Patent Publication Number: US-9407007-B2

Title: Antenna structure in wireless communication system and operation method thereof

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) AND CLAIM OF PRIORITY 
     The present application is related to and claims the benefit under 35 U.S.C. §119(a) of a Korean patent application filed in the Korean Intellectual Property Office on Mar. 14, 2012 and assigned Serial No. 10-2012-0026134, the entire disclosure of which is hereby incorporated by reference. 
     TECHNICAL FIELD 
     The present disclosure relates to a wireless communication system. More particularly, the present disclosure relates to an antenna structure for supporting multi-frequency bands and an operation method thereof. 
     BACKGROUND 
     As various wireless communication technologies for supporting different frequency bands have been provided, technologies for effectively supporting multi-frequency bands have been researched and developed. For example, a wireless communication system has used a method of having a separate transmission and reception module while being classified according to each of frequency bands to support multi-frequency bands. 
       FIG. 1  illustrates a transmission and reception module of a Base Station (BS) for supporting multi-frequency bands. 
     As shown in  FIG. 1 , each of a macro BS  100 - 1  and a distributed BS  100 - 2 , which supports multi-frequency bands of f 1  to f 4 , includes a separate transmission and reception module for supporting each of the multi-frequency bands of f 1  to f 4 . However, as described above, the method in which the BS includes the number of corresponding transmission and reception modules to support a plurality of frequency bands has a problem in that the more the number of supported frequency bands is increased, the more a hardware size is increased. 
     Therefore, recently, in order to miniaturize a size of the BS which supports the multi-frequency bands, there has been a method of reducing a separation distance of an antenna array configuring an antenna unit. However, there is a limit to miniaturize the size of the BS using only the method of the separation distance of the antenna array. 
     SUMMARY 
     To address the above-discussed deficiencies, embodiments of the present disclosure provide an antenna structure in a wireless communication system and an operation method thereof. 
     Certain embodiments of the present disclosure provide an antenna structure for combining and integrating a dipole antenna and a loop antenna in a wireless communication system and an operation method thereof. 
     Certain embodiments of the present disclosure provide a method and apparatus for configuring an antenna array using antennas in which a dipole antenna and a loop antenna are combined and integrated the combined antenna in a wireless communication system. 
     Certain embodiments of the present disclosure provide a method and apparatus for supporting two frequency bands through an antenna array configured using antennas in which a dipole antenna and a loop antenna are combined and integrated in a wireless communication system. 
     In accordance with certain embodiments of the present disclosure, an antenna device in a wireless communication includes antenna wires of four sides. The antenna wires of four sides include three feeding points and have a loop structure and four main switches, which are located among the antenna wires of the four sides. The antenna device operates as a loop antenna when the antenna wires of the four sides are connected according to operations of the main switches, and the antenna device operates as dipole antennas when the antenna wires of the four sides are disconnected according to operations of the main switches. 
     In accordance with certain embodiments of the present disclosure, an antenna array device in a wireless communication includes a plurality of antenna elements. Each of the antenna elements have a predetermined separation distance, wherein each of the antenna elements which has a structure in which a dipole antenna is integrated in each of both sides of one loop antenna, and wherein each of the antenna elements supports different two frequency bands. 
     Before undertaking the DETAILED DESCRIPTION below, it may be advantageous to set forth definitions of certain words and phrases used throughout this patent document: the terms “include” and “comprise,” as well as derivatives thereof, mean inclusion without limitation; the term “or,” is inclusive, meaning and/or; the phrases “associated with” and “associated therewith,” as well as derivatives thereof, may mean to include, be included within, interconnect with, contain, be contained within, connect to or with, couple to or with, be communicable with, cooperate with, interleave, juxtapose, be proximate to, be bound to or with, have, have a property of, or the like; and the term “controller” means any device, system or part thereof that controls at least one operation, such a device may be implemented in hardware, firmware or software, or some combination of at least two of the same. It should be noted that the functionality associated with any particular controller may be centralized or distributed, whether locally or remotely. Definitions for certain words and phrases are provided throughout this patent document, those of ordinary skill in the art should understand that in many, if not most instances, such definitions apply to prior, as well as future uses of such defined words and phrases. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a more complete understanding of the present disclosure and its advantages, reference is now made to the following description taken in conjunction with the accompanying drawings, in which like reference numerals represent like parts: 
         FIG. 1  illustrates a transmission and reception module of a BS for supporting multi-frequency bands according to the present disclosure; 
         FIG. 2  illustrates a loop-dipole antenna in which a dipole antenna and a loop antenna are combined according to embodiments of the present disclosure; 
         FIG. 3  illustrates a detailed structure of a loop-dipole antenna according to embodiments of the present disclosure; 
         FIG. 4  illustrates a separation distance between loop-dipole antennas according to embodiments of the present disclosure; 
         FIGS. 5A to 5C  illustrate a structure of an antenna array which is equipped with loop-dipole antennas and an operation method of the antenna array according to embodiments of the present disclosure; and 
         FIG. 6A  illustrates an antenna array integrated structure of a BS of  FIG. 1  for supporting multi-frequency bands; and 
         FIG. 6B  illustrates an antenna array integrated structure of a BS for supporting multi-frequency bands according to embodiments of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
       FIGS. 2 through 6B , discussed below, and the various embodiments used to describe the principles of the present disclosure in this patent document are by way of illustration only and should not be construed in any way to limit the scope of the disclosure. Those skilled in the art will understand that the principles of the present disclosure can be implemented in any suitably arranged wireless communication system or device. Exemplary embodiments of the present disclosure will be described herein below with reference to the accompanying drawings. In the following description, well-known functions or constructions are not described in detail because they would obscure the invention in unnecessary detail. Also, the terms used in the present disclosure are defined according to the functions of the elements of the present disclosure and can vary depending on user or operator&#39;s intention and usage. That is, the terms used herein should be understood based on the descriptions made throughout the present disclosure. 
     Embodiments of the present disclosure provide a structure of an antenna, in which a dipole antenna and a loop antenna are combined, for supporting two frequency bands and an operation method thereof. 
       FIG. 2  illustrates an antenna of a type in which a loop antenna and a dipole antenna are combined according to embodiments of the present disclosure. 
     As shown in  FIG. 2 , an antenna  221  has a type in which a loop antenna  201  and dipole antennas  211  and  213  are integrated in one structure. Hereinafter, for the convenience of description, the loop antenna  201  are described with reference to a square loop antenna, which is a resonant antenna that operates wherein the sum of the lengths of the four sides of the entire loop is 1λ, and each side thereof is λ/4 in length. The dipole antennas  211  and  213  are described with reference to half wavelength dipole antennas, each of the dipole antennas  211  and  213  operates with a half wavelength length of a center frequency. However, the present disclosure is not limited to the half wavelength dipole antenna and the square loop antenna, and can be also applied to a dipole antenna of a different shape and a loop antenna of a different shape. Hereinafter, for the convenience of description, the antenna  221  of the type in which the loop antenna  201  and the dipole antennas  211  and  213  are combined and integrated is referred to as a loop-dipole antenna. 
       FIG. 3  illustrates a detailed structure of a loop-dipole antenna in which a loop antenna and dipole antennas are combined according to embodiments of the present disclosure. 
     Referring to  FIGS. 2 and 3 , the loop-dipole antenna denoted by  221  includes first to fourth switches  301  to  304 , first and second feeding points  311  and  313  for operations of dipole antennas, and a third feeding point  321  for an operation of a loop antenna. 
     The first to fourth switches  301  to  304  can operate as one loop antenna  201  or two dipole antennas  211  and  213  through switching. That is, when the first to fourth switches  301  to  304  are simultaneously turned off, a wire of four sides of the loop-dipole antenna  221  is divided. Accordingly, wires of symmetric both sides of the loop-dipole antenna  221  can operate as the dipole antennas  211  and  213  by the first and second feeding points  311  and  313  of the symmetric both sides thereof. On the other hand, when the first to fourth switches  301  to  304  are simultaneously turned on, all the wires of the four sides of the loop-dipole antenna  221  are connected with one other. Accordingly, the loop-dipole antenna  221  can operate as the loop antenna  201  by the third feeding point  321 . 
     In accordance with embodiments of the present disclosure, the first to fourth switches  301  to  304  are described above with reference to when they are located on vertices of the loop-dipole antenna  221 . However, the first to fourth switches  301  to  304  can be disposed in certain positions where wires of both sides including the first and second feeding points  311  and  313  have the same length when they are turned off. That is, the first to fourth switches  301  to  304  can be disposed in certain positions where the two dipole antennas  211  and  213 , which operate when they are turned off, have the same length. 
     The first and second feeding points  311  and  313  are symmetrically located on both sides of the loop-dipole antenna  221  and supply current such that the corresponding both sides thereof operate as the dipole antennas  211  and  213 . Particularly, in accordance with embodiments of the present disclosure, each of the first and second feeding points  311  and  313  includes a switch  331 . 
     When the switches  331  included in each of the first and second feeding points  311  and  313  are turned on/off, both wires of the corresponding feeding point are connected or disconnected. Accordingly, the loop-dipole antenna  221  operates as the loop antenna  201  or the dipole antennas  211  and  213 . That is, the switch  331  in the first feeding point  311  disconnects both wires of the first feeding point  311  such that the loop-dipole antenna  221  operates as the two dipole antennas  211  and  213 , or the switch  331  connects both the wires of the first feeding point  311  such that the loop-dipole antenna  221  operates as the one loop antenna  201 . When the switch  331  included in the first feeding point  311  is turned on and both the wires of the first feeding point  311  are connected with each other, a resistance value of a feeding line  333  of the first feeding point  311  is greater than a resistance value of both the wires connected to the switch  331 . Accordingly, the feeding line  333  does not influence the loop-dipole antenna  221  operations as the loop antenna  201 . 
     The third feeding point  321  supplies current such that the loop-dipole antenna  221  operates as the loop antenna. Herein, the third feeding point  321  for supplying current for an operation of the loop antenna and the first and second feeding points  311  and  313  for supplying current for operations of the dipole antennas exist on different sides of the loop-dipole antenna  221 . That is, a side including the third feeding point  321  is orthogonal to both sides that include the first and second feeding points  311  and  313 . 
     As described above, the loop-dipole antenna  221  can operate as the one loop antenna  201  or as the two dipole antennas  211  and  213  by turning on/off the first to fourth switches  301  to  304  and the switch  331  included in each of the first and second feeding points  311  and  313  according to control of a controller (not shown). In certain embodiments, a frequency band supported when the loop-dipole antenna  221  operates as the loop antenna  201  differs from a frequency band supported when the loop-dipole antenna  221  operates as the dipole antennas  211  and  213 . In certain embodiments, the frequency band supported by each of the loop antenna  201  and the dipole antennas  211  and  213  of the loop-dipole antenna  221  can be changed according to a length of each of the loop antenna  201  and the dipole antennas  211  and  213 . Particularly, the frequency band supported by the dipole antennas  211  and  213  can be changed according to positions of the first to fourth switches  301  to  304 . For example, when the first to fourth switches  301  to  304  are located on vertices of the loop-dipole antenna  221  and when the first to fourth switches  301  to  304  are symmetrically located on both wires that include the first and second feeding points  311  and  313 , the dipole antennas  211  and  213  support different frequency bands. 
     Also, as described above, when the first to fourth switches  301  to  304  is turned off and both the sides of the loop-dipole antenna  221  operate as the dipole antennas  211  and  213  according to embodiments of the present disclosure, sides of the loop-dipole antenna  221 , except for both the dipole antenna sides of the loop-dipole antenna  221  are orthogonal to both the sides that operate as the dipole antennas  211  and  213 . Accordingly, the side(s) except for both the dipole antenna sides do not influence operation of the dipole antenna  211  and  213 . 
     Certain embodiments of the present disclosure include a method of configuring an antenna array using loop-dipole antennas. 
       FIG. 4  illustrates a separation distance between loop-dipole antennas according to embodiments of the present disclosure. 
     As shown in  FIG. 4 , in case of square loop-dipole antennas  401  and  403  according to embodiments of the present disclosure, a length of a side on each is shown in Equation 1 below. 
     
       
         
           
             
               
                 
                   
                     A 
                     = 
                     
                       
                         
                           λ 
                           1 
                         
                         4 
                       
                       = 
                       
                         
                           λ 
                           2 
                         
                         2 
                       
                     
                   
                   , 
                   
                     
                       λ 
                       1 
                     
                     = 
                     
                       λ 
                       2 
                     
                   
                 
               
               
                 
                   ( 
                   1 
                   ) 
                 
               
             
           
         
       
     
     Herein, A  411  denotes a length of each of four sides that compose each of the loop-dipole antennas  401  and  403 . λ 1  denotes a corresponding wavelength when each of the loop-dipole antennas  401  and  403  operates as a loop antenna. λ 2  denotes a corresponding wavelength when each of the loop-dipole antennas  401  and  403  operates as dipole antennas. That is, the length A  411  of each of the four sides of the loop-dipole antennas  401  and  403  can be determined using a characteristic of a loop antenna that operates when a length of one side thereof is λ/4 and a characteristic of dipole antennas that operate with a λ/2 length. 
     Also, when an antenna array is configured using a plurality of loop-dipole antennas  401  and  403 , a separation distance between the loop-dipole antennas  401  and  403  is shown in the system of equations in Equation (2). 
     
       
         
           
             
               
                 
                   
                     D 
                     = 
                     
                       
                         λ 
                         1 
                       
                       2 
                     
                   
                   ⁢ 
                   
                     
 
                   
                   ⁢ 
                   
                     d 
                     = 
                     
                       
                         D 
                         - 
                         
                           2 
                           × 
                           
                             
                               λ 
                               1 
                             
                             8 
                           
                         
                       
                       = 
                       
                         
                           
                             λ 
                             1 
                           
                           4 
                         
                         = 
                         
                           
                             λ 
                             2 
                           
                           2 
                         
                       
                     
                   
                 
               
               
                 
                   ( 
                   2 
                   ) 
                 
               
             
           
         
       
     
     Herein, D  413  denotes a separation distance between center points of the loop-dipole antennas  401  and  403 . While d ( 415  denotes a separation distance between adjacent sides of the loop-dipole antennas  401  and  403 . That is, the separation distance D  413  between the center axes of the loop-dipole antennas  401  and  403  for configuring, the antenna array and the separation distance d  411  between sides of the loop-dipole antennas  401  and  403  can be determined such that a separation distance between loop antennas is  212  when each of the loop-dipole antennas  401  and  403  operates as the loop antenna  201  of  FIG. 2 . The separation distance D  413  and the separation distance d  411  can be determined such that the separation distance between dipole antennas is  212  when each of the loop-dipole antennas  401  and  403  operates as the dipole antennas  211  and  213  of  FIG. 2 . 
       FIGS. 5A to 5C  illustrate a structure of an antenna array equipped with loop-dipole antennas and an operation method thereof according to embodiments of the present disclosure. 
     As shown in  FIG. 5A , an antenna array can be configured using a plurality of loop-dipole antennas according to embodiments of the present disclosure. Herein, a length of each of the loop-dipole antennas, a length of each of four sides in each of the loop-dipole antennas, and a separation distance between the loop-dipole antennas can be determined according to Equations (1) and (2) based on frequencies to be supported in a corresponding system. The antenna array can operate as a loop antenna array and can support a low frequency band f L , or can operate as a dipole antenna array and can support a high frequency band f H , by turning on/off switches thereof according to control of a controller (not shown). 
     That is, as shown in  FIG. 5B , an antenna array equipped with four loop-dipole antennas can operate as an antenna array equipped with four loop antennas and supports a low frequency band f L  by turning on switches thereof according to control of the controller (not shown). In certain embodiments, a separation distance between the loop antennas is a half wavelength. 
     Also, as shown in  FIG. 5C , an antenna array equipped with four loop-dipole antennas operates as an antenna array equipped with eight dipole antennas and supports a high frequency band f H  by turning off switches thereof according to control of the controller (not shown). In certain embodiments, a separation distance between the dipole antennas is a half wavelength. 
     As described above, it is ideal that the high frequency band f H  is twice as likely as the low frequency band f L  to have frequencies. However, in applied practice the high frequency band f H  is not twice as likely as the low frequency band  11  to have frequencies according to positions of switches included in each of the loop-dipole antennas. 
       FIG. 6A  illustrates an antenna array integrated structure of a BS for supporting multi-frequency bands according to  FIG. 1  and  FIG. 6B  illustrates a BS for supporting multi-frequency bands according to embodiments of the present disclosure. Herein, it is assumed that the BS according to  FIG. 6A  and the BS of  FIG. 6B  according to embodiments of the present disclosure support multi-frequency bands of f 1  to f 4 . 
     Referring to  FIGS. 6A and 6B , the BS according to  FIG. 6A  includes separate antenna arrays which are configured while being classified according to a frequency band of each of f 1  to f 4 . However, the BS of  FIG. 6B  using a loop-dipole antenna according to embodiments of the present disclosure includes one antenna array while being classified according to two frequency bands. That is, the BS of  FIG. 6B  includes an antenna array for supporting frequency bands of f 1  and f 2  and an antenna array for supporting frequency bands of f 3  and f 4  using the loop-dipole antenna. Accordingly, an antenna module of the BS of  FIG. 6B  can be reduced in size by 50% in comparison with an antenna module of the BS of  FIG. 6A . 
     An antenna device according to embodiments of the present disclosure can reduce a size of a BS through an antenna structure for supporting two frequency bands by combining and integrating a dipole antenna and a loop antenna in a wireless communication system for supporting multi-frequency bands. Also, an antenna device according to embodiments of the present disclosure can configure an antenna array easily by securing a separation distance between positions of feeding points between a dipole antenna and a loop antenna. Also, an antenna device according to embodiments of the present disclosure can implement an antenna array at low cost by using only a dipole antenna and loop antenna. Also, an antenna device according to embodiments of the present disclosure can reduce an error generation probability generated due to a simple structure. 
     While the present disclosure has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present disclosure as defined by the appended claims.