Patent Publication Number: US-2012038533-A1

Title: Broadband antenna and radiation device included in the same

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This is a continuation application of PCT/KR2010/001041 filed on Feb. 19, 2010, which claims the benefit of Korean Application No. 10-2009-014798 filed Feb. 23, 2009, the entire contents of which applications are incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     Example embodiments of the present invention relate to antennas for realizing broadband and/or multi-band using multi current paths and radiation devices included in the same. 
     BACKGROUND ART 
     An antenna transmits/receives electromagnetic wave using at least one radiation device. Here, the radiation device as a radiator has generally a structure shown in following  FIG. 1 . 
       FIG. 1  is a view illustrating structure of common radiation device in an antenna. 
     In  FIG. 1 , a radiation device  100  includes dipole elements  110 ,  112 ,  114  and  116  and a feeding section  118 . 
     The feeding section  118  includes feeing points  120 A,  120 B,  120 C and  120 D and a connection line  122 . 
     The first feeding point  120 A is connected to the fourth dipole element  116 , and the second feeding point  120 B is connected to the third dipole element  114 . 
     The third feeding point  120 C is connected to the second dipole element  112 , and the fourth feeding point  120 D is connected to the first dipole element  110 . 
     In the radiation device  100 , in case that current is inputted into the fourth feeding point  120 D, a part of the current flows to the first dipole element  110  and the other current is provided to the third dipole element  114  through the connection line  122  formed on an upper surface of the feeding section  118  and the second feeding point  120 B. Accordingly, electric field is generated from each of the first dipole element  110  and the third dipole element  114 , and +45° polarized wave is generated by the electric field. In this case, the second dipole element  112  and the fourth dipole element  116  do not affect to generation of generation of +45° polarized wave. 
     In case that current is inputted into the first feeding point  120 A, a part of the current flows to the fourth dipole element  116  and the other current is provided to the second dipole element  112  through a connection line formed on a back side of the feeding section  118  and the third feeding point  120 C. Accordingly, electric field is generated from each of the second dipole element  112  and the fourth dipole element  116 , and −45° polarized wave is generated by the electric field. In this case, the first dipole element  110  and the third dipole element  114  do not affect to the generation of −45° polarized wave. 
     That is, the radiation device  100  generates ±45° polarized wave at single frequency band. 
     Recently, it has been required that a device, e.g. a mobile phone realizes two or more frequency bands. However, the antenna having the radiation device  100  realizes only one frequency band. 
     In other words, the antenna may not realize multi band and broadband, and thus can&#39;t satisfy the requirement. 
     SUMMARY OF THE DISCLOSURE 
     An example embodiment of the present invention provides an antenna for realizing broadband and/or multi-band using branch members and a radiation device included in the same. 
     In one aspect, the present invention provides a radiation device in a broadband antenna comprising: a first feeding point; and a first dipole member electrically connected to the first feeding point. Here, at least one first branch member is formed to one side of the first dipole member, and one or more second branch member is formed to another side of the first dipole member. 
     The first branch members and the second branch members are symmetrically disposed. 
     Length of the first branch member reduces according as distance of the first branch member and the first feeding point increases. 
     At least one of the first branch members is not parallel to the other first branch members. 
     At least one of the first branch members has different width from the other first branch members. 
     The radiation device further includes a second feeding point; and a second dipole member electrically connected to the second feeding point. Here, a third branch member facing to the first branch member is formed to one side of the second dipole member, and electromagnetic coupling generates between the third branch member and the first branch member. 
     The first branch member is disposed in parallel to the third branch member. 
     Space between the first branch member and the third branch member reduces according as distance between the first branch member or the third branch member and corresponding feeding point increases. 
     Space between the first branch member and the third branch member increases according as distance between the first branch member or the third branch member and corresponding feeding point augments. 
     At least one of the first branch members and the second branch members is separable from the first dipole member. 
     In another aspect, the present invention provides a radiation device in a broadband antenna comprising: a first feeding point and a second feeding point; a first dipole member electrically connected to the first feeding point; and a second dipole member electrically connected to the second feeding point. Here, at least one first branch member is formed to a side of the first dipole member, one or more second branch member facing to the first branch member is formed to a side of the second dipole member, and electromagnetic coupling generates between the first branch member and the second branch member. 
     In still another aspect, the present invention provides a broadband antenna comprising: a reflection plate; and a radiation device disposed on the reflection plate. The radiation device includes: a first feeding point; and a first dipole member electrically connected to the first feeding point. Here, at least one first branch member is formed to one side of the first dipole member, and one or more second branch member is formed to another side of the first dipole member. 
     The first branch members are symmetrically disposed to the second branch members, and length of the first branch member reduces according as distance between the first branch member and the first feeding point increases. 
     The antenna of claim further includes a second feeding point; and a second dipole member electrically connected to the second feeding point. Here, at least one third branch member facing to the first branch member is formed to a side of the second dipole member, and electromagnetic coupling generates between the third branch member and the first branch member. 
     A radiation device in an antenna of the present invention has branch members for providing multi current paths, and so the antenna may realize multi band and broadband. For example, the antenna may realize at least two bands of K-PCS band (1.7 GHz to 1.8 GHz), WCDMA band (1.9 GHz to 2.2 GHz), WiBro band (2.3 GHz to 2.327 GHz, 2.331 GHz to 2.358 GHz, 2.363 GHz to 2.390 GHz) and WiMAX band (2.5 GHz to 3.5 GHz). 
     Since the frequency band of the antenna is changed by adjusting number, angle and space, etc. of the branch members formed in the radiation device, the antenna may realize easily various frequency bands using one radiation device. Especially, in case that the branch members are separable from corresponding dipole member, the antenna may realize more easily desired frequency band. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       Example embodiments of the present invention will become more apparent by describing in detail example embodiments of the present invention with reference to the accompanying drawings, in which: 
         FIG. 1  is a view illustrating structure of common radiation device in an antenna; 
         FIG. 2  is a perspective view illustrating a radiation device according to a first example embodiment of the present invention; 
         FIG. 3  is a view illustrating current distribution of the radiation device in  FIG. 2  according to one example embodiment of the present invention; 
         FIG. 4  to  FIG. 7  are views illustrating return loss, isolation and radiation pattern of the radiation device in  FIG. 2 ; 
         FIG. 8  is a view illustrating radiation devices having various branch members according to one example embodiment of the present invention; 
         FIG. 9  is a view illustrating return loss characteristics of the radiation devices in  FIG. 8 ; 
         FIG. 10  is a view illustrating isolation characteristics of the radiation devices in  FIG. 8 ; 
         FIG. 11  is a view illustrating radiation devices having various number of branch members according to one example embodiment of the present invention; 
         FIG. 12  is a view illustrating return loss characteristics of the radiation devices in  FIG. 11 ; 
         FIG. 13  is a view illustrating isolation characteristics of the radiation devices in  FIG. 11 ; and 
         FIG. 14  is a view illustrating an antenna having a radiation device according to one example embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE DISCLOSURE 
     Hereinafter, embodiments of the present invention will be described in detail with reference to accompanying drawings. 
       FIG. 2  is a perspective view illustrating a radiation device according to a first example embodiment of the present invention. 
     In  FIG. 2(A) , a radiation device  200  in an antenna of the present invention outputs a radiation pattern, and includes dipole elements, e.g. four dipole elements  210 ,  212 ,  214  and  216  and a feeding section  218 . 
     Generally, the antenna outputs radiation pattern using a plurality of radiation devices. Here, the radiation device  200  is one of the radiation devices. It is preferable that the radiation devices have structure shown in  FIG. 2 . 
     A first dipole element  210  includes a dipole member  210 A, at least one branch members  210 B formed on one side of the dipole member  210 A and at least one branch members  210 C formed on other side of the dipole member  210 A. 
     The dipole member  210 A is a body of the first dipole element  210 , and is electrically connected to a first feeding point  220 A. As a result, current flows to the dipole member  210 A through the first feeding point  220 A. 
     The branch members  210 B and  210 C are formed on sides of the dipole member  210 A to realize broadband, and may be formed in one body with the dipole member  210 A. Here, the number of the branch members  210 B and  210 C is not limited, and may be variously changed in accordance with an user&#39;s object. 
     In case that the dipole member  210 A has a structure shown in  FIG. 2 , the current provided to the dipole member  210 A flows to the branch members  210 B and  210 C, i.e. multi current paths are formed. 
     In one embodiment of the present invention, the branch members  210 B and the branch members  210 C are formed symmetrically as shown in  FIG. 2 , and length of each of the branch members  210 B and  210 C may reduce according as distance of the branch member  210 B or  210 C and the feeding section  218  increases. Here, the branch member  210 B or  210 C having small length affects mainly to realize high frequency band, and the branch member  210 B or  210 C having great length affects mainly to realize low frequency band. 
     In  FIG. 2 , the branch members  210 B and  210 C have the same width. However, at least one of the branch members  210 B and  210 C may have different width from the other members  210 B and  210 C. In addition, length of the branch members  210 B and  210 C may not reduce according as distance of the branch member  210 B or  210 C and the feeding section  218  increases, but may be disposed irregularly. That is, the branch members  210 B and  210 C may be variously modified as long as they form multi current paths. 
     The second dipole element  212  includes a dipole member  212 A, at least one branch members  212 B formed on one side of the dipole member  212 A and at least one branch members  212 C formed on other side of the dipole member  212 A. The second dipole element  212  is electrically connected to a second feeding point  220 B. 
     The third dipole element  214  includes a dipole member  214 A, at least one branch members  214 B formed on one side of the dipole member  214 A and at least one branch members  214 C formed on other side of the dipole member  214 A. The third dipole element  214  is electrically connected to a third feeding point  220 C. 
     The fourth dipole element  216  includes a dipole member  216 A, at least one branch members  216 B formed on one side of the dipole member  216 A and at least one branch members  216 C formed on other side of the dipole member  216 A. The fourth dipole element  216  is electrically connected to a fourth feeding point  220 D. 
     Hereinafter, disposition of the dipole elements  210 ,  212 ,  214  and  216  will be described. 
     In one embodiment of the present invention, the dipole members  210 A,  212 A,  214 A and  216 A of the dipole elements  210 ,  212 ,  214  and  216  may be vertically disposed in sequence. Furthermore, outermost member of the branch members  210 B of for example the first dipole element  210  may be disposed in parallel to outermost member of the branch members  210 C of the fourth dipole element  216 . However, the outermost member of the branch members  210 B of the first dipole element  210  may not be disposed in parallel to outermost member of the branch members  210 C of the fourth dipole element  216 . In other words, space between the branch members  210 B and  216 C may narrow or increase according as distance between the branch member  210 B or  216 C and the feeding section  218  augments. Capacitance between the branch member  210 B and the branch member  216 C is changed in accordance with space between the branch member  210 B and the branch member  216 C, and so the frequency band of the antenna may be varied depending on the space. Accordingly, the user may set properly the space and disposition of the branch members  210 B and  216 C in accordance with frequency band desired by the user. 
     Now referring to  FIG. 2(A) , the feeding section  218  includes the feeding points  220 A,  220 B,  220 C and  220 D and connection lines  222 A and  222 B. 
     The first feeding point  220 A is connected to the first dipole element  210 , and first current supplied from outside is provided to the first dipole element  210  through the first feeding point  220 A. 
     Additionally, the first feeding point  220 A is connected to the third feeding point  220 C through the first connection line  222 A, and thus the first current supplied to the first feeding point  220 A is provided to the third feeding point  220 C through the first connection line  222 A. 
     In case that the first current is provided to the first dipole element  210  and the third dipole element  214 , electric field is generated from the first dipole element  210  and the third dipole element  214 , respectively. As a result, −45° polarized wave is generated by the electric fields. 
     The second feeding point  220 B is connected to the second dipole element  212 , and second current supplied from outside is provided to the second dipole element  212  through the second feeding point  220 B. 
     Moreover, the second feeding point  220 B is connected to the fourth feeding point  220 D through the second connection line  222 B, and thus the second current supplied to the second feeding point  220 B is provided to the fourth feeding point  220 D through the second connection line  222 B. 
     In case that the second current is provided to the second dipole element  212  and the fourth dipole element  216 , electric field is generated from the second dipole element  212  and the fourth dipole element  216 , respectively. As a result, +45° polarized wave is generated by the electric fields. 
     In brief, in the radiation device  200  of the present invention, the branch members  210 B,  210 C,  212 B,  212 C,  214 B,  214 C,  216 B and  216 C are formed to the dipole members  210 A,  212 A,  214 A and  216 A to realize broadband and/or multi band. For example, the radiation device  200  may realize at least two bands of K-PCS band (1.7 GHz to 1.8 GHz), WCDMA band (1.9 GHz to 2.2 GHz), WiBro band (2.3 GHz to 2.327 GHz, 2.331 GHz to 2.358 GHz, 2.363 GHz to 2.390 GHz) and WiMAX band (2.5 GHz to 3.5 GHz). This will be described in detail with reference to accompanying drawings. 
     In above description, the dipole member and corresponding branch members are formed in one body. However, the branch member, e.g.  210 C may be separable from the dipole member  210 A as shown in  FIG. 2(B) , and be combined with the dipole member  210 A when it is needed. 
       FIG. 3  is a view illustrating current distribution of the radiation device in  FIG. 2  according to one example embodiment of the present invention.  FIG. 3  shows the current distribution of the radiation device  200  having smaller number of the branch members compared with those in  FIG. 2 . 
     In  FIG. 3 , the radiation device  200  of the present embodiment includes four dipole elements  210 ,  212 ,  214  and  216 . In case that current is provided to the second dipole element  212  and the fourth dipole element  216  to generate +45° polarized wave, electromagnetic coupling generates between the dipole element  210  and  214  and the dipole element  212  and  216  by the current provided to the second dipole element  212  and the fourth dipole element  216  as shown in  FIG. 3(A)  and  FIG. 3(B) . As a result, the first dipole element  210  and the third dipole element  214  affect to generation of 45° polarized wave. 
     On the other hand, the branch members in the radiation device  200  may have various structures, e.g. have structures shown in  FIG. 3(A)  and  FIG. 3(B) . Accordingly, coupling amount between the dipole elements is different in accordance with the structure. 
     In case that the branch members of the dipole elements  210 ,  212 ,  214  and  216  are adjacently disposed in parallel as shown in  FIG. 3(A) , capacitance for resonance frequency in following Equation 1 increases. 
     
       
         
           
             
               
                 
                   
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     Whereas, in case that space between the branch members of the dipole elements  210 ,  212 ,  214  and  216  increases according as distance between the branch member and the feeding section  218  augments as shown in  FIG. 3(B) , capacitance reduces. As a result, the resonance frequency of the radiation device  200  in  FIG. 3(B)  is higher than that of the radiation device  200  in  FIG. 3(A) . 
     In short, the radiation device  200  of the present embodiment includes the branch members unlike conventional radiation device. Accordingly, unlike the conventional radiation device in which the dipole elements to which current is not provided do not affect to the other dipole elements to which current is provided, the dipole elements to which current is not provided affect to the dipole elements to which the current is provided in the radiation device  200  of the present embodiment. As a result, the radiation device  200  may realize broadband and/or multi band. 
     The structure of the radiation device  200  of the present embodiment may be variously modified as mentioned above. Here, the branch members affect to inductive characteristic, i.e. inductance, and the space between the branch members of the other dipole elements affects to conductive characteristic, i.e. capacitance. Accordingly, the user may set length, width and space, etc. of the branch members depending on the frequency band desired by the user. 
     In case that the branch member is separable from corresponding dipole member, the user may combine only specific branch members with the dipole member or combine the branch members having different length and width with the dipole member in accordance with the desired frequency band. As a result, it is convenient to make the radiation device. 
       FIG. 4  to  FIG. 7  are views illustrating return loss, isolation and radiation pattern of the radiation device in  FIG. 2 . Here, width of the dipole member  210 A,  212 A,  214 A and  216 A is set as 3.6 mm, length of each of the branch members having the greatest length is set as 18.954 mm, and width of each of the branch members is set as 2 mm. In addition, length of the branch members having the second length is set as 9.954 mm, length of the branch members having the third length is set as 3.954 mm, and length of the branch members having the smallest length is set as 0.954 mm. 
       FIG. 4  shows return loss measured from the radiation device  200 . 
     Referring to a return loss curve  400  of the radiation device  200  for generating +45° polarized wave, it is verified that two resonance frequencies of about 1.87 GHz and approximately 2.85 GHz are realized. 
     Referring to a return loss curve  402  of the radiation device  200  for generating −45° polarized wave, it is verified that two resonance frequencies of about 1.8 GHz and approximately 2.7 GHz are realized. 
     Especially, it is measured that the frequency band of 1.46 GHz (1.73 GHz to 2.19 GHz) and 1.26 GHz (1.69 GHz to 2.95 GHz) satisfies return loss less than −10 dB. That is, it is verified through the experimental result that the radiation device  200  of the present invention has excellent broadband characteristic. 
     Referring to an isolation curve  404 , isolation of the radiation device  200  has value less than −30 dB in desired frequency band as shown in  FIG. 4 . In other words, it is verified that the isolation between the dipole members  210 ,  212 ,  214  and  216  is excellent. 
       FIG. 5(A)  shows +45° vertically polarized wave at 1.88 GHz, and  FIG. 5(B)  illustrates +45° horizontally polarized wave at 1.88 GHz.  FIG. 6(A)  shows +45° vertically polarized wave at 2.17 GHz, and  FIG. 6(B)  illustrates +45° horizontally polarized wave at 2.17 GHz.  FIG. 7(A)  shows +45° vertically polarized wave at 2.5 GHz, and  FIG. 7(B)  illustrates +45° horizontally polarized wave at 2.5 GHz. 
     As shown in  FIG. 5  to  FIG. 7 , +45° polarized waves at frequencies of 1.88 GHz, 2.17 GHz and 2.5 GHz have similar shapes. That is, it is verified that radiation pattern desired by the user is outputted. 
       FIG. 8  is a view illustrating radiation devices having various branch members according to one example embodiment of the present invention, and  FIG. 9  is a view illustrating return loss characteristics of the radiation devices in  FIG. 8 .  FIG. 10  is a view illustrating isolation characteristics of the radiation devices in  FIG. 8 . 
     In  FIG. 8(A) , a radiation device  800  includes a first dipole element  802 , a second dipole element  804 , a third dipole element  806  and a fourth dipole element  808 . 
     Space between branch members, e.g. space between a branch member  802 B formed to a first dipole member  802 A and a branch member  808 B formed to a fourth dipole member  808 A reduces according as distance of the branch member  802 B and  808 B and a feeding section increases. As a result, resonance frequency and capacitance of impedance increase according as the distance of the branch member  802 B and  808 B and a feeding section augments. 
     In  FIG. 8(B) , a radiation device  810  includes a first dipole element  812 , a second dipole element  814 , a third dipole element  816  and a fourth dipole element  818 . 
     Space between branch members, e.g. space between a branch member  812 B formed to a first dipole member  812 A and a branch member  818 B formed to a fourth dipole member  818 A are constant. In other words, the branch member  812 B is disposed in parallel to the branch member  818 B. As a result, resonance frequency and capacitance of impedance are smaller than those of the radiation device  800 . 
     In  FIG. 8(C) , a radiation device  820  includes a first dipole element  822 , a second dipole element  824 , a third dipole element  826  and a fourth dipole element  828 . 
     Space between branch members, e.g. space between a branch member  822 B formed to a first dipole member  822 A and a branch member  828 B formed to a fourth dipole member  828 A increases according as distance of the branch member  822 B and  828 B and a feeding section augments. As a result, resonance frequency and capacitance of impedance are smaller than those of the radiation devices  800  and  810 . 
     Hereinafter, return loss characteristics of the radiation devices  800 ,  810  and  820  will be described. 
     In  FIG. 9 , it is verified that frequency band in a return loss curve  902  for the radiation device  810  is wider than that in a return loss curve  900  for the radiation device  800  on the basis of −10 dB. 
     Additionally, it is verified that frequency band in a return loss curve  904  for the radiation device  820  is wider than that in the return loss curve  902  for the radiation device  810  on the basis of −10 dB. That is, the radiation device  820  in which the space between the branch members increases according as the distance between the branch member and a feeding section augments realizes the widest frequency band. This is because capacitance reduces according as the space between the branch members increases. This broadband is realized because impedance is matched by combining optimally inductance corresponding to length of the branch members and capacitance corresponding to the space between the branch members. 
     Since the capacitance of the radiation device  820  is smallest, resonance frequency of the radiation device  820  is higher than that of the radiation devices  800  and  810 . 
     In  FIG. 10 , the radiation devices  800 ,  810  and  820  has isolation of below −30 dB in wide frequency band, i.e. the radiation devices  800 ,  810  and  820  have excellent isolation characteristics. 
       FIG. 11  is a view illustrating radiation devices having various number of branch members according to one example embodiment of the present invention, and  FIG. 12  is a view illustrating return loss characteristics of the radiation devices in  FIG. 11 .  FIG. 13  is a view illustrating isolation characteristics of the radiation devices in  FIG. 11 . 
     In  FIG. 11 , a branch member of one dipole element in radiation devices  1100 ,  1110 ,  1120  and  1130  is parallel to that of the other dipole element. Here, number of the branch members in the radiation devices  1100 ,  1110 ,  1120  and  1130  is different. In other words, the radiation devices  1100 ,  1110 ,  1120  and  1130  have the same structure, but the number of their branch members is different. 
     Hereinafter, return loss characteristics and isolation characteristics of the radiation devices  1100 ,  1110 ,  1120  and  1130  will be described. 
     As shown in  FIG. 12 , resonance frequencies of the radiation devices  1100 ,  1110 ,  1120  and  1130  are similar though number of the branch members of the radiation devices  1100 ,  1110 ,  1120  and  1130  is different. This is because the radiation devices  1100 ,  1110 ,  1120  and  1130  have the same structure. The radiation devices  1100 ,  1110 ,  1120  and  1130  realize two resonance frequencies. 
     In  FIG. 13 , the radiation devices  1100 ,  1110 ,  1120  and  1130  have isolation of below −30 dB in wide frequency band, i.e. the radiation devices  1100 ,  1110 ,  1120  and  1130  have excellent isolation characteristics. 
     In brief, it is verified that the space between the branch member of one dipole element and the branch member of another dipole element affects mainly to the broadband characteristic of the radiation device. 
       FIG. 14  is a view illustrating an antenna having a radiation device according to one example embodiment of the present invention. 
     In  FIG. 14(A) , an antenna  1400  of the present embodiment includes a reflection plate  1402 , at least one radiation device  1404  disposed on the reflection plate  1402 , and at least one choke member  1406  disposed on the reflection plate  1402 . 
     Various radiation devices  1404 , e.g. two radiation devices shown in  FIG. 14(B)  and  FIG. 14(C)  may be disposed in the antenna  1400  having the choke member  1406 . The radiation device  1404  shown in  FIG. 14(C)  realizes wider frequency band than that shown in  FIG. 14(B) . In addition, isolation of the radiation device  1404  in  FIG. 14(C)  may be better than that of the radiation device  1404  in  FIG. 14(B) . 
     Hereinafter, beam width characteristic and cross-polarization characteristic will be described. 
     The radiation device  1404  in  FIG. 14(B)  has the same beam width as that in  FIG. 14(C) , which is not shown. 
     Cross-polarization characteristics of the radiation device  1404  in  FIG. 14(B)  may be better than that of the radiation device  1404  in  FIG. 14(C) . 
     Any reference in this specification to “one embodiment,” “an embodiment,” “example embodiment,” etc., means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. The appearances of such phrases in various places in the specification are not necessarily all referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with any embodiment, it is submitted that it is within the purview of one skilled in the art to affect such feature, structure, or characteristic in connection with other ones of the embodiments.