Patent Application
20100109840
This invention relates generally to radio frequency identification (RFID) systems, and more particularly to an antenna for RFID systems.
RFID systems are increasingly used to acquire information that may be used, for example, to monitor and track products and processes. For example, RFID systems may be used to monitor the inventory of products in a retail environment. RFID systems provide automatic identification capabilities using the storage and remote retrieval of data from RFID tags or transponders. An RFID tag can be attached to or integrated within a product or product packaging. These RFID tags receive and respond to radio frequency (RF) signals to provide information, for example, related to the product to which the RFID tag is attached. For example, modulators of the RFID tags may transmit back a signal using a transmitter or reflect back a signal to RFID readers. Additionally, information may be communicated to the RFID tags (e.g., encoding information) using RFID encoders.
RFID systems include RFID readers that can detect and receive information from a large number of RFID tags at the same time. These RFID readers may be fixed/stationary and/or portable (e.g., handheld RFID reader). For example, fixed RFID readers may be positioned at dock doors to read the RFID tags of products on pallets or cases that pass by the RFID readers. RFID readers also may be handheld and used, for example, by individuals walking through a retail store or business reading RFID tags of products on shelves or in a storage area. However, RFID readers may be used in many different applications other than product identification and tracking, including, for example, animal identification, file folder identification in an office, airline baggage tracking, building access control, electronic traffic toll collection, among many others.
The required UHF RFID communication range encompasses different frequencies throughout the world. In particular, in European Union (EU) countries, the UHF RFID frequency band is designated from 865 MHz to 868 MHz (0.3% bandwidth). In the United States (U.S.), the UHF RFID frequency band is designated from 902 MHz to 928 MHz (2.8% bandwidth). In Asian countries, the UHF RFID frequency band is designated from 950 MHz to 956 MHz (0.6% bandwidth). Different read antennas configured to operate in each of these frequency ranges are separately provided, for example, in connection with REID readers for use in different countries. Currently, separate antennas configured to operate in each of these designated frequency ranges are needed because the RFID tags are of an arbitrary linear polarization and it is desirable for the interrogator antenna in the RFID reader to be circularly polarized with very good axial ratio, typically 2 dB or less. Antennas designed to support this axial ratio requirement require different configured RFID reader devices to provide the necessary phase and amplitude split.
Thus, although there may be lower cost versions of an RFID reader with an antenna configured for use in the U.S. that is in compliance with the designated U.S. UHF RFID frequency range, the RFID reader fails to comply with the operating requirements in the EU and Asia. In particular, the RFID reader with antenna for use in the U.S. is not capable of supporting operation in an RFID system in the EU or Asia, and in particular, to complying with the different frequency and axial ratio requirements.
In accordance with one embodiment, a radio frequency identification (RFID) antenna is provided that includes an aperture board having at least one opening and a dielectric patch element spaced a distance from the aperture. The RFID antenna further includes a quadrature coupler connected to the aperture board and configured to excite the dielectric patch element to generate RFID signals.
In accordance with another embodiment, a radio frequency (RFID) reader is provided. The RFID reader includes a transceiver configured to generate RFID signals over a UHF RFID frequency range from about 865 MHz to about 956 MHz, with the generated RFID signals having an axial ratio of no more than about two decibels. The RFID reader further includes an antenna connected to the transceiver and having an aperture coupled patch element.
In accordance with yet another embodiment, a method of transmitting RFID signals is provided. The method includes generating an RFID signal in a frequency range of about 865 MHz to about 956 MHz and transmitting the RFID signal using an aperture coupled patch element.
The foregoing summary, as well as the following detailed description of certain embodiments of the present invention, will be better understood when read in conjunction with the appended drawings. To the extent that the figures illustrate diagrams of the functional blocks of various embodiments, the functional blocks are not necessarily indicative of the division between hardware circuitry. Thus, for example, one or more of the functional blocks (e.g., processors or memories) may be implemented in a single piece of hardware (e.g., a general purpose processor or random access memory, hard disk, or the like). Similarly, the programs may be stand alone programs, may be incorporated as subroutines in an operating system, may be functions in an installed software package, and the like. It should be understood that the various embodiments are not limited to the arrangements and instrumentality shown in the drawings.
As used herein, an element or step recited in the singular and proceeded with the word “a” or “an” should be understood as not excluding plural of said elements or steps, unless such exclusion is explicitly stated. Furthermore, references to “one embodiment” of the present invention are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features. Moreover, unless explicitly stated to the contrary, embodiments “comprising” or “having” an element or a plurality of elements having a particular property may include additional such elements not having that property.
Various embodiments of the invention provide an antenna for a radio frequency identification (RFID) reader. The antenna is configured to allow operation in any of the European Union (EU) UHF RFID frequency band from 865 MHz to 868 MHz (0.3% bandwidth), the United States (U.S.) UHF RFID frequency band from 902 MHz to 928 MHz (2.8% bandwidth) and the Asian UHF RFID frequency band from 950 MHz to 956 MHz (0.6% bandwidth), while providing the desired or needed axial ratio, which in at least one embodiment is 2 dB or less (i.e., no more than about 2 dB).
It should be noted that although the various embodiments of an RFID antenna and reader may be described in connection with a particular application or for sensing a particular event, for example, tracking products, the various embodiments are not limited to a particular application or to sensing a particular event. The various embodiments may be implemented in any application or system wherein RFID information is read.
In another configuration, as shown in
In various embodiments, the RFID tags 60 are passive radio reflective identification tags or passive RFID tags as shown in
In other various embodiments, RFID tags 70 are active radio identification tags or active RFID tags as shown in
It should be noted that the objects 54 shown in
It should be noted that the RFID reader 52 may be a stand alone unit, for example, a portable or handheld unit or may be integrated with another communication device, such as mobile or cellular telephones, personal digital assistants (PDAs), Blackberry devices, etc. Alternatively, components within, for example, the cellular telephone, such as the transceiver, processor and/or software may be modified to provide the same functionality and operation of the RFID reader 52. Still other alternatives include a plug-in or add-on unit, such as, a plug-in module for a PDA that includes therein the RFID reader 52.
In various embodiments, as shown in
It should be noted that the antenna 80 may be provided as part of the RFID reader 52, for example, integrated therewith, such as in a single housing. Alternatively, the antenna 80 may be provided as a separate unit that may be connected to the RFID reader 52.
In operation, the antenna 80, which may be configured as a scanning antenna, transmits radio frequency (RF) signals, for example, RFID signals. The transceiver 82 may be configured such that the RF signals are transmitted over a determined range, for example, a short range (e.g., 5 feet or 10 feet). Also, the transceiver 82 may be configured such that RF signals are transmitted from the antenna 80 using any one of the EU UHF RFID frequency band from 865 MHz to 868 MHz, the U.S. UHF RFID frequency band from 902 MHz to 928 MHz and the Asian UHF RFID frequency band from 950 MHz to 956 MHz.
The RF signals, which are essentially RF radiation, allow communication with the RFID tags 60 and 70 (shown in
Upon receiving the signals from the RFID tags 60 and 70 via the antenna 80 using the transceiver 82, and that includes the RFID tag information, the signals are decoded in any known manner, for example, using the decoder 84. It should be noted that RFID tag information from a plurality of RFID tags 60 and/or 70 may be transmitted at the same time. The RFID tag information then may be processed using the processor 86 and the results displayed on the display 90. For example, information relating to the quantity and type of products to which the RFID tags 60 or 70 are attached may be displayed on the display 90. Further, and for example, a user may select the type of information to be displayed or provide other inputs using the user interface 88 (e.g., a keyboard). It should be noted that in various embodiments the RFID reader 52 is a portable device, for example, a handheld device provided, for example, in a scanner type configuration. In another various embodiments, the RFID reader 52 is a fixed or stationary device and configured to be attached to a support structure, for example, a wall, door frame, etc.
In various embodiments, the antenna 80 is configured as shown in
The aperture board 102 includes one or more openings 104 as shown in
In operation, the aperture coupling to the dielectric patch element 100 through the air provides a significant increase in the bandwidth response of the dielectric patch element 100. In one embodiment, the openings 104 are two slots defining a dual aperture with the slots oriented at 90 degrees with respect to each other and fed by output ports 110 of the quadrature coupler 104 shown in
In one embodiment, the openings 104 are orthogonal slots that extend along a portion of a top surface 112 of the aperture board 102 as shown in
The aperture board 102 may be provided on a base 114 as shown in
As shown in
It should be noted that the dielectric patch element 100 alternatively may be provided on an inside surface of the top of the radome 118, which still results in the dielectric patch element 100 being spaced a distance from the aperture board 102. The dielectric patch element 100 also may be positioned at some point intermediate between the radome 118 and the aperture board 102, but still a distance from the aperture board 102, for example, with a bracket 106 (shown in
It also should be noted that although the dielectric patch element 100 is illustrated as a square element, the size and shape can be varied. For example, different shapes or sizes (e.g., different shaped and sized squares and shapes or combinations thereof) of the dielectric patch element 100 may be provided. In general, the dielectric patch element 100 is formed to be symmetric in shape.
In one embodiment, as shown in
Thus, various embodiments of the invention provide an RFID antenna having an aperture coupled patch element having no connection to the aperture board and that provides a broadband response over the entire worldwide UHF RFID frequency range. The dielectric patch element also may be placed on the exterior of the antenna radome such that dielectric losses can be reduced and the height/width of the antenna decreased. The physical layer for the dielectric patch element is thereby eliminated, which includes the eliminating the cost associated therewith.
The various embodiments or components, for example, the RFID reader and components therein or the RFID system communicating with the RFID reader may be implemented as part of one or more computer systems, which may be separate from or integrated with others system. The computer system may include a computer, an input device, a display unit and an interface, for example, for accessing the Internet. The computer may include a microprocessor. The microprocessor may be connected to a communication bus. The computer may also include a memory. The memory may include Random Access Memory (RAM) and Read Only Memory (ROM). The computer system further may include a storage device, which may be a hard disk drive or a removable storage drive such as a floppy disk drive, optical disk drive, and the like. The storage device may also be other similar means for loading computer programs or other instructions into the computer system.
As used herein, the term “computer” may include any processor-based or microprocessor-based system including systems using microcontrollers, reduced instruction set circuits (RISC), application specific integrated circuits (ASICs), logic circuits, and any other circuit or processor capable of executing the functions described herein. The above examples are exemplary only, and are thus not intended to limit in any way the definition and/or meaning of the term “Computer”.
The computer system executes a set of instructions that are stored in one or more storage elements, in order to process input data. The storage elements may also store data or other information as desired or needed. The storage element may be in the form of an information source or a physical memory element within the processing machine.
The set of instructions may include various commands that instruct the computer as a processing machine to perform specific operations such as the methods and processes of the various embodiments of the invention. The set of instructions may be in the form of a software program. The software may be in various forms such as system software or application software. Further, the software may be in the form of a collection of separate programs, a program module within a larger program or a portion of a program module. The software also may include modular programming in the form of object-oriented programming. The processing of input data by the processing machine may be in response to user commands, or in response to results of previous processing, or in response to a request made by another processing machine.
As used herein, the terms “software” and “firmware” are interchangeable, and include any computer program stored in memory for execution by a computer, including RAM memory, ROM memory, EPROM memory, EEPROM memory, and non-volatile RAM (NVRAM) memory. The above memory types are exemplary only, and are thus not limiting as to the types of memory usable for storage of a computer program.
It is to be understood that the above description is intended to be illustrative, and not restrictive. For example, the above-described embodiments (and/or aspects thereof) may be used in combination with each other. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from its scope. While the dimensions and types of materials described herein are intended to define the parameters of the invention, they are by no means limiting and are exemplary embodiments. Many other embodiments will be apparent to those of skill in the art upon reviewing the above description. The scope of the invention should, therefore, be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled. In the appended claims, the terms “including” and “in which” are used as the plain-English equivalents of the respective terms “comprising” and “wherein.” Moreover, in the following claims, the terms “first,” “second,” and “third,” etc. are used merely as labels, and are not intended to impose numerical requirements on their objects. Further, the limitations of the following claims are not written in means-plus-function format and are not intended to be interpreted based on 35 U.S.C. § 112, sixth paragraph, unless and until such claim limitations expressly use the phrase “means for” followed by a statement of function void of further structure.
This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.
