Patent Description:
RFID devices contain an integrated circuit or chip and an antenna and are widely used to associate an object with a unique identification code. The antenna sends and receives signals that are transmitted at a particular frequency or within a particular frequency band. For example, an RFID device may be configured to send and receive signals within a high frequency ("HF") band (i.e., signals having a frequency in the range of approximately <NUM> to <NUM>) or within an ultra-high frequency ("UHF") band (i.e., signals having a frequency in the range of approximately <NUM> to <NUM>,<NUM>). More particularly, a HF RFID device tends to operate at a frequency at or about <NUM>, while a UHF RFID device tends to operate at a frequency in a range of approximately <NUM> to <NUM> (or <NUM> to <NUM> in North America).

In many applications, it is desirable to employ an RFID device that operates in multiple frequency bands, such as HF and UHF. <CIT>, describes an exemplary dual-frequency RFID device. A dual-frequency RFID device may be variously configured, such as employing a dual-mode RFID chip electrically coupled to a pair of antennas configured to send and receive signals in different frequency bands according to one approach. Alternatively, a dual-frequency RFID device includes a first chip/antenna pair and a second chip/antenna pair, with the first and second pairs operating in different frequency bands.

HF antennas, due to their small geometries and need for a connection either between the inner and outer of a coil (a bridge) or interconnection through a substrate (crimps) to a second coil antenna on the other side of the substrate, are frequently made using an etching process. UHF straps (containing an RFID chip and a pair of conductive pads configured to be electrically coupled to a UHF antenna) are also commonly etched, for similar reasons. However, while etching techniques have proven to be effective in creating RFID devices, they may be expensive compared to other approaches.

<CIT> discloses an RFID device including a conductive sheet defining at least first and second portions, with an intermediate portion joining the other portions. One or more RFID chips electrically coupled to the portions, such as one or both of the first and second portions of the conductive sheet and to the intermediate portion. The first portion of the conductive sheet defines a multi-turn high frequency antenna having one or more disruptions in the conductive sheet positioned between and/or defining adjacent turns of the multi-turn antenna. The second portion of the conductive sheet defines a first radiating arm of an ultra high frequency antenna. The disruptions direct a high frequency current around the turns of the multi-turn high frequency antenna, while allowing an ultra high frequency current to flow across the disruptions, resulting in the first portion of the conductive sheet defining a second radiating arm of the ultra high frequency antenna.

<CIT> discloses a combined EAS and RFID circuit includes an HF coil antenna, a UHF tuning loop, and an RFID chip coupled to a strap that includes a first coupling area and a second coupling area. The coil ends of the HF coil antenna are configured to capacitively and/or conductively couple to one or both of the first coupling area or second coupling area of the strap. The HF coil antenna can include a gap between turns for non-interfering placement of the UHF tuning loop. The EAS circuit can be deactivating upon application of a field at the resonant frequency of sufficient intensity to cause the breakdown voltage to be exceeded between a coil end and coupling area. The threshold breakdown voltage between a coil end and a coupling area can be reduced by laser ablation treatment of a conductive surface of one or both of the coil end or coupling area.

There are several aspects of the present subject matter which may be embodied separately or together in the devices and systems described and claimed below. These aspects may be employed alone or in combination with other aspects of the subject matter described herein, and the description of these aspects together is not intended to preclude the use of these aspects separately or the claiming of such aspects separately or in different combinations as may be set forth in the claims appended hereto.

According to the invention there is provided a dual-mode RFID device according to claim <NUM>. Preferred features are set out in the dependent claims.

Dual-mode RFID devices containing an integrated RFID strap having dual-mode capability are described herein. In some examples, the integrated dual-mode RFID strap is configured as a reactive strap and contains a conductive ring and a HF antenna coupled to a RFID chip assembly. In some examples, the integrated dual-mode RFID strap is configured to couple with a UHF antenna without physical contact between the UHF antenna and the integrated dual-mode RFID strap.

In some examples, the integrated dual-mode RFID strap containing the conductive ring and the HF antenna described above, coupled by the RFID chip assembly, is on a single substrate.

In some examples, the integrated dual-mode RFID strap configured as a reactive strap as described above couples magnetically, conductively, and/or capacitively with the UHF antenna.

In some examples, the RFID chip assembly of the integrated dual-mode RFID strap contains a RFID coupling strap and a dual mode RFID chip. In one example, the dual mode RFID chip contains a UHF/HF dual RFID chip. In another example, the dual mode RFID chip contains a combination of a UHF RFID chip and a HF RFID chip, each individually disposed on a RFID coupling strap.

In some examples, the integrated dual-mode RFID strap contains an HF antenna and a conductive ring affixed to the RFID coupling strap by means of an adhesive material including a pressure sensitive adhesive.

Methods (not claimed) for manufacturing a dual-mode RFID device are also described herein. Ir some examples, the methods include providing an integrated dual-mode RFID strap having an RFID chip assembly containing a UHF/HF dual-mode RFID chip or the combination of a UHF RFID chip and an HF RFID chip. In some examples, the integrated dual-mode RFID strap also contains a HF antenna and a conductive ring affixed, attached, or coupled to the RFID chip assembly. In some examples, the HF antenna and the conductive ring are coupled to the RFID chip assembly at its opposing ends. In one example, the conductive ring is a UHF loop. In some examples, the presence of the conductive ring as part of the integrated dual-mode RFID strap enables coupling of the strap with the UHF antenna. In some examples, the UHF antenna is formed without being etched.

In some examples, the method (not claimed) for manufacturing a dual-mode RFID device including a RFID chip assembly thereof involves securing a first RFID chip to a structure of a dual-mode RFID device using a thermode to apply heat and pressure between the first RFID chip and the structure. In some examples, a second RFID chip is then secured to the structure using the thermode, with at least a portion of the first RFID chip being positioned between the thermode and the structure.

In some examples, the method (not claimed) for manufacturing a dual-mode RFID device including a RFID chip assembly thereof involves securing a first RFID chip to a structure of a dual-mode RFID device and then subjecting the first RFID chip to a first test. If the first RFID chip fails the first test, then the dual-mode RFID device is rejected. If the first RFID chip passes the first test, a second RFID chip is secured to the structure, followed by the second RFID chip being subjected to a second test. If the second RFID chip fails the second test, then the dual-mode RFID device is rejected; otherwise, if the second RFID chip passes the second test, then the dual-mode RFID device is accepted.

The embodiments disclosed herein are exemplary only, and the subject matter described herein may be embodied in various forms. Therefore, specific details disclosed herein are not to be interpreted as limiting the subject matter as defined in the accompanying claims.

<FIG> shows a dual-mode RFID device <NUM> (e.g., an RFID tag or label) according to an aspect of the present disclosure. The dual-mode RFID device <NUM> includes an integrated dual-mode RFID strap <NUM> configured to be coupled with a UHF antenna <NUM>. The integrated dual-mode RFID strap <NUM> contains a conductive ring <NUM> and an HF antenna <NUM> coupled to a RFID chip assembly <NUM>. In some embodiments, the integrated dual-mode RFID strap <NUM> enables coupling between the HF antenna <NUM> and the UHF antenna <NUM> via the conductive ring <NUM>. In the present embodiment, the conductive ring <NUM> is a UHF loop coupled to the RFID chip assembly <NUM>. However, other conductive structures can be used.

<FIG> shows a RFID chip assembly <NUM> containing a RFID coupling strap <NUM>, conductive pads <NUM> and one or more RFID chips. The RFID chip assembly <NUM> is coupled on one side to the HF antenna <NUM> and on the other side to the conductive ring <NUM>. Particularly, the HF antenna <NUM> and the conductive ring <NUM> are attached to the RFID coupling strap <NUM>. In one embodiment, an adhesive material such as a pressure sensitive adhesive is used to couple, affix, or attach the HF antenna <NUM> and the conductive ring <NUM> to the RFID coupling strap <NUM>. The HF antenna <NUM>, the conductive ring <NUM>, and the RFID strap assembly <NUM> coupling both the HF antenna <NUM> and the conductive ring <NUM> are incorporated in a common substrate, with the integrated dual-mode RFID strap <NUM> serving as a "combo strap" that is separate from the UHF antenna <NUM>.

The one or more RFID chips of the RFID chip assembly <NUM> includes either a single UHF/HF dual-mode RFID chip <NUM> (<FIG>) or the combination of a UHF RFID chip <NUM> and an HF RFID chip <NUM> (<FIG>). Many aspects of the present disclosure may be employed with the RFID coupling strap <NUM> having either one or two RFID chips. However, certain aspects of the present disclosure are particular to the RFID coupling strap <NUM> having a pair of RFID chips <NUM> and <NUM>, as will be described in greater detail herein.

Regardless of the particular configuration of the RFID chip assembly <NUM>, the integrated dual-mode RFID strap <NUM> is configured for coupling to an HF antenna <NUM> and a UHF antenna <NUM>. <FIG> show RFID coupling straps <NUM> having a pair of HF connections <NUM> (associated with either the UHF/HF dual-mode RFID chip <NUM> (<FIG>) or the HF RFID chip <NUM> (<FIG>)) and a pair of UHF connections <NUM> (associated with either the UHF/HF dual-mode RFID chip <NUM> (<FIG>) or the UHF RFID chip <NUM> (<FIG>)).

The nature and configuration of the HF connections <NUM> and the UHF connections <NUM> may vary, depending on the nature and configuration of the associated antennas. In the embodiment of <FIG>, the HF antenna <NUM> is configured as a coil, in which case the HF connections <NUM> may be configured as conductive leads <NUM> (as shown in <FIG>) that may be coupled to the coil. In the embodiment of <FIG>, the UHF antenna <NUM> is configured as a slotted-loop antenna, in which case the UHF connections <NUM> may be configured as conductive pads <NUM> (as shown in <FIG>) that may be coupled to the slotted-loop antenna.

As noted above, the nature and configuration of the antenna connections of the RFID coupling strap <NUM> may vary, depending on the nature and configuration of the associated antennas. By way of example, <FIG> illustrates a dual-mode RFID device <NUM>' having a differently configured UHF antenna <NUM>'. In the embodiment of <FIG>, rather than the UHF antenna <NUM>' being configured to be connected to the RFID coupling strap <NUM>' at conductive pads, the UHF antenna <NUM>' is instead configured to be coupled to the RFID coupling strap <NUM>' without physical contact between the UHF antenna <NUM>' and the RFID coupling strap <NUM>'. In other words, the RFID coupling strap <NUM>' is configured as a reactive strap, with the conductive ring <NUM>' coupled to the RFID chip assembly to effectively couple the UHF antenna <NUM>' (which may be configured as a dipole antenna) to the integrated dual-mode RFID strap <NUM>'. In the present embodiment, the integrated dual-mode RFID strap <NUM>' is magnetically coupled to the UHF antenna <NUM>'.

While <FIG> shows the conductive ring <NUM>' as being entirely separate from the HF antenna <NUM> (which is shown as being configured as a coil), but it is within the scope of the present disclosure for an HF antenna to define a portion of a conductive ring, as shown in <FIG>. In the embodiment of <FIG>, the HF antenna <NUM> is configured as a coil that is coupled to the RFID chip assembly <NUM>. A conductor <NUM> has first and second ends that are coupled to the HF antenna <NUM> at opposing sides of the RFID chip assembly <NUM>. By such a configuration, a conductive ring is formed by the conductor <NUM> and the portions <NUM> and <NUM> of the HF antenna <NUM> extending between the RFID chip assembly <NUM> and the locations at which the conductor <NUM> is joined to the HF antenna <NUM>. The conductive ring/conductor <NUM> resonates with the RFID chip assembly <NUM> at a desired high frequency (e.g., <NUM>), but the voltage associated with the HF operation is shorter around the RFID chip assembly <NUM> by the low inductance bridge.

Regardless of the particular configuration of the dual-mode RFID device <NUM>, <NUM>', the UHF antenna <NUM>, <NUM>' is formed using an approach other than etching, which is relatively expensive and may be slower than other approaches. In one embodiment, the UHF antenna <NUM>, <NUM>' is formed via a cutting operation, such as die-cutting (e.g., from a paper/foil structure) and/or laser-cutting. In another embodiment, the UHF antenna <NUM>, <NUM>' is formed via a printing operation. It should be understood that cutting and printing are exemplary lower cost approaches to forming the UHF antenna <NUM>, <NUM>', rather than being an exhaustive list of possible approaches. Instead, it should be understood that the present disclosure encompasses any method of forming a UHF antenna that is less expensive than the cost of forming the same UHF antenna via an etching operation.

Once formed, the UHF antenna <NUM>, <NUM>' may then be coupled to the integrated dual-mode RFID strap <NUM>, <NUM>' according to any suitable approach, which may include coupling the UHF antenna <NUM>, <NUM>' to the RFID coupling strap <NUM>, <NUM>' using an adhesive material, such as a pressure-sensitive adhesive, which allows the UHF antenna <NUM>, <NUM>' to be rapidly connected to the RFID strap <NUM>, <NUM>'. In the case of conductive pads <NUM> (as in <FIG>), a thin layer of adhesive is applied between the conductive pads <NUM> and the UHF antenna <NUM>, with the UHF antenna <NUM> being coupled to the conductive pads <NUM> via capacitance.

One consideration when employing an RFID chip assembly <NUM> having a UHF RFID chip <NUM> and an HF RFID chip <NUM> is the separation between the two chips <NUM> and <NUM>. According to one conventional approach to incorporating a pair of RFID chips into a dual-mode RFID device, a chip attach system transfers one chip from a wafer at a time, such that attaching two chips requires two passes through the system. As part of the chip attach process, an anisotropic conductive paste is provided under the chip, with the chip being pushed into the paste and heated by a thermode, which cures the adhesive. If the separation between the two chips is less than the size of the portion of the thermode used to secure the second chip, the thermode will stop at the attached height of the first chip, which may prevent proper bonding of the second chip to a structure of the RFID device.

Therefore, in some embodiments, the limitation of the conventional chip attach process described above may be overcome by providing first and second chips <NUM> and <NUM> having different heights, as shown in <FIG>. The second chip <NUM> has a height "H" that is greater than the height "h" of the first chip <NUM>, such that the first chip <NUM> will not interfere with a thermode attempting to secure the second chip <NUM> to a structure <NUM> of a dual-mode RFID device. By such an arrangement, the separation "d" between the two chips <NUM> and <NUM> may be less than the size of the portion of the thermode used to secure the second chip <NUM>, in which case at least a portion of the first chip <NUM> will be positioned between the thermode and the structure <NUM> of the dual-mode RFID device when securing the second chip <NUM>. More closely positioning the two RFID chips <NUM> and <NUM> allows for creation of a smaller dual-mode RFID strap, which may reduce the cost of the RFID strap.

The heights "h" and "H" of the two chips <NUM> and <NUM> may vary without departing from the scope of the present disclosure, provided that the second chip <NUM> has a greater height than the first chip <NUM>. In one exemplary embodiment, the first chip <NUM> has a height "h" of approximately <NUM>, while the second chip <NUM> has a height "H" of approximately <NUM>. The second chip <NUM> may be configured to have a height "H" that is a particular percentage greater than the height "h" of the first chip <NUM>, such as at least <NUM>% greater or at least <NUM>% greater or at least <NUM>% greater, for example. In yet another embodiment, the second chip <NUM> may be configured to have a height "H" that is a particular amount greater than the height "h" of the first chip <NUM>, such as being at least <NUM> greater than the height "h" of the first chip <NUM> or at least <NUM> greater than the height "h" of the first chip <NUM>. The particular height difference between the two chips <NUM> and <NUM> may be selected based on any of a number of factors, such as the configuration of the thermode system (e.g., the amount of heat and pressure to be applied) and the nature of the adhesive being employed. It should be understood that this aspect of the present disclosure is not limited to use with a dual-mode RFID device having a UHF antenna formed according to any particular approach, but may be more widely employed with any dual-mode RFID device having a pair of RFID chips.

In some embodiments, a sequential test method may be employed to reduce costs associated with chip attach failures or faulty chips for dual-mode RFID devices having a pair of RFID chips. The first chip is attached to a structure of a dual-mode RFID device according to any suitable approach. The first chip is then subjected to a first test to determine whether it is faulty in any way (e.g., due to a chip attach failure or due to the chip itself being faulty). If the first chip fails the test, then the RFID device is rejected as being defective without securing the second chip (which would unnecessarily increase the cost associated with the failure of the first chip). On the other hand, if the first chip passes the first test, then the second chip may be secured to the structure of the dual-mode RFID device according to any suitable approach. The second chip is then subjected to a second test to determine whether it is faulty in any way. If the second chip fails the test, then the RFID is rejected as being defective. Otherwise, if the second chip passes the test, then the dual-mode RFID device may be accepted.

It is possible for the first chip to become damaged in the course of securing the second chip to the structure of the dual-mode RFID device. Accordingly, it may be advantageous to not only test the second chip after securing it, but to also subject the first chip to a third test (which is the second test applied to the first chip). If the first chip fails the third test and/or if the second chip fails the second test, then the dual-mode RFID device is rejected. On the other hand, if the second chip passes the second test and the first chip passes the third test, then the dual-mode RFID device is accepted. It should be understood that the nature of the tests may vary without departing from the scope of the present disclosure. This may include the first chip being subjected to either the same test twice or to a different test before and after the second chip has been secured (in embodiments in which the first chip is tested twice).

If the chips are being incorporated into an integrated dual-mode RFID strap (e.g., one of the type described herein), the second and third tests may be carried out on the strap or one or both of the tests may be carried out after the strap has been coupled to an antenna. This may include one or both of the chips being tested between attachment of the second chip and coupling to the antenna and after coupling to the antenna.

The present configuration of the integrated dual-mode RFID strap enables easy manufacturing of numerous RFID tags with varying configurations while using a common integrated dual-mode RFID strap. Forming the UHF antenna using die-cutting or laser-cutting method also enables minimizing material wastage. Thus, the dual-mode RFID device of the present subject matter is designed to be a sustainable one. It will be understood that the embodiments described above are illustrative of some of the applications of the principles of the present subject matter.

Claim 1:
A dual-mode RFID device (<NUM>, <NUM>') comprising:
a RFID chip assembly (<NUM>, <NUM>'), and
an integrated dual-mode RFID strap (<NUM>, <NUM>') comprising a conductive ring (<NUM>, <NUM>') and a HF antenna (<NUM>) coupled to the RFID chip assembly,
wherein the integrated dual-mode RFID strap is coupled to a UHF antenna (<NUM>, <NUM>').