Radio frequency identification (RFID) systems typically use one or more reader antennae to send radio frequency (RF) signals to items comprising RFID tags. The use of such RFID tags to identify an item or person is well known in the art. In response to the RF signals from a reader antenna, the RFID tags, when excited, produce a disturbance in the magnetic field (or electric field) that is detected by the reader antenna. Typically, such tags are passive tags that are excited or resonate in response to the RF signal from a reader antenna when the tags are within the detection range of the reader antenna.
The detection range of the RFID systems is typically limited by signal strength over short ranges, for example, frequently less than about one foot for 13.56 MHz systems. Therefore, portable reader units may be moved past a group of tagged items in order to detect all the tagged items, particularly where the tagged items are stored in a space significantly greater than the detection range of a stationary or fixed single reader antenna. Alternately, a large reader antenna with sufficient power and range to detect a larger number of tagged items may be used. However, such an antenna may be unwieldy and may increase the range of the radiated power beyond allowable limits. Furthermore, these reader antennae are often located in stores or other locations were space is at a premium and it is expensive and inconvenient to use such large reader antennae. In another possible solution, multiple small antennae may be used but such a configuration may be awkward to set up when space is at a premium and when wiring is preferred or required to be hidden.
Current RFID reader antennas are designed so that a maximum read range may be maintained between the antenna and associated tags, without violating FCC regulations regarding radiated emissions. Often times, when tagged items are stacked, the read range of an antenna is impeded due to “masking” that occurs through the stacking. As a result, the masking limits the number of tags that an antenna may read at a given time, and consequently affect the number of products that may be read. Furthermore, due to FCC regulations regarding radiated emissions, the reader antenna sizes cannot be adjusted to resolve such problems.
Resonant loop reader antenna systems are currently utilized in RFID applications, where numerous reader antennas are connected to a single reader. Each reader antenna may have its own tuning circuit that is used to match to the systems characteristic impedance. However, multiple reader antennae (or components thereof) cannot be individually controlled when they are connected by a single transmission cable to a reader unit.
In accordance with exemplary embodiments of the invention, antenna structures having specified geometries (e.g., serpentine, slot, patch, etc.) are provided for incorporating into fixtures such as shelves. Preferred antenna structures of the invention can be used as tag reader antenna systems in RFID (radio frequency identification) applications and the like. In accordance with an exemplary embodiment, multiple RF (radio frequency) antennae are utilized as part of an intelligent station to track items comprising radio frequency identification (RFID) tags.
Preferred embodiments and applications of the invention will now be described. Other embodiments may be realized and changes may be made to the disclosed embodiments without departing from the spirit or scope of the invention. Although the preferred embodiments disclosed herein have been particularly described as applied to the field of RFID systems, it should be readily apparent that the invention may be embodied in any technology having the same or similar problems.
In accordance with an exemplary embodiment of the invention, a multiple RFID antenna system is illustrated in
The RFID feed system shown in
The RF signal in cable 45 may be routed by gondola controller 30 so that it is sent to shelves on gondola 70, or bypasses gondola 70 and continues on to additional gondolas such as gondola 71. In this embodiment, the term “shelf” refers to one shelf or a group of shelves served by a single shelf controller 40a, 40b, 40c, and the term “gondola” refers to a structure including one or more shelves. The terms “shelf” and “gondola” however are not meant to be limiting as to the physical attributes of any structure that may be used to implement embodiments of the invention, but used merely for convenience in explaining this embodiment. Any known structure for storing, housing, or otherwise supporting an object may be used in implementing the various embodiments of the invention. For example, an RF switch 31 may either cause the RF signal to bypass the gondola 70, and continue on through connection 80a to gondola 71, or the RF switch 31 may cause the RF signal to feed into gondola 70. Furthermore, one or more additional RF switches 32 may route the RF signal to a particular shelf, for example, through connection 61a to shelf 21a upon gondola 70. In a preferred embodiment, a shelf controller (e.g., controller 40a) may switch the RF signal to one or more of the antenna boards 20 and thence to antenna 10. It will be appreciated that while
The use of RF switch 31 may result in an “insertion loss.” That is, some RF power may be lost as the signal passes through the switch. Thus, the level of RF power reaching gondola 71 and successive additional gondolas may be less than the RF power reaching gondola 70. In one embodiment, however, the RF power may be approximately equal at each antenna 10. For example, it may be desired to have the RF power level at a given antenna 10 high enough to read all RFID tags attached to items resting on the given antenna 10, but not so high as to read RFID tags attached to items resting on adjacent antennae. RF attenuators may be used in accordance with preferred embodiments of the invention to adjust (e.g., equalize) the power level at each antenna 10. For example, RF attenuators (not shown) could be placed between a shelf controller (e.g., controller 40a) and each antenna 10 and used to regulate the RF power at each gondola. The RF attenuators may be chosen, for example, to attenuate the RF power more at gondola 70 and less at gondola 71 and successive additional gondolas. In one embodiment, RF attenuators may be placed at other locations within the circuitry (e.g., in connections 61a, 61b, 61c, or between switches 31 and 32) to achieve the same result, as will be apparent to those skilled in the art.
In accordance with a preferred embodiment of the invention, a plurality of antennae 10 optionally having associated antenna boards 20, shelf controllers 40a, 40b, 40c, gondola controllers 30, and associated wiring, may be contained in or on a physical structure, as shown, for example, in
In one preferred embodiment, primary controller 100 may selectively operate any of the switches by sending commands containing a unique address associated with antenna 10 through, for example, a digital data communication cable 105. The addresses could be transmitted through the use of addressable switches (e.g., switches identical or functionally equivalent to a Dallas Semiconductor DS2405 “1-Wire®” addressable switch). Each such addressable switch, for example, provides a single output that may be used for switching a single antenna. Preferably, the primary controller 100 may selectively operate any or all the switches by utilizing one or more gondola controllers 30 and/or shelf controllers 40a, 40b, 40c. For example, these controllers may be a processing device, which can provide multiple outputs for switching more than one antenna (e.g., all the antennas in proximity to the shelf controller 40a, 40b, 40c). The primary controller 100 may also be any processing device. Communications between the primary controller 100 and the gondola controller 30 can be implemented by using communication signals in accordance with well known communication protocols (e.g., CAN bus, RS-232, RS-485 serial protocols, Ethernet protocols, Token Ring networking protocols, etc.). Likewise communications between the gondola controller 30 and shelf controller 40a, 40b, 40c may be implemented by the same or different communication protocols.
The term “intelligent station” generally refers to equipment, such as a shelf, which may include controllers, switches and/or tuning circuitry, and/or antennae. More than one intelligent station may be connected together and connected to or incorporated with an RFID reader. A primary controller can be used to run the RFID reader and the intelligent stations. The primary controller itself may be controlled by application software residing on a computer. In one embodiment, an “intelligent station” is an “intelligent shelf.”
In a preferred embodiment, the intelligent shelf system is controlled through an electronic network 120, as shown in
Likewise, the shelf controllers 40a, 40b, 40c, and the gondola controller controllers 30 can pass data back to the primary controller 100, as can the reader unit 50. The primary controller 100 then relays result data back to the controlling system through the electronic network 120. The inventory control processing unit 130, shown in
Primary controller 100 of
In a preferred embodiment, the primary controller 100 can be placed between the electronic network 120 and the reader as shown, for example, in
In
The item information data collected by the reader units 50 from each of the intelligent shelves is transmitted to an inventory control processing unit 130. The inventory control processing unit 130 is typically configured to receive item information from the intelligent shelves. The inventory control processing unit 130 is typically connected to the intelligent shelves over an electronic network 120 and is also associated with an appropriate data store 140 that stores inventory related data including reference tables and also program code and configuration information relevant to inventory control or warehousing. The inventory control processing unit 130 is also programmed and configured to perform inventory control functions that are well known to those skilled in the art. For example, some of the functions performed by an inventory control (or warehousing) unit include: storing and tracking quantities of inventoried items on hand, daily movements or sales of various items, tracking positions or locations of various items, etc.
In operation, the inventory control system would obtain item information from the intelligent shelves that are connected to the inventory control processing unit 130 through an electronic network 120. In one preferred embodiment, one or more intelligent shelves are controlled by inventory control processing unit 130. Inventory control processing unit 130 can determine when the reader units 50 are under control of primary controller 100 and poll the antennae 10 to obtain item inventory information. In an alternate embodiment, the controller(s) 100 may be programmed to periodically poll the connected multiple antennae for item information and then transmit the determined item information to the inventory control processing unit using a reverse “push” model of data transmission. In a further embodiment, the polling and data transmission of item information by the primary controller 100 may be event driven, for example, triggered by a periodic replenishment of inventoried items on the intelligent shelves. In each case, the primary controller 100 would selectively energize the multiple antennae connected to reader 50 to determine item information from the RFID tags associated with the items to be inventoried.
Once the item information is received from the reader units 50 of the intelligent shelves, the inventory control processing unit 130 processes the received item information using, for example, programmed logic, code, and data at the inventory control processing unit 130 and at the associated data store 140. The processed item information is then typically stored at the data store 140 for future use in the inventory control system and method of the invention.
Circuitry 200 is joined by connection 201 to connector board or boards 145, which bears on one surface one or more microstrip connectors such as 141-144. The opposite surface of connector board 145 is preferably a ground plane, such as a plated layer or foil layer. Preferably, the microstrip connectors are on the top of the connector board and the ground plane is on the bottom. The widths and separations of microstrip connectors 141-144 are designed to give the proper RF impedance (e.g., a 50 ohm impedance). Besides its connection 201 to the connector board, the circuitry 200 may be connected to a circuit ground, which may be provided by a connection to the metal shelf, for example, through a bolt or stud (not shown).
At a convenient point 153, connector board 144 is joined to additional circuitry, for example, switching circuitry, and thence to an RFID reader. At point 153, for example, a coaxial cable 154 may be connected at its center conductor 155, through a solder joint 156, to microstrip conductor 144. The coaxial cable 154 external conductor or shield 157 may in turn be connected by solder joint 158 to ground, for example, to the metal shelf 150.
Each of the microstrip conductors 141-144 may be connected at point 153 to a coaxial cable such as cable 154. Alternately, at point 153, the microstrip conductors may be connected to a shelf controller 40a, 40b, 40c (e.g., as previously described above but not shown in
Connection 201 previously described may be provided for attaching to RF signal pad 220. For example, a solder connection 202 may be used. RF signal pad 220 in turn may be connected to the second end of antenna trace 125, at pad 127, through components 222 and 222′. Component 222 may be one or more capacitors, and component 222′ a short. Alternately, component 222 may be a short, and component 222′ may be one or more capacitors. Alternately, both components 222 and 222′ may be one or more capacitors, preferably with the capacitance of 222 and 222′ being approximately equal. This last alternative may be useful for distributing the voltage drop over the capacitors.
The ground pad 210 and the RF signal pad 220 may be connected through components 232 and 232′. Component 232 may be one or more capacitors, and component 232′ a short. Alternately, component 232 may be a short, and component 232′ one or more capacitors. Alternately, both component 232 and 232′ may be one or more capacitors, preferably with the capacitance of 232 and 232′ being approximately equal. In one embodiment, this last alternative is useful for distributing the voltage drop over the capacitors.
In one embodiment, a resistor 127 (e.g., 200 ohm) may be connected across the slot arm (e.g., just short of the end opening 126). Thus, for example, where each of the four slot arms on the antenna 120 have a 200 ohm resistor, the antenna has four 200 ohm resistors in parallel, giving an effective impedance of 50 ohms. The resistors provide a broadband impedance match, and one or more (or all) of the resistors may be omitted depending on the bandwidth of the antenna. Other feed locations besides the center are also possible, as is the use of more than one feed per antenna.
In accordance with a preferred embodiment, the antenna 152 may be fed an RF signal by a coaxial cable 154 (or microstrip conductor as described above). In the illustrated implementation, for example, the center coaxial conductor 155 may be soldered or connected to an interior quadrant point 156 of the cross-shaped antenna 152. The outer coaxial shield or ground conductor 157 may be soldered or connected at the diagonally opposite interior quadrant point 158. It will be understood that the center coaxial conductor 155 and the outer coaxial shield 157 can be separated by an insulating material 159. Solder is a suitable connection method (e.g., for metals such as copper and the like), but a mechanical connection such as a screw, bolt, clamp, or other type (not shown) may also be utilized (e.g., with metals such as steel).
In one embodiment, at a first end of the slot arm, just short of the end opening 136, a resistor 137 (e.g., 50 ohm) may be connected across the slot arm. As with the cross-shaped antenna structure 152 of
In a preferred embodiment, the line-shaped slot antenna 132 may be fed an RF signal by a coaxial cable 164 (or microstrip conductor as described above). The center coaxial conductor 165 may be soldered or connected at the second end of the slot arm, one side of the slot arm at point 166 as shown, just short of the end opening 138. The outer coaxial shield or ground conductor 167 may be soldered or connected on the other side of the slot arm, at point 168 also just short of the end opening 138. Solder is a suitable connection method, but a mechanical connection such as a screw, bolt, or clamp (not shown) may also be utilized. It will be understood that the center coaxial conductor 165 and the outer coaxial shield 167 can be separated by an insulating material 169.
In accordance with a preferred embodiment, the antenna 720 is fed an RF signal by a microstrip conductor 760 on the surface 722 of the antenna opposite from the surface 721 on which the cross-shaped antenna is made. In the illustrated embodiment, the microstrip conductor 760 passes on a diagonal across the central area of the cross-shaped antenna. The microstrip conductor 760 may be connected to external circuitry by a suitable connector. The microstrip conductor 760 may be connected at point 755 to an RF signal, while the plated surface 721 may be connected to ground as shown by point 758.
In accordance with a preferred embodiment, the antenna 730 may be fed an RF signal by a coaxial cable 764 (or microstrip conductor as described above). The center coaxial conductor 765 may be soldered or otherwise connected at point 766 to a feed stub 760 composed of an insulating material such as PCB board having on it a microstrip line 762 that may extend across slot arm 735 near one end of the slot arm. One or more metallic patch areas 763 may be used to tune the feed stub. The outer coaxial shield or ground conductor 767 may be soldered or connected to a pad 761 (e.g., a grounding pad) that is connected (e.g., through-plating) to a metallic pad on the opposite side of the PCB board, in proximity to or directly connected to the metal substrate in which slot arm 730 is formed. The connection to the metal substrate may be with solder, mechanical connector, or by capacitive coupling. Insulating material 769 may be provided between the center coaxial conductor 765 of coaxial cable 764 and outer shield 767.
As illustrated, on top of the antenna 152B are several objects 421 such as DVD cases, in a “bookshelf” (edge-forward) orientation. Each object 421 has an RFID tag 422 placed at a location suitable for being detected by slot antenna 152B.
Shelf 402 is shown having linear-shaped antennas 132A and 132B. As illustrated, antenna 132A runs front to back on the shelf, and upon it are placed several objects 431 such as DVD cases, in a “face-forward” orientation. Each object 431 has an RFID tag 432 placed at a location suitable for being detected by slot antenna 132A.
On top of antenna 132B are several objects 441 such as DVD cases, in a “bookshelf” orientation. Each object 441 has an RFID tag 442 placed at a location suitable for being detected by slot antenna 132B.
Preferably, linear shaped slot antenna 132A is used to read objects, for example, in a forward-facing orientation, whereas, the linear shaped slot antenna 132B is used to read objects, as shown, in the bookshelf orientation.
It should be understood that other kinds of electrical power (e.g., direct current (DC)) may be used by the antenna system in addition to (or substitution for) RF power. For example, direct current (DC) may be used by the gondola controller 30, as well as by the shelf controllers 40a, etc. and the antenna boards 20. One or more dedicated wires may provide such electrical power, or it may be incorporated into the digital communication highway or with an RF cable. An RF cable may be configured using two conductors (e.g., coaxial cable), wherein both the center conductor and the sheath conductor are utilized in the system. While the RF cable carries an RF signal, a DC voltage may be superimposed on the RF signal, in the same RF cable, to provide DC power to intelligent stations. Voltage regulators may subsequently be used to control or decrease excessive voltages to within usable limits.
While preferred embodiments of the invention have been described and illustrated, it should be apparent that many modifications to the embodiments and implementations of the invention can be made without departing from the spirit or scope of the invention. The implementation of 8 slot antenna structures 152 on a single shelf 151 in
Although embodiments have been described in connection with the use of a particular exemplary shelf structure, it should be readily apparent that any shelf structure, rack, etc. or any structure may be used in selling, marketing, promoting, displaying, presenting, providing, retaining, securing, storing, or otherwise supporting an item or product or used in implementing embodiments of the invention.
Although specific circuitry, components, or modules may be disclosed herein in connection with exemplary embodiments of the invention, it should be readily apparent that any other structural or functionally equivalent circuit(s), component(s) or module(s) may be utilized in implementing the various embodiments of the invention.
The modules described herein, particularly those illustrated or inherent in, or apparent from the instant disclosure, as physically separated components, may be omitted, combined or further separated into a variety of different components, sharing different resources as required for the particular implementation of the embodiments disclosed (or apparent from the teachings herein). The modules described herein, may where appropriate (e.g., reader 50, primary controller 100, inventory control processing unit 130, data store 140, etc.) be one or more hardware, software, or hybrid components residing in (or distributed among) one or more local and/or remote computer or other processing systems. Although such modules may be shown or described herein as physically separated components (e.g., data store 140, inventory processing unit 130, primary controller 100, reader 50, gondola controller 30, shelf controller 40a, 40b, 40c, etc.), it should be readily apparent that the modules may be omitted, combined or further separated into a variety of different components, sharing different resources (including processing units, memory, clock devices, software routines, etc.) as required for the particular implementation of the embodiments disclosed (or apparent from the teachings herein). Indeed, even a single general purpose computer (or other processor-controlled device), whether connected directly to antennas 10, antenna boards 20, gondolas 70, or connected through a network 120, executing a program stored on an article of manufacture (e.g., recording medium such as a CD-ROM, DVD-ROM, memory cartridge, etc.) to produce the functionality referred to herein may be utilized to implement the illustrated embodiments.
One skilled in the art would recognize that inventory control processing unit 130 could be implemented on a general purpose computer system connected to an electronic network 120, such as a computer network. The computer network can also be a public network, such as the Internet or Metropolitan Area Network (MAN), or other private network, such as a corporate Local Area Network (LAN) or Wide Area Network (WAN), Bluetooth, or even a virtual private network. A computer system includes a central processing unit (CPU) connected to a system memory. The system memory typically contains an operating system, a BIOS driver, and application programs. In addition, the computer system contains input devices such as a mouse and a keyboard, and output devices such as a printer and a display monitor. The processing devices described herein may be any device used to process information (e.g., microprocessor, discrete logic circuit, application specific integrated circuit (ASIC), programmable logic circuit, digital signal processor (DSP), MicroChip Technology Inc. PlCmicro® Microcontroller, Intel Microprocessor, etc.).
The computer system generally includes a communications interface, such as an Ethernet card, to communicate to the electronic network 120. Other computer systems may also be connected to the electronic network 120. One skilled in the art would recognize that the above system describes the typical components of a computer system connected to an electronic network. It should be appreciated that many other similar configurations are within the abilities of one skilled in the art and all of these configurations could be used with the methods and systems of the invention. Furthermore, it should be recognized that the computer and network systems (as well as any of their components) as disclosed herein can be programmed and configured as an inventory control processing unit to perform inventory control related functions that are well known to those skilled in the art.
In addition, one skilled in the art would recognize that the “computer” implemented invention described herein may include components that are not computers per se but also include devices such as Internet appliances and Programmable Logic Controllers (PLCs) that may be used to provide one or more of the functionalities discussed herein. Furthermore, while “electronic” networks are generically used to refer to the communications network connecting the processing sites of the invention, one skilled in the art would recognize that such networks could be implemented using optical or other equivalent technologies. Likewise, it is also to be understood that the invention utilizes known security measures for transmission of electronic data across networks. Therefore, encryption, authentication, verification, and other security measures for transmission of electronic data across both public and private networks are provided, where necessary, using techniques that are well known to those skilled in the art.
It is to be understood therefore that the invention is not limited to the particular embodiments disclosed (or apparent from the disclosure) herein, but only limited by the claims appended hereto.
This application claims the benefit of U.S. Provisional Patent Application No. 60/571,877 ('877 application), filed May 18, 2004, incorporated herein by reference in its entirety. This application expressly incorporates the following U.S. patent applications by reference in their entirety: U.S. patent application Ser. Nos. 10/338,892, 10/348,941, 60/346,388, 60/350,023, 60/469,024, and 60/479,846.
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/US05/17106 | 5/16/2005 | WO | 00 | 8/21/2008 |
Number | Date | Country | |
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60571877 | May 2004 | US |