SMALL DIFFERENTIAL ELECTRIC FIELD ACTIVATED UHF RFID DEVICE

A small differential-electric-field-activated UHF RFID device. Such a device may be small and easy to manufacture, improving the viability of incorporating RFID technology into articles like tickets, cards, and tokens. Such a device may also be small and inexpensive enough to allow for redundant RFID chips to be placed on an article, improving the survivability of an RFID-enabled article. Such a device may also reduce the amount of metal or plastic that is used in order to create an article such as a smart ticket or card, improving recyclability.

BACKGROUND

“Smart labels,” also called “smart tags,” are print-coded labels which incorporate extremely flat configured transponders as an inlay inside the label. These transponders typically include a chip, an antenna, and bonding wires.

In many processes, such as in logistics and transportation, “smart labels” or “intelligent labels” have been replacing more conventional optical barcodes, as well as2D barcodes, QR codes and the like, as the key means by which items can be identified and tracked. The automation of such optical coding is limited in appropriate distance for reading success, and typically requires manual manipulation in order to bring the code into the vision range of a scanner (or, alternatively, requires the use of a scanner gate that scans the entire surface of a coded object). Smart labels, however, can be read from a distance, without having to be in the line of sight of the scanner and thus facilitate automation.

However, smart labels do have certain downsides. For example, smart labels are somewhat more susceptible to physical damage than optical barcodes. Smart labels are also somewhat more expensive to use than optical barcodes. While optical barcode labels can be printed using conventional label printers or even standard consumer-grade inkjet printers, smart labels must be printed using more specialized printers, and have a somewhat higher failure rate from printing (often around 5%). Lastly, smart labels can be somewhat larger and more obtrusive than optical barcode labels, limiting their usefulness in some applications. For example, “RFID Tickets” typically have large embedded antennae spanning a large portion of the ticket, meaning that a user may risk damaging the ticket and making it unusable by folding it.

SUMMARY

According to an exemplary embodiment, a small differential-electric-field-activated UHF RFID device may be disclosed. Such a device may be small and easy to manufacture, improving the viability of incorporating RFID technology into articles like tickets, cards, and tokens. Such a device may also be small and inexpensive enough to allow for redundant RFID chips to be placed on an article, improving the survivability of an RFID-enabled article. Such a device may also reduce the amount of metal or plastic that is used in order to create an article such as a smart ticket or card, improving recyclability.

DETAILED DESCRIPTION

According to an exemplary embodiment, and referring generally to the Figures, various exemplary implementations of a small differential-electric-field-activated UHF RFID device (“RFID device”) may be disclosed. In some embodiments, such an RFID device may also be referred to as a “interposer” or comprising a “RFID strap.” In one embodiment presently contemplated, a form of differential electric field device utilized a dipole antenna, with a total length of half wave at the operating frequency, approximately 152.5 mm at FCC band. In one example of the present invention, a device is provided where the total length is less than 1/30th of a wavelength at the operating band, approximately 10.2 mm. It is important to note, however, that the present application is not limited to any particular size.

According to an exemplary embodiment, an RFID device may be designed to be small and easy to manufacture in high volume. The low cost and small size may each improve the viability of incorporating the device into smaller, thinner, and/or lower-cost articles such as tickets, cards (such as payment cards or identification cards) and tokens, allowing such articles to be equipped with RFID technology under circumstances that were not possible or practical before. In some exemplary embodiments, an article may even be equipped with multiple redundant RFID devices in order to improve reliability, allowing the article to still be read by an RFID reader in the event that one or more of the RFID devices breaks or is rendered unusable.

According to an exemplary embodiment, the small size of the RFID device may serve to decrease the amount of metal and plastic that is used to manufacture the RFID device. This may have advantages for manufacturing, but may also serve to make RFID-equipped articles more recyclable.

According to an exemplary embodiment, an RFID device may have approximate measurements of 5 mm by 10 mm. According to another exemplary embodiment, an RFID device may be larger than these dimensions in order to improve readability, may be smaller than these dimensions in some applications (such as where it may be practical to have a higher-precision reader) or may have any other measurements, as desired. According to an exemplary embodiment, the tabs of the RFID device may be a small fraction of the wavelength used at the operating frequency.

In order to read the RFID device, according to some exemplary embodiments, the RFID device may be put in connection with a coupler. In an exemplary embodiment, the coupler may be or may include, for example, two plates, between which may exist a differential electric field designed to operate the RFID device.

Turning now to exemplaryFIG. 1,FIG. 1displays an exemplary embodiment of a pairing100between an RFID strap102and a coupler104. In the exemplary embodiment ofFIG. 1, a coupler104may include one or more sets of a metallic structure that has at one or more points creating a differential electric field such as coupler plates108, which may be connected to an RFID reader106. In an exemplary embodiment, the coupler plates108may be disposed near one another (they may, for example, run parallel or substantially parallel to one another) and may be separated by a gap disposed between them. While the present invention speaks to the utilization of coupler plates108, it is not limited to such and contemplates the utilization of any metallic structure known in the art, such as a bridge, to create a differential electric field.

According to one embodiment, a differential electric field may be provided between the coupler plates108of the coupler104. Such a differential electric field may be provided by, for example, the RFID reader106, or by another component, as desired. Such a differential electric field may act to operate the RFID strap102when the RFID strap102is brought into close connection with the coupler plates108of the coupler104.

According to an exemplary embodiment, an X direction and a Y direction may be established, such that, for example, the X direction runs horizontally and the Y direction runs vertically, as shown inFIG. 1. In the exemplary embodiment shown inFIG. 1, the X direction may be parallel to the length of the gap between the coupler plates108, and the Y direction may be perpendicular to this direction.

According to an exemplary embodiment, a user may operate a coupler104by placing an RFID strap102, which may be located on some other article configured to carry the RFID strap102, over the coupler plates108, such that the RFID strap102bridges the coupler plates108. In an exemplary embodiment, a user may place the RFID strap102, located on the carrier article, over the coupler104, such that there is minimal variation of the RFID strap102in the Y direction. A user may then move the article in the X direction in order to move the RFID strap102in the X direction, over the coupler plates108. In an exemplary embodiment, once the RFID strap102is placed so that it is in an appropriate Y location on the coupler plates108, it may be read.

According to an exemplary embodiment, there may be a significant amount of tolerance in the positioning of the RFID strap102to the coupler104. In an embodiment, there may be a significant amount of tolerance in each of the X, the Y, and the Z directions; in other exemplary embodiments, there may be less tolerance in any of the directions or in any combination of directions. This may ensure that, for example, the RFID strap102may be located at a point having at least some Y offset and can still be read. The positional tolerance is related to the size of the strap pads and the pads and the structures the strap(s) couples to. In one example, the strap pads may be smaller than the plates they are coupling to; for example, the strap pads may be 2 mm×2 mm. In one embodiment, coupler pads may be 3 mm×3 mm in size. In this instance, a +/−0.5 mm movement of the strap in relation to the coupler pad (s) will not change the overlap area between the strap and coupler pad maintain a constant coupling.

Turning now to exemplaryFIG. 2,FIG. 2displays an alternative exemplary embodiment of a pairing200between an RFID strap202and a coupler204, which may include one or more sets of coupler plates208connected to an RFID reader206. In an exemplary embodiment, the coupler plates208may be disposed near one another (they may, for example, run parallel or substantially parallel to one another) and may be separated by a gap disposed between them.

According to an exemplary embodiment, rather than being disposed parallel to the X direction, the gap provided between the coupler plates208may be disposed at an angle such that the gap varies with the X direction. In an embodiment, this may ensure that, when RFID straps202are introduced in the X direction and are misplaced in the Y direction, the RFID straps202will go over an area that has a differential field coupling to each of the two sides of the strap202.

For example, a coupler204having a pair of coupler plates208may also be provided with two points, B and C, shown inFIG. 2. According to an exemplary embodiment, an RFID strap202may be introduced having a certain position along the Y axis. At B, the position of the RFID strap202along the Y axis may have too large an offset to be successfully read, and as such the RFID strap202may not be read at point B. However, at point C, the position of the RFID strap202along the Y axis may coincide with the position of the gap between the coupler plates208, and as such the RFID strap202may be readable.

Turning now to exemplaryFIG. 3,FIG. 3displays an exemplary diagram illustrating the process of coupling by capacitance300using an RFID strap302and an RFID coupler304.

To provide appropriate background, in general, RFID capacitive coupling may be used for short ranges wherein close RFID coupling (i.e. around 1 cm) is needed. Such a system may make use of capacitive effects to provide coupling between the RFID tag and the RFID reader. This system can be used for, for example, smart cards under ISO 10536.

Essentially, in capacitive coupling, an RFID tag may make use of electrodes (specifically the plates of a capacitor) rather than an antenna or a coil in order to provide the required coupling between the RFID tag and the RFID reader. In capacitive coupling, an RFID tag may be placed in close proximity to an RFID reader. The capacitance between the RFID tag and the RFID reader may provide a capacitor through which a signal can be transmitted; in some exemplary embodiments, this may further require an earth return. Once this capacitor has been established, an AC signal may be transmitted through it by the reader, and the AC signal generated by the reader may be picked up and rectified within the RFID tag and used to power the devices within the tag. The data may then be returned to the RFID reader by modulation of the load.

As such, according to the exemplary embodiment shown inFIG. 3, an RFID strap302—a very small differential electric field device—may be brought into proximity with the coupling plates308of a coupler304, which may further have an RFID reader306. According to an exemplary embodiment, the RFID strap302may then be read by the RFID reader306.

Turning now to exemplaryFIG. 4,FIG. 4shows an exemplary embodiment of a side view of a coupler404. According to an exemplary embodiment, a coupler404may have a plurality of coupler plates408, which may all point along the same axis; for example, according to an exemplary embodiment, a coupler404may have two coupler plates408facing up, facing down, or facing sideways.

According to an exemplary embodiment, a user may insert a carrier plate410upon which may be disposed an RFID strap402. The RFID strap402may be positioned over the coupler plate408such that it is spaced a distance “d” apart from the coupler plate408. In an embodiment, the capacitance and coupling of the coupler-strap pairing may be reduced as d is increased, meaning that, in some exemplary embodiments, the RFID strap402may have to be directly placed on top of the coupler plate408in order to be read.

Turning now to exemplaryFIG. 5,FIG. 5shows an exemplary embodiment of a side view of a coupler504. According to an alternative exemplary embodiment, instead of a coupler404having coupler plates408disposed on only one surface, a coupler504may instead have a coupling aperture508. In such an embodiment, the RFID strap502, on its carrier510, may be placed within the arms of a C-shaped structure508. This may ensure that the RFID strap502is connected to the coupler504by two different capacitors (one on top and one below), rather than just one. An RFID strap502may be separated from the top or first portion of the coupling aperture508by a distance “d1” and may be separated from the bottom or second portion of the coupling aperture508by a distance “d2”. As “d1” increases, “d2” may be decreased, and vice-versa. This may ensure that the total capacitance of the coupling that is associated with “d1” and “d2” is substantially constant.

Turning now to exemplaryFIG. 6,FIG. 6shows an exemplary embodiment of an RFID strap602. According to an exemplary embodiment, an RFID strap602may include a chip612and a plurality of attachment pads614. According to an exemplary embodiment, a chip612may be centrally located between the attachment pads614, each of which may be the same size; according to another exemplary embodiment, a chip612may be located elsewhere.

According to some exemplary embodiments, an RFID strap602may be printed on the substrate, such as paper, PE or PET substrate, which may surround the attachment pads614. In another exemplary embodiment, attachment pads614may be free-standing components, as desired.

According to an exemplary embodiment, an RFID strap602may, when fully assembled, extend approximately 10 mm in the X direction and approximately 5 mm in the Y direction, as shown inFIG. 6. According to another exemplary embodiment, an RFID strap602may be a different size. According to an exemplary embodiment, the attachment pads614may be a small fraction of the size of a wavelength of a radio wave used at the operating frequency.

Turning now to exemplaryFIG. 7,FIG. 7displays an exemplary embodiment of an article710configured to carry an RFID strap702. For example, according to an exemplary embodiment, an article710may be a payment card or a ticket to an event. In an exemplary embodiment, an RFID strap702may be centrally disposed on one end of the article710; in another exemplary embodiment, RFID straps702may be disposed elsewhere on the article710, or on multiple locations on the article710.

Turning now to exemplaryFIG. 8,FIG. 8displays an exemplary diagram demonstrating the use of an article810configured to carry an RFID strap802. In order to scan the article810, the user may insert the article810into a ticket or vending system816having a slot or aperture818, in which a coupler804may be disposed. The article810may then be coupled to the coupler804, and may be read by an RFID reader806.

Turning now toFIG. 9,FIG. 9displays an exemplary diagram illustrating the use of an RFID device902with a surface908, specifically a coupling plate908, which may provide coupling regardless of relative, X, Y and theta orientation. According to an exemplary embodiment, a surface908may provide a differential field for all values of X, Y, and theta, ensuring that, regardless of what the values are for X, Y, and theta, the RFID device902can be coupled.

Turning now to exemplaryFIG. 10,FIG. 10displays an exemplary embodiment of an RFID device1002coupled to a far-field antenna1020. According to an exemplary embodiment, it may be desired to locate an RFID reader at a location remote from the coupler1004. According to such an exemplary embodiment, a far-field antenna1020may instead be connected to a coupler1004. When an article1010featuring an RFID device1002is inserted into an appropriate location and coupled to the coupler1004, the RFID reader at the remote location may communicate, through the far-field antenna1020, with the RFID device1002. This may allow for greater flexibility on the placement of reader structures inside machines or ticket reading stations.

The foregoing description and accompanying figures illustrate the principles, preferred embodiments and modes of operation of the invention. However, the invention should not be construed as being limited to the particular embodiments discussed above. Additional variations of the embodiments discussed above will be appreciated by those skilled in the art (for example, features associated with certain configurations of the invention may instead be associated with any other configurations of the invention, as desired).