Containers for holding goods are provided with a relay conductive structure for relaying RFID tags signals from one side of the container to another. The conductive structure includes a first antenna on the first side of the container, a second antenna on a second side of the container and a transmission line connecting the antennas. When the containers are arranged in a stack, the relay of RFID signals past each row of containers enables the interrogation toward the rear of the stack without disassembling the stack of containers.

BACKGROUND OF THE INVENTION

This invention relates to RFID tags for use in identifying packages and the contents thereof. It is currently known to use RFID tags for purposes of identifying packages, containers, and the like. Such identification TAGS can provide the user of an RFID reading device with data which can be correlated to information about the contents of a container. The information may be stored in digital form as part of the RFID response code, or alternately may be maintained in a computer database with a correlation to the RFID identification sent by the tag in response to an interrogation signal.FIG. 1shows an arrangement of containers20having RFID tags22. The stack of containers20may be arranged, for example, in a warehouse or on a pallet for shipment. In connection with identifying the content of the containers or locating a particular container, it is possible to use an RFID interrogator to interrogate the tags22on the face layer of boxes20. However, depending on the contents of the boxes and the number of layers of boxes in the stack, no assurance can be given concerning the interrogation of tags at the center or rear of the stack.

It is an object of the present invention to provide packaging containers which enable an RFID signal to penetrate a stack of containers so that containers located at the center or rear of the stack can be interrogated without moving the containers arranged in the front of the stack.

SUMMARY OF THE INVENTION

In accordance with the present invention, there is provided an improvement in packaging for goods where goods are arranged in containers having RFID tags. The improvement includes a first antenna on a first side of a container for receiving RFID signals, a second antenna on a second side of the container for radiating RFID signals and a transmission line interconnecting the first and second antennas.

In a preferred arrangement, the second side of the container is opposite to the first side. The transmission line may be formed of conductors printed on the container, co-planar twisted pair, or an insert, including dividers of the container. The antennas may also comprise conductors printed on the container or on an insert in the container. The container may include for example, four walls with two of the first antennas, one on each of adjacent front and side walls and two of the second antennas on adjacent rear and opposite side walls. Transmission lines interconnect the antennas on the front and rear walls and the antennas on the side and opposite side walls. An RFID tag may be coupled to either the antennas or the transmission line. The transmission line and antennas from a conductive structure that may be tuned to a frequency corresponding to the frequency of the RFID signals. A tuning structure may be provided for tuning the conductive structure. In one arrangement, the transmission line is a twisted pair transmission line. The antennas may also be formed using twisted pair transmission lines.

In accordance with the invention, there is provided a method for interrogating RFID tags provided on containers arranged in a stack. The containers are provided with conductive structures arranged to couple RFID signals from a first side of each of the containers to a second side of the containers. An RFID interrogation signal is radiated toward the stack and coupled to RFID containers within the stack using the conductive structure on the containers. RFID response signals are coupled from RFID tags on containers, within the stack to the exterior of the stack using the conductive structures on the containers and the RFID response signals are received.

In accordance with the invention, there is provided a container having sides arranged horizontally around goods. Antennas are arranged on the sides of the container for radiating and receiving REID signals in different horizontal directions from the container and a transmission line is provided interconnecting the antennas.

The horizontal directions are preferably opposite directions from the container. The sides may be fabricated from dialectric material and the antennas and transmission lines can be printed on the material. The material can be any non-conductive substrate such as plastic or fiber board. In one arrangement, the antennas and transmission line are fabricated from twisted pair transmission line. The antennas may be folded dipoles formed of twisted pair transmission line. In one arrangement the container can be formed of plastic material having dual walls and reinforcing ribs between the walls, and the transmission line can be arranged between the walls and/or molded within the walls or ribs.

For a better understanding of the present invention, together with other and further objects, reference is made to the following description. Taken in conjunction with the accompanying drawings, and it's scope will be pointed out in the appended claims.

DESCRIPTION OF INVENTION

Referring toFIG. 2, there is schematically illustrated a container24having conductive relay structure for relaying RFID signals according to the invention. The container ofFIG. 2is fabricated by folding fiber board parts from a blank30shown inFIG. 3. The structure includes printed conductive members forming a relay structure which includes antennas26arranged on the side walls of container24in the assembled condition and transmission lines28interconnecting antennas26on opposite sides of the container. In the embodiment illustrated inFIGS. 2 and 3, the conductive structures, comprising dipoles and balanced transmission lines are printed on the container, which may be fiberboard, for example, or on an insert placed within the container. RFID tags32are arranged to receive signals and are connected either to the transmission line28or alternately to one of the dipole antennas26.

Referring toFIG. 4, the operation of the present invention is illustrated in a diagram showing only the conductive structures added to the container according to the present invention. Signals34are received by antenna26and brought by transmission line28to an RFID tag32and another antennas26on the opposite side of a container. Signals are re-radiated from antenna26, preferably as near field signals36and may thereafter be received by an antenna26on a second container in close proximity to the first container. The signals are likewise relayed through the second container and radiate as signals38out the rear thereof. In this manner, RFID interrogation signals or RFID response signals may be relayed through or from containers located within a stack of containers with minimized interference from the containers or the goods contained therein. For example, the containers may include metallic cans or plastic containers filled with beverages, either of which would either reflect, absorb or otherwise interact with signals in the UHF or microwave band which are used for RFID tag interrogation and RFID response signals.FIG. 4further illustrates the equivalent circuit for the conductive structures.

Referring toFIG. 5there is shown a container40, which may be re-useable, for holding bottles of beverages42and incorporating conductive relay structures according to a second embodiment of the present invention. Container40is preferably made of dielectric material, such as plastic, and includes four side walls and a bottom. Antennas26are arranged on the side walls and connected to antennas on opposite side walls with transmission lines28for relaying RFID tag and RFID response signals to and from containers located within a stack of containers. The structure of container40and its RFID relay conductive structure is shown inFIGS. 6 and 7. Antennas26as shown in the simplified drawingsFIG. 6, are located on opposite side walls of container40. For simplicity, the drawing ofFIG. 6shows only the antennas26, on the end side walls.

FIG. 7is a cross-section of the container ofFIG. 6and includes an enlargement of the bottom wall of the container, illustrating an exemplary arrangement wherein the container wall is made from upper and lower walls42and44which are interconnected by ribs46, which are formed of molded plastic. Ribs46may run in the longitudinal direction of the container40or may be an eggcrate structure, including ribs that run in both directions. In the drawing ofFIG. 7transmission line28is shown to be molded within a longitudinal rib46of the container40. Alternately, the transmission line28may run in the hollow space between the inner wall42and the outer wall44of container40.

FIG. 8shows an alternate to the printed embodiment for the relay conductive structure according to the invention, wherein the transmission line28and dipoles26are formed of twisted pair transmission line wire. The length of the transmission line28is shown as being adjustable by break50such that the transmission line can have length corresponding to the length of the container. In the embodiment shown inFIG. 8, the transmission line is a twisted pair line, having a relatively low loss, and can be made to resonate between the antennas26arranged at either end thereof. To achieve the proper resonance with a variable length transmission line28, a tuning structure52, which is shown as an extra piece of twisted pair wire connected to the transmission line, may be provided. An RFID tag32may be connected directly to the twisted tear as shown inFIG. 8. Preferably, the RFID tag has less than complete coupling of signals from the conductive relay structure, so that signals are relayed from the receiving antenna26at one end of the package to be radiated by the antenna26at the opposite end of the package. Experimentation has shown that the signal coupled to the RFID tag32should be coupled at a level of approximately −7 db.

FIG. 9illustrates an alternate method of attaching an RFID tag to a twin wire transmission line. In the structure shown ofFIG. 9, a squeeze-on connector58of the type used to connect trailer electrical connections in an automobile is used to provide a quick and convenient connection between leads54connected to RFID tag32and transmission line wires56.

FIG. 10shows an arrangement of containers62having antennas26on all four side walls and transmission lines28interconnecting those antennas. As shown inFIG. 10, signals received by the antennas26of the outer containers can be relayed through the stack of containers, for example, a stack of containers on a cargo pallet or in a cargo storage area. Interrogation of the packages within the stack60can be made either from the forward facing or side facing walls thereof.

FIGS. 11 and 12illustrate arrangements70of containers72which include a single relay conductive structure78extending horizontally around the container and a pair of conductive relay structures74and76extending around the top, bottom and side walls thereof. The containers can be stacked in a symmetrical arrangement as shown inFIG. 11or in an alternate overlapping stacking arrangement80as shown inFIG. 12.

FIG. 13illustrates an arrangement of beverage containers40having beverage bottles therein arranged in a stack90.

While the examples described use dipole antennas in the conductive structure, those skilled in the art, will recognize that other arrangements, such as loop antennas, spiral antennas and the like may be used. Further the transmission line and antennas may be formed of a common resonant structure acting as both antennas and transmission line.

While there have been described what are believed to be the preferred embodiments of the present invention, those skilled in the art will recognize that other and further changes may be made thereto without departing from the spirit of the invention, and it is intended to claim all such changes and modifications as fall within the true scope of the invention.