Abstract:
A RFID antenna system for communicating with at least one transponder disposed on an object (e.g., product carrier, product, etc.) moveable along an interrogation path comprising at least one antenna panel that defines an antenna region, the antenna panel including at least one substantially continuous antenna loop for transmitting and receiving electromagnetic fields, the antenna panel being oriented such that the antenna panel intersects the interrogation path. The antenna panel can be substantially flexible or rigid.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates in general to radio frequency identification (RFID) devices. More particularly, the invention relates to a flexible RFID antenna panel and system.  
         BACKGROUND OF THE INVENTION  
         [0002]    RFID systems are well known in the art. Such systems include relatively large packages containing battery powered transmission/receiving circuitry, such as the identification system disclosed in U.S. Pat. No. 4,274,083, to passive systems in which the transponder receives its power from the base station or interrogator, such as the identification system disclosed in U.S. Pat. No. 4,654,658.  
           [0003]    A typical RFID system is made up of reusable transponders or tags fixed to or embedded in product carriers, an antenna system that interrogates the tags via a RF link and a controller. The host (or computer) system interfaces with the controller and directs the interrogation of the tags.  
           [0004]    The RFID antenna system typically employs a high frequency signal to interrogate the tags and, hence, product carriers that are moved on an interrogation path, such as a conveyor. The antenna system is generally disposed near the interrogation path to provide effective communication to and from the tags.  
           [0005]    The location of the antenna is critical to the interrogation and receipt of the identification code and other data transmitted to and from the tags. For example, if a relatively small single antenna is employed or the antenna is positioned too far from the interrogation path, inadequate coverage of the interrogation path will occur.  
           [0006]    Several attempts have been made to optimize the RF link and, hence, communication between the antenna and the tags. In one (typically employed) approach, a frame antenna of rectangular or square shape is fitted around the conveyor.  
           [0007]    The noted system has several drawbacks. In particular, the antenna system exhibits one or more dead zones for certain tag positions. For example, there is a dead zone across the very center of the conventional frame antenna. If a tag is located within a window that is parallel to the conveyor belt and comprises some distance on either side of the center frame axis, and maintains this position throughout the read area of the antenna, the tag would not be read.  
           [0008]    Moreover, the accuracy and completeness of the reading also decreases if several tags are following one another in close succession during movement along the conveyor. When tags are in close succession and relatively far from the read antenna, the tags appear to be the same distance from the read antenna and thus send back simultaneous transmissions. The result of a simultaneous transmission is an unintelligible identification code. This is particularly the case in a noisy environment, for which shielding would be necessary.  
           [0009]    It is therefore an object of the present invention to provide a RFID antenna panel and system that overcomes the noted drawbacks associated with prior art antenna systems.  
           [0010]    It is another object of the invention to provide an antenna system having at least one antenna panel that provides optimum coverage over the interrogation path.  
           [0011]    It is another object of the present invention to provide a RFID antenna system that can be readily incorporated into a conveyor system to provide accurate interrogation of tags fixed to or embedded in product carriers.  
           [0012]    It is another object of the present invention to provide a RFID antenna system that can be readily incorporated into the entrance to a building or warehouse (e.g., dock door) to provide accurate interrogation of tags fixed to or embedded in product carriers passing through the entrance.  
           [0013]    It is yet another object of the present invention to provide a RFID antenna system that can be readily incorporated into cargo trucks or trailers to provide accurate interrogation of tags disposed on products or product carriers during loading and unloading.  
         SUMMARY OF THE INVENTION  
         [0014]    In accordance with the objects and advantages of the present invention, the RFID antenna system for communicating with at least one transponder disposed on an object (e.g., product carrier, product, etc.) moveable along an interrogation path generally comprises at least one flexible antenna panel, the antenna panel defining an antenna region, the antenna panel including at least one substantially continuous antenna loop for transmitting and receiving electromagnetic fields, the antenna panel being oriented such that the antenna panel intersects the interrogation path, the antenna panel being adapted to bend about at least a first axis when the object intersects the antenna region. The antenna panel is preferably substantially planar and rectangular in shape.  
           [0015]    In an additional embodiment of the invention, the antenna system comprises at least one substantially rigid antenna panel that similarly defines an antenna region, the antenna panel including at least one substantially continuous antenna loop for transmitting and receiving electromagnetic fields, the antenna panel being oriented such that the antenna panel intersects the interrogation path, the antenna panel being hingedly connected to at least a first hinge connection whereby the antenna panel rotates about the hinge connection when an object intersects the antenna region.  
           [0016]    In an additional embodiment of the invention, the antenna system includes a support member; at least one antenna panel, the antenna panel defining an antenna region, the antenna panel including at least one substantially continuous antenna loop for transmitting at least a first electromagnetic field and receiving at least a second electromagnetic field, the antenna panel being attached to the support member such that the antenna panel intersects the interrogation path; and control means in communication with the antenna loop for controlling said transmittal and receipt of the first and second electromagnetic fields by the antenna loop.  
           [0017]    In one aspect of the noted embodiment, the antenna panel is substantially flexible and adapted to bend about at least a first axis when the object intersects the antenna region. In a further aspect of the invention, the antenna panel is substantially rigid and the support member includes at least one hinge connection that is adapted to hingedly engage the antenna panel, the antenna panel being adapted to rotate about the hinge connection when the object intersects the antenna region.  
           [0018]    In a further embodiment of the invention, the antenna system includes a conveyor system adapted to transport at least one of the objects along the interrogation path.  
           [0019]    In an additional embodiment, the antenna system includes a conveyor antenna disposed proximate the interrogation path. The conveyor antenna is adapted to transmit at least a third electromagnetic field and receive at least a fourth electromagnetic field, the third and fourth electromagnetic fields being directed substantially perpendicular to the interrogation path.  
           [0020]    In yet another embodiment of the invention, the antenna system comprises a support system having a first substantially vertical support member and a second substantially vertical support member; first and second antenna panels, the first antenna panel including at least a first substantially continuous antenna loop for transmitting at least a first electromagnetic field and receiving at least a second electromagnetic field, the second antenna panel including at least a second substantially continuous antenna loop for transmitting at least a third electromagnetic field and receiving at least a fourth electromagnetic field; the first and second antenna panels being substantially rectangular in shape and including first and second vertical edge regions, the first antenna panel first vertical region being engaged to the first vertical support member and the second antenna first vertical region being engaged to the second vertical support member, whereby the first and second antenna panels define an antenna region, the antenna region intersecting the interrogation path.  
           [0021]    In one aspect of the noted embodiment, the first and second antenna panels are substantially flexible. The first flexible antenna panel is rigidly engaged to the first vertical support member and the second flexible antenna panel is rigidly engaged to the second vertical support member, the first flexible antenna panel being adapted to bend about at least a first axis when an object intersects the antenna region and the second flexible antenna panel being adapted to bend about at least a second axis when an object intersects the antenna region.  
           [0022]    In a further aspect of the invention, the first and second antenna panels are substantially rigid. The first rigid antenna panel is hingedly connected to the first vertical support member and the second rigid antenna panel is hingedly connected to the second vertical support member, the first and second rigid antenna panels being adapted to rotate about the hinge connections when an object intersects the antenna region.  
           [0023]    In a further aspect of the noted embodiment, the antenna system similarly includes a conveyor antenna disposed proximate the interrogation path, the conveyor antenna being adapted to transmit at least a fifth electromagnetic field and receive at least a sixth electromagnetic field, the fifth and sixth electromagnetic fields intersecting the interrogation path.  
           [0024]    In a further embodiment of the invention, the RFID antenna system comprises at least one antenna panel system (as described herein) disposed in the entrance to a building, the antenna panel, if flexible, being adapted to bend about a first axis when an object passes through the building entrance or, if rigid, rotate about a hinge connection when an object passes through the building entrance.  
           [0025]    In yet a further embodiment of the invention, the RFID antenna system comprises at least one antenna panel system (as described herein) disposed in the entrance to a transport vehicle (e.g., cargo truck, trailer), the antenna panel, if flexible, being adapted to bend about a first axis when an object passes through the entrance or, if rigid, rotate about a hinge connection when an object passes through the entrance. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0026]    Further features and advantages will become apparent from the following and more particular description of the preferred embodiments of the invention, as illustrated in the accompanying drawings, and in which like referenced characters generally refer to the same parts or elements throughout the views, and in which:  
         [0027]    [0027]FIG. 1 is a schematic illustration of a typical RFID system;  
         [0028]    [0028]FIG. 2 is a perspective view of one embodiment of the flexible RFID antenna system, according to the invention;  
         [0029]    [0029]FIG. 3 is a front plan view of the RFID antenna system shown in FIG. 2;  
         [0030]    [0030]FIG. 4 is an exploded perspective view of one embodiment of the flexible RFID antenna panel, according to the invention;  
         [0031]    [0031]FIG. 5 is a partial section view of the antenna panel shown in FIG. 4;  
         [0032]    [0032]FIG. 6 is a perspective view of a further embodiment of a RFID antenna system employing two flexible antenna panels, according to the invention;  
         [0033]    [0033]FIG. 7 is a front plan view of the RFID antenna system shown in FIG. 6;  
         [0034]    [0034]FIG. 8 is a perspective view of a further embodiment of a RFID antenna system employing two RFID antenna subsystems, according to the invention;  
         [0035]    [0035]FIG. 9 is a schematic illustration of a flexible RFID antenna system incorporated into a building entrance, according to the invention;  
         [0036]    [0036]FIG. 10 is a schematic illustration of a flexible RFID antenna system retrofitted into a trailer, according to the invention; and  
         [0037]    [0037]FIG. 11 is a schematic illustration of a flexible RFID antenna system retrofitted into a cargo truck, according to the invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0038]    The RFID antenna of the present invention substantially reduces or eliminates the disadvantages and shortcomings associated with prior art antenna systems. According to one embodiment of the invention, a flexible antenna panel is disposed proximate the interrogation path for interrogating transponders disposed on objects moving along the interrogation path. The antenna panel is preferably oriented such that the plane defined the antenna panel intersects the interrogation path. As discussed in detail below, the antenna panel is further adapted to bend about at least a first axis when an object (with a transponder thereon) intersects the plane defined by the panel.  
         [0039]    Referring first to FIG. 1, there is shown a simple read/write RFID system. The system typically comprises one or more transponder or tags  10 , at least one antenna  12  to communicate with the tags  10 , and a controller  14  for managing the communications interface. The host system (i.e., computer)  16  interfaces with the controller  14  and directs the interrogation of the tags  10  disposed on or embedded in the product carriers  11  and any following action via parallel, serial or bus communications  18 .  
         [0040]    As illustrated in FIG. 1, each antenna  12  is disposed on one side of the interrogation path, denoted by Arrows A 1 -A 4 , which is defined by the conveyor  5 . As such, the RF link  17  and, hence, active RF zone is limited. By the term “active RF zone”, as used herein, it is meant to mean the zone defined by the effective RF radiation or electromagnetic field component.  
         [0041]    Referring now to FIGS. 2 and 3, there is shown one embodiment of the RFID antenna system  30  of the invention. A key feature of the present invention is the capability of the antenna system  30  to be positioned proximate to or incorporated into a conveyor system  5 . As illustrated in FIG. 2, in one embodiment of the invention the antenna system  30  is disposed proximate the interrogation path of the conveyor system  5 , denoted by Arrow I, for interrogating the tags  10  and, hence, products or product carriers  1 l a ,  1 l b , moving along the interrogation path. As will be appreciated by one having ordinary skill in the art and discussed herein, the antenna panels of the invention can also be secured (hingedly or rigidly) to a ceiling above the interrogation path.  
         [0042]    Referring now to FIG. 2, in one embodiment, the antenna system  30  includes (i) a conveyor system  5  adapted to move the product carriers  11   a ,  11   b  (or products) with tags  10  disposed thereon along the interrogation path (denoted by Arrow I) that is, in this instance, defined by the conveyor system  5 , (ii) an antenna support  32  having at least first and second side supports  34 ,  36  and a top member  38  attachable to the side supports  34 ,  36 , (iii) at least one antenna panel  20  having at least one antenna loop  25  (see FIG. 4) adapted to transmit and receive electromagnetic fields (i.e., provide an active RF zone), and (iv) an antenna head assembly (i.e., reader/writer)  40 .  
         [0043]    According to the invention, the antenna panel  20  can be constructed of substantially rigid or flexible material. In a preferred embodiment of the invention, the antenna panel  20  is substantially flexible.  
         [0044]    As further illustrated in FIG. 2, the antenna system  30  can, if desired, include a RFID conveyor antenna  31  to further enhance the active RF zone provided by the system  30 . Details of the noted RFID conveyor antenna are set forth in U.S. Pat. No. 5,929,760, which is incorporated by reference herein.  
         [0045]    As discussed in detail in U.S Pat. No. 5,929,760, the conveyor antenna  31  is preferably disposed proximate an interrogation path and is positioned (and adapted) to transmit and receive electromagnetic fields (and, hence provide a further active RF zone) that intersect the interrogation path. Preferably, the electromagnetic fields provided by the conveyor antenna  31  substantially intersect the interrogation path.  
         [0046]    Referring now to FIG. 3, the antenna support  32  includes at least one, preferably two antenna panel connectors  33   a ,  33   b  adapted to engage and connect the top portion  22  of the flexible antenna panel  20  to the top antenna support member  38  such that (i) the plane defined by the panel  20  (shown in phantom and denoted  23 ) intersects the interrogation path (and, hence, defines an antenna region) and (ii) the flexible antenna panel  20  is allowed to bend about at least one panel axis (denoted X) disposed proximate the top portion  22  thereof when a product carrier  11   a ,  11   b  (or product) intersects the plane  23  (or antenna region) defined by the panel  20 . In a preferred embodiment, the antenna panel  20  is disposed substantially perpendicular to and intersects the interrogation path.  
         [0047]    As illustrated in FIG. 2, by virtue of the flexible material employed to construct the panel  20  (discussed in detail below), the panel  20  is also adapted to bend about its body to accommodate a multitude of different size and shape product carriers  11   a ,  11   b  (and products).  
         [0048]    According to the invention, the antenna support  32  can comprise various lightweight materials, such acrylonitrile butadiene-styrene (ABS), polycarbonate, or polyvinyl chloride (PVC). The support  32  material must, however, provide minimal interference and/or restriction of the antenna RF radiation or electromagnetic field.  
         [0049]    In an additional envisioned embodiment of the invention, not shown, the panel connectors comprise conventional hinge connectors that are adapted to hingedly engage the antenna panel  20 . In this embodiment, the antenna panels  20  can be either substantially flexible or rigid, preferably, substantially rigid, and would rotate (i.e., swing open) when a product carrier (e.g.,  11   a ) intersects the plane defined by the panel  20 .  
         [0050]    As will be appreciated by one having ordinary skill in the art, the hinge connectors can be attached to an antenna support, such as support member  38  shown in FIG. 2, the ceiling above the conveyor system  5 , the top of an entrance to a building (e.g., header), such as illustrated in FIG. 9, or the top of the entrance (or ceiling) of a transport vehicle, such as the cargo truck and trailer illustrated in FIGS. 10 and 11.  
         [0051]    Referring back to FIG. 2, the antenna head assembly  40 , which includes the antenna logic and associated circuitry for the antenna system  30 , is operatively connected to the antenna panel  20  and conveyor antenna  31 . Preferably, the head assembly  40  comprises a LRP 820  Reader/Writer. The noted device is manufactured and distributed by Escort Memory Systems, Scotts Valley, Calif.  
         [0052]    In one embodiment of the invention, the antenna panel  20  and conveyor antenna  31  are designed and adapted to provide 100-ohms of impedance and are connected in parallel to achieve a 50-ohm load. In an alternative embodiment, a power splitter is employed.  
         [0053]    Because of the close proximity that the antenna system  30  provides, read range is not critical and a smaller tag  10  can be used. Single or multiple tag commands can thus be sent to the head assembly  40  and both antennas  20 ,  31  will read either the tag  10  placed on the top of the carrier or carriers  11   a ,  11   b  or a tag placed on the bottom (not shown).  
         [0054]    As will be appreciated by one having ordinary skill in the art, since the RFID antenna systems of the present invention include all the circuitry necessary to convert the digital signals received from a controller to high speed RF signals for the transponder tags, and conversely to convert the RF signals from the tags back into digital signals for the controller, numerous controllers can be employed with the antenna panel  20  and conveyor antenna  31 .  
         [0055]    Referring now to FIGS. 4 and 5, the flexible antenna panel  20  of the invention will be described in detail. Referring first to FIG. 4, in one embodiment of the invention, the panel  20  includes first and second substantially flexible panel members  24   a ,  24   b  and at least one antenna loop (or circuit)  25 . In a further embodiment of the invention, the panel members  24   a ,  24   b  are constructed of a substantially rigid material. According to the invention, the antenna loop  25  is adapted to provide an effective RF zone, more preferably transmit at least a first electromagnetic field and receive at least a second electromagnetic field.  
         [0056]    Referring to FIG. 5, in one embodiment, the panel members  24   a ,  24   b  are substantially planar and are preferably laminated together by conventional means with the antenna loop  25  disposed therebetween. In additional envisioned embodiments, one panel member (e.g.,  24   a ) having at least one antenna loop or circuit disposed on at least one surface thereof is employed.  
         [0057]    As will be appreciated by one having ordinary skill in the art, the panel members  24   a ,  24   b  can comprise various shapes (e.g., square, oblong, semi-circular, etc.) and dimensions, and be constructed of various flexible or rigid materials. Preferably, the panel members  24   a ,  24   b  are substantially planar, substantially rectangular in shape and constructed of commercial grade Neoprene™.  
         [0058]    It will be further appreciated by one having skill in the art, that the panel member(s) material and thickness thereof should be selected to provide the least resistance to the product carrier&#39;s movement along the interrogation path.  
         [0059]    Referring now to FIGS. 6 and 7, there is shown an additional embodiment of the antenna system, designated  50 . In the noted embodiment, at least two flexible antenna panels  60 ,  62  and, if desired, the antenna conveyor  31  are employed.  
         [0060]    In one embodiment of the invention, each panel  60 ,  62  is hingedly connected to the first and second side supports  34 ,  36  by conventional means. The panels  60 ,  62  are preferably oriented such that the planes defined by the panels  60 ,  62  (shown in phantom and designated  63   a ,  63   b , respectively) are substantially perpendicular to and preferably intersect the interrogation path. In a preferred embodiment of the invention, the planes  63   a ,  63   b  are substantially coincident and, hence, define an antenna region  63   c.    
         [0061]    As illustrated in FIG. 6, the antenna panels  60 ,  62  are further adapted to rotate about the hinge connections  64   a ,  64   b  when a product carrier  11   a ,  11   b  or product intersects the planes  63   a  and  63   b  defined by the panels  60 ,  62 . As will be appreciated by one having ordinary skill in the art, in the noted “hinge connection” embodiment, the panel members  24   a ,  24   b  shown in FIG. 4 can be constructed of a substantially flexible material or a substantially rigid material, such as ABS.  
         [0062]    According to the invention, each hinge connection  64   a ,  64   b  includes conventional biasing means to provide an adjustable closing force (or moment) to the hinge connections  64   a ,  64   b  and, hence, panels  60 ,  62 .  
         [0063]    In an additional envisioned embodiment (not shown), the panels  60 ,  62  are rigidly connected to the side supports  34 ,  36  via panel connectors similar to the panel connectors  33   a ,  33   b  shown in FIG. 2. In this embodiment, the antenna panels  60 ,  62  would be constructed of a substantially flexible material and, hence, bend upon contact with a product carrier or carriers (e.g.,  11   a ,  11   b ) providing a path therebetween.  
         [0064]    In a further envisioned embodiment of the invention (not shown), the antenna system  50  shown in FIG. 6, includes an upper panel, such as antenna panel  20  shown in FIG. 2. According to the invention, the upper antenna panel can be substantially flexible or rigid. In this embodiment, the upper antenna panel would similarly be connected to the top antenna support member  38  or ceiling above the antenna system  5  and adapted to bend or rotate (depending on the antenna panel material) open upon contact with a product carrier (e.g.,  11   a ).  
         [0065]    Referring now to FIG. 8, there is shown yet another embodiment of the RFID antenna system  70  of the invention. As illustrated in FIG. 8, the antenna system  70  employs the single and dual panel antenna systems  30 ,  50 , as described above.  
         [0066]    According to the invention, the antenna systems  30 ,  50  can be disposed on or incorporated into the conveyor system  5  in any order, proximate to each other or at a substantial distance apart. Further, a single antenna head assembly  40  or multiple head assemblies can be employed.  
         [0067]    Referring now to FIG. 9, there is shown yet another embodiment of the invention wherein the antenna system  30  of the invention is disposed proximate the entrance  81  to a building or warehouse  80 . As will be appreciated by one having ordinary skill in the art, the illustrated antenna system  30  ensures that a RFID tagged carriers  11   e  and/or items will be interrogated and tracked whenever they leave or enter the building  80 . The system  30  also facilitates tracking of RFID tagged carriers  11   e  and items when they are stored on a loading dock  82 , for example, prior to warehousing or loading onto a transport device  83 .  
         [0068]    Alternatively, antenna system  50  shown in FIGS. 6 and 7 can be incorporated into the building entrance  81 . Antenna system  50  would similarly facilitate tracking of tagged carriers  11   e  and items that are transported through the building entrance  81 .  
         [0069]    The antenna systems  30 ,  50  can also be employed with a modular RFID antenna system  90  disposed at the building entrance  81  to enhance the active RF zone. Details of the modular antenna system  90  are set forth in Co-Pending application Ser. No. 09/925,129, filed Aug. 8, 2001, which is incorporated by reference herein.  
         [0070]    Referring now to FIG. 10, there is shown an additional embodiment of the invention wherein the RFID antenna system  30  of the invention is retrofitted into a trailer  100 . In a preferred embodiment, the antenna system  30  includes a modular antenna system  90  that are powered by external battery (not shown). In an additional envisioned embodiment of the invention, the antenna systems  30 ,  90  are powered by the electrical or battery system of the tractor-trailer.  
         [0071]    Referring now to FIG. 11, the RFID antenna system  30  of the invention can also be retrofitted into a cargo truck  102 , with a modular antenna system  90  or without. In this embodiment, the antenna system  30  is preferably powered by an existing vehicle battery.  
         [0072]    In the embodiments shown in FIGS. 10 and 11, the antenna system  30  communicates with tagged items (product carriers  11 , products, etc.) as they are loaded to and unloaded from the trailer  100  or truck  102 , allowing accurate tracking of the tagged items throughout the transport chain. In addition to trailers or trucks, the system can be used with any suitable transport vehicle.  
         [0073]    While preferred embodiments and their technical advantages have been described in the above detailed description and illustrated in the drawings, the present invention is not limited thereto but only by the scope and spirit of the appended claims.