WO2016049844A1

WO2016049844A1 - Radio frequency identification (rfid) tag

Info

Publication number: WO2016049844A1
Application number: PCT/CN2014/087922
Authority: WO
Inventors: Jingtian XI; Chunwai LEUNG; Chilun MAK
Original assignee: Hong Kong R&D Centre for Logistics and Supply Chain Management Enabling Technologies Limited
Priority date: 2014-09-30
Filing date: 2014-09-30
Publication date: 2016-04-07
Also published as: CN107087433B; CN107087433A

Abstract

A radiofrequency identification (RFID) tag comprising a slotted antenna coupled with an integrated circuit module on a substrate, wherein the slotted antenna includes at least one primary opening for receiving the integrated circuit module and for controlling a resonance frequency of the RFID tag.

Description

RADIO FREQUENCY IDENTIFICATION (RFID) TAG

TECHNICAL FIELD

The present invention relates to a radio frequency identification tag and particularly， although not exclusively， to a radio frequency identification windshield tag for vehicle applications.

BACKGROUND

RFID technologies have been widely employed for object tracking and identification applications. Typically in an RFID system there is an RFID tag attached to an object and an RFID reader. The RFID reader communicates with and/or powers up the RFID tag with EM/RF fields/waves/signals. The RFID tag usually contains information associated with the object (for example， the nature of the object， the amount， the time of production， etc. ) and can be read by the RFID reader. In some situations， the RFID reader may also write information into the RFID tag.

There are currently different types of classifications for RFID tags. For example， RFID tags may be classified into active， passive， or semi-passive type depending on whether they include a power source and how the power source operates. Other types of classifications relate to the antenna of the tag， which may utilize linear polarization or circular polarization for RF signal communication. Clearly， different types of RFID tags are adapted or particularly suitable for specific applications.

For RFID tags for vehicle applications (e.g. vehicle tracking， auto-toll， car park management， etc. ) ， RFID tags are usually attached to the vehicle， most commonly to the windshield of the vehicle. This type of windshield tags usually have to conform to the “credit card” type form factor， and thus are often limited to using dipole or T-matched dipole as their antenna design. There is a continuous heavy bias for manufacturers of windshield tags to continue manufacturing windshield RFID tags using existing known technologies， and this render the tags rather inflexible in terms of design and manufacture.

It is an object of the present invention to address the above needs， to overcome or substantially ameliorate the above disadvantages or， more generally， to provide an improved RFID tag， in particular， an improved windshield RFID tag.

SUMMARY OF THE INVENTION

In accordance with a first aspect of the present invention， there is provided a radiofrequency identification (RFID) tag comprising a slotted antenna coupled with an integrated circuit module on a substrate， wherein the slotted antenna includes at least one primary opening for receiving the integrated circuit module and for controlling a resonance frequency of the RFID tag.

Preferably， the resonance frequency of the RFID tag is controlled by：

a size of the at least one primary opening； a displacement of the at least one primary opening from an edge of the slotted antenna； and/or a size of the slotted antenna.

In a preferred embodiment of the first aspect， the resonance frequency of the RFID tag decreases as the size of the at least one primary opening increases， and/or as the displacement of the at least one primary opening from an edge of the slotted antenna decreases.

Preferably， the at least one primary opening is arranged in a central portion of the slotted antenna. The slotted antenna may comprise any shape but is preferably rectangular.

Preferably， the slotted antenna includes two primary openings substantially aligned with one another in the central portion of the slotted antenna.

Preferably， a shape of the at least one primary opening is quadrilateral， triangular， ellipse， circular， sector or polygonal.

In one embodiment of the first aspect， the slotted antenna further comprises at least one secondary openings arranged adjacent one or both sides of the at least one primary openings.

Preferably， the at least one secondary opening has no substantial effect on the resonance frequency of the RFID tag.

In one embodiment of the first aspect， the substrate comprises ceramic， paper or plastic materials.

In a particular embodiment of the first aspect， the ceramic material comprises aluminium oxide.

In one embodiment of the first aspect， the RFID tag is arranged to be attached to a glass material.

Preferably， the RFID tag is a passive RFID tag.

Preferably， the RFID tag is at least partially encased in a packaging material， and the packaging material， in one embodiment， comprises plastic materials.

Preferably， the RFID tag is arranged to be attached to a windshield of a vehicle.

In accordance with a second aspect of the present invention， there is provided vehicle attached with an RFID tag in accordance with the first aspect of the present invention. Preferably， the radiofrequency identification (RFID) windshield tag is attached on the windshield of the vehicle.

In accordance with a third aspect of the present invention， there is provided a radiofrequency identification (RFID) windshield tag for vehicles， comprising： an RFID tag having a slotted antenna coupled with an integrated circuit module on a substrate， wherein the slotted antenna includes at least one primary opening for receiving the integrated circuit module and for controlling a resonance frequency of the RFID tag， and the integrated circuit module stores information relating to the vehicle； a packaging material for at least partially encasing the RFID tag； wherein the RFID windshield tag is arranged to be attached to a windshield of a vehicle such that the information relating to the vehicle contained in the integrated circuit module may be read by an RFID reader arranged external to the vehicle.

Preferably， the resonance frequency of the RFID tag is controlled by： a size of the at least one primary opening； a displacement of the at least one primary opening from an edge of the slotted antenna； and/or a size of the slotted antenna.

In a preferred embodiment of the third aspect， the resonance frequency of the RFID tag decreases as the size of the at least one primary opening increases， and/or as the displacement of the at least one primary opening from an edge of the slotted antenna decreases.

In one embodiment of the third aspect， the substrate comprises ceramic， paper or plastic materials.

In one embodiment of the third aspect， the packaging material comprisiug plastic materials.

In one embodiment of the third aspect， the RFID windshield tag is a passive type RFID tag.

In accordance with a fourth aspect of the present invention， there is provided a vehicle attached with a radiofrequency identification (RFID) windshield tag in accordance with the third aspect of the present invention. Preferably， the radiofrequency identification (RFID) windshield tag is attached on the windshield of the vehicle.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention will now be described， by way of example， with reference to the accompanying drawings in which：

Figure 1 is a schematic diagram of an antenna for an RFID tag in accordance with one embodiment of the present invention；

Figure 2 is a schematic diagram of an antenna for an RFID tag in accordance with another embodiment of the present invention；

Figure 3 is a schematic diagram of an antenna for an RFID tag in accordance with yet another embodiment of the present invention；

Figure 4 is a diagram for illustrating the key dimensions of the antenna of Figure 1；

Figure 5A is a schematic diagram for illustrating how the RFID tag is attached to a glass material in one embodiment of the present invention；

Figure 5B is a schematic diagram for illustrating how the RFID tag is attached to a glass material in another embodiment of the present invention； and

Figure 6 illustrates an exemplary application of the RFID tag of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to Figures 1-3， there are shown different embodiments of a radiofrequency identification (RFID) tag comprising a slotted antenna arranged to couple with an integrated circuit module on a substrate， wherein the slotted antenna includes at least one primary opening for receiving the integrated circuit module and for controlling a resonance frequency of the RFID tag.

Figure 1 shows a schematic diagram of an antenna 100 for an RFID tag in accordance with one embodiment of the present invention. As shown in Figure 1， the antenna 100 is substantially planar and has a substantially rectangular shape. The antenna 100 includes two smaller central openings 102 arranged in its central portion. The smaller central openings 102 as shown in Figure 1 have a substantially square shape and are aligned with one another. Two larger side openings 104 are arranged on both sides of the two smaller central openings 102. As shown in the Figure， the larger side openings 104 are of rectangular shape. The small and

large openings

102， 104 are arranged in a substantially symmetric manner about a central short axis of the slotted antenna 100.

In the present embodiment， the feed part 106 accommodates the integrated circuit module/chip (not shown) . Depending on the interface of the integrated circuit module/chip， the feed part 106 may consist of one or multiple feed gaps. The two smaller central openings 102 are arranged to couple with the feed part. More particularly， the coupling between the antenna 100 and the integrated circuit module/chip allows data communication between the antenna 100 and the integrated circuit module/chip such that the RFID tag can interact with an external RFID reader for reading or writing information from or into the integrated circuit module/chip. In one embodiment， the two larger side openings 104 could be arranged to receive objects therein， although this is not preferred in some other embodiments. Preferably， the slotted antenna 100 and the integrated circuit module/chip are formed on a substrate material such as ceramic (e.g. Al₂O₃) ， plastic or paper materials by printing or other attachment methods.

Figure 2 shows an antenna 200 for an RFID tag in accordance with another embodiment of the present invention. As shown in Figure 2， the antenna 200 is substantially planar and has a substantially rectangular shape. The antenna 200 includes two smaller central openings 202 arranged in its central portion. The smaller central openings 202 as shown have a substantially circular shape and are aligned with one another. Two larger side openings 204 are arranged on both sides of the two smaller central openings 202. As shown in Figure 2， the larger side openings 204 are of rectangular shape. Unlike the embodiment of Figure 1， the smaller central openings 202 and larger side openings 204 are arranged in an asymmetric manner about a central short axis of the slotted antenna 200.

In the present embodiment， the feed part 206 accommodates the integrated circuit module/chip (not shown) . Depending on the interface of the integrated circuit module/chip， the feed part 206 may consist of one or multiple feed gaps. The two smaller central openings 202 are arranged to couple with the feed part closely. More particularly， the coupling between the antenna 200 and the integrated circuit module/chip allows data communication between the antenna and the integrated circuit module/chip such that the RFID tag can interact with an external RFID reader for reading or writing information from or into the integrated circuit module/chip. In one embodiment the two larger side openings 204 could be arranged to receive objects therein， although this is not preferred in some other embodiments. Preferably， the slotted antenna 200 and the integrated circuit module/chip are formed on a substrate material such as ceramic (e.g. Al₂O₃) ， plastic or paper materials by printing or other attachment methods.

Figure 3 shows an antenna for an RFID tag 300 in accordance with yet another embodiment of the present invention. As shown in Figure 3， the antenna 300 is substantially planar and has a substantially rectangular shape. The antenna 300 includes three central openings 302 arranged in its central portion. The three central openings 302 as shown have a substantially rectangular shape and are aligned with one another. Unlike the previous two embodiments in Figures 1 and 2， there are no side openings in the slotted antenna 300 of the present embodiment.

In the present embodiment， the feed part 306 accommodates the integrated circuit module/chip (not shown) . Depending on the interface of the integrated circuit module/chip， the feed part 306 may consist of one or multiple feed gaps. The three central openings 302 are arranged to couple with the feed part closely. . More particularly， the coupling between the antenna 300 and the integrated circuit module/chip allows data communication between the antenna 300 and the integrated circuit module/chip such that the RFID tag can interact with an external RFID reader for reading or writing information from or into the integrated circuit module/chip. Preferably， the slotted antenna 300 and the integrated circuit module/chip are formed on a substrate material such as ceramic (e.g. Al₂O₃) ， plastic or paper materials by printing or other attachment methods.

Although in the various embodiments of the antenna of the RFID tag (or RFID tag) as shown in Figure 1-3 the slotted antenna 100， 200， 300 resembles a substantially rectangular shape， it is also possible for the slotted antenna to have other shapes such as other quadrilateral， circular， ellipse， triangular or even polygonal in other embodiments. In addition， in the present invention， the slotted antenna must include at least one or preferably at least two central openings. The number of central opening may vary in different embodiments. The shape of the central opening may also vary， having other shapes such as other quadrilateral， circular， ellipse， triangular or even polygonal in different embodiments. Preferably in the present invention the slotted antenna includes at least one side opening (although this is not absolutely necessary) . In other embodiments， the slotted antenna may have no side openings. The shape of the side openings may also vary in different embodiments， by having any regular or irregular shapes. Although in the embodiments as shown in Figures 1 and 3 the slotted antennas 100， 300 are substantially symmetric about their short or long axis， it is again not absolutely necessary to have the openings/slots arranged in a symmetric manner. The alignment of the central openings and/or the side openings is also non-essential， although in some embodiments this is preferred. In the various embodiments of the RFID tag as shown， the RFID tag is preferably a passive RFID tag. However， it is also possible for the RFID tag to be an active or semi-passive tag having a power source.

Figure 4 illustrates the key dimensions of the antenna in the RFID tag antenna 100 of Figure 1. In the present embodiment the key dimensions include an overall size of the slotted antenna (C x D) ， a size of the central opening (A) ， and a offset distance (B) of the central opening from an edge of the slotted antenna 100. More specifically， in this embodiment the key dimensions are： the length (C) and width (D) of the slotted antenna 100， the length (A) of the central opening (along the long axis of the slotted antenna) ， and an offset (B) of the central opening from the long edge of the slotted antenna 100 (i.e. the shortest distance of the central opening to the long edge of the slotted antenna) . Depending on the design of the slotted antenna in other embodiments， other factors may also affect the tag resonance frequency (f_res) although the major governing factors of the tag resonance frequency in a slotted antenna are the parameters listed above.

A simulation of the effects of some of the key dimensions of the antenna on the tag resonance frequency (f_res) of the RFID tag (the frequency at which the best tag performance is achieved) are shown in the following tables.

FABLE 1

TABLE 2

As illustrated by the simulation results shown in Tables 1 and 2， as the offset (B) increases， the tag resonance frequency increases. More particularly， the rate of increase in tag resonance frequency due to the change in offset (B) is 26.5 MHz/mm. On the other hand， as the length (A) increases， the tag resonance frequency decreases. More particularly， the rate of increase in tag resonance frequency due to the change in length (A) is 22 MHz/mm. This shows that in the present invention the smaller the area of the central openings， the higher the tag resonance frequency (f_res) . This analysis can preferably be extended to central openings having other shapes.

Figures 5A and 5B show how the RFID tag of the present invention is arranged to be attached to a glass material. As shown in Figures 5A and 5B， the RFID tag includes a slotted antenna 502A， 502B coupled with an integrated circuit chip (hidden by the slotted antenna) . The slotted antenna 502A， 502B with the integrated circuit chip is formed on a substrate 504A， 504B. In one example， the substrate 504A， 504B is a ceramic material， and the slotted antenna with the integrated circuit chip is printed on it. In Figure 5A， the RFID tag is encased in a packaging material 506A. The packaging material 506A is in turn attached to the glass material layer 508A so that the RFID tag is “indirectly” coupled with or mounted on the glass material layer 508A. Examples of the packaging material 506A include plastic or paper material， and the material is preferably water or dust proof/impermeable. By packaging the RFID tag in such packaging material， the tag could be protected from wearing or damaging by the environment for example due to dust or moisture. In the embodiment of Figure 5B， the RFID tag is “directly” attached to the glass material layer 508B without being packaged in any packaging material.

Figure 6 illustrates an application of the RFID tag of the present invention. In particular， Figure 6 shows that the RFID tag 602 of the present invention is attached to a windshield of a vehicle 604. Although in the present example the vehicle 604 is a car， in other embodiments the vehicle may be a lorry or ship or any other types of vehicles. Preferably， the RFID tag 602 is attached to the windshield in a similar manner to that illustrated in Figures 5A and 5B. In some embodiments， the tag may be attached to other parts of the vehicle 604， i.e. not necessary the windshield.

In one example， an RFID reader 606 is arranged in a car park entrance for management purposes. When the car 604 attached with the RFID tag 602 arrives at the car park entrance， the RFID reader 606 (a transceiver in nature) detects the presence (e.g. by other sensors) of the car 604 and transmits EM/RF waves (which may include a power signal and a read signal) 607 to the RFID tag 602. The RFID tag 602， without any internal power source， is then powered up to receive a command (which may be in the read signal) from the RFID reader 606. Upon processing in the circuits in the RFID tag 602， data associated with the vehicle is retrieved from the integrated circuit chip in the RFID tag 602 and is transmitted back to the RFID reader 606. The data associated with the vehicle may include the number of the plate of the car， the type of the car， the owner of the car， the entry time， etc. The data transmitted to the RFID reader 606 will then be stored in a local or remote database 608. When the car leaves the car park later， the RFID reader 606 again detects the presence of the tag 602 and transmits a power and a read signal 607 to the tag. The tag 602 may then transmits to the reader 606 information relating to the leaving time， the number of the plate of the car， the type of the car， the owuer of the car， etc. The tag reader 606， upon receiving this information， can then transmit the information to the local or remote database 608， which is responsible for calculating charges and send the bill to the user.

It should be noted that the above exemplary application is only one of the many applications that are possible with the RFID tag of the present invention. Other examples relating to the theft， vehicle body parts identification， cat plate management， or highway electronic identification charges applications are also possible as would be appreciated by a person skilled in the art.

The RFID tag in different embodiments of the present invention presents a number of distinct advantages. Firstly， the tag in the present invention does not utilize dipole or T-matched dipole antennas， but a “true” slotted antenna with at least one (preferably at least two) central openings and optionally any number of side openings. The provision of the at least one (preferably at least two) central openings allows for a more flexible impedance matching and a wider impedance bandwidth (more robust performance) compared to existing RFID tags， especially existing tags for windshield or vehicle applications which is of the credit card type form factor. Furthermore the provision of the side openings facilitates the reduction of consumption of conductive ink and hence reduces fabrication costs， without affecting the performance of the tag or the tag resonance frequency substantially. Other advantages of the present invention in terms of structure， function， costs， effectiveness， ease of manufacture， efficiency， etc. will be apparent to a person skilled in the art by reference to the above description.

It will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the invention as shown in the specific embodiments without departing from the spirit or scope of the invention as broadly described. The present embodiments are， therefore， to be considered in all respects as illustrative and not restrictive.

Any reference to prior art contained herein is not to be taken as an admission that the information is common general knowledge， unless otherwise indicated.

Claims

A radiofrequency identification (RFID) tag comprising a slotted antenna coupled with an integrated circuit module on a substrate， wherein the slotted antenna includes at least one primary opening for receiving the integrated circuit module and for controlling a resonance frequency of the RFID tag.
An RFID tag in accordance with claim 1， wherein the resonance frequency of the RFID tag is controlled by：

a size of the at least one primary opening；

a displacement of the at least one primary opening from an edge of the slotted antenna； and/or

a size of the slotted antenna.
An RFID tag in accordance with claim 2， wherein the resonance frequency of the RFID tag decreases as the size of the at least one primary opening increases， and/or as the displacement of the at least one primary opening from an edge of the slotted antenna decreases.
An RFID tag in accordance with any one of claims 1-3， wherein the at least one primary opening is arranged in a central portion of the slotted antenna.
An RFID tag in accordance with claim 4， wherein the slotted antenna includes two primary openings substantially aligned with one another in the central portion of the slotted antenna.
An RFID tag in accordance with any one of claims 1-5， wherein a shape of the at least one primary opening is quadrilateral， triangular， ellipse， circular， sector or polygonal.
An RFID tag in accordance with any one of claims 1-6， wherein the slotted antenna further comprises at least one secondary openings arranged adjacent one or both sides of the at least one primary openings.
An RFID tag in accordance with claim 7， wherein the at least one secondary opening has no substantial effect on the resonance frequency of the RFID tag.
An RFID tag in accordance with any one of claims 1-8， wherein the substrate comprises ceramic， paper or plastic materials.
Au RFID tag in accordance with claim 9， wherein the ceramic material comprises aluminium oxide.
An RFID tag in accordance with any one of claims 1-10， wherein the RFID tag is arranged to be attached to a glass material.
An RFID tag in accordance with any one of claims 1-11， wherein the RFID tag is a passive RFID tag.
An RFID tag in accordance with any one of claims 1-12， wherein the RFID tag is at least partially encased in a packaging material.
An RFID tag in accordance with claim 13， wherein the packaging material comprising plastic materials.
An RFID tag in accordance with any one of claims 1-14， wherein the RFID tag is arranged to be attached to a windshield ofa vehicle.
A vehicle attached with an RFID tag of any one of the preceding claims.
A radiofrequency identification (RFID) windshield tag for vehicles， comprising：

an RFID tag having a slotted antenna coupled with an integrated circuit module on a substrate， wherein the slotted antenna includes at least one primary opening for receiving the integrated circuit module and for controlling a resonance frequency of the RFID tag， and the integrated circuit module stores information relating to the vehicle；

a packaging material for at least partially encasing the RFID tag；

wherein the RFID windshield tag is arranged to be attached to a windshield of a vehicle such that the information relating to the vehicle contained in the integrated circuit module may be read by an RFID reader arranged external to the vehicle.
An RFID windshield tag in accordance with claim 17， wherein the resonance frequency of the RFID tag is controlled by：

a size of the at least one primary opening；

a displacement of the at least one primary opening from an edge of the slotted antenna； and/or

a size of the slotted antenna.
An RFID windshield tag in accordance with claim 18， wherein the resonance frequency of the RFID tag decreases as the size of the at least one primary opening increases， and/or as the displacement of the at least one primary opening from an edge of the slotted antenna decreases.
An RFID windshield tag in accordance with any one of claims 17-19， wherein the at least one primary opening is arranged in a central portion of the slotted antenna.
An RFID windshield tag in accordance with any one of claims 17-20， wherein the substrate comprises ceramic， paper or plastic materials.
An RFID windshield tag in accordance with claim 21， wherein the packaging material comprising plastic materials.
An RFID windshield tag in accordance with any one of claims 17-22， wherein the RFID tag is a passive type RFID tag.
An vehicle attached with an RFID windshield tag of any one of the claims 17-23.