Patent Description:
The use of radio frequency identification (RFID) to identify one of a plurality of items is well known. Typical RFID tags or integrated circuits include a microprocessor, also known as a microchip, electrically connected to an antenna. Alternatively, the microchip is first attached to a pad having electrical leads that provides a larger attachment of "landing" area. This is typically referred to as a "strap" or "interposer. " The strap is then attached to the antenna.

The microprocessor stores data, which can include identifying data unique to a specific item, which is transmitted to an external receiver for reading by an operator and processing of the item. RFID tags can be attached to or associated with items for inventory control, shipment control, loss prevention, and the like. RFID tags are particularly useful in identifying, tracking and controlling items such as packages, pallets, and other product containers. The location of each item can be tracked and information identifying the owner of the item or specific handling requirements, can be encoded into the chip contained in the RFID tag and later read by a scanning device or reader which is capable of decoding and displaying the information previously encoded on the chip.

Accordingly, RFID tags can be attached to or associated with items entering or within a supply chain or retail environment and the identifying information received can be processed for various reasons in a variety of manners. RFID tags are particularly useful in identifying, tracking and controlling items such as pallets, packages, consumer goods and individual product containers. However, the tuning of an RFID tag can be dependent on the contents of the container. For example, conductive materials or materials having a high dielectric constant, for example, liquids or metals, can detune an RFID tag or substantially interfere with the RFID tag. Consequently, communications with such a tag are difficult and often ineffective. <CIT> discloses a chip module for an RFID system, in particular for an RFID label, a coupling label for use in an RFID label, an RFID inlay for an RFID label, and an RFID label produced using an RFID inlay on a web-shaped carrier material, in particular a carrier film, on which an RFID chip and a coupling antenna electrically, in particular galvanically, connected to the RFID chip are arranged. <CIT> discloses a wireless IC device including a substantially rectangular parallelepiped dielectric body, a metal pattern that is provided on the surface of the dielectric body via a film and functions as a radiator, and a wireless IC element coupled to feeding portions of the metal pattern. The dielectric body has a laminated structure including a folded flexible dielectric layer. Surfaces of the dielectric layer which face each other after the dielectric layer has been folded are non-bonded surfaces.

The invention is defined by the independent claim.

Advantages of embodiments of the present invention will be apparent from the following detailed description of the exemplary embodiments. The following detailed description should be considered in conjunction with the accompanying figures in which:.

Aspects of the invention are disclosed in the following description and related drawings directed to specific embodiments of the invention. Alternate embodiments may be devised without departing from the scope of the invention. Additionally, well-known elements of exemplary embodiments of the invention will not be described in detail or will be omitted so as not to obscure the relevant details of the invention. Further, to facilitate an understanding of the description discussion of several terms used herein follows.

As used herein, the word "exemplary" means "serving as an example, instance or illustration. " The embodiments described herein are not limiting, but rather are exemplary only. it should be understood that the described embodiment are not necessarily to be construed as preferred or advantageous over other embodiments. Moreover, the terms "embodiments of the invention", "embodiments" or "invention" do not require that all embodiments of the invention include the discussed feature, advantage or mode of operation.

According to at least one exemplary embodiment, an RFID inlay incorporating a ground plane is disclosed. The ground plane can interact with the antenna structure of the RFID inlay so as to mitigate the effects of RFID-unfriendly materials (metals, liquids, etc.) on the performance of the RFID inlay.

<FIG> show a first exemplary embodiment of an RFID inlay <NUM> that does not form part of the present invention. The inlay <NUM> can include a substrate <NUM> having an antenna structure <NUM> disposed thereon. Substrate <NUM> can be any material, for example paper, coated paper, films, polyester, polyethylene terephthalate (PET), laminations of film and paper or any other suitable substrate that can be desired. Substrate <NUM> may be divided into a first portion 102a and a second portion 102b. Substrate <NUM> may have a first face 103a on which antenna structure <NUM> may be disposed, and a second face 103b which may be suitable for printing thereon.

As can be seen from the drawings, the substrate <NUM> is substantially quadrate in shape and is generally larger than the antenna structure104 that is disposed on the substrate. That is the antenna <NUM> is fully contained within the perimeter of the substrate. Other geometric configurations are of course possible.

As shown in <FIG>, the fold line <NUM> runs substantially medially of the substrate such that portion <NUM> is has less conductive material making up the antenna portion than antenna portion <NUM>. Strap <NUM> is also shown on portion <NUM>. When folded over, portion <NUM> does not extend to a longitudinal end edge of portion <NUM> and portion <NUM> extends beyond the longitudinal end edge of portion <NUM>. As can be seen from the figures, neither of the longitudinal edges of the antenna portions align with one another when the structure is folded on itself. The transverse edges of portions <NUM> and <NUM> are substantially aligned with one another.

Antenna structure <NUM> can be any of a variety of materials, for example aluminum, copper, silver or another thin, conductive material, for example etched or hot-stamped metal foil. Antenna structure <NUM> may be coupled to an RFID integrated circuit <NUM> that may be part of a strap or interposer <NUM>. Strap or interposer <NUM> may further include conductive leads <NUM>, <NUM> to facilitate coupling between antenna structure <NUM> and integrated circuit <NUM>. In some embodiments, strap or interposer <NUM> may also include a substrate to facilitate supporting integrated circuit <NUM> and conductive leads <NUM>. Coupling between antenna structure <NUM> and strap or interposer <NUM> may be a direct, conductive coupling or may be an indirect coupling, such as a capacitive or inductive coupling or any combination of conductive, capacitive and inductive coupling.

Antenna structure <NUM> may be a continuous, unitary layer of conductive material. A slot <NUM> defined in the antenna structure can partition antenna structure <NUM> into a first area <NUM> and a second area <NUM>. First area <NUM> can include a radiating element 114a. For operation at UHF, radiating element 114a may be a monopole. Second area <NUM> of antenna structure <NUM> can include a first portion 116a disposed over first portion 102a of substrate <NUM>, and a second portion 116b disposed over second portion 102b of substrate <NUM>. In the exemplary embodiment, first area <NUM> and second area <NUM> may be conductively coupled by a bridge <NUM> extending between first portion 116a of second area <NUM> and a second end 114b of first area <NUM> disposed opposite the radiating element 114a. Slot <NUM> may also be bridged by strap or interposer <NUM>.

An overlaminate layer <NUM> may be disposed over the first face 103a of substrate <NUM> and antenna structure <NUM>. The overlaminate may be a film which may be formed from any suitable material, for example polyester, cellulose acetate, polyethylene, polypropylene or the like and can be adhesively applied to the substrate <NUM>, heat bonded, sonically sealed or otherwise fused together.

Disposed over the overlaminate layer <NUM> may be a dielectric layer <NUM>. Dielectric layer <NUM> may be coextensive with antenna structure <NUM> or substrate <NUM>. In some exemplary embodiments, dielectric layer <NUM> may have a thickness of approximately <NUM>. The dielectric layer <NUM> may be formed from any suitable material. For example, the dielectric layer may be formed foam, such as polypropylene foam, or any other low-density structure. A thickness of approximately <NUM> for dielectric layer <NUM> is sufficiently thin to allow for the inlay <NUM> to be received through printing apparatuses. Furthermore, both surfaces of dielectric layer <NUM> may be provided with a self-adhesive coating.

In some exemplary embodiments, an adhesive layer <NUM> may be disposed on the second surface 103b of substrate <NUM>. Adhesive layer <NUM> may be disposed such that it is positioned proximate the second portion 102b of substrate <NUM>. Adhesive layer <NUM> may be any known adhesive, for example a transfer tape, and may be provided with a release layer on the exposed surface thereof.

RFID inlay <NUM> may be manufactured in a roll-to-roll manufacturing process, as discussed further below. During manufacture, inlay <NUM> may have a flat configuration, as shown in <FIG>. Such a configuration can reduce issues relating to tension and stress on the inlay during the manufacturing process. However, in such a configuration, the operation of inlay <NUM> is likely to be sub-optimal and inefficient if inlay <NUM> is affixed to an object having conductive materials or materials having a high dielectric constant. To ameliorate this problem, subsequent to manufacture, RFID inlay <NUM> may be folded along a fold axis <NUM>, shown in <FIG> , such that the first portion 102a of substrate <NUM> is disposed over the second portion 102b of substrate <NUM>. In some exemplary embodiments, when folded, inlay <NUM> may have a thickness of about <NUM>, a length of about <NUM> and a width of about <NUM>.

<FIG> shows an exemplary embodiment of RFID inlay <NUM> in a folded configuration. In the folded configuration, the second area 116b of second portion <NUM> of antenna structure <NUM> functions as a ground plane element with respect to first portion <NUM> of antenna structure <NUM>. As adhesive layer <NUM> is used to couple inlay <NUM> to an object, the second area / ground plane element 116b is consequently disposed between the object and radiating element <NUM> when inlay <NUM> is in the folded configuration. The presence of a ground plane 116b between the object and radiating element <NUM> can mitigate the effect of conductive materials or materials having a high dielectric constant on the operation of inlay <NUM>. Thus, inlay <NUM> can operate efficiently even when affixed to objects containing such materials. Furthermore, in the folded configuration, the dielectric layer <NUM> is disposed between the first area <NUM> of antenna structure <NUM> and the ground plane element 116b of antenna structure <NUM>. The adhesive disposed on the face of dielectric layer <NUM> can serve to maintain inlay <NUM> in the folded configuration. Furthermore, dielectric layer <NUM> can serve to prevent undesired interaction between radiating element <NUM> and ground plane 116b.

Furthermore, in one exemplary embodiment inlay <NUM> can include two main tuning elements, the first of these tuning elements being radiating element 114a. The second tuning element can be a loop formed by the combination of strap <NUM> and bridge <NUM>. If the total thickness of the substrate drops when inlay <NUM> is folded, radiating element 114a can act to decrease the radio frequency radiated from antenna structure <NUM>, while the loop can act to increase the radio frequency radiated from antenna structure <NUM>. Consequently, the tuning elements can serve to stabilize the operating point of inlay <NUM> against variations in the gap between radiating element <NUM> and ground plane <NUM> caused by manufacturing tolerances and the properties of the materials used.

Also as shown in <FIG> each of the first and second patterns <NUM>, <NUM> have first and second longitudinal edges and first and second transverse edges (see <FIG> and wherein the first and second transverse edges are in substantial alignment with one another and at least one of the first and second longitudinal edges of each of the first and second patterns <NUM>, <NUM> is out of alignment with another of the first and second edges of the first and second portions of the conductive pattern.

<FIG> show a second exemplary embodiment of RFID inlay <NUM> that does not form part of the present invention. For convenience of illustration, substantially similar elements to those in the first exemplary embodiment of inlay <NUM> are represented by similar numerals, with the leading digit incremented to <NUM>. Thus, a detailed description of the similar elements may be omitted. The second exemplary embodiment has substantially similar structure and functionality to the first exemplary embodiment, except for the features described below.

In the second exemplary embodiment of inlay <NUM>, disposed over the overlaminate layer <NUM> may be a dielectric layer <NUM>. Dielectric layer <NUM> may overlap a portion of substrate <NUM> and antenna structure <NUM>, as shown in <FIG>. In some exemplary embodiments, dielectric layer <NUM> may have a thickness of approximately <NUM>. When inlay <NUM> is in a folded configuration, as shown in <FIG>, radiating element <NUM> and the loop formed by bridge <NUM> and strap <NUM> are over dielectric layer <NUM> to ensure correct operation of the antenna.

<FIG> show an exemplary schematic of a manufacturing process <NUM> for the embodiments of inlay <NUM>, <NUM> that does not form part of the present invention. The schematic illustrates a web to facilitate a roll to roll or continuous process. At step <NUM>, substrate media <NUM> having a plurality of antenna structures <NUM> disposed on a first surface 102b of the web thereof may be provided. The substrate media may be any suitable material, such as paper or film and as shown in the figure is provided in a continuous format. It should be understood that practice of this invention may also be done in a cut sheet configuration.

At step <NUM>, an overlaminate layer <NUM> may be applied to the first surface of the substrate, on which the antenna structures <NUM> are disposed. At step <NUM>, a layer of dielectric material <NUM>, such as foam, may be applied over the overlaminate layer. The dielectric material may be applied as a sheet or as strips, depending on the embodiment of the inlay that is being manufactured. Alternatively, the dielectric and overlaminate may be previously die cut such that upon attachment and alignment over the designated antenna areas, the matrix portion can be readily stripped away leaving a substantially completed assembly on the base or carrier web. Otherwise, the die cutting can occur post application such that the individual RFID inlays can be removed from the web.

At step <NUM>, the laminated sheet resulting from step <NUM> is turned over with the dielectric element <NUM> now on the bottom of the web. At step <NUM>, strips of transfer tape are applied to the second surface 102b of the substrate media. At step <NUM>, the resulting laminated structure may be die cut into separate inlays. At this point, the inlays can have a flat configuration. Folding of the inlays may subsequently be performed by a suitable folding apparatus, or by an end user of the inlays. In use, the liner on the transfer tape is peeled away such that the substrate can be folded onto itself and secured. The transfer tape is only applied to one side of the RFID inlay or covers only one portion of the antenna structure.

<FIG> show a third exemplary embodiment of an inlay <NUM>. The inlay <NUM> can include a substrate <NUM> having a ground plane <NUM> disposed on a first surface 403a thereof, an adhesive layer <NUM> disposed over the ground plane <NUM>, an antenna structure <NUM> provided separately from the ground plane <NUM> and disposed over the adhesive layer <NUM>, and a dielectric layer <NUM> disposed between a portion of the antenna structure <NUM> and the dielectric layer <NUM>.

Substrate <NUM> can be any material, for example paper, coated paper, polyethylene terephthalate (PET), laminations of film and paper or any other suitable substrate that can be desired. A bottom surface 403b of the substrate may include an adhesive covered by a release layer so as to allow coupling of inlay <NUM> to a desired object.

Antenna structure <NUM> and ground plane <NUM> can be any of a variety of materials, for example aluminum, copper, silver or another thin, conductive material, for example etched or hot-stamped metal foil. Antenna structure <NUM> may be coupled to an RFID integrated circuit that may be part of a strap or interposer <NUM>. Strap or interposer <NUM> may further include conductive leads to facilitate coupling between the antenna structure and the integrated circuit. In some embodiments, strap or interposer <NUM> may also include a substrate to facilitate supporting the integrated circuit and the conductive leads. Coupling between antenna structure <NUM> and strap or interposer <NUM> may be a direct, conductive coupling or may be an indirect coupling, such as a capacitive or inductive coupling.

Antenna structure <NUM> may be provided on a second substrate <NUM>, shown in <FIG>. Similarly to substrate <NUM>, the second substrate <NUM> can be any material, for example paper, coated paper, polyethylene terephthalate (PET), laminations of film and paper or any other suitable substrate that can be desired. A first surface 429a of second substrate <NUM> may be suitable for printing thereon, while antenna structure <NUM> may be disposed on a second surface 429b of the second substrate.

Antenna structure <NUM> and ground plane <NUM> may be a continuous, unitary layer of conductive material. A pair of slots 412a, 412b defined in the antenna structure can partition antenna structure <NUM> into three arms 414a, 414b, 414c. One of slots <NUM> may be bridged by strap or interposer <NUM> extending between a pair of adjacent arms <NUM>. Ground plane <NUM> may have a non-partitioned configuration.

The dielectric layer <NUM> may have a length and a width substantially similar to those of an arm <NUM>. Dielectric layer <NUM> may be disposed between adhesive layer <NUM> and an arm <NUM>, for example central arm 414b, as in the illustrated exemplary embodiment. In some exemplary embodiments, dielectric layer <NUM> may have a thickness of approximately <NUM>. The dielectric layer <NUM> may be formed from any suitable material. For example, the dielectric layer may be formed foam, such as polypropylene foam, or any other low-density structure. The dielectric layer <NUM> can serve to separate central arm 414b from ground plane layer <NUM> so as to control the coupling there between in a way that facilitates operation of the structure as an antenna for the RFID device <NUM>. Conversely, side arms 414a, 414c may be separated from ground plane layer <NUM> only by the adhesive layer <NUM>, thereby resulting in a strong capacitive coupling between ground plane <NUM> and arms 414a, 414c.

<FIG> show an exemplary manufacturing process <NUM> for the embodiments of inlay <NUM>. At step <NUM>, substrate media <NUM> having a plurality of antenna structures <NUM> disposed on a second surface 402b thereof may be provided. The schematic provides a web for operation in a roll to roll or continuous format. At step <NUM>, a layer of transfer tape <NUM>, may be applied over the substrate. The transfer tape may be applied as a sheet or as strips. At step <NUM>, the substrate may be cut and the unwanted matrix may be stripped, thereby leaving appropriately-sized portions of the transfer tape in the appropriate position on antenna structure <NUM>.

At step <NUM>, substrate media <NUM> having a ground plane <NUM> disposed on a first surface 403a thereof may be applied to the sheet output from step <NUM>. The substrate media <NUM> may be applied such that the first surface 403a of the substrate media <NUM> is facing the second surface 429b of the substrate media <NUM>. At step <NUM>, the resulting laminated structure may be compressed and die cut into separate inlays. The compression of the laminated structure results in the dielectric layer being pushed towards substrate media <NUM>, thereby resulting in the configuration of inlay <NUM> that is shown in <FIG>.

<FIG> show a fourth exemplary embodiment of an RFID inlay <NUM> that does not form part of the present invention. RFID inlay <NUM> can include a substrate <NUM>, an antenna structure <NUM> disposed on a first surface 603a of substrate <NUM>, and a ground plane <NUM> disposed on a second surface 603b of substrate <NUM>. Substrate <NUM> can be any material, for example paper, coated paper, polyethylene terephthalate (PET), laminations of film and paper or any other suitable substrate that can be desired.

Antenna structure <NUM> and ground plane <NUM> can be any of a variety of materials, for example aluminum, copper, silver or another thin, conductive material, for example etched or hot-stamped metal foil. Antenna structure <NUM> may be coupled to an RFID integrated circuit that may be part of a strap or interposer <NUM>. Strap or interposer <NUM> may further include conductive leads to facilitate coupling between antenna structure <NUM> and the integrated circuit. In some embodiments, strap or interposer <NUM> may also include a substrate to facilitate supporting the integrated circuit and conductive leads. Coupling between antenna structure <NUM> and strap or interposer <NUM> may be a direct, conductive coupling or may be an indirect coupling, such as a capacitive or inductive coupling.

Substrate <NUM> can be partitioned into an outer area <NUM> and an inner area <NUM>. Outer area <NUM> may be physically separated from inner area <NUM> by a plurality of cuts, slits, or incisions <NUM> defined in substrate <NUM>. Portions of inner area <NUM> may also be coupled to outer area <NUM> by way of hinges <NUM>. In the illustrated embodiment, the hinges <NUM> may be provided at an end of inner area <NUM> as well as adjacent a pair of tabs <NUM> extending from inner portion <NUM>. Hinges <NUM> may be formed by scoring or perforating substrate <NUM> so as to facilitate the folding thereof.

<FIG> is a top plan view of inlay <NUM>, illustrating the configuration of antenna structure <NUM>, which is shown as the stippled area in the figure. Antenna structure <NUM> may be a continuous, unitary layer of conductive material and can be substantially coextensive with the first surface 603a of substrate <NUM>, except for a gap <NUM> extending along a longitudinal edge of inner area <NUM> and a transverse edge of inner area <NUM>. A strap or interposer <NUM> can bridge gap <NUM>. In the illustrated embodiment, strap or interposer <NUM> can be disposed over a tab <NUM> and a portion of antenna structure <NUM> that is disposed over inner area <NUM>.

<FIG> is a bottom plan view of inlay <NUM>, illustrating the configuration of ground plane <NUM>, which is shown as the stippled area in the figure. Ground plane <NUM> may be a continuous, unitary layer of conductive material and can be substantially coextensive with only the outer area <NUM> of second surface 603b of substrate <NUM>.

Subsequent to manufacture and prior to use, inlay <NUM> may be substantially flat. To place inlay <NUM> into an operating configuration, as shown in <FIG> , a force may be applied to inner area <NUM>. The hinges provided in substrate <NUM> can allow the inner area <NUM> to be vertically displaced from outer area <NUM>. The inner area portion of antenna structure <NUM> consequently can act as a radiating element, while the outer area portion of antenna structure <NUM> is capacitively coupled to ground plane <NUM> and is conductively coupled to the radiating element. The vertical displacement of inner area <NUM> introduces a gap between the radiating element and the ground plane, thereby allowing air to act as a dielectric element for the inlay <NUM>.

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.

Claim 1:
An RFID inlay (<NUM>), comprising:
a first substrate (<NUM>) having a ground plane layer (<NUM>) disposed thereon;
a second substrate (<NUM>) having an antenna structure (<NUM>) disposed thereon;
a strap or interposer (<NUM>);
wherein the antenna structure (<NUM>) comprises a pair of slots (412a, 412b) partitioning the antenna structure into three arms (414a, 414b, 414c);
wherein one of the slots (412a, 412b) is bridged by the strap or interposer (<NUM>) extending between a pair of adjacent arms (414a, 414b, 414c);
wherein a dielectric layer (<NUM>) is disposed between the ground plane layer (<NUM>) and one of the three arms (414a, 414b, 414c)of the antenna structure (<NUM>); and
wherein the other two of the three arms (414a, 414b, 414c) of the antenna structure (<NUM>) are capacitively coupled to the ground plane layer (<NUM>).