Patent Description:
RFID labels are attached to or associated with items to track inventory. They can be used on a variety of items such as packages, pallets, containers, etc. The labels can be encoded with identifying information related to the tagged item. The label can be read by a scanner or reader that can decode the information on the chip and display information related to the label or package on a display device. <CIT>, discloses an RFID tag for mounting on a metallic member via a first spencer.

Standard RFID labels are generally not suitable for tagging conductive materials or materials having a high dielectric constant. When label approaches such objects, the RFID antenna becomes detuned (mismatch loss). The efficiency in which the antenna generates a plane wave is also reduced (radiation efficiency loss). These losses severely reduce the antenna's read range. Therefore, communication with such tags are is difficult, which leads to ineffectiveness and inconsistencies in tracking items.

One approach to overcoming these issues is to place a standard RFID inlay on a spacer material where the inlay is positioned a fixed distance from the conductive object. To completely isolate the RFID label from the object, the spacer needs to be a quarter of a wavelength thick based on the dielectric constant of the material used in creating the spacer. That requirement results in constructions having a thickness that is not suitable for customer's purposes and may be too thick for printing and encoding processes.

In other constructions, manufacturers have often selected antenna structures intended for use above a ground plane, using the metallic object as the ground plane. These structures also require a dielectric spacer, typically foam or rubber, but are considerably thinner than described in the previous example. The drawback of these antenna structures is that they are generally larger in size. For example, RFID inlays disposed on spacers of foam or rubber may have to be in excess of <NUM> in length and <NUM> in width. That increases the cost of the products and may not be suitable for customers in terms of aesthetics.

Still another approach is to employ a structure that resonates in the presence of a ground plane such as, for example, a metallic item that receives a RFID tag. In labels that are currently able to function in this manner, the resonant structure needs to wrap around opposite ends of the spacer for coupling to the ground plane. While these types of structures do demonstrate better radiation efficiencies with thinner spacers than is required for the other approaches described above, construction and manufacturing of such labels is complex and requires specialized equipment and capital expense.

The following presents a summary of this disclosure to provide a basic understanding of some aspects. This summary is intended to neither identify key or critical elements nor define any limitations of embodiments or claims. Furthermore, this summary may provide a simplified overview of some aspects that may be described in greater detail in other portions of this disclosure.

Provided is a RFID label suitable for tagging metallic objects. The RFID label has an antenna configuration such that the antenna resonates in the presence of a ground plane. The label has a profile or footprint that is suitable for labeling applications and still provides excellent sensitivity in the radio frequency range such that the label exhibits good read range.

In one aspect, a RFID label comprises a RFID component disposed on a first side of a dielectric substrate, an inductor element disposed on a second side of the dielectric substrate opposite the first side, and a spacer layer overlying the inductor layer. The RFID component is coupled to capacitor elements. The inductor element is in parallel with the RFID component. The antenna resonates and radiates a plane wave when placed on a ground plane (metallic object). The antenna exhibits excellent sensitivity in the radio frequency band.

According to one aspect of the present invention, an RFID label includes a combined structure having an RFID component layer and an inductive component layer separated by and placed on opposite sides of a dielectric substrate. The RFID component layer includes an antenna segment having a first antenna segment and a second antenna segment. An integrated circuit located along the first antenna segment, a first capacitor segment attached to the first and second antenna segments, and a second capacitor segment attached to the first and second antenna segments. The first capacitor segment is located on an opposite distal end of the antenna segment from the second capacitor segment.

The inductive component layer having a first capacitor segment and a second capacitor segment being joined by a trace. The first capacitor segment of the inductive component layer aligns and couples with the first capacitor segment of the RFID component layer, thereby forming a first capacitor assembly. The second capacitor segment of the inductive component layer aligns and couples with the second capacitor segment of the RFID component layer, thereby forming a second capacitor assembly. The first and second capacitor assembly couples the RFID component layer and the inductive component layer. The combined structure is adhered to a spacer layer. The antenna segment radiates a plane wave when the combined structure is coupled to a ground plane via the spacer layer.

In an exemplary embodiment, the ground plane is an item having metallic packaging to which the spacer layer is adhered. The combined structure and item are located on opposite sides of the spacer layer.

In a further embodiment, the ground plane is a foil layer placed on the spacer layer. The foil layer and combined structure are located on opposite sides of the spacer layer.

In an additional embodiment, the foil layer has an adhesive layer opposite the spacer layer for attaching the RFID label to an item.

In another embodiment, the foil layer has a thickness between about <NUM> to about <NUM> microns.

In a further embodiment, the foil layer has a thickness of <NUM>,<NUM> Angstroms or less.

In an additional embodiment, the foil layer has a thickness of <NUM>,<NUM> Angstroms of less.

In another embodiment, the dielectric substrate has a thickness between about <NUM> to about <NUM>.

In a further embodiment, the dielectric substrate has a thickness between about <NUM> to about <NUM>.

In an additional embodiment, the dielectric substrate has a thickness between about <NUM> to about <NUM>.

In another embodiment, the spacer layer has a thickness between about <NUM> to about <NUM>.

In a further embodiment, the spacer layer has a thickness between about <NUM> to about <NUM>.

In an additional embodiment, the spacer layer has a thickness between about <NUM> to about <NUM>.

In another embodiment, the dielectric substrate, the spacer layer, or both are formed of a closed cell foam material.

According to another aspect of the invention, a method of tracking an item includes applying an RFID label to the item. The RFID label having a combined structure comprising an RFID component layer and an inductive component layer separated by and placed on opposite sides of a dielectric substrate.

The RFID component layer includes an antenna segment having a first antenna segment and a second antenna segment. An integrated circuit is located along the first antenna segment. A first capacitor segment is attached to the first and second antenna segments. A second capacitor segment is attached to the first and second antenna segments. The first capacitor segment is located on an opposite distal end of the antenna segment from the second capacitor segment.

The inductive component layer has a first capacitor segment and a second capacitor segment being joined by a trace. The first capacitor segment of the inductive component layer aligns and couples with the first capacitor segment of the RFID component layer, forming a first capacitor assembly. The second capacitor segment of the inductive component layer aligns and couples with the second capacitor segment of the RFID component layer, forming a second capacitor assembly. The first and second capacitor assembly coupling the RFID component layer and the inductive component layer. The combined structure is adhered to a spacer layer. The item has metallic packaging to which the spacer layer of the RFID label is adhered. The metallic packaging functions as a ground plane for the combined structure, when the metallic packaging is coupled to the combined structure. The antenna segment radiates a plane wave, when the combined structure is coupled to the metallic packaging via the spacer layer.

According to yet another aspect of the invention, an item having an RFID label includes the RFID label having a combined structure having an RFID component layer and an inductive component layer separated by and placed on opposite sides of a dielectric substrate. The RFID component layer having an antenna segment with a first antenna segment and a second antenna segment, an integrated circuit located along the first antenna segment, a first capacitor segment attached to the first and second antenna segments, and a second capacitor segment attached to the first and second antenna segments. The first capacitor segment is located on an opposite distal end of the antenna segment from the second capacitor segment.

The inductive component layer having a first capacitor segment and a second capacitor segment being joined by a trace. The first capacitor segment of the inductive component layer aligns and couples with the first capacitor segment of the RFID component layer, thereby forming a first capacitor assembly. The second capacitor segment of the inductive component layer aligns and couples with the second capacitor segment of the RFID component layer, thereby forming a second capacitor assembly. The first and second capacitor assembly couples the RFID component layer and the inductive component layer. The combined structure is adhered to a spacer layer. The item having metallic packaging to which the spacer layer of the RFID label is adhered. The metallic packaging is a ground plane for the combined structure, when the metallic packaging is coupled to the combined structure. The antenna segment radiates a plane wave when the combined structure is coupled to the metallic packaging via the spacer layer.

The following description and the drawings disclose various illustrative aspects. Some improvements and novel aspects may be expressly identified, while others may be apparent from the description and drawings.

The accompanying drawings illustrate various systems, apparatuses, devices and related methods, in which like reference characters refer to like parts throughout, and in which:.

Reference will now be made to exemplary embodiments, examples of which are illustrated in the accompanying drawings. It is to be understood that other embodiments may be utilized and structural and functional changes may be made. Moreover, features of the various embodiments may be combined or altered. As such, the following description is presented by way of illustration only and should not limit in any way the various alternatives and modifications that may be made to the illustrated embodiments. In this disclosure, numerous specific details provide a thorough understanding of the subject disclosure. It should be understood that aspects of this disclosure may be practiced with other embodiments not necessarily including all aspects described herein, etc..

As used herein, the words "example" and "exemplary" means an instance, or illustration. The words "example" or "exemplary" do not indicate a key or preferred aspect or embodiment. The word "or" is intended to be inclusive rather than exclusive, unless context suggests otherwise. As an example, the phrase "A employs B or C," includes any inclusive permutation (e.g., A employs B; A employs C; or A employs both B and C). As another matter, the articles "a" and "an" are generally intended to mean "one or more" unless context suggest otherwise.

Provided is a RFID label suitable for use on metallic items. Such items are known to detune conventional RFID labels. The present RFID labels comprise a RFID component layer defined as a parallel configuration of a resistor and a capacitor, and an inductive component layer placed in parallel with the RFID component player. The RFID component layer is further comprised of an antenna segment. The RFID component layer and the inductive component layer are separated by a dielectric layer. The RFID component layer and the inductor component layer are coupled together by a first capacitor assembly and a second capacitor assembly. The first and second capacitor assemblies are formed by elements on opposite sides of the RFID antenna and the inductive component layer.

<FIG> shows an embodiment of an RFID label in accordance with the present technology. The RFID label <NUM> includes a RFID component layer <NUM> disposed on a first side of a dielectric substrate <NUM>, and an inductive component layer <NUM> disposed on a second side of dielectric substrate <NUM> opposite the first side. A spacer layer <NUM> is disposed over the inductive component layer <NUM> opposite the dielectric substrate <NUM>.

The RFID component layer <NUM> comprises an antenna segment <NUM> defined by traces 112a and 112b. The RFID component layer includes an integrated circuit <NUM> attached to a portion of the antenna segment <NUM> (112b in <FIG>). The RFID component layer <NUM> includes capacitor segments 114a and 114b on opposite distal ends of the antenna segment <NUM>.

The inductive component layer <NUM> is formed from a trace <NUM> and rectangular capacitor segments 134a and 134b that align with the capacitor segments 114a and 114b of the RFID component layer <NUM>. The capacitor segments 114a and 114b of the RFID component layer <NUM> couple with the capacitor segments 134a and 134b of the inductive component layer <NUM>, thereby coupling the RFID component layer <NUM> and the inductive component layer <NUM>.

Further, the first capacitor segment 134a of the inductive component layer <NUM> aligns and couples with the first capacitor segment 114a of the RFID component layer <NUM>, thereby forming a first capacitor assembly <NUM> of the RFID label <NUM>. The second capacitor segment 134b of the inductive component layer <NUM> aligns and couples with the second capacitor segment 114b of the RFID component layer <NUM>, thereby forming a second capacitor assembly <NUM> of the RFID label <NUM>.

<FIG> shows the arrangement or orientation of the RFID component layer <NUM> and the inductive component layer <NUM> relative to one another in space within the label <NUM>. The dielectric substrate layer <NUM> and spacer layer <NUM> are not shown in <FIG>.

The RFID component layer <NUM> and the inductive component layer <NUM> may be formed as electrically conductive traces formed on the dielectric substrate layer <NUM>. The conductive traces can be formed from any suitable material. Examples of suitable material includes, but is not limited to, copper, aluminum, silver, gold, other metals, or carbon. The antennas <NUM> may also be printed in conductive inks comprising dispersions of silver, gold, or other metals, or particles coated with silver, gold or other metallic conductors, or nonmetallic conductors such as carbon or polyaniline. The antennas <NUM> can be manufactured using commercially available flexible circuits that are produced using processes and designs of proven high yield.

The dielectric substrate <NUM> and spacer layer <NUM> can be formed from any suitable dielectric material. Examples of suitable dielectric materials include, but are not limited to, paper, foam, rubber, a polymeric material, a ceramic material and the like. In one embodiment, the spacer layer <NUM> is selected from paper. In one embodiment, the spacer layer <NUM> is formed from a foam material.

In one embodiment, the dielectric substrate <NUM> can have a thickness of from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, or from about <NUM> to about <NUM>. In one embodiment, the spacer layer <NUM> can have a thickness of from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, or from about <NUM> to about <NUM>. The present antenna structure allows for providing a thinner profile than is possible with a conventional RFID antenna configuration.

The label <NUM> can be formed by providing or forming the RFID component layer <NUM> to a surface on one side of a dielectric substrate <NUM>. The integrated circuit <NUM> may be attached to the RFID antenna segment <NUM> by any suitable means prior to or subsequent to the RFID component layer <NUM> being provided on the dielectric substrate <NUM>. The inductive component layer <NUM> is also formed on the dielectric substrate <NUM>. The order in which the RFID component layer <NUM> and the inductive component layer <NUM> are formed on the dielectric substrate <NUM> is not critical, as long as the RFID component layer <NUM> and inductive component layer <NUM> are located on opposite sides of the dielectric substrate <NUM>. The RFID component layer <NUM>, inductive component layer <NUM>, and dielectric substrate <NUM> form a combined structure <NUM>. After the combined structure <NUM> is formed comprised of the RFID component layer <NUM>, dielectric substrate layer <NUM>, and inductive component layer <NUM>, the combined structure <NUM> is attached to a top surface of a spacer layer <NUM>. This can be accomplished using any suitable method. In one embodiment the combined structure <NUM> is adhered to the spacer layer <NUM>. An adhesive layer <NUM> may be provided on the underside of the spacer layer <NUM>, opposite of the combined structure <NUM>, to allow for attachment of the label <NUM> to an item.

When the RFID label <NUM> is placed on a ground plane, e.g., a metallic substrate <NUM> as shown in <FIG>, the entire structure begins to radiate a plane wave. Stated alternatively, the antenna RFID antenna segment <NUM> radiates a plane wave when the combined structure <NUM> is placed on a ground plane <NUM>. Stated otherwise, the antenna RFID antenna segment <NUM> radiates a plane wave when the combined structure <NUM> is coupled to a ground plane <NUM>. The label <NUM> exhibits excellent sensitivity in the radio frequency band when placed in the proximity of a ground plane. Stated alternatively, the RFID antenna segment <NUM> of label <NUM> exhibits excellent sensitivity when coupled to a ground plane <NUM>. The sensitivity allows the label to be suitable for labeling items <NUM> having sufficient metal content to act as a ground plane <NUM>.

In one embodiment, when the item to which the label will be applied is an item <NUM> made of a material with a high dielectric constant that is not metal or does not contain a substantial quantity of a metal material to act as a ground plane <NUM>, the label <NUM> structure may include an additional layer of a metallic foil <NUM> that may function as ground plane <NUM>. <FIG> illustrates an embodiment, the RFID label <NUM>' includes the same structural layers shown in <FIG> but further includes a foil layer <NUM>. The foil layer <NUM> can be selected as desired. The foil layer <NUM> can be provided by a self-supporting sheet of metal. The foil layer <NUM> provided by a self-supporting sheet can have a thickness of from about <NUM> to about <NUM> micron. In another embodiment, the foil layer <NUM> can be provided by a plastic film layer sputtered or vacuum metalized with a thin layer of continuous metal. Sputtering can lay down a continuous metal coating of <NUM> Angstroms or less. Vacuum metallizing can lay down a metal coating of <NUM> Angstroms or less. Vacuum metallizing and sputtering, as generally practiced, provide a continuous layer of metal mounted on the plastic. In one embodiment, the metal forming the foil layer is aluminum. The foil layer <NUM> can be applied in any suitable manner such as bonding, welding, or otherwise adhering the foil layer <NUM> to the spacer layer <NUM>, opposite of the combined structure <NUM>. An adhesive layer <NUM> can be applied to the back side of the foil layer <NUM>, opposite of the spacer layer <NUM>, for adhering the RFID label <NUM>' to an item.

Resonant antenna segments <NUM> were constructed with a structure and antenna configuration as depicted in <FIG>. The dielectric substrate <NUM> and the spacer layer <NUM> were formed from a closed cell foam material.

Antenna segments <NUM> were constructed with the following dimensions:.

The antenna segments <NUM> were brought in contact with (coupled with) a ground plane <NUM>, and the RF sensitivity was measured. <FIG> is a graph showing the sensitivity of the antenna segments when brought in contact with a ground plane <NUM>. As shown in <FIG>, antenna segments <NUM> with the same RF sensitivity can be provided by varying the dimensions. Generally, as the width of the antenna segments <NUM> is reduced, the length is increased to provide the same RF sensitivity.

Antenna segments <NUM> were also constructed where the length was held constant at <NUM> and the width was varied. The dimensions of those structures are shown in Table <NUM>.

The RF sensitivity of the antennas in Table <NUM> are shown in <FIG>. As shown in the graph in <FIG> the antenna segments <NUM> generally have the same bandwidth, but sensitivity of the antenna segments <NUM> decreases as the footprint decreases.

As can be seen the RFID label <NUM> as described permits for the use of antenna segments <NUM> having a smaller footprint than conventional antennas and do not require the wrapping of the antenna segments <NUM> around the spacer layer <NUM> to function.

Claim 1:
A RFID label (<NUM>,<NUM>') comprising:
a combined structure (<NUM>) comprising an RFID component layer (<NUM>) and an inductive component layer (<NUM>) separated by and placed on opposite sides of a dielectric substrate (<NUM>);
the RFID component layer (<NUM>) comprising an antenna segment (<NUM>) having a first antenna segment (112b) and a second antenna segment (112a), an integrated circuit (<NUM>) located along the first antenna segment (112b), a first capacitor segment (114a) attached to the first and second antenna segments (112b, 112a), and a second capacitor segment (114b) attached to the first and second antenna segments (112b, 112a), with the first capacitor segment (114a) being located on opposite distal ends of the antenna segment from the second capacitor segment (114b);
the inductive component layer (<NUM>) having a first capacitor segment (134a) and a second capacitor segment (134b) being joined by a trace; the first capacitor segment (134a) of the inductive component layer (<NUM>) aligning and coupling with the first capacitor segment (114a) of the RFID component layer (<NUM>), thereby forming a first capacitor assembly (<NUM>); the second capacitor segment (134b) of the inductive component layer (<NUM>) aligning and coupling with the second capacitor segment (114b) of the RFID component layer (<NUM>), thereby forming a second capacitor assembly (<NUM>);
the first and second capacitor assembly coupling the RFID component layer (<NUM>) and the inductive component layer (<NUM>);
the combined structure (<NUM>) adhered to a spacer layer (<NUM>);
wherein the antenna segment (<NUM>) radiates a plane wave when the combined structure is coupled to a ground plane (<NUM>) via the spacer layer (<NUM>).