Patent Description:
Generally stated, RFID is the use of electromagnetic energy to stimulate a responsive device (known as an RFID "tag" or transponder) to identify itself and, in some cases, provide additional information and/or data stored in the tag. RFID tags and/or labels typically contain a combination of antennas and analog and/or digital electronics, which may include, for example, a semiconductor device commonly referred to as the "chip", communications electronics, data memory, and control logic. Typical RFID tags have a microprocessor electrically connected to an antenna, and act as transponders, providing information stored in the chip memory in response to a radio frequency interrogation signal received from a reader, also referred to as an interrogator. The reader/interrogator, in turn, converts the radio waves from the RFID device into a form that can be utilized by a computer. In the case of passive RFID devices, the energy of the interrogation signal also provides the necessary energy to operate the RFID tag device.

RFID tags may be incorporated into or attached to any object or articles that a user wishes to later identify and/or track, such as products, equipment, individuals, vehicles, machinery, livestock, etc. In some cases, the RFID tag may be attached to the outside of the article with a clip, adhesive, tape, or other means and, in other cases, the RFID tag may be inserted within the article, such as being included in the packaging, or located within the container of the article or plurality of articles.

RFID tags are typically manufactured with a unique identification number which is usually a simple serial number of a few bytes with a check digit attached. This identification number is typically incorporated into the RFID tag during its manufacture. The user cannot alter this serial/identification number, and manufacturers guarantee that each RFID tag serial number is used only once and is, therefore, unique. Such read-only RFID tags typically are permanently attached to an article to be identified and/or tracked and, once attached, the serial number of the tag is associated with its host article in a computer database. When used to track or manage inventory, the microprocessor stores unique identifying data associated with the inventory into the RFID tag, and an operator can use an external receiver/reader to retrieve the stored data and process or track the inventory.

One difficulty associated with the manufacturing of RFID devices is the need to impart some degree of flexibility and durability to the RFID device without damaging the same. Historically, antenna structures used with RFID devices have been formed from a conductive material (e.g., copper, silver, or aluminum) and configured in various constructions, which may be formed by being printed or placed onto an object such as a carrier. Unfortunately, such RFID antenna structures have not, historically, always been particularly flexible or durable when subjected to flex forces. Therefore, it would also be advantageous to provide an RFID antenna structure that is both durable and flexible, and an RFID antenna structure formed from a variety of different conductive materials with more than one conductor construction would also permit the RFID device to perform differently in response to applied external events.

Therefore, there exists in the art a long felt need for an RFID device and RFID antenna that are both relatively flexible and durable when exposed to flex forces. There also exists in the art a long felt need for an RFID device having multiple conductors that allow the RFID device to, either permanently or reversibly, change the performance of the RFID device.

Therefore, the present invention discloses a RFID device having more than one RFID antenna structure that, when combined, enable changes in the performance of the RFID device. More specifically, the RFID device includes a multiple RFID antenna structure containing more than one material and that changes the performance of the RFID device following exposure to an external stimulus or event such as, but not limited to, washing, stretching, heating, or exposure to a received electrical signal.

<CIT> discloses an RFID device including a first, relatively permanent portion and a second alterable or inactivatable portion. Upon the occurrence of some predetermined event, the second portion and/or its coupling to the first portion is physically altered, inactivating it. The first portion may itself be an antennaless RFID device that may be read at short range, and the second portion may be an antenna that, when coupled to the first portion, substantially increases the range at which the first portion may be read. The second portion may be configured to be altered or inactivated by any of a variety of predetermined events, such as involving physical, chemical or electrical forces, performed either on the RFID device, or upon an object to which the RFID device is coupled.

<CIT> discloses a method of using shielded straps with RFID tag designs. Specifically, the RFID device, in one embodiment, comprises a bridge conductor which couples the antenna and pair of strap pads together. Thus, the coupling between the bridge conductor and the strap conductor, the coupling between the bridge conductor and the antenna conductor, and the coupling between the antenna conductor and the strap conductor increases the total capacitance of the RFID strap device. Further, the presence of the bridge conductor also reduces the area occupied for a given inductance, and provides a higher effective capacitance when the bridge strap is connected to the antenna.

<CIT> discloses methods, apparatuses and systems for radio frequency identification (RFID)-enabled information collection, including an enclosure, a collector coupled to the enclosure, an interrogator, a processor, and one or more RFID field sensors, each having an individual identification, disposed within the enclosure. In operation, the interrogator transmits an incident signal to the collector, causing the collector to generate an electromagnetic field within the enclosure. The electromagnetic field is affected by one or more influences. RFID sensors respond to the electromagnetic field by transmitting reflected signals containing the individual identifications of the responding RFID sensors to the interrogator. The interrogator receives the reflected signals, measures one or more returned signal strength indications ("RSSI") of the reflected signals and sends the RSSI measurements and identification of the responding RFID sensors to the processor to determine one or more facts about the influences.

To the accomplishment of the foregoing and related ends, certain illustrative aspects of the disclosed innovation are described herein in connection with the following description and the annexed drawings. These aspects are indicative, however, of but a few of the various ways in which the principles disclosed herein can be employed and is intended to include all such aspects and their equivalents. Other advantages and novel features will become apparent from the following detailed description when considered in conjunction with the drawings.

As noted above, there exists in the art a long felt need for a RFID tag or device that is attachable to a garment, fabric, or wearable article that may be subjected to flex forces and that contains an antenna structure formed from multiple conductive materials and elements in different configurations. More specifically, the RFID device may contain more than one conductive material and/or configuration that can enable changes (either reversible or permanent) in the performance of the RFID device in relation to external events or other stimuli including, without limitation, washing, stretching, etc..

Referring initially to the drawings, <FIG> illustrates a perspective view of a plurality of conductive materials and potential configurations for use with an RFID device, which may contain, by way of example and not limitation, (a) a wire <NUM> made of copper, or other conductive material; (b) a conductive foil material <NUM> that is either cut (e.g., laser or die) or etched, including, but not limited to, aluminum or copper; (c) a printed conductor <NUM>, such as a matrix coating (e.g., inks) of particles of copper, silver, graphene or other inorganic or organic conducting materials or combinations thereof; or (d) a metallic mesh <NUM>. Although the plurality of conductive materials and configurations can singularly adapt somewhat to an event or external stimulus, greater flexibility is provided to an RFID device by using two or more conductors as part of a common antenna structure.

<FIG> illustrates a schematic diagram of a RFID device <NUM> having multiple conductors. More specifically, the RFID device <NUM> contains an RFID chip <NUM>, a first conductive structure <NUM>, and a second conductive structure <NUM>. The second conductive structure <NUM> is operatively coupled to the first conductive structure <NUM> when in a first operating condition 100A, as best illustrated in <FIG>, and the RFID chip <NUM> is operatively coupled to the second conductive structure <NUM>. The initial coupling between the first conductive structure <NUM> and the second conductive structure <NUM> can vary. In some embodiments, the initial coupling between the first conductive structure <NUM> and the second conductive structure <NUM> is conductive coupling.

In some embodiments, the first conductive structure <NUM> is manufactured from a first conductive material, and the second conductive structure <NUM> is manufactured from a different conductive material. Additionally, in some embodiments, the first conductive structure <NUM> is constructed in a first configuration, and the second conductive structure <NUM> is preferably constructed in a different configuration. For example, the first conductive structure <NUM> may be a pair of printed areas of conductive ink, such as the printed conductor <NUM> of <FIG>, and the second conductive structure <NUM> may be a wire <NUM> (as also shown in <FIG>). Further, the wire of the second conductive structure <NUM> is conductively coupled to the pair of printed areas of the first conductive structure <NUM>, as the wire overlaps a part of the pair of printed areas of conductive ink. Alternatively, in some embodiments, the coupling may be via capacitance.

<FIG> illustrates a schematic diagram of an RFID device <NUM> containing a RFID chip <NUM>, a first conductive structure <NUM>, and a second conductive structure <NUM>, wherein the first conductive structure <NUM> further contains a shunt element <NUM> for initially connecting the first conductive structure <NUM> to the second conductive structure <NUM>. More specifically, the shunt element <NUM> of the first conductive structure <NUM> overlaps portions of the second conductive structure <NUM> when the RFID device <NUM> is in a first operating condition.

In both the configurations of <FIG> and <FIG>, the first conductor <NUM> and the second conductor <NUM> may have differing responses to an external event due to being manufactured from different materials and/or different configurations. For example, exposure to the external event (or a series of external events) will cause the RFID device <NUM> to change from the first operating condition to a second operating condition. The change in operating conditions may be permanent or reversible depending on the materials used to construct each of the conductive structures, the configurations of the conductive structures, the type of external event, the number of external events, and/or combinations thereof.

As stated above, the external event may be a single event or a series of events including, without limitation, washing, stretching, heating, receiving an electrical signal, etc. For example, if the first conductive structure <NUM> is water soluble, such as a conductive ink with a water-soluble binder, the conductive ink could be removed by a washing event, thereby changing the characteristics of the RFID device <NUM>. More specifically, as the first conductive structure <NUM> is washed away and removed (or partially removed), the performance of the RFID device <NUM> is altered, either reversibly or permanently.

<FIG> illustrates a schematic diagram of the RFID device <NUM> containing a RFID chip <NUM>, a first conductive structure <NUM> having a first operating condition, and a second conductive structure <NUM> having a second operating condition, and the ability to experience a change in its performance in response to the removal of the first conductive structure <NUM>. Before removing the first conductive structure <NUM>, the entire antenna configuration of the first conductive structure <NUM> and the second conductive structure <NUM> is longer. Stated differently, the first conductive structure <NUM> and the second conductive structure <NUM> function as a series RFID antenna with two tuning states based on the properties of the first and second conductive structures <NUM>, <NUM>. As such, the RFID device <NUM> functions in the first operating condition (100A of <FIG>) with a frequency of f1, for example, in the region of <NUM> to <NUM>. When the first conductive structure <NUM> is removed, the entire antenna configuration is shortened, so the optimum frequency moves up to f2 in the second operating condition (100B of <FIG>). The f2 frequency may be a band where RFID systems do not operate, so the effect of the change would be either to prevent or reduce the range of operation in the <NUM>-<NUM> band.

<FIG> illustrates a graphical representation of a first conductive structure of an RFID device having a resistance that is altered following exposure of the first conductive structure of the RFID device to a plurality of repeated external events, and <FIG> illustrates a graphical representation of a second conductive structure of an RFID device having a resistance that is unaltered following exposure to the same plurality of repeated external events. More specifically, <FIG> illustrate a visualization of how a key operating parameter, such as a resistance of the first conductive structure <NUM> material, may change with exposure to an external event compared to a resistance of the second conductive structure <NUM> material. In this particular example, a single event, such as washing the RFID device <NUM>, may cause the first conductive structure <NUM> to move from a low resistance to a higher resistance (as shown in <FIG>), wherein the second conductive structure <NUM> remains relatively unaffected after exposure to the first event (as shown in <FIG>). As best shown in <FIG>, following the first event, the resistance remains relatively the same with repeated events, such as further washing cycles.

<FIG> illustrates an alternative graphical representation of the resistance of the first conductive structure of the RFID device being altered following exposure to a plurality of repeated events, and <FIG> illustrates an alternative graphical representation of the resistance of the second conductive structure of the RFID device being altered following exposure to the same plurality of repeated events. More specifically, <FIG> illustrate alternative changes in resistance patterns for the first conductive structure <NUM> material and the second conductive structure <NUM> material in response to a plurality of same or similar events, such as multiple washing cycles. In this particular example and as best illustrated in <FIG>, a resistance of the first conductive structure <NUM> material remains relatively low after exposure to the first two events, and then increases with the third event and levels off thereafter with the fourth event. By comparison and as best illustrated in <FIG>, the resistance of the second conductive structure <NUM> increases gradually throughout the first three events and then levels off with the passage of the fourth event.

<FIG> illustrates a schematic diagram of an RFID device <NUM> operating in a first operating condition 100A, and <FIG> illustrates a schematic diagram of the RFID device <NUM> operating in a second operating condition 100B. More specifically, <FIG> illustrate how the first conductive structure <NUM> and the second conductive structure <NUM>, containing different materials and configurations, may be used to change a behavior or the performance of the RFID device <NUM> in response to an external event. In this particular case, the second conductive structure <NUM> (illustrated as a wire antenna) is initially in contact with the first conductive structure <NUM> (illustrated as a pair of printed conductors). In accordance with the invention, the second conductive structure <NUM> is sewn into a substrate, such as a fabric, whereas the first conductive structure <NUM> is attached to a surface of the substrate.

When the RFID device is in the first operating condition 100A, the first conductive structure <NUM> and the second conductive structure <NUM> are coupled together, ohmically or reactively. In addition, the first conductive structure <NUM> and the second conductive structure <NUM> may be coupled with a mechanical bond. If the fabric is part of a garment that stretches when worn, the RFID device is in the first operating condition 100A while the garment is hanging, for example, in a store. When in the first operating condition 100A, the frequency (as best illustrated in FIG. 4A) will want to be tuned for maximum range in the relatively light dielectric loading environment of the RFID device.

Additionally, when the external event is a stretching of the garment bearing the RFID device, the first conductive structure <NUM> and the second conductive structure <NUM> are stretched and pulled apart as the garment is worn which will, in turn, move the RFID device to the second operating condition 100B. Further, the presence of the dielectric associated with a person will reduce the operating frequency of the RFID device <NUM>, as illustrated in FIG. 4B, from the optimum when the RFID device is in the first operating condition 100A. However, the RFID device in the second operating condition 100B has an effectively shorter overall antenna structure which is better suited to operating when in the vicinity of a person. As mentioned previously, the change from functioning in the first operating state to functioning in the second operating state may occur in response to a single event. In this example, if the wire of the second conductive structure <NUM> is bonded mechanically to the printed ink of the first conductive structure <NUM>, the ink may be ripped and distorted by the stretching event of the garment leading to an irreversible change in operating performance of the RFID device <NUM>. Alternatively, the wire of the second conductive structure <NUM> may be free to slide over the printed ink of the first conductive structure <NUM>, thereby making the process reversible.

<FIG> illustrates a schematic diagram of an alternative embodiment not according to the claimed invention of the RFID device <NUM> containing a RFID chip <NUM>, a first conductive structure <NUM>, and a second conductive structure <NUM>. More specifically, RFID device <NUM> utilizes two separate antenna elements manufactured from different materials that couple via magnetic, capacitive, or a combination of fields. The second conductive structure <NUM> is operatively coupled to the first conductive structure <NUM> when the RFID device <NUM> is in a first operating condition, as best illustrated in <FIG>, and the initial coupling between the first conductive structure <NUM> and the second conductive structure <NUM> is typically a non-mechanical coupling <NUM> such as, a magnetic, a capacitive, or a combination of fields. The RFID chip <NUM> is also operatively coupled to the first conductive structure <NUM> and/or the second conductive structure <NUM>, and the first and second conductive structures <NUM> and <NUM> are typically disposed on a substrate, such as a fabric used for a garment.

As previously stated, the first conductive structure <NUM> is typically manufactured from a first conductive material, and the second conductive structure <NUM> is manufactured from a different conductive material. Additionally, the first and second conductive structures <NUM> and <NUM> have different configurations having different mechanical properties. For example, the first conductive structure <NUM> may be a conductive loop that is stretchable, and the second conductive structure <NUM> may be a wire that is relatively rigid. An external event, such as an applied force like stretching, will alter the coupling <NUM>.

For example, a first conductive structure 220A of the RFID device in the first operating condition 200A in a non-deformed state may be substantially circular in configuration with an initial coupling 240A, as best illustrated in <FIG>. In response to the aforementioned stretching event, the first conductive structure <NUM> may deform, as best illustrated in <FIG>. The deformed first conductive structure 220B of the RFID device in the second operating condition 200B may be configured as a deformation of the loop between a circle and an ellipse. The deformation of the first conductive structure 220B creates a modified coupling 240B as the deformed first conductive structure 220B is pulled away from the second conductive structure <NUM>, thereby altering the performance of RFID device <NUM> as discussed previously.

<FIG> illustrates a schematic diagram of an alternative embodiment of an RFID device, wherein the first conductive structure <NUM> partially overlaps the second conductive structure <NUM> in the first operating condition 200A, and <FIG> illustrates a schematic diagram of the alternative embodiment of the RFID device, wherein the first conductive structure <NUM> no longer overlaps the second conductive structure <NUM> in response to an event causing the RFID device to operate in a second operating condition 200B. Each of the first and second conductive structures <NUM>, <NUM> may further contain a RFID chip <NUM> operatively coupled thereto. More specifically, the first conductive structure <NUM> may be configured in a generally U-shape and as a single element, and may contain a bridge where the first conductive structure <NUM> partially overlaps the second conductive structure <NUM> in a wire configuration for the RFID device in the first operating condition 220A. In response to an external event, such as tension, the first conductive structure <NUM> shifts away from the second conductive structure <NUM>, so that the two conductive structures no longer overlap for the RFID device in the second operating condition 220B, thereby reducing the coupling between the first and second conductive structures <NUM> and <NUM>.

In an alternative embodiment not according to the claimed invention as illustrated in <FIG> and <FIG>, a RFID device <NUM> utilizes two separate antenna elements manufactured from the same material, but each having different configurations that are encapsulated or attached to a substrate in different ways. More specifically, the RFID device <NUM> contains a RFID chip <NUM> operatively coupled to a first conductive structure <NUM>, and a second conductive structure <NUM> operatively coupled to the first conductive structure <NUM> when in a first operating condition. The initial coupling between the first conductive structure <NUM> and the second conductive structure <NUM> is typically a non-mechanical coupling such as, a magnetic, a capacitive, or a combination of fields. The first and second conductive structures <NUM> and <NUM> are separately attached to a substrate <NUM>, such as a fabric used for a garment, so that the first and second conductive structures <NUM>, <NUM> respond differently to an event.

The first and second conductive structures <NUM> and <NUM> in this particular embodiment are typically manufactured from the same conductive material. However, the first and second conductive structures <NUM> and <NUM> have different configurations having different mechanical properties. For example, the first conductive structure <NUM> may be a conductive loop that is movably attached to the substrate <NUM>, and the second conductive structure <NUM> may be a wire that is relatively rigidly attached to the substrate <NUM> initially, as best illustrated in <FIG>. Alternatively, the first conductive structure <NUM> may be a conductive loop that is non-movably attached to the substrate <NUM>, and the second conductive structure <NUM> may be a dipole antenna element attached to the substrate <NUM> in a manner that is relatively free to move, as best illustrated in <FIG>. An event, such as an applied force like stretching, will alter the coupling between the first and second conductive structures <NUM> and <NUM>.

As illustrated in <FIG>, the loop of the first conductive structure <NUM> may be elastically encapsulated in a first encapsulation portion <NUM>, which is then attachable to the substrate <NUM>. The material of the first encapsulation portion <NUM> is preferably a stretchable material that when exposed to an event, such as stretching, will permit movement of the first conductive structure <NUM> on or within the substrate <NUM>. The wire of the second conductive structure <NUM> is relatively rigidly encapsulated in a second encapsulation portion <NUM>, which is also attachable to the substrate <NUM>. When the RFID device <NUM> is put under strain, exposed to heat, or some other external event occurs, the loop of the first conductive structure <NUM> may move relative to the wire of the second conductive structure <NUM>, or distort in shape or position, thereby changing the coupling between the first and second conductive structures <NUM> and <NUM> which changes the performance of the RFID device <NUM> as discussed previously.

As illustrated in <FIG>, the first and second conductive structures <NUM> and <NUM> may be non-encapsulatedly attached to the substrate <NUM> in a way so that they each respond differently to an external event, such as stretching. For example, the dipole antenna structure of the second conductive structure <NUM> may be sewn into the fabric of the substrate <NUM> so that it is relatively free to move when the fabric is stretched. In comparison, the loop antenna of the first conductive structure <NUM> may be adhesively bonded to the fabric of the substrate <NUM> so that it does not move unless enough force is applied to non-reversibly detach the first conductive structure <NUM> from the fabric. As before, the purpose of changes in performance or tuning of the RFID device <NUM> in response to an event may be retuning of the RFID device <NUM>. Examples of purposes include adapting the RFID device <NUM> to work better when near a person, the reduction of long range reading to protect consumer privacy while retaining the capability of short-range reading for a user to scan items themselves, or total cessation of operation of the RFID device <NUM>.

Claim 1:
A RFID device (<NUM>) comprising:
a first conductive structure (<NUM>);
a second conductive structure (<NUM>) operatively coupled to the first conductive structure in a first operating condition;
an RFID chip (<NUM>) operatively coupled to the second conductive structure; and
a substrate;
wherein the second conductive structure is sewn into the substrate, and the first conductive structure is attached to a surface of the substrate.