EP4348499A1

EP4348499A1 - Capacitive coupled rfid tag reader

Info

Publication number: EP4348499A1
Application number: EP22729766.0A
Authority: EP
Inventors: Marco Mazza; Peter Boylan
Original assignee: Frisense Ltd
Current assignee: Frisense Ltd
Priority date: 2021-06-04
Filing date: 2022-06-01
Publication date: 2024-04-10
Also published as: GB202108000D0; WO2022254222A1

Abstract

A capacitive coupled, CC, radio frequency identification, RFID, tag reader comprising a power source. An electronic circuit configured to receive electrical power from the power source, generate a radio frequency, RF, signal and provide the RF signal to an interface and having a decoder configured to decode a data signal received at the interface. An electrode pair coupled to the interface of the electronic circuit, the electrode pair comprising a first electrode and a second electrode surrounding the first electrode. There is also provided a capacitive coupled, CC, radio frequency identification, RFID, tag reader comprising a power source. An electronic circuit configured to receive electrical power from the power source, generate a radio frequency, RF, signal and provide the RF signal to an interface and having a decoder configured to decode a data signal received at the interface. A case enclosing the electronic circuit. a first connector in electrical connection with the interface and providing an electrical connection through the case.

Description

Capacitive coupled RFID tag reader

Field of the Invention

The present invention relates to a RFID tag reader and in particular, a capacitive coupled RFID tag reader used to interrogate capacitive coupled RFID tags.

Background of the Invention

Capacitive coupled tags (CC-tag or CCT) provide increased security whilst providing authenticity and tracking functionality. CC-tags have particular advantages as they can be made smaller and so can have wider use with a larger range of artefacts or items to be tagged.

CC-tags may be read using a tag reader having plates either side of the CC-tag (and item attached to the CC-tag). The reader then detects changes in electrical impedance caused by the tag implementing a signal modulation. Such CC-tags have top and bottom electrodes to interact with the parallel metal plates of the reader.

WO 2020/148550 describes a CC-tag that can be read from a single side as it includes a metal plate that extends beyond an edge of the CC-tag so that a tag reader can instead utilise reader electrodes that are adjacent to each other or side by side (see Figure 4 of this document). This is useful when the tag is placed on an item that cannot be placed between parallel planar plates.

Flowever, for small CC-tags, it can be difficult to align the electrodes of the CC-tag with the electrodes of the reader (and especially a single-sided reader). Enlarging the electrodes of the CC-tag aid alignment but negates its advantages regarding small size.

Therefore, there is required a CC-tag reader that is easier to align with such single sided CC-tags.

There is also a required a CC-tag reader that can be used with different applications and types of CC-tag or where CC-tags are located on different items having different configurations. Summary of the Invention

A capacitive coupled (CC) radio frequency identification (RFID) tag reader is provided that includes a power source and an electronic circuit that generates a radio frequency (RF) signal. The electronic circuit has an interface that provides the RF signal as an output and in response receives a modulated data signal as an input. This data signal is also read by the electronic circuit. A CC-tag can be powered from the signal provided by the electronic circuit, at least temporarily whilst it provides its data signal in response. The input and output interface is coupled to an electrode pair that is configured to radiate the RF signal and receive the data signal. A first or central electrode takes the form of a point source or point radiator. Surrounding or encircling this central electrode is a second electrode that is separated from the first electrode either by air or a solid dielectric material (or both). The second electrode or surrounding electrode can completely encircle the first or central electrode or may only partially surround it in an arc or other shape. The central and surrounding electrodes can be located in a flat planar configuration, a curved surface or other generally flat or undulating surface. The form of this surface may be configured to conform to an item to be tagged. For instance, if the item is not completely flat or contains protrusions then the surface of the antenna can contain corresponding conforming regions to facilitate close contact with the item containing the CC-tag. Furthermore, the item containing the CC-tag may contain marks or locating points corresponding with similar locating points or features in the plane surface of the antenna.

Therefore, it is only necessary to align the central electrode of the antenna with one of the electrodes of the CC-tag as the surrounding or second electrode of the reader antenna extends around the central electrode and so has a better opportunity for overlapping or intersecting with the second electrode of the CC-tag (or signal emanating from the second electrode).

There is also provided a CC-tag reader with a similar power source and electronic circuit. This further CC-tag reader includes a case or housing for the electronic circuit and optionally, the power source (e.g. a battery). The interface providing the output and input to the electronic circuit provides an electronic connection through the case. Flowever, the antenna of the CC-tag reader is not necessarily permanently attached to this connector. Instead, the connector is configured to make an electrical connection with different electrodes (or corresponding connectors of different electrodes) within different devices or objects. Therefore, the same reader circuit can be moved between applications more conveniently and separate antennas can be installed on different peripheral devices. Peripherals can be interchanged with this CC-tag reader repeatedly because the connector or connection external to the case, provides a removable electrical interface.

This interface can take the form of a simple touching interface design. Therefore, an electrical connection may be made by simply touching the interface with a corresponding interface on the peripheral. Alternatively, removable locking means may be used such as clips, clamps or interference fittings, for example.

There is also provided a system comprising any of the CC-tag readers described and one or more CC-tags.

Against this background and in accordance with a first aspect there is provided a A capacitive coupled, CC, radio frequency identification, RFID, tag reader comprising: a power source; an electronic circuit configured to receive electrical power from the power source, generate a radio frequency, RF, signal and provide the RF signal to an interface and having a decoder configured to decode a data signal received at the interface; and an electrode pair coupled to the interface of the electronic circuit, the electrode pair comprising a first electrode and a second electrode surrounding the first electrode. Therefore, a single CC tag can be read (and written to) more because alignment with its electrodes can be improved. Preferably, the second electrode is larger than the first electrode (e.g. in terms of surface are and/or linear size).

Optionally, the first electrode and the second electrode may extend to a planar surface. Therefore, the electrode pair can be placed closer to a CC-tag affixed to a flat object.

Optionally, the first electrode and the second electrode extend to a curved surface Therefore, the electrode pair can be placed closer to a CC-tag affixed to a curved object.

Advantageously, the first electrode and the second electrode may be embedded in a dielectric material. This provides ensures that the electrode pair is structurally secure and also provides a solid base for placing the antenna close to an object with a CC-tag. Preferably, the first electrode, the second electrode and the dielectric material may form a smooth surface. This provides an electrode pair that is less likely to snag or damage an item.

Optionally, the first electrode may have a circular and solid cross-section. Other configurations may be used.

Optionally, the second electrode may form a closed shape around the first electrode. A closed shape has no breaks in two dimensions. However, the shape may be open in some examples.

Optionally, the shape may be a polygon, a circle, an ellipse, a square, a rectangle, a triangle, or a hexagon. Other regular or non-regular shapes may be used.

Optionally, the first electrode may be at the centre of the closed shape. It may also be off-centre, adjacent or outside of the closed (or open) shaped second electrode.

Preferably, the first electrode and the second electrode may be electrically isolated.

Advantageously, the electrode pair may be interchangeable. Therefore, different electrode pairs may be used with the same tag reader.

Optionally, the CC RFID tag reader may further comprise a matching network to match impedance between the CC RFID tag reader and a CC RFID tag. This may be formed from one or more suitable inductors and/or capacitors, for example. This may optimise power transmission between the reader and a CC RFID tag being read.

Optionally, the electrode pair may form an antenna (e.g. having dimensions proportional to a fraction or a whole of the RF signal wavelength). However, the electrode pair does not necessarily need to take this form and the electrodes do not need to have physical dimensions proportional to the wavelength (or inversely proportional to the frequency) of the RF signal. In accordance with a second aspect, there is provided a capacitive coupled, CC, radio frequency identification, RFID, tag reader comprising: a power source; an electronic circuit configured to receive electrical power from the power source, generate a radio frequency, RF, signal and provide the RF signal to an interface and having a decoder configured to decode a data signal received at the interface; a case enclosing the electronic circuit; a first connector in electrical connection with the interface and providing an electrical connection through the case. Therefore, different electrode pairs can be used more easily.

Optionally, the CC RFID tag reader may further comprise: an electrode pair having a second connector configured to make a releasable electrical connection with the first connector. The electrode pair may be integral, form part of or physically connected to another object, such as a holder or cradle for an item having a CC-tag attached or placed on or in it, for example. In some examples, the antenna may be integral to a device for using a consumable product like an electronic cigarette, cosmetic dispenser, food or beverage dispenser, etc.

Optionally, the first connector and second connector may comprise electrodes configured to form a releasable interference fit.

Optionally, the decoder may be further configured to detect a signal encoded by a varying impedance or capacitance.

Preferably, the first connector may comprises two electrodes or contacts.

It should be noted that any feature described above may be used with any particular aspect or embodiment of the invention. Brief description of the Figures

The present invention may be put into practice in a number of ways and embodiments will now be described by way of example only and with reference to the accompanying drawings, in which:

Figure 1 shows a side view of a capacitive coupled RFID tag on an item together with a portion of an antenna of a tag reader, the antenna including two electrodes;

Figure 2 shows a top view of the CC-tag, item and tag reader of Figure 1 ;

Figure 3 shows a perspective view of an antenna of the tag reader of Figure 1 ;

Figure 4 shows a perspective view of a further example antenna of the tag reader of

Figure 1 ;

Figure 5 shows a perspective view of an item and CC-tag attached to that item;

Figure 6 shows a perspective view of the tag reader of Figure 1 ;

Figure 7 shows an exploded perspective view of the tag reader;

Figure 8 shows a further exploded perspective view of the tag reader;

Figure 9 shows a perspective view of an electronic circuit within the tag reader;

Figure 10 shows a perspective view of an underside of the circuit of Figure 9;

Figure 11 shows a portion of the antenna of the tag reader of Figure 1 ;

Figure 12 shows a perspective view of the front and back sides of the antenna of the tag reader of Figure 1 ;

Figure 13a shows an overhead view of a top and a bottom portion of a case of the tag reader of Figure 1 ;

Figure 13b shows a top view of a further example implementation of the tag reader of Figure 1 ;

Figure 14 shows a schematic view of the tag reader of Figure 13B together with an item including a separate antenna

Figure 15 shows a flowchart of firmware processes within the tag reader of figure 1 ; and

Figure 16 shows a flowchart of further firmware processes within the tag reader of figure 1.

It should be noted that the figures are illustrated for simplicity and are not necessarily drawn to scale. Like features are provided with the same reference numerals. Detailed description of the preferred embodiments

Single-sided capacitive coupled (CC) radio frequency identification (RFID) tags can be read from one side without requiring electrode plates either side of the tag to power the CC-tag or to read its response signal. Whilst such CC-tags can be made relatively small (around 1-2mm across), this can present a problem with alignment. This problem may be less apparent with CC-tags that are read using parallel plates either side of the CC-tag and item. Items to be tagged may include bank notes, electronic cigarettes, cosmetics, consumables, stackable items or individual products, for example.

Figure 1 shows a side view schematic diagram of such a single-sided CC-tag 10, and an item being tagged 50. The CC-tag 10 has an electrode 20 on one side (top in this figure) which may be in the form of a metal pad. Whilst figure 1 shows the electrode 20 being separate from the CC-tag 10 (e.g. formed from metal), this electrode may be formed from the surface of a substrate (e.g. silicon) of the CC-tag 10 itself. In this alternative example, the CC-tag 10 may be an integrated circuit with the surface of the substrate of the integrated circuit acting as or forming the electrode 20. The CC-tag 10 and electrode 20 is embedded in an insulator 40 (e.g. plastics material). A backplate metal layer 30 (e.g. metallic sheet or plate) is attached to the insulator 40 so that it is on the opposite side of the electrode 20 (bottom side in this figure). This backplate metal layer 30 extends beyond the extent of a surface of the CC-tag 10. This exposes a portion of the backplate metal layer 30 so that this portion is not obscured by the CC-tag 10 when viewed from the top side in figure 1. Figure 1 also shows a portion of an antenna of a CC-tag reader. This portion of the antenna has two electrodes. A first electrode or central electrode 60 is placed over, covering or adjacent the metal electrode 20 of the CC-tag. In this example implementation, the second electrode 70 takes the form of a ring, torus or annulus that surrounds or rings the first or central electrode 60. At least a portion of the second or annular electrode 70 covers at least a part (or all) of the metal backplate layer 30 of the C- tag 10. Therefore, the antenna and its electrodes 60, 70 can provide a radio frequency (RF) signal to the single-sided CC-tag 10 and receive a data signal in response. As the second electrode or annular electrode 70 has a larger surface area than the first electrode 60 then only a portion needs to overlap in order to provide and receive a sufficient signal to enable the CC-tag 10 to be energised and read (or written to). In example implementation, the insulator may be a tape insulator that may take the form of a flexible plastics material with an adhesive backing. The tape insulator may extend far beyond (e.g. at least 1 or 2 cm around the CC-tag 10). The backplate metal layer 30 may take the form of a foil backing, e.g. of aluminium or copper. Therefore, the tape insulator may extend beyond the backplate metal layer 30 or foil backing and provide an adhesive bond to the artefact or item to be tagged 50. Further adhesive may be placed on the foil, if necessary.

Figure 2 shows a top schematic view of the arrangement shown in Figure 1. The circular or annular shape of the second electrode 70 becomes apparent in figure 2. This second electrode partially overlaps the backplate metal layer 30 or foil backing of the CC- tag 10. Other structural parts of the antenna are not shown in Figures 1 or 2 but may take different forms. A dotted line (circular) has been used to show the outer edge of the first electrode 30 so as not to obscure the other features in figure 2.

Figure 3 shows a perspective schematic diagram of the antenna 100 of Figures 1 and 2. In this example implementation of the antenna 100, the electrodes are mounted within a metal body 110 with an air gap 105 between the metal body 110 and the annular electrode 70. A dielectric material 140, such as a plastics material, separates the first electrode 60 from the second electrode or annular electrode 70. A threaded mount 120 enables an electrical coupling to be formed with a coaxial cable 130, for example. In this example antenna 100, the first electrode 60 and second electrode 70, as well as the insulator 140 and metal body 110 extend to a planar or flat surface so that the antenna 100 can be laid flat or pressed closely against an item having a CC-tag 10. Figure 4 shows a similar example antenna 200, with similar components having the same reference numerals. Flowever, in this example antenna 200, the antenna face takes the form of a curve or portion of a cylinder with the metal body 220 also being curved. Therefore, the first and second electrode 60, 70 as well as the insulator 140 take the same curved shape. The second electrode 70 takes the form of a ring or annulus that has a side curve to conform to the contour of a cylinder. Such an antenna 200 may conform to a cylindrical shaped item having a CC-tag 10 attached. This may be applied to a tube or cylinder (e.g. a bottle), for example.

Figure 5 shows a schematic diagram of a CC-tag 10 attached to an item 300. This Figure shows how the insulator or tape 40 extends beyond the backed plate metal layer or foil 30 with the CC-tag 10 in the centre. The insulator 40 also acts as an adhesive to bond to the item 300.

In this example implementation, the backplate metal layer 30 and insulator 40 are square, with the CC-tag 10 in the centre of both flexible sheets but other shapes may be used. Different sizes and shapes of backplate metal layer 30 and insulator 40 may be used for different applications. The CC-tag 10, backplate metal layer 30 and insulator 40 are aligned centrally in this example but again, different configurations may be used.

In some example implementations, the antenna 100 may take the form of a modified SMA connector, for example. In such examples, the antenna may have a size of around 5mm to 20mm, for example.

Figure 6 shows a schematic diagram of a reader having a threaded connector that may accept a corresponding threaded connector from an antenna 100, 200. In this figure, a switch or button is shown to activate the CC-tag reader and provide a user interface.

Figure 7 shows a partially exploded schematic diagram of the CC-tag reader of Figure 6. In this figure, a cover of a case of the CC-tag reader has been removed to show a reader circuit and interface providing an RF output in the form of a threaded connector for accepting a corresponding connector of the antenna 100, 200. The CC-tag reader also includes a power source in the form of a battery circuit to power the electronic circuit. In this figure, the battery is not shown. The electronic circuit is configured to receive electrical power from the power source or battery and generate a radio frequency signal that is provided to the interface. The electronic circuit also includes a decoder configured to decode data signals received from the interface when the antenna 100, 200 is attached. Any of the antennas described may be attached to the connector or interface.

Figure 8 shows a further exploded view of the CC-tag reader with the electronic circuit removed from the case. This figure also shows the activating switch.

Figure 9 shows the electronic circuit in more detail and Figure 10 shows components placed on the opposing side of such an electronic circuit to enable a more compact device. Figure 11 shows a top view of an example antenna interface. This interface includes inductors, L1 , L2 to provide tuning between the electronic circuit and the antenna 100, 200.

Figure 12 shows a perspective view of a further example antenna having two electrodes 60, 70. In this example, the central electrode 60 is larger than indicated in other example antennas. The ratio of surface areas between the inner or central electrode 60 and the outer or annular electrode 70 is also greater in the example shown in this figure.

Whilst circular or annular electrodes 70 have been shown in these example, it should be noted that other shapes and configurations may be used. For example, the electrode 70 that surrounds the central electrode 60 may take other shapes such as square, triangle, rectangle, hexagon, pentagon and octagon, for example. Furthermore, whilst the second electrode 70 shown in these examples have all been closed shapes, it may have an opening or take the form of an open shape such as a horseshoe or v-shape, for example. Furthermore, asymmetrical shapes may also be used and the thickness of one part of the electrode 70 may vary as it surrounds the central electrode 60.

The previous figures show a CC-tag reader that include interfaces so that an antenna can be fixed permanently or semi-permanently. Flowever, the interface may be non-removable from the antenna or take different forms to be used with different fixing means.

The CC-tag reader may be used with many different types of items and CC-tags 10 having different shapes and sizes. When different configurations of CC-tags 10 are required for the same tag reader then the fixed antenna 100, 200 may not be appropriate or may not fit a particular item attached to a CC-tag 10. Figures 13a and 13b show a further example implementation of the CC-tag reader. In this further example implementation, additional electrode contact points are provided through the case of the CC-tag reader.

This may be in addition to the interface for fixing a semi-permanent (or permanent) antenna or instead of it. In this example, the additional electrode connection points form a first connector through the case. This first connector or pair of additional electrode connection points can make electrical contact with a second connector attached to a further item or artefact. This is shown schematically in Figure 14 where the artefact comprising a corresponding second connector also in the form of electrode connection points. In this case, an antenna is incorporated within the artefact so that an optimally configured antenna can be used. The connection between the first connector and the second connector are releasable an interchangeable and so a single CC-tag reader can be used with one or more different artefacts and antenna configurations.

In the example shown in Figure 14, the first connection electrodes extend partially into corresponding openings within the artefact. For example, the electrodes may be spring-loaded or provide an interference fit, or may be simply pressed against the corresponding second connector electrodes whilst a CC-tag or CC-tags are read. Locators and/or temporary and releasable fixings (not shown here in this figure) may be used to provide a more secure physical connection.

Whilst the electronic circuit described throughout this description has not been described in detail, it may include UFIF RFID integrated circuits and other components familiar to the skilled person and operate at a suitable frequency (e.g. 868MFIz). The printed circuit board forming the electronic circuit may have several layers that may be used for RF isolation, for example. Other filtering, power management and communication protocols may be used. For example, the electronic circuit may also include Bluetooth or WiFi connectivity for communicating with other devices or peripherals. This electronic circuit may also incorporate mobile device control using apps and other software.

Firmware may be stored and potentially upgraded within the CC-tag reader. For example, this firmware may control the on/off powering of the device, checking Bluetooth packet control and electronic product code (EPC) or other RFID standards. The firmware may also control writing EPC and reading EPC data to a CC-tag 10 (or other data types). Success and failure modes may be managed by monitoring and limiting multiple attempts. LED indicators may also be present on the device and controlled using the firmware.

Such firmware is illustrated as flowcharts in Figures 15 and 16 but other firmware steps may be used. In these figures, NRF stands for National Retail Federation.

The CC-tag reader may write data to CC-tags 10 and/or read data from them. The CC-tag reader may report that no tag is present, a tag is recognised, a tag has been

Claims

recognised and action taken, a tag has expired or a tag is stolen, for example. Such reports may be provided to an external device such as a mobile device running a suitable mobile application over Bluetooth or WiFi, for example. The electronic circuit may include a processor or processors such as a Central Processing unit (CPU), and/or a single or a collection of Graphics Processing Units (GPUs). The processor may execute logic in the form of a software program or firmware. The computer system may include a memory including volatile and non-volatile storage medium. A computer-readable medium may be included to store the logic or program instructions. The different parts of the system may be connected using a network (e.g. wireless networks and wired networks). The computer system may include one or more interfaces. The computer system may contain a suitable operating system such as UNIX, Windows (RTM) or Linux, for example. In some example implementations, the CC-tag 10 may be placed directly onto metal artefacts which removes the need for a separate metallic backplate layer 30. In this case, the second electrode 70 may cover any part of the artefact, making reading and writing more accurate and effective. Typically, the CC-tag reader may be approximately 10cm by 1 .5cm, but other sizes may be used. As will be appreciated by the skilled person, details of the above embodiment may be varied without departing from the scope of the present invention, as defined by the appended claims. For example, the tag reader may be incorporated into other devices. The CC-tag may take the form of different sizes and shapes. The CC-tag may be place within an item rather than on its surface. More than one CC-tag may be read at the same time. Many combinations, modifications, or alterations to the features of the above embodiments will be readily apparent to the skilled person and are intended to form part of the invention. Any of the features described specifically relating to one embodiment or example may be used in any other embodiment by making the appropriate changes. CLAIMS:

1. A capacitive coupled, CC, radio frequency identification, RFID, tag reader comprising: a power source; an electronic circuit configured to receive electrical power from the power source, generate a radio frequency, RF, signal and provide the RF signal to an interface and having a decoder configured to decode a data signal received at the interface; and an electrode pair coupled to the interface of the electronic circuit, the electrode pair comprising a first electrode and a second electrode surrounding the first electrode.

2. The CC RFID tag reader of claim 1 , wherein the first electrode and the second electrode extend to a planar surface.

3. The CC RFID tag reader of claim 1 , wherein the first electrode and the second electrode extend to a curved surface

4. The CC RFID tag reader according to any previous claim, wherein the first electrode and the second electrode are embedded in a dielectric material.

5. The CC RFID tag reader of claim 4, wherein the first electrode, the second electrode and the dielectric material form a smooth surface.

6. The CC RFID tag reader according to any previous claim, wherein the first electrode has a circular and solid cross-section.

7. The CC RFID tag reader according to any previous claim, wherein the second electrode forms a closed shape around the first electrode.

8. The CC RFID tag reader of claim 7, wherein the shape is a polygon, a circle, an ellipse, a square, a rectangle, a triangle, or a hexagon.

9. The CC RFID tag reader of claim 7 or claim 8, wherein the first electrode is at the centre of the closed shape.

10. The CC RFID tag reader according to any previous claim, wherein the first electrode and the second electrode are electrically isolated.

11 . The CC RFID tag reader according to any previous claim, wherein the electrode pair is interchangeable.

12. The CC RFID tag reader according to any previous claim, further comprising a matching network to match impedance between the CC RFID tag reader and a CC RFID tag.

13. The CC RFID tag reader according to any previous claim, wherein the electrode pair forms an antenna.

14. A capacitive coupled, CC, radio frequency identification, RFID, tag reader comprising: a power source; an electronic circuit configured to receive electrical power from the power source, generate a radio frequency, RF, signal and provide the RF signal to an interface and having a decoder configured to decode a data signal received at the interface; a case enclosing the electronic circuit; a first connector in electrical connection with the interface and providing an electrical connection through the case.

15. The CC RFID tag reader of claim 14 further comprising: an electrode pair having a second connector configured to make a releasable electrical connection with the first connector.

16. The CC RFID tag reader of claim 15, wherein the first connector and second connector comprise electrodes configured to form a releasable interference fit.

17. The CC RFID tag reader according to any of claims 14 to 16, wherein the decoder is further configured to detect a signal encoded by a varying impedance.

18. The CC RFID tag reader according to any of claims 14 to 17, wherein the first connector comprises two electrodes.