|Publication number||USRE40972 E1|
|Application number||US 11/267,920|
|Publication date||Nov 17, 2009|
|Filing date||Nov 4, 2005|
|Priority date||Mar 25, 2000|
|Also published as||DE60132881D1, DE60132881T2, EP1269395A2, EP1269395B1, US6628237, US6642897, US6985119, US7432869, US7528785, US20020177408, US20030058180, US20060250314, US20070075906, WO2001073675A2, WO2001073675A3|
|Publication number||11267920, 267920, US RE40972 E1, US RE40972E1, US-E1-RE40972, USRE40972 E1, USRE40972E1|
|Inventors||Ian J. Forster, Peter Robert George Horrell|
|Original Assignee||Forster Ian J, Peter Robert George Horrell|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (38), Classifications (32), Legal Events (3)|
|External Links: USPTO, USPTO Assignment, Espacenet|
More than one reissue application has been filed for the reissue of U.S. Pat. No. 6,642,897. The reissue applications are application Ser. No. 11/267,920 (the present application), Ser. No. 11/484,325, now abandoned, and Ser. No. 11/728,713, now abandoned, all of which are continuations of Ser. No. 11/267,920. The present application is a continuation-in-part of co-pending application Ser. No. 09/536,334 filed Mar. 25, 2000, entitled “Remote communication using slot antenna”.
The present invention relates generally to a device and method for identifying a container and, more particularly, to a device and method for using the slot of the container as an antenna for remote communications.
It is often necessary to monitor the location and movement of materials within a distribution center or manufacturing facility. One method of tracking the materials is to attach a wireless communication device, such as a radio frequency identification (RFID) transponder or other identification device, to containers that are housing the materials. By way of example, a liquid container, such as a barrel or keg, may include an identification device indicative of the liquid contained inside. A transmission device, such as an interrogation reader or transmitter, having an antenna device, is able to send information remotely through electronic signals. Such transmission device is placed throughout the distribution or manufacturing facility to receive signals transmitted from wireless communication devices. The signals are then passed to a central control system that monitors and records the applicable information. The central control system can also send information to its interrogation readers to send to the transponders for response and/or to be stored in the transponder's memory.
The information communicated by the containers in the system to the interrogation readers may be used for a number of reasons. For example, a statistical analysis may be made of the materials to maintain accurate inventories, production flow rates, and other production standards. Additionally, the identification devices may include specific information about the materials housed within the containers, including date of manufacture, place of manufacture, type of product within the container, temperature of the container and ambient air, temperature of the contents of the container, and pressure of the container, etc.
The wireless communication device must have an antenna arrangement to communicate information about the containers to the interrogation readers. It is generally known for wireless communication devices to include an antenna. It is often a problem for many wireless communication devices to provide an antenna, especially if the wireless communication device is small or is required to be placed in a contained area. The length of the antenna must be tailored to the specific frequency at which the wireless communication device is designed to operate. For low frequencies in the MHz range or lower, an antenna may have to be several inches long to several feet long. The antenna may have to be several inches long for higher frequencies, to allow successful communication at the desired operating frequency.
Additionally, the antenna must either be packaged inside the wireless communication packaging that houses the wireless communication device, or located external to the wireless communication device. External positioning of the antenna to the wireless communication device provides several other challenges when placing the wireless communication device in a confined area, such as in a container. The antenna may have additional problems radiating energy effectively if the antenna is contained internal to a device, such as a container.
Some containers have a natural slot as a characteristic of their manufacture. A slot may be formed by edges of a conductive material coming together in close proximity forming a gap of air between the edges. A slot may also be formed by cutting out or removing material from a conductive surface to form an open or hollow area of free space or air. A slot could be formed by a curl of a cylinder or other surface to form a rim, whereby a slot is created by the gap between the end of the curl and the surface.
For example, a beer keg is made out of a metal material that has an outer wall with a curled end to form a rim. The keg rim is used for handling and movement of the keg. The curled portion of the rim bends inward towards the outer wall, leaving a small gap between the edge of the rim and outer wall. This small gap forms a slot that extends circularly around the keg, and can be used to provide a slot antenna for the wireless communication device. The wireless communication device can be designed to provide electronic connectivity to the slot when installed, so that the slot can be used to provide the effect of an antenna. Since the slot of the container may be several feet long, using the slot for the antenna may be advantageous for communication at lower frequencies where providing an antenna of sufficient length for communication at the desired frequency is problematic.
Therefore, it is advantageous to use the slot of a container to provide an effective antenna for a wireless communication device. One drawback of using the slot of a container to provide an effective antenna is that the impedance of the slot antenna should be matched to the impedance of the communications electronics, which is typically 50 Å. While this is not a problem to provide in a static environment, the impedance of the slot antenna may change as a function of its environment. Specifically, the temperature or atmospheric conditions may affect the size and shape of the slot as the material forming the slot changes shape in response to the changes in the atmospheric conditions or temperature. Further, as these containers may be subjected to robust physical conditions, the shape of the slot may be deformed by dents or other imperfections introduced to the container by handling. Thus, there remains a need for a technique to allow impedance matching in the face of the changing impedance of the slot antenna.
The present invention includes a wireless communication device using a slot antenna arrangement formed by the slot of a container. A wireless communication device is provided with the container to provide information about the identification or other aspects of the container as it moves through manufacturing, tracking or shipping facilities.
An antenna is provided for the wireless communication device so that it can communicate remotely with a transmitter/receiver. One embodiment of the present invention includes an interrogation reader as the transmitter/receiver. The present invention capitalizes on the phenomenon that exists whereby a slot in a conductive material, such as metal, aluminum, copper, or iron for instance, can be coupled to a wireless communication device's communications electronics to provide the effect of a pole antenna.
Some containers have, by the nature of their construction, a slot that can be used as a slot antenna. Alternatively, a slot can also be cut out of the container. Using a slot antenna, instead of a pole antenna, provides several advantages. The length of the slot necessary for the wireless communication device to operate at the desired frequency may be more suitable than could be provided by using a pole antenna. This is especially true for lower frequency communications that require longer length antennas. Additionally, the slot does not require that a pole device be placed inside or proximate to the container. Using the slot may also be less expensive than using a pole antenna. Additionally, a pole antenna may extend from the container, exposing it to damage.
In one embodiment, the wireless communication device uses feed lines directly connected to the each edge of the slot.
In another embodiment, the wireless communication device includes feed lines that reactively couple with each edge of the slot.
In another embodiment, a conductive device is placed between the slot to couple the wireless communication device to the slot to provide the slot antenna.
In another embodiment, the wireless communication device is mounted on a nonconductive substrate in the slot. A feed line from the wireless communication device rests on the substrate, such that the feed line reactively couples with the slot to provide the slot antenna.
The operating frequency of the slot is substantially matched to the operating frequency of the wireless communication device to maximize the slot antenna radiation efficiency. A circuit is provided between the slot and the wireless communication device to match the impedance of the slot to the impedance of the wireless communication device.
In an alternative embodiment, shorting posts are provided on the ends of the slot to create a slot with the desired length. The shorting posts are constructed out of a conductive material, such as metal, aluminum, copper or iron for example, and are placed between the slot's edges to short both sides of the slot together. Examples of conductive materials include, but are not limited to, metal, aluminum, copper, and iron.
Variable impedance matching is provided between the wireless communication device and the slot. The variable impedance matching may take a number of different forms, but four variable impedance matching device embodiments are disclosed herein. The first embodiment comprises placing an approximately V-shaped clip that acts as a variable capacitor in the slot. In particular, as the distance between the arms of the clip closes in response to changes in the shape of the slot, the capacitance increases.
A second variable impedance matching embodiment decreases capacitance as the width of the slot decreases. This is accomplished by placing two parallel plates proximate to one another and perpendicular to the longitudinal axis of the slot. The two plates act as a capacitor. As the shape of the slot changes, the plates move from a first position, substantially overlapping, to a non-overlapping second position. This movement reduces the capacitance between the plates.
A third variable impedance matching embodiment increases the inductance as the width of the slot decreases. This is accomplished by placing a helical coil parallel to the lateral axis of the slot. As the slot compresses, the coil compresses such that the inductance increases.
A fourth variable impedance matching embodiment flips the coil such that it is perpendicular to both the lateral and longitudinal axes of the slot. As the width of the slot decreases, the inductance of the coil decreases.
These embodiments allow for a number of different variations to be made so that impedance matching may be effectuated as needed.
The invention also includes a method of monitoring the container. While the container is within a facility, such as during manufacturing, filling, or storing, the container is moved through at least one interrogation point containing an interrogation reader. Communication between the wireless communication device and the interrogation reader is established for monitoring the location and/or content information about the container. A central control system may be in communication with the interrogation point for monitoring the movement of the container. The central control system may monitor the position of the container, or it may monitor specific information that is stored within memory in the device, or both.
The present invention is directed to a device and method of using a slot in a container as an antenna for a wireless communication device. As illustrated in
The transponder 30 includes a control system 34 and wireless communication electronics 32. The transponder 30 may also contain local memory 36 for storage of information to be communicated to an interrogation reader 40. Alternatively, the transponder 30 may store information, such as an identification number or indicia, by using diodes, a dip switch or some other like circuitry. However, the present invention is not limited to transponders 30 that contain memory 36. An antenna 38 is also provided for communication and may be either external to or incorporated internal to the packaging of the transponder 30. The packaging may be constructed out of a plastic or other epoxy material, such that the transponder 30 is protected for the environment. The particular type and location of the antenna 38 will depend on the operating frequency of the transponder 30 and the particular design desired.
The control system 34 is an integrated circuit or other type of microprocessor or micro-controller electronics that controls the substantive operations of the transponder 30. The control system 34 is connected to the wireless communication electronics 32 to communicate and receive transmissions. The control system 34 is also connected to memory 36 for storing and retrieving information. The control system 34 may further include a clock.
When the transponder antenna 38 is in the presence of the field 48 emitted by the interrogation reader antenna 44, the wireless communication electronics 32 are energized, thereby energizing the transponder 30. The transponder 30 remains energized so long as its antenna 38 is in the field 48 of the interrogation reader 40. The wireless communication electronics 32 demodulates the signal 46 and send the message containing information and/or specific instructions to the control system 34 for appropriate actions. For example, the request in the message may be for the transponder 30 to communicate its identification information about the container 10 or the materials 16 housed within the container 10, including, but not limited to, date of manufacture, place of manufacture, and type of product within the container 10. The message may also be instructions to communicate information regarding the environmental information, such as temperature of the container 10, or pressure levels. The transponder 30 communicates information requested to the interrogation reader 40 by altering the contents of the signal 46 for whatever type of information is requested.
Alternative forms exist for communicating with a transponder 30, or other wireless communication device. For instance, the transponder 30 may have a transmitter that can send information to the interrogation reader 40 without having to alter the content of the signal 46. The transponder 30 may contain its own power source, such as a battery, or other energy storage unit charged when the transponder 30 is in the field 48, to power the transmitter. It is understood to one of ordinary skill in the art that there are many other manners in which to communicate with a wireless communication device, such as a transponder 30, and that the present invention is not limited to the particular manner described above.
Voltage signals are provided by the transponder 30 to opposites sides of the slot 20. In the beer keg container 10 embodiment, one side of the slot 20 is formed by the outer wall 12, and the other side of the slot 20 is formed by the rim edge 52. When the voltage signals are applied across the slot 20, the slot 20 radiates electromagnetic waves similar to the manner in which a pole antenna arrangement would radiate to effectuate communications.
Container 10 has a continuous slot 20 that extends in a circular path. It may be desired to provide a technique or manner in which to define the length of the slot 20 so that the slot antenna 38 radiates in an improved manner at the operating frequency of the transponder 30. One method of defining the slot 20 length is to provide shorting posts 82 as illustrated in
Alternatively as illustrated in
When using a slot antenna 38, it is desired for the impedance of the slot 20 to match the impedance of the transponder 30 at the desired frequency to maximize energy transfer from the transponder 30 to the slot antenna 38. Such maximization of energy transfer allows the transponder 30 to emit a maximum radiation pattern. Maximum energy transfer occurs when the impedance of the transponder 30 is the conjugate of the slot 20 impedance. If the transponder 30 has a characteristic impedance that is not the conjugate of the slot 20, a matching network can be provided to do so. An antenna itself can be considered a matching network of sorts, transforming its terminal impedance to 377 ohms, the impedance of free space. However, the impedance of the transponder 30 may not be the same as the slot 20. In this instance, the slot antenna 38 may not perform optimally since the maximum energy transfer would not occur between the transponder 30 and the slot antenna 38.
The slot 20 of the present invention has a fairly low impedance. Therefore, it may be necessary to transform the slot 20 impedance into the impedance of transponder 30 to maximum energy transfer and therefore maximize the strength of the radiation pattern emitted by the slot antenna 38. An impedance matching network, as illustrated in
To allow for proper impedance matching between a transponder 30 and a slot 20, that may change shape as a function of environmental conditions or handling, the present invention allows for a variable reactance element to be positioned in conjunction with the slot antenna 38, and more particularly within the impedance matching network between the slot 20 and the transponder 30. The variable reactance element may be a variable capacitor or a variable inductor, and in each case may take at least two aspects. The first aspect increases the reactance of the element as the width of the slot decreases, and the second aspect decreases the reactance of the element as the width of the slot decreases. An embodiment of each is presented in
A first embodiment comprises a variable capacitor, whose capacitance increases as the width of the slot antenna 38 decreases. In particular,
Alternatively, if the capacitance needs to decrease as the width of the slot antenna 38 decreases, a capacitor 210, as illustrated in
A third embodiment, illustrated in
A fourth embodiment, illustrated in
These four embodiments allow the impedance matching circuit illustrated in
It should be appreciated that each of these variable reactance elements includes sub-elements. In the case of the capacitors, the sub-elements are the parallel plates. In the case of the inductors, the sub-elements are the loops of the coil.
Note that these variable reactance elements and the associated impedance matching circuit may be integrated into the transponder 30 or merely electrically connected thereto as needed or desired. Another option (not shown) to vary the inductance of a coil is to move a small piece of either ferrite or metal into close proximity to the coil. For example, if a coil were fabricated on the surface of an inserted substrate, moving a ferrite element of suitable characteristics toward the coil would increase the inductance. A piece of aluminum moved similarly will reduce the inductance, at least a VHF and UHF frequencies. High dielectric constant materials may also be used as appropriate, and have the added advantage, at least for doped barium titanate materials, that the change of dielectric constant with temperature can be controlled to give both positive and negative coefficients.
It should further be appreciated that a plurality of reactive elements may be combined as needed or desired to effectuate the impedance matching. These may be multiple capacitors, multiple inductors, or some mix thereof, e.g., a capacitor and an inductor. The last may be implemented through a capacitor as described, co-located with a ferrite piece that changes the inductance of a second element as described.
A central control system 100 maintains the information from the interrogation readers 40 and monitors the movement of the containers 10 through the facility. The information received by each of the interrogation readers 40 may be forwarded to the central control system 100 either through direct wire or LAN connection. The central control system 100 could also send information to the interrogation reader 40 to be transmitted to the transponder 30 for identification purposes. The central control system 100 tracks the expected location of the containers 10 and may be altered if it expects to receive information about a particular container and does not.
During commissioning of each container 10, it may be necessary to place the container 10 containing the transponder 30 in range of an interrogation reader 40 in order to erase previously stored information in memory 36 or to store particular data or configuration information about the container 10 in memory 36 for later use.
In the foregoing description, like-reference characters designate like or corresponding parts throughout the several views. Certain modifications and improvements will occur to those skilled in the art upon a reading of the foregoing description. It should be understood that the present invention is not limited to any particular type of container or slot arrangement. One of ordinary skill in the art will recognize that there are different manners in which containers with slots can be used to provide antenna functionality for a wireless communication device in accordance with the present invention. It should be understood that all such modifications and improvements have been deleted herein for the sake of conciseness and readability, but are properly within the scope of the following claims.
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|U.S. Classification||343/746, 343/767, 340/539.1|
|International Classification||B65D25/20, G06K19/077, H01Q1/44, B65G63/00, H01Q1/22, H01Q13/10|
|Cooperative Classification||H01Q1/2225, G06K19/07786, H01Q1/44, H01Q1/22, G06K19/041, H01Q13/10, B65D25/205, H01Q1/2208, H01Q13/12, H01Q13/18, B65D2203/10, G06K19/07749|
|European Classification||G06K19/077T7E, H01Q1/22C, G06K19/04K, H01Q13/12, H01Q13/18, B65D25/20B, H01Q1/44, H01Q13/10, H01Q1/22C4, G06K19/077T, H01Q1/22|
|Apr 22, 2011||FPAY||Fee payment|
Year of fee payment: 8
|Aug 17, 2012||AS||Assignment|
Owner name: MINERAL LASSEN LLC, NEVADA
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:MARCONI INTELLECTUAL PROPERTY (US), INC.;REEL/FRAME:028808/0767
Effective date: 20050106
|Apr 24, 2015||FPAY||Fee payment|
Year of fee payment: 12