Patent Application
20080122631
This disclosure generally relates to the field of automatic data collection (ADC), for example, data acquisition via radio frequency identification (RFID) tags. More particularly but not exclusively, the present disclosure relates to a structural configuration of an RFID tag.
The ADC field includes a variety of different types of ADC data carriers and ADC readers operable to read data encoded in such data carriers. For example, data may be encoded in machine-readable symbols, such as barcode symbols, area or matrix code symbols, and/or stack code symbols. Machine-readable symbols readers may employ a scanner and/or imager to capture the data encoded in the optical pattern of such machine-readable symbols. Other types of data carriers and associated readers exist, for example magnetic stripes, optical memory tags, and touch memories.
Other types of ADC carriers include RFID tags that may store data in a wirelessly accessible memory, and may include a discrete power source (i.e., an active RFID tag), or may rely on power derived from an interrogation signal (i.e., a passive RFID tag). RFID readers typically emit a radio frequency (RF) interrogation signal that causes the RFID tag to respond with a return RF signal encoding the data stored in the memory.
Identification of an RFID device or tag generally depends on RF energy produced by a reader or interrogator arriving at the RFID tag and returning to the reader. Multiple protocols exist for use with RFID tags. These protocols may specify, among other things, particular frequency ranges, frequency channels, modulation schemes, security schemes, and data formats.
Many ADC systems that use RFID tags employ an RFID reader in communication with one or more host computing systems that act as central depositories to store and/or process and/or share data collected by the RFID reader. In many applications, wireless communications is provided between the RFID reader and the host computing system. Wireless communications allow the RFID reader to be mobile, may lower the cost associated with installation of an ADC system, and permit flexibility in reorganizing a facility, for example a warehouse.
RFID tags typically include a semiconductor device (such as a chip) having the memory, circuitry, and one or more conductive traces that form an antenna. Typically, RFID tags act as transponders, providing information stored in the memory in response to the RF interrogation signal received at the antenna from the reader or other interrogator. Some RFID tags include security measures, such as passwords and/or encryption. Many RFID tags also permit information to be written or stored in the memory via an RF signal.
The read/write range of an RFID tag is often strongly dependent on the type of material composition of the object on which RFID tag is attached. Since an RFID tag is generally an antenna connected to an RFID chip, the performance of the antenna can be severely affected by the presence of metal or other objects in the near-field zone around the antenna. This effect is especially severe for metallic objects, such as for example, airplane parts, metal containers, etc. When a typical passive RFID tag is mounted on such metallic objects, the object(s) will change characteristics of the antenna. These changes can include, for instance, detuning of the resonant frequency of the RFID tag, changing the bandwidth of the RFID tag, lowering the range of the RFID tag, and so forth.
Moreover, various different RFID frequency bands, RFID standards and protocols, RFID applications, etc. are present. For instance, different countries may allocate different frequency bands for RFID use. Existing RFID tags are rather inflexible in that they are manufactured for a specific frequency band, standard/protocol, application etc., and would therefore be incompatible or otherwise inoperative with an RFID reader or other RFID system that is operating based on a different frequency band, standard/protocol, application, etc. Such limitations can limit worldwide use/compatibility of a particular RFID tag designed to operate only at a specific frequency, for example.
One aspect provides a radio frequency identification (RFID) tag apparatus that includes a flexible antenna inlay structure having a substrate material and an antenna trace affixed to the substrate material. The antenna trace includes a first structure to set a first resonant frequency and a second structure to set a second resonant frequency. An operating frequency band is defined at least in part between the first and second resonant frequencies. The apparatus includes a dielectric having the antenna inlay structure affixed thereto. A metallized label affixed to the dielectric shields the antenna inlay structure from effects of a background object. A protective structure houses and protects the antenna inlay structure, dielectric, and metallized label.
Non-limiting and non-exhaustive embodiments are described with reference to the following drawings, wherein like reference numerals refer to like parts throughout the various views unless otherwise specified. The sizes and relative positions of elements in the drawings are not necessarily drawn to scale. For example, the shapes of various elements and angles are not drawn to scale, and some of these elements are arbitrarily enlarged and positioned to improve drawing legibility. Further, the particular shapes of the elements as drawn, are not intended to convey any information regarding the actual shape of the particular elements, and have been solely selected for ease of recognition in the drawings.
In the following description, numerous specific details are given to provide a thorough understanding of embodiments. One skilled in the relevant art will recognize, however, that the embodiments can be practiced without one or more of the specific details, or with other methods, components, materials, etc. In other instances, well-known structures, materials, or operations associated with RFID tags and RFID readers, computer and/or telecommunications networks, and/or computing systems are not shown or described in detail to avoid obscuring aspects of the embodiments.
Unless the context requires otherwise, throughout the specification and claims which follow, the word “comprise” and variations thereof, such as, “comprises” and “comprising” are to be construed in an open, inclusive sense, that is as “including, but not limited to.”
Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, the appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.
Reference throughout this specification and claims to “radio frequency” or RF includes wireless transmission of electromagnetic energy, including, but not limited to, energy with frequencies or wavelengths typically classed as falling in the radio and microwave portions of the electromagnetic spectrum.
The headings provided herein are for convenience only and do not interpret the scope or meaning of the embodiments.
As an overview, an embodiment provides a data carrier, such as an RFID tag, having an antenna printed on a substrate to thereby form an antenna inlay structure. The antenna inlay structure of one embodiment is flexible and can be folded to provide a more compact form factor. The antenna inlay structure of one embodiment can be attached to a dielectric and then placed in a rigid enclosure or coated with a special material to provide a rigid RFID tag (or otherwise covered by a protective structure), such as a metal mount RFID tag that can be affixed to a metallic object or other object.
In one embodiment, a metallic ground plane (such as provided by a metallized label) can be provided inside the rigid enclosure or inside some other protective structure (such as a coating) to serve as electrical shield to minimize the effect of the object on the antenna. The antenna of one embodiment can be provided with several resonant frequencies and is further able to operate according to different frequency bands, standards/protocols, applications, etc. Such embodiments of the RFID tag having the antenna inlay structure thus provides improved and increased capabilities and flexibility as compared to existing RFID tags.
According to various embodiments, the antenna inlay structure, dielectric, and metallized label are either housed in the rigid enclosure or coated with a special vacuum-deposited material (such as Parylene) or other protective structure made from a protective material that covers and protects the antenna inlay structure and/or other internal elements of the RFID tag from chemical exposure, mechanical stress, electrostatic discharge, and so forth.
In one possible application, the antenna inlay structure 100 may be part of an RFID tag present in a thin “smart label” 102. The relatively thin and flexible characteristics of the antenna inlay structure 100 allows the antenna inlay structure 100 to be used in the smart label 102, without unduly increasing the bulkiness/thickness of the smart label 102 and/or without unduly decreasing the flexibility of the smart label 102. The antenna inlay structure 100 can be coupled to an RFID chip (such as those that will be explained later below), and then appropriately packaged into the smart label 102 using laminates or other suitable material that provides coating, protection, sealant, adhesion, etc. for smart labels.
In another possible application, the antenna inlay structure 100 may be part of a high-performance rigid RFID tag 104. One example of the high-performance rigid RFID tag 104 is a rigid metal mount RFID tag having wide and multiple frequency bands. Embodiments of such a rigid metal mount RFID tag will be described later below.
In another possible application, the antenna inlay structure 100 may be part of a compact rigid RFID tag 106. One example of the compact rigid RFID tag 106 is a compact rigid metal mount RFID tag having a folded antenna inlay structure. Embodiments of such a compact rigid metal mount RFID tag will also be described later below.
The antenna trace 202 of the antenna inlay structure 100 can comprise a conductive ink printed on the PET label 204, wire(s) or other conductive metallic structure formed in or on the PET label 204, or other suitable antenna material (e.g., copper, aluminum, silver, conductive fluid, etc.) that can be placed on and/or embedded in the substrate material. For instance, to form the antenna inlay structure 100, such antenna material can be formed on the surface of the substrate, embedded at least in part in the substrate, “sandwiched” between two substrates, and other configuration(s) including combinations thereof. Further, it is possible in another embodiment wherein multiple substrate layers are provided, with a same and/or different antenna portions being formed in or on the respective substrate layers. The substrate layers and/or antenna portions can further be made of the same material or different materials. For the sake of simplicity of explanation, the antenna inlay structure 100 will be described hereinafter in the context of the antenna trace 202 being formed on (or over) the substrate material, such as the PET label 204.
The antenna trace 202 is electrically coupled to an RFID chip 206. In one embodiment, the RFID chip 206 is a passive RFID chip. In other embodiments, the RFID chip 206 is actively powered by a battery (not shown).
The RFID chip 206 can be compliant with standards/protocols such as ISO 18000-6B or other ISO standard, EPC Global Gen 2, Class 0, Class 1, and so forth. Thus, the RFID tag 200 is compatible and interoperable with RFID readers that support such standards/protocols. The RFID chip 206 has a front end impedance that can be matched with the antenna trace 202, as will be described in further detail below.
The antenna inlay structure 100 of one embodiment is affixed to a dielectric 208, using any suitable affixation technique (e.g., gluing via use of an adhesive), such that the antenna trace 202 is placed against a first surface of the dielectric 208. The dielectric 208 of one embodiment is homogenous and provides a substrate for the antenna inlay structure 100. The dielectric 208 has some flexibility in an embodiment. A person skilled in the art having the benefit of this disclosure will be familiar with the type of materials that can be used for the dielectric 208, such as plastic. To accommodate the RFID chip 206, a hollow cavity 210 can be formed in the first surface of the dielectric 208.
In one embodiment, a metallized label 212 can be affixed to a second surface of the dielectric 208, using any suitable affixation technique (e.g., gluing via use of an adhesive). In the embodiment of
The metallized label 212 can be made of copper, aluminum, silver ink, or other suitable conductive material. The metallized label 212 forms a ground plane for the antenna trace 202, and serves as an electrical shield for the antenna trace 202 against the effects of the background object (e.g., a metallic object or other object that may be made of wood, plastic, liquid, or other material) on which the RFID tag 200 is attached. Thus, the performance of one embodiment of the RFID tag 200 is insensitive to the electric and/or magnetic properties of the background object. Examples of such objects on which the RFID tag 200 is attachable can include, but not be limited to, tractors and trailers, airplane parts, reusable plastic containers (RPC), metal cages or containers, wood and plastic pallets, unit loading devices, vehicles, personal items (e.g., luggage), appliances, and so on.
In one embodiment, the metallized label 212 has a surface area (or other dimensional characteristic) that exceeds the surface area (or other dimensional characteristic) of the antenna trace 202, thereby further providing adequate shielding/coverage against the background object. Depending on the thickness and/or material composition of the metallized label 212, the metallized label 212 may have some flexibility.
In an embodiment, an enclosure 214 houses the antenna inlay structure 100 and its components, the RFID chip 206, the dielectric 208, and the metallized label 212. The enclosure 214 can be made out of any suitable material that provides some rigidity to these otherwise flexible elements housed therein. An example material for the enclosure 214 is plastic, such as 2-piece plastic enclosure having a base and a cover.
The enclosure 214 further protects the elements housed internally therein against environmental conditions that may otherwise damage such internal elements. For instance in one embodiment, the enclosure 214 is made from impact-resistant plastic that provides rugged protection against extreme temperatures and hazardous exposures that are common in manufacturing and material handling operations. Examples of these temperatures are −40 to +250 degrees Fahrenheit or −40 to +121 degrees Celsius. Examples of the hazardous exposures against which the enclosure 214 is resistant include chemical exposures to machining oil/fluid, gasoline, motor oil, methyl ethyl ketone (MEK), isopropyl alcohol, methyl alcohol, mineral spirits, acetone, kerosene, and others. As will be discussed in further detail below, other embodiments can provide a protective coating, instead of the enclosure 214, to house or otherwise cover and protect the internal components of an RFID tag.
The RFID tag 200 can be attached to an object using screws, rivets, double-sided adhesive strips, hook and loop fastener, or any other suitable attachment method. In one embodiment, for example, the enclosure 214 (or coating) may be provided with mounting holes (not shown) to accommodate screws or rivets.
Moreover, because of the robustness and ruggedness of the RFID tag 200, as provided by the enclosure 214 (or coating) and by the design/configuration of the antenna inlay structure 202 and other internal elements, the RFID tag 200 of one embodiment is reusable. For instance, the enclosure 214 protects the internal elements to extend their useful life and allow continued use of the RFID tag 200 and also provides mounting holes for repeated attachment/detachment. The RFID chip 206 can be provided with a memory having a sufficient size (such as 2048 bits, 96 bits, etc.) and reliability to permit potentially thousands of rewriting operations. Thus, an embodiment of the reusable RFID tag 200 can provide a significant cost savings per unit.
Example dimensions of the RFID tag 200 (in its encapsulated form that includes the enclosure 214 or coating) are a respective length and width of approximately 6 inches by 1 inch (e.g., approximately 15 cm by 2.5 cm). Example dimensions of some of the other elements of the RFID tag 200 are: antenna trace 202 (1 mil thick, wherein 1 mil= 1/1000 inches or approximately 0.0025 cm); PET label 204 (2 mil thick); and metallized label 212 (1 mil thick). The RFID chip 206 of one embodiment can have dimensions consistent with thin-shrink small outline package (TSSOP) chip packaging.
The RFID tag 400 differs from the RFID tag 200 in that the RFID tag 400 has a more compact form factor relative to the RFID tag 200. In particular, the antenna inlay structure 100 of the RFID tag 400 has been folded over the dielectric 408 to thereby reduce the overall size of the RFID tag 400 without changing the inlay design itself.
In the specific embodiment shown in
It is noted that instead of being entirely affixed to the first surface (e.g., the top surface) of the dielectric 408 as with the embodiment of
In one embodiment, the antenna inlay structure 100 is folded such that the antenna trace 402 is affixed proximate to the dielectric 408 and the PET label 404 is distal to the dielectric 408. Moreover, while
The folding of the antenna inlay structure 100 reduces the “footprint” of the antenna inlay structure 100, thereby allowing a decrease in the size of the dielectric 408, the metallized label 412, and the enclosure 414. This collective reduction in size of these internal elements contributes to an overall reduction in size of the RFID tag 400.
For instance, example dimensions of the RFID tag 400 (in its encapsulated form that includes the enclosure 414 or coating) are a respective length and width of approximately 3 inches by 1 inch (e.g., approximately 7.5 cm by 2.5 cm)—thus, the overall length of the RFID tag 400 can be reduced by half, for example, as compared to the length of the RFID tag 200 of
While embodiments have been described above in which the enclosure 214 (such as in the form of rigid plastic) has been provided to house the internal elements of the RFID tag 200/400, it is appreciated that other embodiments can provide other types of protective structure to cover the internal elements of the RFID tag. For example, one or more other embodiments coat the antenna inlay structure 100, RFID chip, dielectric, and metallized label with a suitable protective material. Such coating protects the RFID tag from chemical exposure, mechanical stress, and electrostatic discharge and eliminates the need for a plastic housing in many RFID tag applications.
However, instead of using an enclosure (such as the enclosure 214 of
Parylene is produced by vapor-phase deposition and polymerization of para-xylylene (or its substituted derivatives). Parylene as a vacuum deposited plastic has the quality of coating in a uniform manner. Parylene further has the qualities of resistance to chemical attacks, superior dielectric strength, a very low dissipation factor, excellent mechanical strength, very high surface and volume resistivities, and other superior electrical properties that exhibit low sensitivity to changes in temperature.
To apply parylene, a vacuum application process may be used, in which a dimer is placed in a vacuum system and converted to a reactive vapor of the monomer. When passed over room temperature objects, this vapor will rapidly coat the objects with a polymer. The result is a substantially impervious uniform finish/coating.
In some embodiments, the protective coating 1214/1314 provides rigidity to the RFID tag 1200/1300. In other embodiments, the protective coating 1214/1314 is made of a material that has some flexibility, thereby providing the RFID tag 1200/1300 with some flexibility as well. Various embodiments of the RFID tags 1200/1400 that use a protective coating can have dimensions similar to those previously described above for the RFID tags 200/400.
An impedance matching element (symbolically depicted by the broken lines 604) couples the stub structure 602 to the RFID chip 206/406 and to the ring structure 600. The impedance matching element 604 of one embodiment can comprise a trace having a tapered, meandered, rectangular, or other suitable shape. The impedance matching element 604 operates to match the front end input impedance of the RFID chip 206/406 to the antenna inlay structure 100. Thus, given that various RFID chips 206/406 may have different front end input impedances depending on various design parameters of the RFID chips 206/406, a different impedance matching element 604 may be present from one RFID tag to another, so as to optimally match the front end input impedance of the RFID chip to the antenna inlay structure 100.
In an embodiment, the antenna inlay structure 100 of one embodiment has at least two resonant frequencies. In general, the stub structure 602 sets an upper resonant frequency, while the ring structure 600 sets a lower resonant frequency. Since the stub structure 602 and the ring structure 600 are coupled together, the frequency separation between the upper and lower resonant frequencies is related to an overall length/width of the ring structure 600 and to the length of the stub structure 602 with the impedance matching element 606. This frequency separation between the upper and lower resonant frequencies define at least a portion of the operating frequency band(s) (e.g., the read frequencies or read range bandwidth) of the RFID tag 200/400.
Accordingly, by manipulating such dimensional characteristics of the ring structure 600 and the stub structure 602, a desired read range bandwidth of the RFID tag 200/400 can be achieved by matching the upper and lower resonant frequencies for a particular impedance of the RFID chip 206/406.
Example dimensions of the antenna trace 202/402 of
For instance, the embodiment of the stub structure 802 of
To provide a comparison of range or bandwidth between the embodiments of the RFID tags 200 and 400 of
The various antenna trace designs shown and described above can be adapted for use in the RFID tags 1200 and 1300 of
Thus, one embodiment of the RFID tag 200 is able to operate in various countries around the world that designate different ultrahigh frequency (UHF) bands for RFID use. Examples of such UHF RFID frequencies include, but are not limited to, 869 MHz, 915 MHz, and 955 MHz. Accordingly, one embodiment of the RFID tag 200 having such multiple-band capability can be used for global operations, thereby allowing an enterprise (e.g., a company) to use a single RFID tag 200 for its products worldwide, in which such RFID tag 200 might travel across different countries that use different frequency bands for reading RFID tags. Such an enterprise can therefore eliminate the expensive and inefficient need to create/design customized RFID tags for each individual country, where such RFID tags might have limited operability outside of their country-of-design.
As with the RFID tag 200 described with reference to
Embodiments of the RFID tags 1200 and 1300 that use the outer protective coating (instead of the enclosures 214 and 414) exhibit performance characteristics similar to those shown and described above. Thus in some embodiments, using the protective coating (such as a coating made from Parylene) does not significantly affect the read range performance in comparison to using the enclosures 214 and 414.
With the ruggedness, reusability, and worldwide compatibility of embodiments of the various RFID tags described above, an enterprise (or other party) can use a single RFID tag to identify and track objects (such as subassemblies, work-in-process components, finished goods, material handing equipment, logistics containers, etc.) through production, supply chains, and asset/inventory management operations that may span different countries or other geographic regions having different environments and requirements. The reusability of embodiments of such RFID tags further reduces the total cost of ownership.
All of the above U.S. patents, U.S. patent application publications, U.S. patent applications, foreign patents, foreign patent applications and non-patent publications referred to in this specification and/or listed in the Application Data Sheet, are incorporated herein by reference, in their entirety.
The above description of illustrated embodiments, including what is described in the Abstract, is not intended to be exhaustive or to limit the invention to the precise forms disclosed. While specific embodiments and examples are described herein for illustrative purposes, various equivalent modifications are possible within the scope of the invention and can be made without deviating from the spirit and scope of the invention.
For example, embodiments have been described above for the antenna inlay structure 100 corresponding to the rigid metal mount RFID tags 200 and 400 (as well as the RFID tags 1200 and 1300). It is appreciated that such embodiments of the antenna inlay structure 100 (e.g., the material composition, antenna trace and substrate configuration, etc. of the antenna inlay structure) can be adapted or otherwise used for the smart label 102 of
Further, specific embodiments have been described above in the context of the protective structure of the RFID tags being the enclosure 214 or 414. Such description can be applied to embodiments wherein the protective structure is made from a protective coating, such as Parylene or other suitable material.
These and other modifications can be made to the embodiments in light of the above detailed description. The terms used in the following claims should not be construed to limit the invention to the specific embodiments disclosed in the specification and the claims. Rather, the scope of the invention is to be determined entirely by the following claims, which are to be construed in accordance with established doctrines of claim interpretation.
