Abstract:
Disclosed is a gate system arranged on two gate frames and detects a tag passing between the two gate frames, the gate system including at least two gate frames that are vertically arranged facing with each other; at least two antenna units that are arranged on the at least two gate frames, respectively; and a reader that is arranged on each of the at least two gate frames and enables the at least two antenna units to emit electromagnetic wave to an article passing between the at least two gate frames using a predetermined frequency signal, and obtains information stored in a tag using a signal that the at least two antenna units receives from the at least two antenna units.

Description:
[0001]    Pursuant to 35 U.S.C. §119 (a), this application claims the benefit of earlier filing date and right of priority to Korean Patent Application No. 10-2010-0023806, filed on Mar. 17, 2010, the contents of which are hereby incorporated by reference in their entirety. 
       BACKGROUND OF THE DISCLOSURE 
       [0002]    1. Field of the Invention 
         [0003]    The present disclosure relates to a gate system, and more particularly, to a gate system that has a radio frequency identification (RFID) system of an ultra high frequency band arranged on two gate frames and detects a tag passing between the two gate frames. 
         [0004]    2. Description of the Related Art 
         [0005]    Generally, a gate system is widely used in an electronic article surveillance system and a burglar detection system at a library. 
         [0006]    The gate system commonly includes two gate frames that are vertically arranged at an entrance and an RFID system in the two gate frames. 
         [0007]    The RFID system has antenna units arranged on the two gate frames and a reader, the two gate frames each having an antenna unit and the antenna units facing each other. 
         [0008]    The gate system enables the reader to periodically apply a predetermined frequency signal to the antenna unit such that the antenna unit generates electromagnetic wave. 
         [0009]    When a tag attached to an article passes between the two gate frames, the tag receives the electromagnetic wave generated in the antenna unit where the wave is activated, and transmits prestored information, that is, information on the article. 
         [0010]    The antenna unit receives the certain information transmitted by the tag and provides the information for the reader. Further, the reader reads out the information input from the tag through the antenna unit and obtains the information on the article. 
         [0011]    Further, recently, the gate system includes a monitoring camera, thereby increasing a tag recognition function. For example, the gate frame includes a monitoring camera arranged therein so that the monitoring camera takes a picture of a passing article, that is, the article is attaching a tag. At this time, when an unrecognized tag has passed between the gate frames, the gate system implements a function to update data. 
         [0012]    The RFID system mounted in the gate system uses a high frequency (HF) band. Since the RFID system that uses the HF band has a short recognition distance, it can precisely recognize only information on a tag of an article passing between the gate frames and cannot obtain information on tags of articles that are positioned nearby and have not passed between gate frames, so that the gate system operates normally. 
         [0013]    Recently, the RFID system included in the gate system uses an ultra high frequency (UHF) band signal. 
         [0014]    When the RFID system uses the UHF band signal, a tag recognition distance becomes about 5 cm, so errors often occur where the RFID system recognizes tag information of an article adjacently positioned to the gate frame that has not passed between the gate frames and tag information of an article that has passed between the gate frames. 
       SUMMARY OF THE INVENTION 
       [0015]    The present disclosure provides a gate system capable of precisely recognizing only information of a tag, passing between gate frames while using a UHF band signal, not recognizing tag information of an article positioned adjacently to the gate frames, that has not passed between gate frames, whereby a recognition error does not occur. 
         [0016]    According to an aspect of the present disclosure, a gate system includes at least two gate frames that are vertically arranged facing with each other; at least two antenna units that are arranged on the at least two gate frames, respectively; and a reader that is arranged on each of the at least two gate frames and enables the at least two antenna units to emit electromagnetic wave to an article passing between the at least two gate frames using a predetermined frequency signal, and obtains information stored in a tag using a signal that the at least two antenna units receives from the at least two antenna units, wherein each of the at least two antenna units includes: a ground plate; a plurality of unit antennas partly arranged on the ground plate; and an electromagnetic wave absorber that is attached on the ground plate except for an area of the ground plate where the plurality of unit antennas are arranged. 
         [0017]    Preferably each of the at least two antenna units includes at least two array antennas, and each of the array antennas includes a ground plate, a plurality of unit antennas partly arranged on the ground plate and an electromagnetic wave absorber that is attached on the ground plate except for an area where the plurality of unit antennas are attached and absorbs the electromagnetic wave. 
         [0018]    Preferably the ground plate is formed of a metal material. 
         [0019]    Preferably the reader includes at least two readers that apply a predetermined frequency signal to the at least two antenna units arranged on each of the at least two gate frames so as to emit electromagnetic wave. 
         [0020]    Preferably the reader is a reader that apply a predetermined frequency signal to the at least two antenna units arranged on each of the at least two gate frames so as to emit electromagnetic wave. 
         [0021]    Preferably the reader enables the at least two antenna units arranged in each of the at least two gate frames to emit electromagnetic wave alternately. 
         [0022]    Preferably the reader applies an ultra high frequency band signal to the at least two antenna units so as to emit electromagnetic wave. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0023]    The accompanying drawings, which are included to provide a further understanding of the disclosure and are incorporated in and constitute a part of this application, illustrate embodiments of the disclosure and together with the description, serve to explain the principle of the disclosure. In the drawings: 
           [0024]      FIG. 1  is a schematic constructional view illustrating a general gate system; 
           [0025]      FIG. 2  is a schematic plane view illustrating a construction of an antenna units used in a general gate system; 
           [0026]      FIG. 3  is a view explaining an intensity of a reflected wave generating in an antenna unit that is used in a general gate system; 
           [0027]      FIG. 4  is a constructional view illustrating a gate system according to a preferred embodiment of a present disclosure; 
           [0028]      FIGS. 5   a  and  5   b  are a plane view illustrating a construction of an antenna unit used in a gate system according to the present disclosure and a sectional view taken along line A-A, respectively; 
           [0029]      FIG. 6  is a view explaining an intensity of a reflected wave occurring in an antenna unit that is used in a gate system of the present disclosure; 
           [0030]      FIGS. 7   a  and  7   b  are views illustrating intensity results of reflected waves occurring in antenna units that are used in a general gate system and a gate system of the present disclosure, respectively. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0031]    Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. In this procedure, size and shape of the components shown in the drawings may be exaggerated for the sake of clarity and convenience. Further, terms that are specifically defined in consideration of construction and operation of the present disclosure may be changed according to operator&#39;s intention or custom. Definition of such items should be made on the basis of entire contents of the specification. 
         [0032]    Hereinafter, a detailed description is an embodiment of the present disclosure only and nothing but an illustration. Further, principle and concept of the present disclosure are provided for the purpose of describing the present disclosure with ease. 
         [0033]    Accordingly, a detailed construction that is not necessarily needed to take a basic understanding of the present disclosure is not of course provided and various forms embodied by those skilled in the art in a substance of the present disclosure are illustrated through the drawings 
         [0034]      FIG. 1  is a schematic constructional view illustrating a general gate system. Reference numerals  100  and  110  denote gate frames, respectively. The gate frames  100  and  110  are vertically arranged to face each other. 
         [0035]    Further, the gate frames  100  and  110  have antenna units  102  and  112  arranged to face each other. 
         [0036]    Reference numeral  120  denotes a monitoring camera. The monitoring camera  120  is arranged on any one of the gate frames  100  and  110 , for example, on the gate frame  100  and then takes a picture of an article  130  having a tag  132  attached thereto that passes between the gate frames  100  and  110 . 
         [0037]    The gate system having such a construction has a reader (not shown) that generates a predetermined frequency signal and applies it to the antenna units  102  and  112 . 
         [0038]    Then, the antenna units  102  and  112  generate and emit electromagnetic wave signals according to the predetermined frequency signal. 
         [0039]    In such a state, when a purchaser who wishes to purchase a desired article having a tag  132  attached thereto passes between the gate frames  100  and  110 , the tag  132  receives electromagnetic wave emitted from the antenna units  102  and  112  and generates energy. The tag  132  normally operates using the energy so that it transmits information of the article  130  that has been stored in advance in the tag. 
         [0040]    The antenna units  102  and  112  receive the information of the article  130  that is transmitted by the tag  132  and the information of the article  130  is input to the reader. 
         [0041]    Then, the reader analyzes the information of the article  130  input and determines kind and price of the article  130 . 
         [0042]    Further, when the tag  132  passes between the gate frames  100  and  110 , there may be a case that the tag  132  does not operate normally and the reader can not obtain information. 
         [0043]    Therefore, the monitoring camera  120  takes a picture of the article  130  having a tag  132  attached thereto that passes between the gate frames  100  and  110 , and analyzes information of the article using a taken image of the article  130 . 
         [0044]      FIG. 2  is a schematic plane view illustrating antenna units  102  and  112  used in a general gate system. Here, a reference numeral  200  denotes a ground plate made of metal. An upper surface of the ground plate  200  has a plurality of antennas  210  arranged in an array. For example, the plurality of antennas  210  is arranged in a 4×4 array. The plurality of antennas  210  emits electromagnetic wave according to a predetermined frequency signal output by the reader, receives information of the article  130  transmitted by the tag  132  and provides the reader with it. 
         [0045]    In such a gate system, the reader generates a high frequency (HF) band signal having a frequency of 13.56 MHz and outputs it to the antenna units  102  and  112 . Further, recently, the reader recognizes the tag  132  as the antenna units  102  and  112  enable the antenna units  102  and  112  to emit electromagnetic wave using the ultra high frequency (UHF) band signal. 
         [0046]    However, since the antenna units  102  and  112  arranged facing each other have a plurality of antennas  210  in a 4×2 array on the ground plate  200  made of metal, electromagnetic wave emitted from the antenna units  102  and  112  is reflected on the ground plate  200  of the antenna units  102  and  112 . Due to the electromagnetic wave reflected on the ground plate  200 , an error frequently occurred that a tag  132  positioned adjacently to gate frames  100  and  110  as well as the tag  132  passing between the gate frames  110  and  110  was recognized. 
         [0047]    For example, as illustrated in  FIG. 3 , a reflected wave is generated when electromagnetic wave emitted from the antenna  210  of the antenna unit  102  arranged in the gate frame  100  is reflected on the ground plate  200  of the antenna unit  112  arranged in the gage frame  110 . 
         [0048]    In the case of using the UHF band signal, since intensity of the reflected wave that is reflected on the ground plate  200  is so high that its recognition distance reaches about 5 cm. Therefore, an error frequently occurred that the tag  132  positioned adjacently to the gate frames  100  and  110  other than the tag  132  passing between the gate frames  100  and  110  was recognized. 
         [0049]      FIG. 4  is a constructional view illustrating a gate system according to a preferred embodiment of a present disclosure. Here, reference numerals  400  and  410  denote gate frames arranged facing each other. The gate frames  400  and  410  have antenna units  420  and  430  arranged facing each other, and readers  440  and  450  are arranged on the antenna units  420  and  430  to apply a predetermined frequency signal and recognize tag information. 
         [0050]    The antenna units  420  and  430  each include a plurality of array antennas  442  and  432 , for example. The plurality of array antennas  422  and  432  each include a plurality of unit antenna  510  on the ground plate  500  made of metal arranged as illustrated in  FIGS. 5   a  and  5   b , and an electromagnetic wave absorber  520  arranged on the surface of the ground plate  500  that is exposed externally, except for the area of the ground plate  500  where the plurality of unit antennas are arranged. 
         [0051]    When the gate system of the present disclosure constructed as described above recognizes the tag, the readers  440  and  450  generate a predetermined frequency signal and the generated predetermined frequency signal is applied to each of the plurality of unit antennas  510  of the plurality of array antennas  422  and  432  included in the antenna units  420  and  430 . 
         [0052]    Then, the each of plurality of unit antennas  510  each generates electromagnetic wave according to the applied predetermined frequency signal and emits it in the forward direction. 
         [0053]    Here, the generated predetermined frequency signal applied to the plurality of unit antennas  510  of the plurality of array antennas  422  and  432  included in each of the antenna units  420  and  430  using any one of the readers  440  and  450 . 
         [0054]    Further, in order to reduce recognition error of the tag, when the readers  440  and  450  generate a predetermined frequency signal so that the plurality of unit antennas  510  each emits electromagnetic wave, it is desirable that the plurality of unit antennas  510  of the plurality of array antennas  422  and  432  included in each of the antenna units  420  and  430  emits electromagnetic wave alternately. 
         [0055]    For example, when the plurality of unit antennas  510  of the plurality of array antennas  422  included in each of the antenna unit  420  emits electromagnetic wave, the plurality of unit antennas  510  of the plurality of array antennas  432  included in each of the antenna unit  430  does not emit electromagnetic wave. Further, when the plurality of unit antennas  510  of the plurality of array antennas  420  included in each of the antenna unit  430  emits electromagnetic wave, the plurality of unit antennas  510  of the plurality of array antennas  422  included in each of the antenna unit  420  does not emit electromagnetic wave. 
         [0056]    The electromagnetic wave emitted from the plurality of unit antennas  510  advances to the gate frame  400  and  410  positioned ahead. For example, assuming that the plurality of unit antennas  510  of the plurality of array antennas  422  included in each of the antenna unit  420  emits electromagnetic wave as illustrated in  FIG. 6 , the emitted electromagnetic wave can be propagated to the plurality of array antennas  432  of the antenna unit  430  included in the gate frame  410 . In this case, the electromagnetic wave emitted by the plurality of unit antennas of the array antenna  422  may interfere with the electromagnetic wave emitted by the plurality of unit antennas of the array antennas  432 . Further, the electromagnetic wave emitted by the array antenna  422  may hit the array antenna  432  and then be reflected on it. 
         [0057]    Here, the plurality of array antennas  422  and  432  each has the plurality of unit antennas  510  partly arranged on the ground plate made of metal and an electromagnetic wave absorber  520  attached on the front surface of the ground plate  500  except for an area where the plurality of unit antennas  510  are arranged. 
         [0058]    Therefore, most of the electromagnetic wave hit on the plurality of array antennas  430  of the antenna unit  430  included in the gate frames  410  is absorbed by the electromagnetic wave absorber  520 , and the readers  440  and  450  detect information of the tag passing between the gate frames  400  and  410  only, not that of the tag  132  positioned adjacently to the gate frames  400  and  410 . 
         [0059]      FIGS. 7   a  and  7   b  are views illustrating measured intensities of reflected waves generated in antenna units used in a general gate system and a gate system according to the present disclosure. Referring to  FIG. 7   a , an intensity of electromagnetic wave generated in the antenna units  102  and  112  that are used in a general gate system was very high. 
         [0060]    However, in the gate system of the present disclosure, most of the electromagnetic wave emitted as illustrate in  FIG. 7   b  is absorbed by the electromagnetic wave absorber  520  and electromagnetic wave of very thin intensity only is emitted. 
         [0061]    Accordingly, it may be possible to precisely detect information of the tag passing between the gate frames  400  and  410  and it may not possible to obtain information of the tag positioned adjacently to the gate frames  400  and  410  that does not pass between the gate frames  400  and  410 . 
         [0062]    Hereinbefore, while the embodiments of the present disclosure are described, they are exemplary ones only and one of ordinary skill in the art may recognize that various alterations and modifications that fall within the scope of the present disclosure may be possible. Accordingly, the true technical protection scope of the present disclosure should be defined by the following claims.