAS security system with the item identification features of an RFID identification system. The system 100 has the capability of alerting the entire staff of potential theft while the customer is still in the store. Combining EAS technology and RFID technology can potentially provide manufacturers with greater interest because they can use RFID to track inventory throughout the supply chain and use EAS protected merchandise on the retail floor.

Referring again to FIG. 1, the combination EAS/RFID reader 102 may be, for example, in the form of a reader unit for communicating an interrogation signal 106 to tags 104. Reader 102 may include a radio frequency module (transmitter and receiver), a control unit, a coupler element coupled to the tag, and a power source. In addition, many readers are equipped with interface hardware to enable them to transmit data received from the tag to another system, e.g., a PC, an automated control system, etc.

Reader 102 includes a combination EAS/RFID antenna 108 having an EAS element and an RFID element. The antenna 108 emits a radio signal to activate the tag 104 and read and/or write data to it. Antenna 108 provides a channel for data acquisition and communication between tag 104 and reader 102 to control the system. If multiple tags are continuously moving through the interrogation zone, the electromagnetic field generated by antenna 108 is continuously present. If the continuous interrogation is not an application requirement, the detection device may activate the electromagnetic field, thereby conserving power.

The tag 104 is an electronic transmitter/transponder typically disposed on or embedded in an object, which corresponds to the actual data carrying device of an EAS/RFID interrogation system. Tag 104 responds to its interrogation signal 106 of transmission or communication of encoded data from an interrogator, i.e., reader 102. Tags 104 use radio frequency waves to transmit wireless signals over an open air interface (open air interface) to communicate with each other. The tag includes an EAS element such as an acousto-magnetic ("AM") component and/or an active or passive RFID component.

Reader 102 emits radio waves at an interrogation range that varies depending on the power output and the frequency used. As tag 104 enters and passes through the electromagnetic field, it detects the reader's activation signal. Reader 102 then decodes the encoded data within the tag's Integrated Circuit (IC) and transmits the data to the host for processing.

Typically, antenna 108 is packaged using a transmitter and decoder in reader 102. The EAS/RFID reader 102 may be a handheld device or in a fixed location/fixed mounting arrangement depending on the desired application. The antenna 108 includes an EAS loop antenna and an RFID patch antenna, each of which is described in more detail below. The antenna 108 is capable of transmitting EAS and/or RFID interrogation signals 106 to the tag 104 and is also capable of receiving responsive communication signals 110 from the tag 104.

In fig. 2, an EAS loop antenna 112 is shown. As described above, the combination EAS/RFID antenna 108 has both an EAS element and an RFID element. EAS loop antenna 112 represents the EAS component of antenna 108. The EAS loop antenna 112 is typically generally circular or rectangular in shape, and when the EAS loop antenna 112 is used as a transmit antenna, the EAS loop antenna 112 is driven by a transmitter line. The EAS loop antenna 112 is also electronically coupled to the receiver line and drives the receiver line when the antenna is used as a receiver antenna. Other loop sizes, shapes or configurations, in addition to the antenna configuration depicted in fig. 2, may also be utilized and used with the present invention. The current may flow in the EAS loop antenna 112 in either a clockwise or counterclockwise direction.

The current flowing through the loop of the EAS antenna 112 defines an electromagnetic field having a magnetic flux extending concentrically from at least a portion of the antenna and generally perpendicular to the direction of current flow as is known in the art. A current source electronically coupled to the EAS loop antenna 112 provides current to the antenna 112, which is capable of providing sufficient current to the antenna 112 to generate an electromagnetic energy field. The current source may be a conventional transmitter with a signal oscillator and a suitable amplifier/filter network of the type capable of driving the load impedance presented by the EAS loop antenna 112. As will be appreciated, the frequency at which the antenna 112 transmits the electromagnetic field is substantially dependent on the oscillation rate of the transmitter. Thus, the frequency can be set and adjusted by appropriately adjusting the transmitter in a known manner.

Additionally, the receiver circuitry may be an electronically coupled EAS loop antenna 112 for receiving electromagnetic energy from the transmit antenna and/or the tag's resonant circuit to generate a signal indicating whether a tag is present near the EAS loop antenna 112.

In fig. 3 and 4, an embodiment of an RFID patch antenna 114 for use in accordance with the present invention is shown. In one embodiment, the RFID patch antenna 114 includes a ground plane 116, and the dielectric element 118 is located on the ground plane 116. A patch antenna 120 is located on the dielectric element 118. The embodiments described in fig. 3 and 4 are merely exemplary, and other configurations of RFID patch antennas may be used.

Fig. 5 shows an embodiment of the present invention in which the RFID patch antenna 114 includes a hatch pattern in the ground plane 116 and also in the patch 120. In another embodiment, the hatch pattern is present only in the patch 120. In another embodiment, only ground plane 116 includes the hatch pattern. The hatch pattern depicted in fig. 5 represents a division of the conductors throughout the patch antenna 120 and/or the ground plane 116, for example by etching during the manufacturing process. By dividing the plane of the EAS frequencies produced by the EAS loop antenna signal transmission, the discontinuity of the conductors minimizes eddy currents produced by the EAS loop antenna 112.

Fig. 6 shows a hatched RFID antenna 114 that is substantially coplanar with respect to the EAS loop antenna 112, the hatched RFID antenna 114 including a hatched ground plane 116 and a hatched patch 120. In this embodiment, the RFID antenna 114 is disposed within the interior of the EAS loop antenna 112. The result is a combined antenna 108 with both RFID and EAS transmission capabilities, resulting in a reduced overall footprint. Combined antenna 108 advantageously occupies less space relative to other combined antennas, thus allowing combined antenna 108 to be incorporated into readers, pedestals, desktops, and other locations where other combined antennas are not suitable. In other embodiments, the RFID patch antenna 114 is located proximate to, rather than inside, the EAS loop antenna 112. For example, the RFID patch antenna 114 may be non-coplanar with respect to the EAS loop antenna 112, such as being located behind or in front of the EAS loop antenna 112. The result of these configurations results in a combined antenna 108 having a reduced footprint compared to other combined antennas. A split or discontinuous pattern or screen of hatch design is used to divide the EAS frequency while allowing the transmission frequency of the RFID antenna to be unaffected.

The shadow designs shown in fig. 5 and 6 are merely illustrative, and the present invention is not limited to a particular shadow design. In one embodiment, the RFID antenna 114 is located inside the EAS loop antenna 112, thereby keeping the overall size of the combined antenna to a minimum, which allows it to be embedded in small readers, pedestals, and the like. In addition, despite the close proximity of the RFID antenna 114 to the EAS loop antenna 112, the attenuation of the EAS transmission field caused by eddy currents is reduced by the splitting of the RFID hatch pattern.

Fig. 7 and 8 illustrate embodiments of the present invention in which handheld reader 102 includes a transmission line configured to output an interrogation signal. The interrogation signal includes at least one of an EAS signal and an RFID signal. Reader 102 also includes a receive line configured to receive a response signal in response to the interrogation signal. Reader 102 further comprises: an EAS loop antenna 112 for transmitting EAS signals, wherein the EAS loop antenna 112 defines an interior portion; and an RFID antenna element having an RFID patch antenna 114 for transmitting RFID signals, wherein the RFID patch antenna 114 is disposed inside the open loop EAS antenna 112. The hatched ground plane 116, dielectric 118, and patch 120 are clearly visible inside the EAS loop antenna 112. This embodiment shows a handheld reader 102 with a non-hatched patch 120. However, handheld reader 102 may include patch 120 having a hatch pattern that closely resembles the pattern of ground plane 116. Alternatively, the ground plane 116 may have a different pattern of hatches than the pattern of hatches of the patches 120.

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. In addition, it should be noted that, unless mention was made above to the contrary, all of the accompanying drawings are not to scale. 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. A combination electronic article surveillance/radio frequency identification antenna, the antenna comprising:

an EAS loop antenna defining an interior portion; and

an RFID antenna element including an RFID patch antenna having a hatched conductor pattern, the RFID antenna element being positioned proximate the EAS loop antenna.

2. The combination EAS/RFID antenna of claim 1, wherein the RFID antenna element is substantially non-coplanar with respect to the EAS loop antenna.

3. The combination EAS/RFID antenna of claim 1, wherein the RFID antenna element is substantially coplanar with respect to the EAS loop antenna.

4. The combination EAS/RFID antenna of claim 1, wherein the RFID antenna element is located substantially in the interior portion of the EAS loop antenna.

5. The combination EAS/RFID antenna of claim 1, wherein the RFID antenna element further comprises a ground plane and a dielectric element disposed between the ground plane and the RFID patch antenna.

6. The combination EAS/RFID antenna of claim 5, wherein the ground plane comprises a hatched conductor pattern.

7. The combination EAS/RFID antenna of claim 6, wherein the hatched conductor pattern of the ground element is different than the hatched conductor pattern of the RFID patch antenna.

8. The combination EAS/RFID antenna of claim 6, wherein the hatched conductor pattern of the ground element is the same as the hatched conductor pattern of the RFID patch antenna.

9. A combination electronic article surveillance/radio frequency identification antenna, the antenna comprising:

an EAS loop antenna defining an interior portion; and

an RFID antenna element, the RFID antenna element comprising:

an RFID patch antenna having a hatched conductor pattern,

a ground plane; and

a dielectric element disposed between the RFID patch antenna and the ground plane, the RFID antenna element disposed substantially coplanar and in the interior portion of the EAS loop antenna.

10. The combination EAS/RFID antenna of claim 9, wherein the ground plane includes a hatched conductor pattern.

11. The combination EAS/RFID antenna of claim 10, wherein the hatched conductor pattern of the ground plane is different from the hatched conductor pattern of the RFID patch antenna.

12. The combination EAS/RFID antenna of claim 10, wherein the hatched conductor pattern of the ground plane is the same as the hatched conductor pattern of the RFID patch antenna.

13. A combination electronic article surveillance/radio frequency identification reader, the reader comprising:

a transmit line configured to output an interrogation signal, the interrogation signal comprising at least one of an EAS signal and an RFID signal;

a receiving line configured to receive a response signal in response to the interrogation signal;

an EAS loop antenna for transmitting the EAS signal, the EAS loop antenna defining an interior portion; and

an RFID antenna element including an RFID patch antenna for transmitting the RFID signal, the RFID patch antenna having a hatched conductor pattern, the RFID antenna element being positioned proximate the EAS loop antenna.

14. The combination EAS/RFID reader of claim 13, wherein the RFID antenna element is substantially non-coplanar with respect to the EAS loop antenna.

15. The combination EAS/RFID reader of claim 13, wherein the RFID antenna element is substantially coplanar with respect to the EAS loop antenna.

16. The combination EAS/RFID reader of claim 13, wherein the RFID antenna element is located substantially in the interior portion of the EAS loop antenna.

17. The combination EAS/RFID reader of claim 13, wherein the RFID antenna element further comprises a ground plane and a dielectric element disposed between the ground plane and the RFID patch antenna.

18. The combination EAS/RFID reader of claim 17, wherein the ground plane includes a hatched conductor pattern.

19. The combination EAS/RFID reader of claim 18, wherein the hatched conductor pattern of the ground element is different than the hatched conductor pattern of the RFID patch antenna.

20. The combination EAS/RFID reader of claim 18, wherein the hatched conductor pattern of the ground element is the same as the hatched conductor pattern of the RFID patch antenna.