Apparatus for and method of using a diversity antenna

In accordance with a preferred embodiment of the invention, an antenna structure is provided having one or more antennae arranged so as to read all possible orientations of a randomly placed tag. Also provided in accordance with a preferred embodiment of the invention, is a method of configuring one or more antennae composed of the steps of: identifying the “dead zones” of each discrete antennae used, and orienting each antennae such that there are no “dead zones” common to all antennae. The unique antenna structure (and corresponding method) has particular application in tag reader antenna systems for use in RFID (radio frequency identification) applications (13.56 MHz) 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 tagged with radio frequency identification (RFID) tags.

BACKGROUND

Radio frequency identification (RFID) systems typically use one or more reader antennae to send radio frequency (RF) signals to items tagged with RFID tags. The use of such RFID tags to identify an item or person is well known in the art. In response to the radio frequency (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 to 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 where 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 running afoul of FCC limitations on 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 through, and consequently affects the number of products that may be read. Furthermore, due to FCC limitations on 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. Multiple antennae (or components) may require the use of multiple transmission cables to connect a reader unit to the multiple antennae and/or to individually control the multiple antennae when they are all connected by a single transmission cable to the reader unit.

RFID applications incorporating random placement of a product may result in formation of “dead zones” for orientations in which the tag and reader antenna are in orthogonal planes. Dead zones are areas (dependent upon tag/reader antenna orientation) in which the level of coupling between the reader antenna and tag is not adequate for the system to perform a successful read of the tag. Thus, products placed in dead zones may not be detected resulting in potentially inaccurate tracking of tagged products.

SUMMARY

In accordance with a preferred embodiment of the invention, an antenna structure is provided having one or more antennae arranged so as to read all possible orientations of a randomly placed tag. Also provided in accordance with a preferred embodiment of the invention is a method of configuring one or more antennae composed of the steps of: identifying the “dead zones” of each discrete antennae used, and orienting each antennae such that there are no “dead zones” common to all antennae. The unique antenna structure (and corresponding method) has particular application in tag reader antenna systems for use in RFID (radio frequency identification) applications (13.56 MHz) 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 tagged with radio frequency identification (RFID) tags.

DETAILED DESCRIPTION

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.

FIG. 1shows an ideal orientation in which the plane of a reader antenna100is parallel to the X-Y plane, and an RFID tag110is also parallel to the X-Y plane. The reader antenna100and the RFID tag110are thus parallel to each other. The reader antenna100has a feed point101that would be connected to circuitry such as tuning components, switching components, and an RFID reader (not shown here but described in previously referenced applications). Having RFID tag110parallel to reader antenna100generally allows for good RF coupling between the tag and reader antenna so that the tag may be read by the reader antenna.

FIG. 2shows an example of some orientations that may result in a “dead zone” in which an RFID tag may not be read by a reader antenna. Reader antenna100is shown parallel to the X-Y plane. An RFID tag111is shown in the Y-Z plane (orthogonal to the X-Y plane and orthogonal to the reader antenna100), while RFID tag112is shown in the X-Z plane (orthogonal to the X-Y plane and orthogonal to the reader antenna100). RFID tags, such as111and112, which are oriented as orthogonal to the reader antenna100, may not allow for good RP coupling between the tag and reader antenna, and thus the tag may not be read by the reader antenna. In addition to the orientations shown for RFID tags111and112, any orthogonal plane in the inter-cardinal planes will also result in a dead zone. For example, if RFID tags111or112are rotated about the Z-axis, they will still be orthogonal to the X-Y plane and orthogonal to reader antenna100. Hence, it may be difficult or impossible for the reader antenna100to read the RFID tags111and112. These tags may be considered to be in a “dead zone” with respect to the reader antenna. In this embodiment, the term “dead zone” refers to a volume and/or area where an antenna has limited ability to or cannot detect an RFID contained within the volume and/or area.

In accordance with a preferred embodiment of the invention, in order to reduce or eliminate the dead zones, additional reader antennae may be utilized.FIG. 3illustrates one manner of permitting at least one non-orthogonal configuration of reader antennae and tags in accordance with a preferred embodiment of the invention. For example, to read RFID tag130, which may be oriented in a random orientation, RFID antennae may be situated as follows: reader antenna120in the X-Y plane, reader antenna121in the X-Z plane, and reader antenna122in the Y-Z plane. Each reader antenna may have a feed point (126,127, and128, respectively) connected to circuitry such as tuning components, switches, wiring, an RFID reader, etc. (not shown), as is well known in the art.

In accordance with a preferred embodiment of the invention, form factors may be incorporated which force specific orientations of reader and tags in order to reduce the number of reader antennae. One such form factor is the RFID shelf140shown inFIG. 4and described in a previously referenced application, which is adapted to read tags associated with a product, for example, optical disks such as DVDs150. The product such as DVDs150used with this antenna form factor can be placed in the X-Z plane, that is, “face forward” as shown inFIG. 4. Each DVD150has an associated RFID tag151(although any location may be used, the tag is shown for illustration purposes attached to the face of the DVD). A rear plane141contains one or more rear plane reader antennae142that are parallel to the orientation of the RFID tags151. There is also a supporting surface143such as horizontal or sloped shelf or other support, and a front retaining lip144(alternatively, a bar, wire, other structure (or no structure at all) could also be used). The front retaining lip144may serve to contain DVDs150within the structure, so they do not slide forward and fall from the shelf140. In one embodiment, front retaining lip144encourages a preferred orientation of RFID tag151, that is, the front retaining lip144acts to encourage a parallel orientation of RFID tag151with respect to rear plane antennae142. The preferred orientation can be realized because the distance on surface143between the rear plane141and the front retaining lip144is large enough to hold one or more DVDs150in the preferred face-forward orientation, but not large enough to hold a DVD150in an edge-forward (top forward, bottom forward, or spine-or side-forward orientation). Thus, due to the physical constraint formed by surface143and/or the front retaining lip144, the DVD150cannot conveniently be positioned in the X-Y (“face up”) or the Y-Z (“face sideways”) planes. In this embodiment, only one (or a minimal number of) rear plane reader antenna142is required.

In accordance with a preferred embodiment, a tag may be placed on a non-planar product (preferably, having a curvature that does not seriously de-tune the tag performance). The non-planar tag (e.g., one that is adhered, affixed, or otherwise coupled to a cylindrical surface) will have a finite projection in two orthogonal planes throughout 360° of rotation. If the projection is large enough to allow for adequate coupling, only two reader antennae will be required.

FIG. 5shows an RFID tag162that has been applied to the non-planar surface such as the surface of a bottle or vial160. Affixing an RFID tag to a non-planar surface can avoid creation of dead zones. In accordance with a preferred embodiment, the tag can be adhered, affixed, or otherwise coupled to a doubly curved surface such as that of a sphere. This results in the use of only one reader antenna with no dead zones present. To the extent it may be difficult to adhere a non-flexible tag to a doubly curved surface, a minimum of two reader antennae may be required for random placement of products having form factors that do not force specific orientations. In another embodiment, an RFID tag can be applied to the bottom of the vial160, or to the cap161. These locations would lend themselves to planar tag placement rather than the curved tag placement shown for the RFID tag162.

A relatively flat, planar, or rectilinear product such as the DVD150discussed previously lends itself to placement in a preferred orientation (such as a face-forward orientation). That is, such a product may be encouraged into predictable orientations by the geometry of a supporting structure (such as shelf140) or may be encouraged by a retailer's orderly placement of merchandise (e.g., with one side forward to the customer, or in a “this end up” orientation). There are instances, however, where a product may be orientated randomly and unpredictably, which may make it more difficult to read an attached RFID tag with a simple reader antenna. An example is a pharmacy environment where merchandise such as prescription medicines, drugs, etc. (“prescriptions”) may be placed in containers such as vial160, which in turn may be placed randomly into prescription envelopes or bags. To read an RFID tag162on vial160thus may require a specially designed reader antenna.

An exemplary RFID antenna system for use in a pharmacy application is shown inFIGS. 6A and 6B. A container or bin170may be provided to hold prescription bags, vials, and the like. In accordance with a preferred embodiment of the invention, associated with the bin170is an antenna configuration that incorporates both diversity and form factor. This exemplary system is designed with two antennae and may be used with either planar or non-planar tags. If non-planar tags are used, any random orientation of the product may be read. The majority of pharmacy products (pill bottles, liquid containers, etc.) have a cylindrical shape (single curved surface) to which a tag may be easily applied. As seen inFIGS. 6A and 6B, one of the antennae is a loop171, preferably encircling (or otherwise surrounding a volume of) the bin. As shown in this exemplary implementation, loop171is configured with a slight horizontal forward tilt. A second antenna loop172is configured in parallel with and, preferably, attached to a side of bin170. Preferably, for RFID applications, each antenna loop171and172would be connected to additional circuitry (not shown) that may include tuning components, switching components, wiring, etc., and an RFID reader, as is well known in the art. To optimize the system for use with a planar tag, a form factor is preferably used which does not permit the tag to lean forward.

FIG. 7shows an exemplary implementation of bin170as used in a pharmacy or other similar environment. As shown, the RFID tagged products such as vials160are placed in bags175and are stood upright or most commonly with a slight backward tilt such that only infrequently will there be an unfavorable orientation between the reader antennae171,172, and the products160(shown in phantom by dashed lines) and their RFID tags162(not shown).

In certain applications (e.g., pharmacies), multiple bins170may be used to hold products. It may furthermore be desirable to isolate the reading of RFID tags within each bin170, in order to locate the products associated with the tags. For example, bin170may have an associated RF shield such as a metal enclosure174to reduce the ability of RFID antenna reader to locate products outside of bin170.

EXAMPLES

The following are examples of specific implementations of preferred embodiments of the invention. As can be appreciated by those of ordinary skill in the art, any number of other implementations of the embodiments of the invention may be achieved when reducing embodiments of the invention to practice.

FIG. 8shows an exemplary implementation of a bin200used to hold tagged items such as prescriptions. The bin preferably includes an inner shell201that is transparent to RF energy using any such known material (e.g., molded plastic, fiberglass, etc.). Prescriptions can be placed within this inner shell201, preferably within envelopes as is the usual case in a pharmacy environment. The inner shell201may be partially enclosed within an outer shell202that blocks RF energy, for example, to confine the read range of reader antennae within the bin200.

Preferably, circuitry205is associated with the bin200. Circuitry205, for example, may include tuning components, switching components, wiring, connections, etc., as needed for the reader antennae associated with bin200. For example, such circuitry may include tuning boards206and207. A connector such as a BNC connector211may be used to provide an RF connection between circuitry205and external circuitry such as an RFID reader (not shown). Additional connections (not shown) may be made to external circuitry, for example, control or power connections, as have been described in previously referenced applications which have been incorporated herein by reference. The RF connection from connector211may be made through a coaxial cable212. A device such as rubber grommet213may be used to protect coaxial cable212where it passes through an opening or hole (not shown) in outer shell202. RF connections may be made, for example, by connecting or soldering the coaxial cable jacket to a ground pad214, and the coaxial cable center conductor to a tie point215, both on tuning board206. Likewise the RF connection may be carried via coaxial cable216to a ground pad217and a tie point218on tuning board207.

Diagonal reader antenna220may be tied to tuning board206through connection points221. One implementation of the diagonal reader antenna220, as shown inFIG. 8, is a coaxial cable with its center conductor attached at connection points221. The outer shield conductor need not be connected to any other circuitry. If the balun225(discussed below) is used, the ends of the outer shield conductor may optionally be joined as shown at222. The diagonal reader antenna220may be attached to the inner shell201using adhesive devices223, or any other connection means. The exemplary diagonal reader antenna220thus essentially surrounds the bin200, with a sloping orientation.

Another reader antenna, a wrap-around reader antenna240is provided in this exemplary implementation. In this example, a loop is wrapped around both sides of inner shell201. The implementation shown inFIG. 8uses a microstrip construction, which consists of a wider conductive strip and a narrower conductive strip, separated by an insulating material. An example embodiment uses foil conductors on a flexible plastic sheet. At point241, preferably near the mid-point of the wraparound reader antenna240, is an exemplary gap in the wider conductor, forming a balanced feed (balun) antenna as described in the previously referenced '721 application. In this example, the wraparound reader antenna240continues around the inner shell201to the opposite side (shown onFIG. 9). Preferably, connections to the tuning board207are made at point242, using wiring or other connectors243.

FIG. 9shows the view from the opposite side of bin200shown inFIG. 8. In this embodiment, the connectors243attach to points244, on the ends of the narrower conductor of wraparound reader antenna240. The wider conductor of wraparound reader antenna240need not be connected to any external circuitry.

Also shown at approximately the midpoint (relative to the ends) of diagonal reader antenna220is a balun225provided on diagonal reader antenna220. This balun is formed (as described in the previously referenced '721application) by removing a portion of the shielding (outer) coaxial cable. Thus, approaching the balun point, the diagonal reader antenna220is in the form of the usual coaxial cable construction226, with the shield intact. At the balun point, a short gap227is made in the shield, leaving the center conductor intact. The insulation around the center conductor is preferably left intact, but may also be removed. After a short gap227, the diagonal reader antenna220continues at point228as, for example, a coaxial cable with the outer shield intact.

Any number of variations, changes, or modifications may be made to these implementations. For example, the balun may be omitted on either or both reader antennae. Either or both antennae may be constructed using coaxial cable, microstrip, or other conductive material such as wires, conductive paint, etc. The antennae may be on the outside of inner shell201, on the inside, or molded or otherwise contained partly or fully within the inner shell201. The diagonal reader antenna may be composed of additional loops in series or in parallel. The wraparound antenna may be composed of a single path as shown inFIGS. 8 and 9, or may be composed of a loop on each side, with the two loops being in series or parallel.

It may be desired to have a bin larger than the bin illustrated inFIGS. 7 through 9.FIG. 10shows one example of an “oversize bin”300, which may be used to hold items larger than typical prescription envelopes. The oversize bin300preferably includes an inner shell301that is transparent to RF energy (e.g., molded plastic, fiberglass, etc.). Items are placed within this inner shell301. The inner shell301may be partially enclosed within an outer shell (not shown) that blocks RF energy, for example, to confine the read range of reader antennae within the bin300.

Associated with the bin300is circuitry305that may include tuning components, switching components, wiring, connections, etc., as needed for the reader antennae associated with bin300. For example, such circuitry may include tuning boards306and307. A connector such as a BNC connector311may be used to provide an RF connection between circuitry305and external circuitry such as an RFID reader (not shown). Additional connections (not shown) may be made to external circuitry, for example, control or power connections, as have been described in previously referenced applications. The RF connection from connector311may be made through a coaxial cable312. RF connections may be made, for example, by connecting or soldering the coaxial cable jacket to a ground pad314, and the coaxial cable center conductor to a tie point315, both on tuning board307. Likewise the RF connection may be carried via coaxial cable316to a ground pad317and a tie point318on tuning board306.

Diagonal reader antenna320may be tied to tuning board306through connection points321. Antenna320, as shown inFIG. 10, is a coaxial cable with its center conductor attached at connection points321. The outer shield conductor need not be connected to any other circuitry. If the balun325(discussed below) is used, the ends of the outer shield conductor may optionally be joined as shown at322. The diagonal reader antenna320may be attached to the inner shell301using adhesive devices323or any other connection means. In this embodiment, the diagonal reader antenna320essentially surrounds the bin300with a sloping orientation.

A side reader antenna340can also be provided. This is shown as a loop antenna on one side of inner shell301, although a wraparound antenna may also be used as discussed previously. The embodiment shown inFIG. 10uses a loop construction, which consists of a conductive strip. An example embodiment uses foil conductors on a plastic sheet. The side reader antenna340is connected from feed points344by wiring or other connectors343to points342on tuning board307. Instead of the side reader antenna340being a loop antenna, it may also be a microstrip construction as previously described, and may incorporate a balun, also previously described.

A secondary controller345may be included in the bin as shown. The secondary controller345may receive RF energy through connector346, and may route the RF energy through connection347to the tuning boards306and307, instead of using connector311. RF energy may also be routed from secondary controller345to antennae on other bins or other devices (not shown).

FIG. 11shows the view from the opposite side of bin300. Diagonal reader antenna320may be provided with a balun325as described earlier.

Any number of variations, changes, or modifications may be made to these implementations. For example, the balun may be omitted on either or both reader antenna. Either or both antennae may be constructed using coaxial cable, microstrip, or other conductive material such as wires, conductive paint, etc. The antennae may be on the outside of inner shells201or301, on the inside, or molded or otherwise contained partly or fully within the inner shells201or301.

FIG. 12shows a sample of some of the many possible implementations of antennae for use in the system in accordance with embodiments of the invention. For example, diagonal loop antenna220consisting of a single loop, previously discussed, is shown having feed points221and an optional balun225. A dual-loop-in-series antenna230is shown having feed points231and an optional balun232. A dual-loop-in-parallel antenna235is shown having feed points236and optional balun237.

FIG. 12also shows the wraparound antenna240, previously discussed, in the form of a single loop having feed points242and an optional balun241. A dual-loop-in-parallel wraparound antenna245is shown having feed points247and an optional balun246.

Besides the diversity reader antennae described here as particularly useful for detecting randomly oriented RFID tags within a container, it may also be desired to provide reader antennae for use within a shelf. Previously referenced application No. 60/479,846, disclosed a “figure-eight” antenna used in a vertical orientation.FIG. 13Ashows a horizontal orientation. A fixture such as a shelf450is provided to hold items. The shelf may incorporate a supporting or weight bearing structure451. This structure451may be metal or other RF—blocking material. The shelf450may include at least one antenna tuning board452, and optionally one or more secondary controllers453. Connectors454may be provided for RF connections, and connectors455for non-RF connections such as serial communications, etc. The wiring within the shelf is not shown but has been described earlier in this or the previously referenced applications.

Antenna support plane460can be included within shelf450. This support plane may be an insulating material such as plastic or fiberglass. The support plane460supports a reader antenna461that may be provided in loop form, preferably in the “figure-eight” form as shown made of metal foil. However, other fabrication methods may be used such as wire, coaxial cable, or other conductors. A feed point462is provided for the antenna to be connected to circuitry such as tuning board452. Openings463may be provided in support plane460, for example, to allow access to circuitry or reduce weight or cost

Shelf cover470is provided to cover the antenna461. The shelf cover is preferably transparent to RF energy.

Besides the figure-eight form factor of antenna461, any number of antenna form factors may be used in accordance with preferred embodiments of the invention, as, for example, within a shelf. Some exemplary form factors are shown inFIG. 13B. For some applications, these may perform better than simple loop antennae. Antenna480includes a loop conductor481with a feed point482. Also incorporated in antenna480are one or more additional conductive pathways483connecting into the loop conductor, and forming conductive paths in parallel to some portions of the loop conductor. In antenna480, the additional conductive pathways483are essentially straight. The loop conductor481and additional conductive pathways483may be made of conductive materials, for example, wire, metal foil, printed circuitry, or the outer jacket of a coaxial cable.

Antenna485includes a loop conductor486with a feed point487. Also incorporated in antenna485are one or more additional conductive pathways488connecting into the loop conductor and forming conductive paths in parallel to some portions of the loop conductor. In antenna485, the additional conductive pathways488are generally serpentine in shape, made of a series of straight segments.

Antenna490can include a loop conductor491with a feed point492. Also incorporated in antenna490are one or more additional conductive pathways493connecting into the loop conductor, and forming conductive paths in parallel to some portions of the loop conductor. In antenna490, the additional conductive pathways493are generally serpentine in shape, made of a series of curved segments.

Antenna495includes a loop conductor496with a feed point497. Also incorporated in antenna495are one or more additional conductive pathways498connecting into the loop conductor, and forming conductive paths in parallel to some portions of the loop conductor.

FIG. 14illustrates an exemplary wiring connection method in accordance with an embodiment of the invention. An RFID reader500connects to a ¼ wavelength of 75 ohm coaxial cable501(in this example, being approximately 12 feet long), which in turn connects to a ¼ wavelength of 50 ohm coaxial cable502(12′ 1″ long). Coaxial cable502is connected to branching connector503that branches the coaxial line into multiple additional 50 ohm coaxial cables, including the following:

A short 50 ohm cable to a 50 ohm resistor504for circuit protection purposes. A DC-blocking capacitor505can be used if any DC is superimposed on the RF signal.

Multiple 50 ohm cables507, each leading to a group of bins (for example, group or rack531composed of bins200a-200h). Cable507is approximately 4′ 9″ long.

In this example, cable507leads to a pair of secondary controllers520and521. Each secondary controller may, for example, feed RF to and control switching of eight reader antennae, for example, secondary controller520may control a diagonal antenna and a wraparound antenna on each of bins200a-200d, while secondary controller521may control antennae on each of bins200e-200h. The use of a secondary controller to control antennae has been described in the previously referenced applications.

The RF connection can continue past secondary controller521to a 6′ long coaxial cable522and then is shorted to ground at point523, that is, the center conductor of the coaxial cable is connected here to the outer sheath. If any DC is superimposed on the RF signal, a DC blocking capacitor524may be used, for example, a 0.01 microfarad capacitor. A DC blocking capacitor is used in order to prevent a DC short which may affect the performance of the reader. A 0.01 uF capacitor is frequency dependent. At 13.56 MHz, the capacitor performs very dose to a short circuit and at DC it appears to be an open circuit which masks the physical short circuit from the reader for DC conditions.

Although the example shown inFIG. 14connects the reader to six racks531-536, each having eight bins, it should be understood that more or fewer racks may be connected, and each rack may have more or fewer than eight bins.

FIG. 15illustrates another exemplary implementation of an embodiment of the invention in the form of an RFID antenna system. The exemplary antenna system includes diagonal reader antennae220and wraparound reader antennae240, each paired within a bin200, and having associated antenna tuning boards206and207. A rack531of several bins200is controlled by secondary controllers520-521. Also included are the impedance matching circuitry (elements501-505), a primary controller550, and an RFID reader500. (Although not shown, it should be apparent that antenna tuning boards206and207may include a selector switch, tuning components, a switch to tune or detune the associated antenna on demand, and other necessary components, and that secondary controllers30may include logic and switching controls as necessary to perform the operations described herein.)

Each secondary controller520,521of the exemplary system is connected to one or more of the antenna tuning boards206,207by a connection such as a coaxial cable509for transmission of RF signals and control cables554for digital signals. InFIG. 15, for each secondary controller there are shown three bins200, each bin having a tuning board206with a diagonal antenna220and a tuning board207with a wraparound antenna240(although there may be more or less bins, tuning boards, and antennae per secondary controller in reducing the exemplary system to practice). Preferably, the tuning boards are at similar short distances from their respective secondary controllers.

The RFID feed system shown inFIG. 15incorporates an RFID reader500and an impedance matching circuit incorporating elements501-505as discussed previously.

Parts or all of the systems described so far may be contained within a structure or structures such as pharmacy storage bins, shelves, counters, etc., and certain elements may be contained within a rack531of bins.

In another exemplary implementation, a matching circuit may be formed from common coaxial cable. In this configuration, a 50 Ω terminator504(whose impedance is equal to the characteristic impedance of the system) is placed in parallel (using connection503) with the RF cables507leading to each rack of bins such as531, etc. For each rack531of bins, after the last secondary controller521on the RF cable (507,508), there is placed a length of coaxial cable522leading through a DC blocking capacitor524to a ground523(the center of the RF cable at this point being shorted to the ground sheath of the RF cable).

In accordance with an embodiment of the invention, a plurality of antennae220,240having associated tuning circuits206,207, secondary controllers520,521, and associated wiring may all be contained in or on a physical structure, as shown, for example, inFIG. 15as rack531of bins. (For convenience, the term “rack” used herein will be taken to mean one unit or group of bins preferably in physical proximity to one another, and served by one or a few secondary controllers520,521. The term “rack” however is 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 the embodiment.) As shown inFIG. 15, rack531is provided with multiple antennae that are each connected to a reader500by one or more transmission cables including cables501,502,507,508,509. The cable509interconnects between the tuning circuits206,207and the secondary controllers520,521. Cables508interconnect secondary controllers within a rack, and cable507connects the rack to the common point503and thence back through impedance matching coaxial cables501,502to reader500.

The example inFIG. 15illustrates the reader500being controlled by a primary controller or controller550that sends commands or control signals along control cables551,552,553to select which antenna is active at any time. These control cables may be in series as shown inFIG. 15or may be in parallel or series-parallel connections. Between racks, the commands or control signals may be carried on control cable553. Within a shelf, the commands or control signals may be carried by cables552,554. The primary controller550may be a microprocessor or any processing device (e.g., discrete logic circuit, application specific integrated circuit (ASIC), programmable logic circuit, digital signal processor (DSP), etc.). Furthermore, the racks may also be configured with secondary controllers520,521that co-operate with the primary controller550to select antennae. The secondary controllers520,521may also be microprocessors (or other processing devices) with sufficient outputs to control all the antennae within the associated rack.

The controller550may selectively operate any or all the switches by sending commands through a digital data communication cable551by sending a unique address associated with each tuning circuit206,207. The addresses could be transmitted through the use of addressable switches such as, for example, ones identical or similar to a Dallas Semiconductor DS2405 “1-Wire®” addressable switch. Each such addressable switch provides a single output that may be used for switching a single antenna. Preferably, the controller550may selectively operate any or all the switches by utilizing one or more secondary controllers520,521. For example, the secondary controller520,521may be a microprocessor such as a Microchip Technology Incorporated PICmicro® Microcontroller which can provide multiple outputs for switching more than one antenna, such as all the antennas in proximity to the secondary controller. The controller550may also be a microprocessor such as a MicroChip Technology Incorporated PICmicro® Microcontroller, or a microprocessor such as an Intel Incorporated Microprocessor. Communications between the controller550and the secondary controller520,521can be implemented by using digital communication signals in accordance with well known communication protocols (e.g., RS-232, RS-485 serial protocols, Ethernet protocols, Token Ring networking protocols, etc.).

In the previously referenced patent applications, the term “intelligent station” is used as a general term to describe equipment, such as a rack531, which may include a secondary controller, switches and/or tuning circuitry, and/or antennae. More than one intelligent station may be connected together and connected and 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 a preferred embodiment, the intelligent station system is controlled through an electronic network570, as shown inFIG. 15. A controlling system that controls the intelligent station system will send command data to the primary controller550via Ethernet, RS-232 or similar protocol. These commands include but are not limited to instructions for operating the RFID reader unit500and antenna switches associated with tuning circuit206,207The controller550is programmed to interpret the commands that are transmitted through the unit. If a command is intended for the reader unit500, the controller550passes that command to the reader unit500. Other commands could be used for selecting antennae220,240, and these commands will be processed if necessary by controller550to determine what data should be passed through digital data communication cable551to the secondary controllers520,521.

Likewise, the secondary controllers520,521can pass data back to the primary controller550, as can the reader unit500. The controller550then relays result data back to the controlling system through the electronic network570. The inventory control processing unit580, shown inFIG. 15, is one example of such a controlling system. As discussed further herein with respect to the intelligent station system, the electronic network and controlling system are used interchangeably to depict that the intelligent station system may be controlled by the controlling system connected to the intelligent station system through an electronic network570.

Controller550ofFIG. 15typically decides whether a command from the electronic network570should be sent to reader500, or should be sent through the digital communication cable551. Also, controller550must relay data it receives from the digital communication cable551, and from reader unit500, back to the electronic network. Under one configuration, the electronic network would issue a command to read a single antenna. The controller550would then (a) set the proper switch for that antenna, (b) activate the reader, (c) receive data back from the reader, (d) deactivate the reader, and (e) send the data back to the electronic network. Further details of the processing of command signals from a host by the controller can be found in U.S. provisional patent application 60/346,388 (filed Jan. 9, 2002), which has been incorporated by reference in its entirety herein.

An additional advantage of placing the controller550between the electronic network570and the reader unit as shown inFIG. 15is that different types of readers500can be used as needed. The commands from the electronic network to the controller may be transmitted using generic control data (not reader-specific), thus allowing for expanded uses by various types of readers. For example, the electronic network can send to the controller a “read antennas” command. The controller in turn can then translate this command into the appropriate command syntax required by each reader unit. Likewise, the controller can also receive the response syntax from the reader unit (which may differ based on the type of the reader unit), and parse it into a generic response back to the electronic network. The command and response syntax may differ for each type of reader unit500, but the controller550makes this transparent to the electronic network.

FIG. 15further shows digital communication cable551connecting primary controller550to the secondary controllers520,521, and RF transmission cable507connects the reader500to the antennae220,240. In this embodiment, the primary controller550or secondary controller520,521may operate a tee switch560that selects which of the racks (for example, rack531) or which group of bins200will be selected. The tee switch560may be separate from or part of a shelf as would be recognized by one skilled in the art. InFIG. 15, the tee switch560is used with a “parallel-series” RF connection arrangement. That is, controller550and reader500operate the antenna within a rack, with the RF and digital communication lines branched off (i.e., connected with a multi-drop or “tee” arrangement with each of the branches arranged in parallel) to antennae within racks that are arranged in series or in series-parallel. This configuration allows the RF signal to be switched by the tee switch560into a rack or group of bins, or to bypass them altogether. In parallel with the RF connections to rack531through one RF cable507, RF connections may be made in parallel to other racks (not shown) through other cables507. The tee or multi-drop configuration shown inFIG. 15may be used to reduce the number of switching elements through which the RF transmission cable passes en route to any given antenna.

InFIG. 15, a portion of the control cable553that extends beyond rack531, and a portion of the RF cable508between secondary controllers are shown outside of the rack. However, as would be recognized by those skilled in the art, these extended portions of the cables may also be contained within the rack. Additional extended control cable portions553may be used to connect to more racks.

The item information data collected by the reader units500is transmitted to an inventory control processing unit580. The inventory control processing unit580is typically configured to receive item information from the intelligent stations or racks531, etc. The inventory control processing unit580is typically connected to the intelligent stations over an electronic network570and is also associated with an appropriate data store590that stores inventory related data including reference tables and also program code and configuration information relevant to inventory control or warehousing. The inventory control processing unit580is 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 determine item information from the intelligent stations (531, etc.) that are connected to the inventory control processing unit580through an electronic network570. In one embodiment, the various intelligent stations531, etc. would be under the control of inventory control processing unit580that would determine when the reader units500under control of controller550would poll the antennae220,240to determine item information of items to be inventoried. In an alternate embodiment, the controller(s)550may 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 controller550may be event driven, for example, triggered by a periodic replenishment of inventoried items on the intelligent shelves. In each case, the controller550would selectively energize the multiple antennae connected to reader500to determine item information from the RFID tags associated with the items to be inventoried.

Once the item information is received from the reader units500of the intelligent stations531, etc., the inventory control processing unit580processes the received item information using, for example, programmed logic, code, and data at the inventory control processing unit580and at the associated data store590. The processed item information is then typically stored at the data store590for future use in the inventory control system and method of the invention.

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. Although embodiments have been described in connection with the use of a bin structure, it should be readily apparent that any structure that may be used in selling, marketing, promoting, displaying, presenting, providing, retaining, securing, storing, or otherwise supporting an item or product, may be used in implementing embodiments of the invention.

Although specific circuitry, components, or modules (e.g., tuning circuit206-207, tee switch560, impedance matching components501,502, RF switch, etc.) 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., reader500, primary controller550, inventory control processing unit580, data store590, 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 store590, inventory processing unit580, controller550, reader500, secondary controller520, 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 antennas220,240, tuning circuits206,207, racks531, or connected through a network570executing 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 unit580could be implemented on a general purpose computer system connected to an electronic network570, 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 computer system generally includes a communications interface, such as an Ethernet card, to communicate to the electronic network570. Other computer systems may also be connected to the electronic network570. 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 system and network 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.