Abstract:
Disclosed is a circular array antenna. The circular array antenna includes: an input/output unit receiving electromagnetic waves from a transmitter and distributing the received electromagnetic waves to the antenna; a primary feeder connected with the input/output unit and placed at the center of the circular array antenna; a plurality of secondary feeders radially connected to the primary feeder; a plurality of patch units connected to the respective secondary feeders to generate an electric field radially; and a plurality of length controllers formed at terminals of the respective secondary feeders in a direction to extend the lengths of the respective secondary feeders, of which the lengths are controllable.

Description:
[0001]    This application claims the benefit of priority of Korean Patent Application No. 10-2014-0069454 filed on 9 Jun., 2014, which is incorporated by reference in its entirety herein. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to wireless communication, and more particularly, to a circular array antenna. 
         [0004]    2. Discussion of the Related Art 
         [0005]    In modern times, a demand for a service that transmits and receives mass data such as video, voice, and the like at a high speed has been rapidly increased. As a result, in recent years, in order to increase a data capacity in a high-speed point-to-point system under a visible distance environment, a research into communication using an orbital angular momentum (OAM) has been actively made worldwide in Sweden, Italia, Japan, Australia, and the like. 
         [0006]    The OAM was predicted by Poynting in 1909 and thereafter, introduced in an optical field in 1992 and thus an active research has been in progress. Further, an applicability of the OAM in electromagnetic wave and a microwave fields was presented in 2007. 
         [0007]    As a device for generating an OAM mode, a metallic reflection plate and an exciton element are used, but the metallic reflection plate and the exciton element has a form of a 3D structure, and as a result, the metallic reflection plate and the exciton element are influenced by wind or rainfall, snowfall, and the like. 
         [0008]    Accordingly, in the technical field, an antenna device not influenced by the wind or the rainfall, the snowfall, and the like is required. 
       SUMMARY OF THE INVENTION 
       [0009]    An object of the present invention is to provide a  2 D plane structure antenna generating an orbital angular momentum mode radiation pattern. 
         [0010]    Another object of the present invention is to provide an antenna of an orbital angular momentum mode radiation pattern not influenced by wind or rainfall, snowfall, and the like. 
         [0011]    In accordance with an embodiment of the present invention, a circular array antenna is provided. The circular array antenna includes: an input/output unit receiving electromagnetic waves from a transmitter and distributing the received electromagnetic waves to the antenna; a primary feeder connected with the input/output unit and placed at the center of the circular array antenna; a plurality of secondary feeders radially connected to the primary feeder; a plurality of patch units connected to the respective secondary feeders to generate an electric field radially; and a plurality of length controllers formed at terminals of the respective secondary feeders in a direction to extend the lengths of the respective secondary feeders, of which the lengths are controllable. 
         [0012]    The lengths of the plurality of respective length controllers may be set so that direction of electric field vectors generated in the plurality of patch units are all formed in the same direction. 
         [0013]    The circular array antenna may be formed on one same plane. 
         [0014]    All of the plurality of secondary feeders may have the same length. 
         [0015]    All of the patch units may be connected to the plurality of secondary feeders at the same interval. 
         [0016]    The primary feeder may be formed in a ring type of which one side is opened. 
         [0017]    The primary feeder may be formed in a triangular shape or a quadrangular shape of which one side is opened. 
         [0018]    The patch unit may be formed in a circular shape. 
         [0019]    In accordance with another embodiment of the present invention, a circular array antenna is provided. The circular array antenna includes: an input/output unit receiving electromagnetic waves from a transmitter and distributing the received electromagnetic waves to the antenna; a primary feeder connected with the input/output unit and placed at the center of the circular array antenna; a plurality of secondary feeders radially connected to the primary feeder; a plurality of patch units connected to the respective secondary feeders to generate an electric field radially; and a plurality of length controllers formed between the respective secondary feeders and the respective patch units, of which the lengths are controllable. 
         [0020]    The lengths of the plurality of respective length controllers may be set so that direction of electric field vectors generated in the plurality of patch units are all formed in the same direction. 
         [0021]    The circular array antenna may be formed on one same plane. 
         [0022]    All of the plurality of secondary feeders may have the same length. 
         [0023]    All of the patch units may be connected to the plurality of secondary feeders at the same interval. 
         [0024]    The primary feeder may be formed in a ring type of which one side is opened. 
         [0025]    The primary feeder may be formed in a triangular shape or a quadrangular shape of which one side is opened. 
         [0026]    The patch unit may be formed in a comb line shape. 
         [0027]    The circular array antenna may further include a plurality of connectors formed between the respective length controllers and the respective patch units so that the respective length controls and the respective patch units are separated from each other. 
         [0028]    The patch unit may be formed in a square shape. 
         [0029]    The patch unit may be formed in any one shape of a rectangular shape, a circular shape, a triangular shape, and a cross shape. 
         [0030]    According to the present invention, there is provided a  2 D plane structure antenna generating an orbital angular momentum mode radiation pattern not influenced by wind or rainfall, snowfall, and the like. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0031]      FIG. 1  is a plan view of a circular array antenna according to an embodiment of the present invention; 
           [0032]      FIG. 2  is a plan view of a circular array antenna according to another embodiment of the present invention; and 
           [0033]      FIG. 3  is a plan view of a circular array antenna according to yet another embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
       [0034]    The present invention will be described more fully hereinafter with reference to the accompanying drawings, in which embodiments of the invention are shown. However, the present invention can be realized in various different forms, and is not limited to the embodiments described herein. Accordingly, the drawings and description are to be regarded as illustrative in nature and not restrictive. Like reference numerals designate like elements throughout the specification. 
         [0035]    In the specification, unless explicitly described to the contrary, the word “comprise” and variations such as “comprises” or “comprising”, will be understood to imply the inclusion of stated elements but not the exclusion of any other elements. Further, terms including “unit” disclosed in the specification mean a unit that processes at least one function or operation and this may be implemented by hardware or software or a combination of hardware and software. 
         [0036]    Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. 
         [0037]      FIG. 1  is a plan view of a circular array antenna according to an embodiment of the present invention. 
         [0038]    Referring to  FIG. 1 , the circular array antenna according to the embodiment is configured to include an input/output unit  110 , a primary feeder  130 , a secondary feeder  150 , a patch unit  170 , and a length controller  190 . 
         [0039]    The input/output unit  110  may serve as a passage through an electromagnetic wave generated from a transmitter into an antenna in a transmission mode and serve as a passage through which the electromagnetic wave reaching the antenna is transmitted to a receiver in a reception mode. In the embodiment, a process in which the electromagnetic wave generated from the transmitter is input into the antenna through the input/output unit  110  and a radio wave is emitted will be described. The input/output unit  110  may be directly connected to the primary feeder  130  by using a coaxial cable and indirectly connected by using a slot, and the like. 
         [0040]    The primary feeder  130  sequentially distributes the electromagnetic wave input from the input/output unit  110  to the secondary feeder  150  configured by a microstrip line. In the embodiment, the primary feeder  130  is configured in a circular shape, but may be transformed to various shapes such as a triangular shape, a quadrangular shape, and the like for easiness of a design, and the like. 
         [0041]    The secondary feeder  150  supplies the electromagnetic wave input from the primary feeder  130  to the patch unit  170 . The patch unit  170  receives the electromagnetic wave from the secondary feeder  150  to form a radiation wave. The secondary feeder  150  and the patch unit  170  are together bound to be defined as a sub array. When the electromagnetic wave is supplied to the input/output unit  110 , the electromagnetic waves are sequentially supplied to respective secondary feeders  151  and  153  from the primary feeder  130  and the radiation wave is generated through the patch unit  170 . In this case, an electric field direction of the generated radiation wave needs to be constant. However, since the sub array constituted by the secondary feeder  153  and the circular patch  173  extends in a different direction from the sub array constituted by the secondary feeder  151  and the patch unit  171 , generation direction of the radiation wave are different from each other. Therefore, the length controller  190  which may control the length of the secondary feeder in an extension direction is formed at a terminal of the secondary feeder  150 , and as a result, the length may be set so that the directions of the electric fields are the same as each other. When the length of the length controller  191  is ¼ wavelength (λ), the electric field direction of the sub array constituted by the secondary feeder  150  and the patch array may be a y-z direction. However, when the length of the length controller  193  is configured by ¼ wavelength similarly to the length controller  191 , the electric field direction of the sub array constituted by the secondary feeder  153  and the patch unit  173  is a direction different from the y-z direction. In this case, the electric field may be formed in the y-z direction by controlling the length of the length controller  193 . For example, the electric field may be formed in the y-z direction by controlling the length of a tuning line  191  to be short. The electric field direction may be configured to be formed in the y-z direction by controlling the length of the length controller  190  with respect to all secondary feeders  150  connected to the primary feeder  130 . A method for configuring the electric field direction to be the y-z direction has been described in the embodiment, but the electric field directions may be configured to be homogenized as different directions according to the lengths of the length controllers  191  and  193 . The patch unit  173  has a circular shape in  FIG. 1 , but the patch unit  173  may have various shapes such as a ring or a circular slot. 
         [0042]      FIG. 2  is a plan view of a circular array antenna according to another embodiment of the present invention. 
         [0043]    Referring to  FIG. 2 , the circular array antenna according to the embodiment is configured to include an input/output unit  210 , a primary feeder  230 , a secondary feeder  250 , a length controller  270 , and a patch unit  270 . 
         [0044]    The input/output unit  210  may serve as a passage through an electromagnetic wave generated from a transmitter into an antenna in a transmission mode and serve as a passage through which the electromagnetic wave reaching the antenna is transmitted to a receiver in a reception mode. In the embodiment, a process in which the electromagnetic wave generated from the transmitter is input into the antenna through the input/output unit  210  and a radio wave is emitted will be described. The input/output unit  210  may be directly connected to the primary feeder  230  by using a coaxial cable and indirectly connected by using a slot, and the like. 
         [0045]    The primary feeder  230  sequentially distributes the electromagnetic wave input from the input/output unit  210  to the secondary feeder  250  configured by a microstrip line. In the embodiment, the primary feeder  230  is configured in a circular shape, but may be transformed to various shapes such as a triangular shape, a quadrangular shape, and the like for easiness of a design, and the like. 
         [0046]    The secondary feeder  250  supplies the electromagnetic wave input from the primary feeder  230  to the patch unit  290 . The patch unit  290  may generate an orbital angular momentum mode radiation pattern together with the secondary feeder  250 . When the electromagnetic wave is supplied to the input/output unit  210 , the electromagnetic waves are sequentially supplied to the respective secondary feeders  250  from the primary feeder  230  and the radiation wave is generated through the patch unit  290 . In this case, an electric field direction of the generated radiation wave needs to be constant. However, when the electric field direction of the radiation wave generated from the patch unit  291  connected to the secondary feeder  251  is set to a y-z direction, the electric field direction of the radiation wave generated from the patch unit  293  connected to the other secondary feeder  253  is different from the y-z direction. Therefore, the circular array antenna needs to be configured so that the radiation waves generated from the patch unit s 290  connected to the respective secondary feeders  250  form the electric field in the same direction. Accordingly, as illustrated in  FIG. 2 , all electric fields transmitted from a comb line may be set to be generated in the same direction by controlling the length of the length controller  270  between the patch unit  290  and the secondary feeder  250 . For example, when the length of the length controller  271  has a predetermined length and the electric field direction of the radiation pattern generated from the patch unit  291  is set to the y-z direction, the electric field direction of the radiation pattern generated from the patch unit  293  may be set to the y-z direction by controlling the length of the length controller  273  to be longer or shorter. A method for configuring the electric field direction to be the y-z direction has been described in the embodiment, but the electric field directions may be configured as different directions according to the length of the length controller  270 . The patch unit  290  is formed in the comb line shape in  FIG. 2 , but the shape of the patch unit  290  may be modified in various shapes. 
         [0047]      FIG. 3  is a plan view of a circular array antenna according to yet another embodiment of the present invention. 
         [0048]    Referring to  FIG. 3 , the circular array antenna according to the embodiment is configured to include an input/output unit  310 , a primary feeder  320 , a secondary feeder  330 , a length controller  350 , and a connector  370 . 
         [0049]    The input/output unit  310  may serve as a passage through an electromagnetic wave generated from a transmitter into an antenna in a transmission mode and serve as a passage through which the electromagnetic wave reaching the antenna is transmitted to a receiver in a reception mode. In the embodiment, a process in which the electromagnetic wave generated from the transmitter is input into the antenna through the input/output unit  310  and a radio wave is emitted will be described. The input/output unit  310  may be directly connected to the primary feeder  330  by using a coaxial cable and indirectly connected by using a slot, and the like. 
         [0050]    The primary feeder  320  sequentially distributes the electromagnetic wave input from the input/output unit  310  to the secondary feeder  330  configured by a microstrip line. In the embodiment, the primary feeder  320  is configured in a circular shape, but may be transformed to various shapes such as a triangular shape, a quadrangular shape, and the like for easiness of a design, and the like. 
         [0051]    The secondary feeder  330  supplies the electromagnetic wave input from the primary feeder  320  to the patch unit  390 . Similarly to the embodiment of  FIG. 2 , the circular array antenna according to the embodiment further includes a length controller  350  of which the length is controllable between the secondary feeder  330  and the patch unit  370  so as to constantly maintain the direction of the electric field vector regardless of the direction of the secondary feeder  330 . Meanwhile, in the embodiment, the circular array antenna may further include a connector  370  that makes the length controller  350  and the patch unit  390  be separated between the length controller  350  and the patch unit  390 . 
         [0052]    The patch unit  390  may generate a radiation wave together with the secondary feeder  330 . When the electromagnetic wave is supplied to the input/output unit  310 , the electromagnetic waves are sequentially supplied to respective secondary feeders  331  and  333  from the primary feeder  320  and the radiation wave is generated through the patch unit  390  via the length controller  350  and the connector  370 . In this case, an electric field direction of the generated radiation wave needs to be constant. However, when the electric field direction of the patch unit  391  connected to the secondary feeder  331  is set to the y-z direction, the electric field direction of the patch unit  393  connected to the other secondary feeder  333  is formed as a direction different from the y-z direction. Therefore, the patch units  391  and  393  connected to the respective secondary feeders  331  and  333  need to be set to form the electric field in the same direction. Therefore, electric field vectors forming directions of all radiation waves generated from the patch unit  390  may be set to coincide with each other by controlling the lengths of the length controllers  371  and  373 . A method for setting the electric field forming method of the radiation wave to the y-z direction has been described in the embodiment, but the electric field forming direction may be set to be homogenized to a direction different from the y-z direction by configuring the lengths of the length controllers  371  and  373  to be different. The patch unit  390  may have a square shape as illustrated in  FIG. 3  and as the patch unit  390 , patches having various shapes such as a rectangular shape, a circular shape, a triangular shape, an oval shape, a cross shape, and the like may be used. 
         [0053]    Various exemplary embodiments of the present invention have been just exemplarily described, and various changes and modifications may be made by those skilled in the art to which the present invention pertains without departing from the scope and spirit of the present invention. Accordingly, the various embodiments disclosed herein are not intended to limit the technical spirit but describe with the true scope and spirit being indicated by the following claims. The scope of the present invention should be interpreted by the appended claims, and all the technical spirit in the equivalent range should be interpreted to be embraced in the scope of the present invention.