Abstract:
The present invention relates to a multi-band antenna, which comprises: a first antenna array of a first band configured by a radiation module of the first band; a (2-1)th antenna array of a common band between a second band and third band, the (2-1)th antenna array including radiation modules for the common band between the second band and third band; a (2-1)th phase shifter for receiving an input signal of the second band, distributing signals having phase difference therebetween to pre-configured radiation modules or groups of multiple radiation modules among the radiation modules of the (2-1)th antenna array, respectively, and then providing the signals; a (3-1)th phase shifter for receiving an input signal of the second band, distributing signals having phase difference therebetween to pre-configured radiation modules or groups of multiple radiation modules among the radiation modules of (2-1)th antenna array, respectively, and then providing the signals; a plurality of (2-1)th frequency combiners for combining one pre-configured signal among output signals of the (2-1)th phase shifter with one corresponding signal among output signals of the (3-1)th phase shifter, and providing a combined signal to each pre-configured radiation module among the radiation modules of the (2-1)th antenna array or a pre-configured group among groups of multiple radiation modules among the radiation modules of the (2-1)th antenna array.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of International Application No. PCT/KR2014/009829 filed on Oct. 20, 2014, which claims priority to Korean Application No. 10-2013-0135481 filed on Nov. 8, 2013, which applications are incorporated herein by reference. 
     
    
     TECHNICAL FIELD 
       [0002]    The present disclosure relates to an antenna technology suitable for a mobile communication (personal communication service (PCS), cellular, international mobile telecommunication-2000 (IMT-2000) or the like) base station or relay, and more particularly, to a multi-band antenna. 
       BACKGROUND ART 
       [0003]    Along with the popularity of mobile communications and wireless broadband data communication, efforts are now made to render various frequency bands to be available due to the lack of frequency bands. Multiple input and multiple output (MIMO) based on multiple antennas is a requisite technology to increase data rate, finding its applications in mobile communication network systems such as long term evolution (LTE) and mobile worldwide interoperability for microwave access (Mobile WiMAX). 
         [0004]      FIG. 1  illustrates an exemplary structure of a general multi-band antenna. For example, the multi-band antenna is a triple-band antenna. Referring to  FIG. 1 , the multi-band antenna may include, for example, a first antenna array  9  of a first band, (2-1) th  and (2-2) th  antenna arrays  11  and  12  of a second band, and (3-1) th  and (3-2) th  antenna arrays  31  and  32  of a third band, which are arranged, for example, on a single reflective plate (not shown) standing upright in a lengthwise direction. The first band may be an 800-MHz (for example, 808-MHz to 860-MHz) cellular band, the second band may be a 2.5-GHz (for example, 2.495-GHz to 2.690-GHz) broadband radio service (BRS) band, and the third band may be a 1.9-GHz (for example, 1.850-GHz to 1.995-GHz) US-PCS band. 
         [0005]    The first antenna array  9  may be arranged at the center of the reflective plate, the (2-1) th  and (3-1) th  antenna arrays  11  and  31  may be arranged on the right side of the first antenna array  9 , and the (2-2) th  and (3-2) th  antenna arrays  12  and  32  may be arranged on the left side of the first antenna array  9 . It may be understood that the (2-1) th  and (2-2) th  antenna arrays  11  and  12 , and the (3-1) th and ( 3-2) th  antenna arrays  31  and  32  are installed in a double structure to implement a MIMO antenna of the second band and a MIMO antenna of the third band, respectively in the above-described structure. 
         [0006]    The first antenna array  9  is configured generally to include a plurality of radiation modules for the first band arranged vertically in a row. Similarly, each of the (2-1) th  and (2-2) th  antenna arrays  11  and  12  is configured generally to include a plurality of radiation modules for the second band arranged vertically in a row, and each of the (3-1) th  and (3-2) th  antenna arrays  31  and  32  is configured generally to include a plurality of radiation modules for the third band arranged vertically in a row. Each of the radiation modules for the first, second, and third bands is configured generally to include four 4-directional radiation elements arranged at +45 degrees and −45 degrees on the whole with respect to a vertical (or horizontal) direction, so that two mutually orthogonal linear polarizations (that is X polarizations) are generated. 
         [0007]    Meanwhile, as radiation elements and radiation modules with broadband characteristics have recently been demanded, radiation elements covering a band with a fractional band width of about 45% are offered. Such a radiation element may have an operation characteristic of, for example, a 1710-MHz to 2690-MHz band. If a multi-band antenna is implemented with such broadband radiation elements, the radiation modules for the second and third bands may be configured with broadband radiation elements all having substantially identical structures. 
         [0008]    To provide an electrical vertical tilt to total radiation beams emitted from the first antenna array  9  of the first band, the multi-band antenna illustrated in  FIG. 1  includes a first phase shifter  10  for receiving an input signal of the first band, dividing the input signal, and providing the divided signals to the radiation modules of the first antenna array  9  in such a manner that the divided signals provided to the radiation modules arranged vertically in a row may have a predetermined phase difference between them. 
         [0009]    To provide an electrical vertical tilt to radiation beams emitted from the (2-1) th  antenna array  11 , the multi-band antenna further includes a (2-1) th  phase shifter  41  for receiving an input signal of the second band, dividing the input signal, and providing the divided signals to the radiation modules of the (2-1) th  antenna array  11 , so that each radiation module or each group of radiation modules may have a predetermined phase difference. The radiation modules of the (2-1) th  antenna array  11  may be grouped, for example, by pair, and each group of radiation modules may be connected to the (2-1) th  phase shifter  41  through a (2-1) th  power divider  13  for the second band. In this case, it may be noted that a phase difference is generated on a radiation module group basis. 
         [0010]    Likewise, the multi-band antenna further includes a (2-2) th  phase shifter  42  for receiving an input signal of the second band, dividing the input signal, and providing the divided signals to the radiation modules of the (2-2) th  antenna array  12 , so that the radiation modules or groups of radiation modules may have a predetermined phase difference between them. Each of a plurality of groups of radiation modules in the (2-2) th  antenna array  12  may be connected to the (2-2) th  phase shifter  42  through a (2-2) th  power divider  14  for the second band. 
         [0011]    The multi-band antenna also includes a (3-1) th  phase shifter  51  for receiving an input signal of the third band, dividing the input signal, and providing the divided signals to the radiation modules of the (3-1) th  antenna array  31 , so that the radiation modules or groups of radiation modules may have a predetermined phase difference between them. Each of a plurality of groups of radiation modules in the (3-1) th  antenna array  31  may be connected to the (3-1) th  phase shifter  51  through a (3-1) th  power divider  33  for the third band. 
         [0012]    The multi-band antenna further includes a (3-2) th  phase shifter  52  for receiving an input signal of the third band, dividing the input signal, and providing the divided signals to the radiation modules of the (3-2) th  antenna array  32 , so that the radiation modules or groups of radiation modules may have a predetermined phase difference between them. Each of a plurality of groups of radiation modules in the (3-2) th  antenna array  32  may be connected to the (3-2) th  phase shifter  52  through a (3-2) th  power divider  34  for the third band. 
         [0013]    The (2-1) th  and (2-2) th  power dividers  13  and  14  for the second band, and the (3-1) th  and (3-2) th  power dividers  33  and  34  for the third band may be designed so as to be used substantially commonly for the second and third bands. In this case, all of the (2-1) th  and (2-2) th  power dividers  13  and  14 , and the (3-1) th  and (3-2) th  power dividers  33  and  34  may be configured in the substantially same structure. While the term, power divider has been used above, it will be understood that if the directions of input and output signals are reserved, such a power divider may have a configuration for serving as a power combiner. 
         [0014]    The multi-band antenna may be configured as illustrated in  FIG. 1 . In the multi-band antenna, for example, the first antenna array  9 , the (2-1) th  and (2-2) th  antenna arrays  11  and  12 , and the (3-1) th  and (3-2) th  antenna arrays  31  and  32  may be installed on the front surface of the reflective plate, whereas the other components related to a feeding network may be installed on the rear surface of the reflective plate. 
         [0015]    The multi-band antenna illustrated in  FIG. 1  has the (2-1) th  and (3-1) th  antenna arrays  11  and  31  arranged on the right side of the first antenna array  9 , and the (2-2) th  and (3-2) th  antenna arrays  12  and  32  arranged on the left side of the first antenna array  9 . Thus, the overall antenna size of the multi-band antenna, particularly the latitudinal width of the multi-band antenna is very large. 
         [0016]      FIG. 2  illustrates another exemplary structure of the general multi-band antenna. As illustrated in  FIG. 1 , the multi-band antenna includes the first antenna array  9  of the first band, the (2-1) th  and (2-2) th  antenna arrays  11  and  12  of the second band, and the (3-1) th  and (3-2) th  antenna arrays  31  and  32  of the third band. Like the structure of  FIG. 1 , the multi-band antenna illustrated in  FIG. 2  includes the first phase shifter  10 , the (2-1) th  and (2-2) th  phase shifters  41  and  42 , the (3-1) th  and (3-2) th  phase shifters  51  and  52 , and the (2-1) th  and (2-2) th  power dividers  13  and  14 . 
         [0017]    In the multi-band antenna illustrated in  FIG. 2 , however, the radiation modules of the (2-1) th  and (3-1) th  antenna arrays  11  and  31  are arranged in a row along the same vertical axis on the right side of the first antenna array  9 . Likewise, the radiation modules of the (2-2) th  and (3-2) th  antenna arrays  12  and  33  are arranged in a row along the same vertical axis on the left side of the first antenna array  9 . 
         [0018]    Although the multi-band antenna illustrated in  FIG. 2  has a relatively small latitudinal width compared to the multi-band antenna illustrated in  FIG. 1 , the former has a very large longitudinal length. 
         [0019]    As illustrated in  FIGS. 1 and 2 , the conventional multi-band antennas are large in size. As a result, their installation cost increases and constraints are imposed on a tower space in which the antennas are to be installed in a real outdoor environment. 
       SUMMARY 
       [0020]    Accordingly, an object of the present disclosure is to provide a multi-band antenna which has an optimized structure and decreases an antenna size, for facilitating antenna design and offering more stable characteristics. 
         [0021]    In an aspect of the present invention, a multi-band antenna includes a first antenna array of a first band, including radiation modules for the first band, a (2-1) th  antenna array of second and third common bands, including radiation modules for the second and third common bands, a (2-1) th  phase shifter for receiving an input signal of the second band, dividing the input signal, and providing divided signals having a phase difference to predetermined radiation modules or a plurality of radiation module groups on a radiation module basis or a radiation module group basis among the radiation modules of the (2-1) th  antenna array, a (3-1) th  phase shifter for receiving an input signal of the third band, dividing the input signal, and providing divided signals having a phase difference to predetermined radiation modules or a plurality of radiation module groups on a radiation module basis or a radiation module group basis among the radiation modules of the (2-1) th  antenna array, and a plurality of (2-1) th  frequency combiners each for combining a predetermined one of signals output from the (2-1) th  phase shifter with one of signals output from the (3-1) th  phase shifter corresponding to the (2-1) th  frequency combiner, and providing the combined signal to each of predetermined radiation modules or a predetermined one of a plurality of radiation module groups among the radiation modules of the (2-1) th  antenna array. 
         [0022]    The radiation modules of the (2-1) th  antenna array are divided into a group used for the second or third band, a group for the third band, and a group common for the second and third bands, the group for the second or third band is connected to one of the (2-1) th  phase shifter and the (3-1) th  phase shifter, corresponding to the group for the second or third band, and the group common for the second and third band is connected to the (2-1) th  phase shifter and the (3-1) th  phase shifter, through the (2-1) th  frequency combiners. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0023]      FIG. 1  illustrates an exemplary structure of a general multi-band antenna. 
           [0024]      FIG. 2  illustrates another exemplary structure of the general multi-band antenna. 
           [0025]      FIG. 3  illustrates a structure of a multi-band antenna according to an embodiment of the present disclosure. 
           [0026]      FIG. 4  illustrates a structure of a multi-band antenna according to another embodiment of the present disclosure. 
           [0027]      FIG. 5  illustrates a structure of a multi-band antenna according to a third embodiment of the present disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0028]    Preferred embodiments of the present disclosure will be described below in detail with reference to the attached drawings. Specific details such as components are given to help comprehensive understanding of the present disclosure, and those skilled in the art will understand that various modifications or variations can be made to the specific details without departing from the scope and spirit of the present disclosure. 
         [0029]      FIG. 3  is a diagram illustrating a structure of a multi-band antenna according to an embodiment of the present disclosure. For example, the multi-band antenna is a triple-band antenna. Referring to  FIG. 3 , the multi-band antenna according to the embodiment of the present disclosure may include, for example, the first antenna array  9  of the first band, and (2-1) th  and (2-2) th  antenna arrays  21  and  22  for second and third common bands, which are arranged on, for example, a single reflective plate (not shown) standing upright in a lengthwise direction. 
         [0030]    The first antenna array  9  may be arranged at the center of the reflective plate, and the (2-1) th  and (2-2) th  antenna arrays  21  and  22  may be arranged on the left and right sides of the first antenna array  9 , respectively. It may be understood that the (2-1) th  and (2-2) th  antenna arrays  21  and  22  are installed in a double structure to implement a MIMO antenna of the second and third bands in the above-described structure. 
         [0031]    The first antenna array  9  is configured generally to include a plurality of radiation modules for the first band arranged vertically in a row. Similarly, each of the (2-1) th  and (2-2) th  antenna arrays  21  and  22  is configured generally to include a plurality of radiation modules for the second and third common bands arranged vertically in a row. That is, the radiation modules for the second and third common bands may be configured with broadband radiation elements covering both of the second and third bands. 
         [0032]    To provide an electrical vertical tilt to total radiation beams emitted from the first antenna array  9  of the first band, the multi-band antenna includes the first phase shifter  10  for receiving an input signal of the first band, dividing the input signal, and providing the divided signals to the radiation modules of the first antenna array  9  in such a manner that the divided signals provided to the radiation modules arranged vertically in a row may have a predetermined phase difference between them. 
         [0033]    To provide an electrical vertical tilt to radiation beams emitted from the (2-1) th  antenna array  21 , the multi-band antenna further includes the (2-1) th  phase shifter  41  for receiving an input signal of the second band, dividing the input signal, and providing the divided signals to the radiation modules of the (2-1) th  antenna array  21 , so that the radiation modules or groups of radiation modules may have a predetermined phase difference between them. The radiation modules of the (2-1) th  antenna array  21  may be grouped, for example, by pair, and each group of radiation modules may be connected to the (2-1) th  phase shifter  41  through one of a plurality of (2-1)&#39; th  power dividers  25 , provided on a group basis and one of a plurality of (2-1) th  frequency combiners  63 , provided on a group basis. In this case, it may be noted that a phase difference is generated on a group basis. 
         [0034]    The (2-1) th  power dividers  25  may be configured as general 2-way power dividers. Besides, the (2-1) th  power dividers  25  may be designed to be suitable for the characteristics of the second and third common bands. 
         [0035]    Meanwhile, the multi-band antenna further includes the (3-1) th  phase shifter  51  for receiving an input signal of the third band, dividing the input signal, and providing the divided signals to the radiation modules of the (2-1) th  antenna array  21 , so that the radiation modules or groups of radiation modules may have a predetermined phase difference between them. 
         [0036]    One output terminal (combined terminal) of each of the plurality of (2-1) th  frequency combiners  63  is connected to one of the plurality of (2-1) th  power dividers  25 , corresponding to the (2-1) th  frequency combiner  63 . One of two input terminals of the (2-1) th  frequency combiner  63  is connected to the (2-1) th  phase shifter  41  and thus to a corresponding one of divided outputs of the (2-1) th  phase shifter  41 , whereas the other input terminal of the (2-1) th  frequency combiner  63  is connected to a corresponding one of divided outputs of the (3-1) th  phase shifter  51 . Each of the (2-1) th  frequency combiners  63  combines a signal output from the (2-1) th  phase shifter  41  with a signal output from the (3-1) th  phase shifter  51 , and provides the combined signal to a (2-1) th  power divider  25  corresponding to the (2-1) th  frequency combiner  63 . 
         [0037]    Each (2-1) th  frequency combiner  63  may be a diplexer or duplexer having a filter for filtering the second band and a filter for filtering the third band in combination. While the term, frequency combiner has been used above, it will be understood that if the directions of input and output signals are reserved, this frequency combiner may have a configuration for serving as a frequency divider. 
         [0038]    Likewise, the multi-band antenna further includes the (2-2) th  phase shifter  42  for receiving an input signal of the second band, dividing the input signal, and providing the divided signals to the radiation modules of the (2-2) th  antenna array  22 , so that the radiation modules or groups of radiation modules may have a predetermined phase difference between them. Each group of radiation modules in the (2-2) th  antenna array  22  may be connected to the (2-2) th  phase shifter  42  through a corresponding one of a plurality of (2-2) th  power dividers  27  and a corresponding one of a plurality of (2-2) th  frequency combiners  64 . 
         [0039]    The multi-band antenna further includes the (3-2) th  phase shifter  52  for receiving an input signal of the third band, dividing the input signal, and providing the divided signals to the radiation modules of the (2-2) th  antenna array  22 , so that the radiation modules or groups of radiation modules may have a predetermined phase difference between them. 
         [0040]    In this case, each of the plurality of (2-2) th  frequency combiners  64  combines a corresponding one of signals output from the (2-2) th  phase shifter  42  with a corresponding a corresponding one of signals output from the (3-2) th  phase shifter  52 , and provides the combined signal to the (2-2) th  power divider  27 . 
         [0041]    The structure of the multi-band antenna according to the embodiment of the present disclosure, illustrated in  FIG. 3  enables the (2-1) th  and (2-2) th  antenna arrays  21  and  22  to commonly process wireless signals of the second and third bands using the (2-1) th  frequency combiners  63  and the (2-2) th  frequency combiners  64 . Therefore, while the multi-band antenna still performs conventional functions, its total antenna size can be reduced. 
         [0042]      FIG. 4  is a diagram illustrating a structure of a multi-band antenna according to another embodiment of the present disclosure. Like the example of  FIG. 3 , the multi-band antenna is a triple-band antenna, by way of example. Referring to  FIG. 4 , the multi-band antenna according to the second embodiment of the present disclosure includes the first antenna array  9  of the first band, the first phase shifter  10 , the (2-1) th  and (2-2) th  phase shifters  41  and  42 , and the (3-1) th  and (3-2) th  phase shifters  51  and  52 . 
         [0043]    Similarly to the embodiment illustrated in  FIG. 3 , the (2-1) th  and (2-2) th  antenna arrays  21  and  22  of the second and third common bands are provided. The (2-1) th  and (2-2) th  antenna arrays  21  and  22  include radiation modules for the second and third common bands,  21 - 1 ,  21 - 2 , . . . ,  21 - 14 , and  22 - 1 ,  22 - 2  . . . ,  22 - 14 , which are arranged vertically in a row. That is, the radiation modules for the second and third common bands,  21 - 1 ,  21 - 2 , . . . ,  21 - 14 , and  22 - 1 ,  22 - 2  . . . ,  22 - 14  include broadband radiation elements having broadband characteristics covering both of the second and third bands. 
         [0044]    In the structure according to the second embodiment of the present invention, the radiation modules for the second and third common bands,  21 - 1 ,  21 - 2 , . . . ,  21 - 14 , and  22 - 1 ,  22 - 2  . . . ,  22 - 14  of the (2-1) th  and (2-2) th  antenna arrays  21  and  22  may be divided into three groups: a group for the second band, a group for the third band, and a group common for the second and third bands. 
         [0045]    Among the radiation modules  21 - 1 ,  21 - 2 , . . . ,  21 - 14 , of the (2-1) th  antenna array  21 , in a sequential order, for example, the first to fourth radiation modules  21 - 1 ,  21 - 2 ,  21 - 3 , and  21 - 4  are used for the third band, the 5 th  to 10 th  radiation modules  21 - 5 ,  21 - 6 ,  21 - 7 ,  21 - 8 ,  21 - 9 , and  21 - 10  are used commonly for the second and third bands, and the 11 th  to 14 th  radiation modules  21 - 11 ,  21 - 12 ,  21 - 13 , and  21 - 14  are used for the second band,. 
         [0046]    That is, in the (2-1) th  antenna array  21 , the first and second radiation modules  21 - 1  and  21 - 2  are connected to a corresponding one of outputs of the (3-1) th  phase shifter  51  through a (2-1- 1 ) th  power divider  231 , and the third and fourth radiation modules  21 - 3  and  21 - 4  are connected to a corresponding one of the outputs of the (3-1) th  phase shifter  51  through a (2-1- 2 ) th  power divider  232 . Also, in the (2-1) th  antenna array  21 , the 11 th  and 12 th  radiation modules  21 - 11  and  21 - 12  are connected to a corresponding one of outputs of the (2-1) th  phase shifter  41  through a (2-1-3) th  power divider  233 , and the 13 th  and 14 th  radiation modules  21 - 13  and  21 - 14  are connected to a corresponding one of the outputs of the (2-1) th  phase shifter  41  through a (2-1-4) th  power divider  234 . 
         [0047]    In the (2-1) th  antenna array  21 , the 5 th  and 6 th  radiation modules  21 - 5  and  21 - 6  are connected to corresponding ones of the outputs of the (3-1) th  phase shifter  51  and the (2-1) th  phase shifter  41  through a (2-1-5) th  power divider  251  and a (2-1-1) th  frequency combiner  631 , the 7 th  and 8 th  radiation modules  21 - 7  and  21 - 8  are connected to corresponding ones of the outputs of the (3-1) th  phase shifter  51  and the (2-1) th  phase shifter  41  through a (2-1-6) th  power divider  252  and a (2-1-2) th  frequency combiner  632 , and the 9 th  and 10 th  radiation modules  21 - 9  and  21 - 10  are connected to corresponding ones of the outputs of the (3-1) th  phase shifter  51  and the (2-1) th  phase shifter  41  through a (2-1-7) th  power divider  253  and a (2-1-3) th  frequency combiner  633 . 
         [0048]    The (2-1- 1 ) th  to (2-1-4) th  power dividers  231  to  234  may be designed suitably for characteristics of the second and third common bands, and the (2-1-5) th , (2-1- 6 ) th , and (2-1-7) th  power dividers  251 ,  252 , and  253  may be configured as general 2-way power dividers. 
         [0049]    In the above structure, each of the (2-1-1) th , (2-1-2) th , and (2-1- 3 ) th  frequency combiners  631 ,  632 , and  633  is configured to combine a corresponding one of signals output from the (2-1) th  phase shifter  41  with a corresponding one of signals output from the (3-1) th  phase shifter  51  and provide the combined signal to a corresponding one of the (2-1-5) th , (2-1-6) th  , and (2-1-7) th  power dividers  251 ,  252 , and  253 . 
         [0050]    Meanwhile, the (2-2) th  antenna array  22  and its feeding network structure may be designed to be symmetrically same as the (2-1) th  antenna array  21  and its feeding network structure. That is, among the radiation modules  22 - 1 ,  22 - 2 , . . . ,  22 - 14 , of the (2-2) th  antenna array  22 , in a sequential order, for example, the first to fourth radiation modules  22 - 1 ,  22 - 2 ,  22 - 3 , and  22 - 4  are used for the third band, the 5 th  to 10 th  radiation modules  22 - 5 ,  22 - 6 ,  22 - 7 ,  22 - 8 ,  22 - 9 , and  22 - 10  are used commonly for the second and third bands, and the 11 st  to 14 th  radiation modules  22 - 11 ,  22 - 12 ,  22 - 13 , and  22 - 14  are used for the second band. 
         [0051]    Further, for the radiation modules  22 - 1 ,  22 - 2 , . . . ,  22 - 14  of the (2-2) th  antenna array  22  which are divided as described above, (2-2-1) th  to (2-2-7) th  power dividers  241  to  244 , and (2-2-1) th , (2-2-2) th , and (2-2-3) th  frequency combiners  641 ,  642 , and  643  are provided. 
         [0052]      FIG. 5  is a diagram illustrating a structure of a multi-band antenna according to a third embodiment of the present disclosure. The structure according to the third embodiment of the present disclosure illustrated in  FIG. 5  is almost same as the structure according to the second embodiment of the present disclosure illustrated in  FIG. 4 . However, the structures of  FIGS. 4 and 5  differ in that while the (2-1-1) th  to (2-1-4) th  power combiners  231  to  234  and the (2-2-1) th  to (2-2-4) th  power combiners  241  to  244  are designed to be suitable for characteristics for the second and third common bands in  FIGS. 4 , (2-1-1) th  to (2-1-4) th  power combiners  254  to  257  and (2-2-1) th  to (2-2-4) th  power combiners  274  to  277  may be configured as general  2 -way power dividers in  FIG. 5 . 
         [0053]    The structures and operations of the multi-band antennas according to the foregoing embodiments of the present disclosure may be implemented as described above. While specific embodiments of the present disclosure have been described above, those skilled in the art will appreciate that the present disclosure may be carried out in other specific ways than those set forth herein without departing from the scope of the present disclosure. 
         [0054]    For example, although it has been described above that a multi-band antenna of the present disclosure is provided with, for example, (2-1) th  and (2-2) th  antenna arrays in order to implement a MIMO antenna, the multi-band antenna may be configured to include, for example, only the (2-1) th  antenna array in other embodiments of the present disclosure. 
         [0055]    Also, while it has been described above that the radiation modules of the (2-1) th  and (2-2) th  antenna arrays, for example, are divided into three groups: a group for the second band, a group common for the second and third groups, and a group for the third band, the radiation modules of the (2-1) th  and (2-2) th  antenna arrays may be divided into two groups: a group for the second band and a group common for the second and third groups in other embodiments of the present disclosure. Obviously, the radiation modules of the (2-1) th  and (2-2) th  antenna arrays may also be divided into two groups: a group common for the second and third groups and a group for the third band. 
         [0056]    Therefore, the scope of the present disclosure should be determined by the appended claims and their legal equivalents, not by the above description, and all changes coming within the meaning and equivalency range of the appended claims are intended to be embraced therein. As described above, the multi-band antenna according to the present disclosure has an optimized structure and enables optimization of an antenna size, thereby facilitating antenna design and offering more stable characteristics.