Patent Publication Number: US-10777910-B2

Title: High-isolation dual-band antenna

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application also claims priority to Taiwan Patent Application No. 107114678 filed in the Taiwan Patent Office on Apr. 30, 2018, the entire content of which is incorporated herein by reference. 
     TECHNICAL FIELD 
     The present disclosure relates to an antenna, in particular to a high-isolation dual-band antenna and applicable to wireless transmission devices. 
     BACKGROUND 
     As the advance of technology, portable electronic devices (e.g. mobile phones, tablet computers and notebook computers, etc.) and wireless transmission devices (e.g. USB connection devices, wireless network cards and access points) are becoming more and more powerful, so these devices&#39; requirements for antennas are also becoming stricter. 
     Currently, planar inverse-F antennas (PIFA) of compact size and with great transmission performance have been comprehensively applied to portable electronic devices and wireless transmission devices. Antennas may need several operating frequency bands in order to satisfy the requirements of different frequency bands. However, the antenna characteristics of the currently available dual-band antennas cannot be easily adjusted because of the limitations in their structure designs; for the reason, antenna designers always need to spend a lot of time on adjusting the structures of these antennas in order to realize desired antenna characteristics. 
     In addition, the isolation is another important factor capable of influencing the performance of antennas. However, the isolations of the currently available dual-band antennas usually cannot meet the requirements because of the limitations in their structure designs, so the performances of these antennas are influenced accordingly. 
     Therefore, it has become an important issue to provide a dual-band antenna capable of improving the limitations of the currently available antennas. 
     SUMMARY 
     The present disclosure is related to a dual-band antenna. In one embodiment of the disclosure, the dual-band antenna may include a substrate, a grounding-layer, two radiating-layers and two feed points. The substrate has a surface. The grounding-layer is formed on the surface of the substrate and includes two accommodating cavities, an isolation cavity, a first-slot and two second-slots. The accommodating cavities are disposed at the two top corners of the grounding-layer; each is respectively surrounded by a first-extension at the side of the grounding-layer and a second-extension at the top side of the grounding-layer. The isolation cavity is disposed between the accommodating cavities and includes a main-block. The first-slot is disposed at the bottom end of the main-block, extends from the main-block toward the bottom side of the grounding-layer and then extends toward the accommodating cavities respectively to form two branches. The second-slots are disposed at the both sides of the main-block respectively, extend from the main-block toward the accommodating cavities respectively and then extend toward the top side of the grounding-layer. Each of the radiating-layers is disposed inside each of the accommodating cavities. The feed points are located oppositely on the first-extension side of the radiating-layers, and connect the radiating-layers to the grounding-layer respectively. 
     The present disclosure is further related to a high-isolation antenna. In one embodiment of the disclosure, the high-isolation dual-band antenna may be operated in a first frequency band and a second frequency band, and include a ground zone, two radiators and an isolation zone. The radiators may be disposed at the both sides of the ground zone respectively. The isolation zone may include a main body, a first-slot and two second-slots; the first-slot may be disposed at one end of the main body and the second-slots may be disposed at both sides of the main body respectively. At least a portion of the first-slot and the second-slots may serve as the isolation section of the first frequency band, and at least a portion of each second-slot may serve as the isolation section of the second frequency band, such that the isolation section of the first frequency band may partially overlap the isolation section of the second frequency band. 
     In a preferred embodiment, the frequency of the second frequency band may be higher than the frequency of the first frequency band. 
     In a preferred embodiment, the high-isolation dual-band antenna may further include two feed points connecting the radiators to the ground zone respectively; one side of each of the feed point may generate a first current and the first current may flow along a path extending from one side of the feed point to the ground zone to generate a first exciting current in the ground zone; the resonance between the first current and the first exciting current may generate the signals of the first frequency band. 
     In a preferred embodiment, the other side of each of the feed point may generate a second current and the second current may flow along a path extending from the other side of the feed point to the ground zone to generate a second exciting current in the ground zone; the resonance between the second current and the second exciting current generates the signals of the second frequency band. 
     In a preferred embodiment, each of the both sides of the ground zone may include a first extension and a second extension, and an accommodating zone may be formed between the first extension, the second extension and the grounding zone; the radiators may be disposed inside the accommodating zones respectively. 
     In a preferred embodiment, the length of the first extension may be related to at least the central frequency point of the first frequency band, and the width of the first extension may be related to at least the matching characteristic of the first frequency band. 
     In a preferred embodiment, the length of the second extension may be related to at least the central frequency point of the second frequency band, and the width of the second extension may be related to at least the matching characteristic of the second frequency band. 
     In a preferred embodiment, the length of the isolation section of the first frequency band may be related to at least one of the central frequency point of the isolation of the first frequency band and the isolation of the first frequency band. 
     In a preferred embodiment, the length of the isolation section of the second frequency band may be related to at least one of the central frequency point of the isolation of the second frequency band and the isolation of the second frequency band. 
     In a preferred embodiment, the first-slot may extend from the main body and toward the bottom of the ground zone first, and then extend toward the radiators respectively; the second-slots may extend from the main body and toward the radiators respectively first and then extend toward the top of the main body. 
     As described above, the high-isolation dual-band antenna according to the embodiments of the present disclosure may have one or more than one of the following advantages: 
     (1) In one embodiment of the present disclosure, the dual-band antenna has a special structure design, so antenna designers do not need to spend a lot of time on adjusting the structure of the antenna according to different requirements but can directly realize the desired antenna characteristics just by adjusting the size of each part of the antenna; therefore, the antenna designers can more efficiently design the antennas so as to conform to their requirements. 
     (2) In one embodiment of the present disclosure, the dual-band antenna has a special structure design, so antenna designers can directly realize the desired antenna characteristics meeting different requirements just by adjusting the size of each part of the antenna; therefore, the application of the dual-band antenna can be more comprehensive. 
     (3) In one embodiment of the present disclosure, the isolation zone of the dual-band antenna has a special structure design, so the isolation zone can achieve higher isolation; therefore, the performance of the dual-band antenna can be optimized to significantly better the performance of the dual-band antenna. 
     Further scope of applicability of the present application will become more apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating exemplary embodiments of the disclosure, are given by way of illustration only, since various changes and modifications within the spirit and scope of the disclosure will become apparent to those skilled in the art from this detailed description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present disclosure will become more fully understood from the detailed description given herein below and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present disclosure and wherein: 
         FIG. 1  is a structure diagram of a high-isolation dual-band antenna in accordance with a first embodiment of the present disclosure. 
         FIG. 2  is a first schematic view of the high-isolation dual-band antenna in accordance with the first embodiment of the present disclosure. 
         FIG. 3  is a third schematic view of the high-isolation dual-band antenna in accordance with the first embodiment of the present disclosure. 
         FIG. 4  is a schematic view of the high-isolation dual-band antenna in accordance with a second embodiment of the present disclosure. 
         FIG. 5  is a schematic view of the high-isolation dual-band antenna in accordance with a third embodiment of the present disclosure. 
         FIG. 6  is a schematic view of the high-isolation dual-band antenna in accordance with a fourth embodiment of the present disclosure. 
         FIG. 7  is a schematic view of the high-isolation dual-band antenna in accordance with a fifth embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     In the following detailed description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the disclosed embodiments. It will be apparent, however, that one or more embodiments may be practiced without these specific details. In other instances, well-known structures and devices are schematically shown in order to simplify the drawing. It should be understood that, when it is described that an element is “coupled” or “connected” to another element, the element may be “directly coupled” or “directly connected” to the other element or “coupled” or “connected” to the other element through a third element. In contrast, it should be understood that, when it is described that an element is “directly coupled” or “directly connected” to another element, there are no intervening elements. 
     Please refer to  FIG. 1 ˜ FIG. 3 , which are a structure diagram, a first schematic view and a second schematic view in accordance with a first embodiment of the present disclosure. As shown in  FIG. 1 , the dual-band antenna  1  includes a substrate S, a conductive grounding-layer  11 , two conductive radiating-layer  12  and two feed points  14 . The substrate S includes a substrate S having a surface. The grounding-layer  11  is formed on the surface of the substrate S, and includes two accommodating cavities A 1 , an isolating cavity  13 , a first-slot  132  and two second-slots  133 . The accommodating cavities A are disposed at the two top corners of the grounding-layer  11 ; each respectively surrounded by a first-extension  111  at the side of the grounding-layer  11  and a second-extension  112  at the top side of the grounding-layer  11 ; there is a gap G between the ends of the first-extension  111  and the second-extension  112 . The isolation cavity  13  are formed by removing the material on the grounding-layer  11  and disposed between the accommodating cavities A 1 ; the isolation cavity  13  includes a main-block  131 . The first-slot  132  is disposed at the bottom end of the main-block  131 , extends from the main-block  131  toward the bottom side of the grounding-layer  11  and then extends toward the accommodating cavities A 1  respectively to form two branches. The second-slots  133  are disposed at the both sides of the main-block  131  respectively, extend from the main-block  131  toward the accommodating cavities A 1  respectively and then extend toward the top side of the grounding-layer  11 . Each of the radiating-layers  12  is disposed inside each of the accommodating cavities A 1 . The feed points  14  is located oppositely on the first-extension  111  side of the radiating-layers  12 , and connects the radiating-layers  12  to the grounding-layer  11  respectively. 
     As shown in  FIG. 2 , when the signals are fed into the feed point  14 , a first current C 1  generates at one side of the feed point  14 ; the first current C 1  flows along the path extending from one side of the feed point  14  to the grounding-layer  11  to generate a first exciting current C 1 ′ in the grounding-layer  11 ; the resonance between the first current C 1  and the first exciting current C 1 ′ generates the signals of a first frequency band. 
     When the signals are fed into the feed point  14 , a second current C 2  also generates at the other side of the feed point  14 ; the second current C 2  flows along the path extending from the other side of the feed point  14  to the grounding-layer  11  to generate a second exciting current C 2 ′ in the grounding-layer  11 ; the resonance between the second current C 2  and the second exciting current C 2 ′ generates the signals of a second frequency band. 
     As describe above, the two frequency bands of the antenna  1  in the embodiment can be realized by the coupling between the monopole antennas and the grounding-layer  11 . 
     As shown in  FIG. 3 , at least a portion of each second-slot  133  can serve as an isolation section IS 2  of the second frequency band; besides, the length of the isolation section IS 2  of the second frequency band may be ¼ wavelength of the second frequency band or proportional to ¼ wavelength of the second frequency band. In the embodiment, the second frequency band may be 5G, so the length of the isolation section IS 2  of the second frequency band may be ¼ wavelength of 5G or proportional to ¼ wavelength of 5G. 
     Adjust the sizes of the second-slots  133  and change the length of the isolation section IS 2  of the second frequency band can adjust the antenna characteristics of the dual-band antenna  1  in order to satisfy different requirements. The length of the isolation section IS 2  is related to at least one of the central frequency point of the isolation of the second frequency band. 
     At least a portion of the first-slot  132  and the second-slots  133  can serve as an isolation section IS 1  of the first frequency band; besides, the length of the isolation section IS 1  of the first frequency band may be ¼ wavelength of the first frequency band or proportional to ¼ wavelength of the first frequency band. In the embodiment, the first frequency band may be 2.4G, so the length of the isolation section IS 1  of the first frequency band may be ¼ wavelength of 2.4G or proportional to ¼ wavelength of 2.4G. 
     Adjust the size of the first-slot  132  or the second-slots  133  and change the length of the isolation section IS 1  of the first frequency band can adjust the antenna characteristics of the dual-band antenna  1  in order to satisfy different requirements. The length of the isolation section IS 1  of the first frequency band is related to at least one of the central frequency point of the isolation of the first frequency band. 
     Please refer to  FIG. 1 ˜ FIG. 3 , which are a structure diagram, a first schematic view and a second schematic view in accordance with the other embodiment of the present disclosure. As shown in  FIG. 1 , the dual-band antenna  1  has two operating frequency bands, the first frequency band and the second frequency band, and includes a ground zone  11 , two radiators  12 , an isolation zone  13  and two feed points  14 . In the embodiment, the frequency of the second frequency band is higher than the frequency of the first frequency band; for example, the first frequency band may be 2.4G and the second frequency band may be 5G. 
     One side of the ground zone  11  includes a first extension  111  and a second extension  112 . The ground zone  11  has a missing corner at one side thereof; the first extension  11  extends toward the top of the ground zone  11  and the second extension  112  extends toward the left side of the ground zone  11 , such that the space between first extension  111 , the second extension  112  and the ground zone  11  can form an accommodating zone A 1  not completely sealed. 
     Similarly, the other side of the ground zone  11  also includes a first extension  111  and a second extension  112 . The ground zone  11  also has a missing corner at the other side thereof; the first extension  11  extends toward the top of the ground zone  11  and the second extension  112  extends toward the right side of the ground zone  11 , such that the space between first extension  111 , the second extension  112  and the ground zone  11  can form an accommodating zone A 1  not completely sealed. 
     The radiators  12  are disposed in the accommodating zones A 1  of the both sides of the ground zone  11 ; these radiators  12  may be monopole antennas. Besides, the first extensions  111  and the second extensions  112  of the ground zone  11  can couple to the radiators  12  to generate signals, so can be considered part of the radiators  12 . 
     The isolation zone  13  is disposed between the radiators  12 . More specifically, the isolation zone  13  is formed by removing the material on the ground zone  11 . The isolation zone  13  is a part of the dielectric zone; the isolation zone  13  includes a main body  131 , a first-slot  132  and two second-slots  133 ; the first-slot  132  and the second-slots  133  can provide the isolation effect. The first-slot  132  extends from the main body  131  toward the bottom of the ground zone  11  and then extends toward the radiators  12  respectively. 
     The second-slots  133  are disposed at the both sides of the main body  131  respectively; more specifically, one of the second-slots  133  extends from the main body  131  toward the radiator  12  at the left side and then extends toward the top of the main body  131 ; the other one of the second-slots  133  extends from the main body  131  toward the radiator  12  at the right side and then extends toward the top of the main body  131 . 
     The feed points  14  connect the radiators  12  to the ground zone  11  respectively. 
     The antenna characteristics of the dual-band antenna  1  can be adjusted by changing the sizes of the parts of the dual-band antenna  1  respectively. For example, adjusting the sizes of the radiators  12 , the first extensions  111  and the second extension  112  can change the central frequency point of the first frequency band, the central frequency point of the second frequency band, the matching characteristic of the first frequency band and the matching characteristic of the second frequency band respectively. In addition, adjusting the sizes of the first-slot  132  and the second-slots  133  can change the central frequency point of the isolation of the first frequency band and the central frequency point of the isolation of the second frequency band respectively. 
     As shown in  FIG. 2 , when the signals are fed into the feed point  14 , a first current C 1  generates at one side of the feed point  14 ; the first current C 1  flows along the path extending from one side of the feed point  14  to the ground zone  11  to generate a first exciting current C 1 ′ in the ground zone  11 ; the resonance between the first current C 1  and the first exciting current C 1 ′ generates the signals of the first frequency band. 
     When the signals are fed into the feed point  14 , a second current C 2  generates at the other side of the feed point  14 ; the second current C 2  flows along the path extending from the other side of the feed point  14  to the ground zone  11  to generate a second exciting current C 2 ′ in the ground zone  11 ; the resonance between the second current C 2  and the second exciting current C 2 ′ generates the signals of the second frequency band. 
     As describe above, the two frequency bands of the antenna  1  in the embodiment can be realized by the coupling between the monopole antennas and the ground zone  11 . 
     As shown in  FIG. 3 , at least a portion of each second-slot  133  can serve as the isolation section IS 2  of the second frequency band; besides, the length of the isolation section IS 2  of the second frequency band may be ¼ wavelength of the second frequency band or proportional to ¼ wavelength of the second frequency band. In the embodiment, the second frequency band may be 5G, so the length of the isolation section IS 2  of the second frequency band may be ¼ wavelength of 5G or proportional to ¼ wavelength of 5G. 
     Adjusting the sizes of the second-slots  133  can change the length of the isolation section IS 2  of the second frequency band to adjust the antenna characteristics of the dual-band antenna  1  in order to satisfy different requirements. The length of the isolation section IS 2  of the second frequency band is related to at least one of the central frequency point of the isolation of the second frequency band and the isolation of the second frequency band. Adjusting the length of the isolation section IS 2  of the second frequency band can change one or more than one of the central frequency point of the isolation of the second frequency band and the isolation of the second frequency band. 
     At least a portion of the first-slot  132  and the second-slots  133  can serve as the isolation section IS 1  of the first frequency band; besides, the length of the isolation section IS 1  of the first frequency band may be ¼ wavelength of the first frequency band or proportional to ¼ wavelength of the first frequency band. In the embodiment, the first frequency band may be 2.4G, so the length of the isolation section IS 1  of the first frequency band may be ¼ wavelength of 2.4G or proportional to ¼ wavelength of 2.4G. 
     Adjusting the size of the first-slot  132  or the second-slots  133  can change the length of the isolation section IS 1  of the first frequency band to adjust the antenna characteristics of the dual-band antenna  1  in order to satisfy different requirements. The length of the isolation section IS 1  of the first frequency band is related to at least one of the central frequency point of the isolation of the first frequency band and the isolation of the first frequency band. Adjusting the length of the isolation section IS 1  of the first frequency band can change one or more than one of the central frequency point of the isolation of the first frequency band and the isolation of the first frequency band. 
     Therefore, as described above, the isolation section IS 1  of the first frequency band of the high-isolation dual-band antenna  1  according to the present disclosure may partially overlap the isolation section IS 2  of the second frequency band thereof. 
     In addition, please note that the extension directions and the lengths of the first-slot  132  and the second-slot  133  can be adjusted according to actual conditions in order to conform to satisfy the requirements of different frequency bands. For instance, the first-slot  132 , in the embodiment, extends from the main body  131  toward the bottom of the ground zone  11  and then extends toward the radiators  12  respectively to form two branches; then, each branch further extends toward the bottom of the ground zone  11 . In another embodiment, the antenna designer can bend the branches or form the branches in different shapes, instead of extending the branches to the bottom of the ground zone  11 , according to the requirements of the design. 
     As described above, the isolation zone  13  of the dual-band antenna  1  has a special structure design; in other words, the isolation of the dual-band antenna  1  can be effectively increased because the isolation section IS 1  of the first frequency band partially overlaps the isolation section IS 2  of the second frequency band; thus, the performance of the dual-band antenna  1  can be significant improved. 
     Via the above special structure design, the dual-band antenna  1  of the embodiment can achieve excellent isolation, so the performance of the dual-band antenna  1  can be optimized. In addition, the antenna characteristics of the dual-band antenna  1  can be directly adjusted just by changing the parts of the dual-band antenna  1  respectively in order to conform to different requirements. 
     The embodiment just exemplifies the present disclosure and is not intended to limit the scope of the present disclosure; any equivalent modification and variation according to the spirit of the present disclosure is to be also included within the scope of the following claims and their equivalents. 
     It is worthy to point out that the antenna characteristics of the currently available dual-band antennas cannot be easily adjusted because of the limitations in their structure designs; for the reason, antenna designers always need to spend a lot of time on adjusting the structures of these antennas in order to realize desired antenna characteristics. On the contrary, according to one embodiment of the present disclosure, the dual-band antenna has a special structure design, so antenna designers do not need to spend a lot of time on adjusting the structure of the antenna according to different requirements but can directly realize the desired antenna characteristics just by adjusting the size of each part of the antenna; therefore, antenna designers can more efficiently design the antennas able to conform to their requirements. 
     Besides, according to one embodiment of the present disclosure, the dual-band antenna has a special structure design, so antenna designers can directly realize the desired antenna characteristics meeting different requirements just by adjusting the size of each part of the antenna; therefore, the application of the dual-band antenna can be more comprehensive. 
     Moreover, according to one embodiment of the present disclosure, the isolation zone of the dual-band antenna has a special structure design, so the isolation zone can achieve higher isolation; therefore, the performance of the dual-band antenna can be optimized to significantly better the performance of the dual-band antenna. 
     Please refer to  FIG. 4 , which is a schematic view of the high-isolation dual-band antenna in accordance with a second embodiment of the present disclosure. As shown in  FIG. 4 , the size of the first extensions  111  of the dual-band antenna  1  can be adjusted to change the antenna characteristics of the dual-band antenna  1  so as to conform to different requirements. The length L 1  of the first extensions  111  is related to at least the central frequency point of the first frequency band. Increasing the length L 1  of the first extensions  111  can adjust the central frequency point of the first frequency band in the direction of low frequency; on the contrary, decreasing the length L 1  of the first extensions  111  can adjust the central frequency point of the first frequency band in the direction of high frequency. Besides, adjusting the length L 1  of the first extensions  111  can also slightly adjust the central frequency point of the isolation of the second frequency band and the matching characteristic of the second frequency band. 
     The width W 1  of the first extensions  111  is related to at least the matching characteristic of the first frequency band. The width W 1  of the first extensions  111  should be proper; if the width W 1  of the first extensions  111  is too wide or too narrow, the matching characteristic of the first frequency band deteriorates. Besides, adjusting the width W 1  of the first extensions  111  can also slightly adjust the central frequency point of the first frequency band, the central frequency point of the isolation of the first frequency band, the matching characteristic of the second frequency band, the central frequency point of the second frequency band and the central frequency point of the isolation of the second frequency band. 
     Please refer to  FIG. 5 , which is a schematic view of the high-isolation dual-band antenna in accordance with a third embodiment of the present disclosure. As shown in  FIG. 5 , the size of the second extensions  112  of the dual-band antenna  1  can be adjusted to change the antenna characteristics of the dual-band antenna  1  so as to conform to different requirements. The length L 2  of the second extensions  112  is related to at least the central frequency point of the second frequency band. Increasing the length L 2  of the second extensions  112  can adjust the central frequency point of the second frequency band in the direction of low frequency; on the contrary, decreasing the length L 2  of the second extensions  112  can adjust the central frequency point of the second frequency band in the direction of high frequency. Besides, adjusting the length L 2  of the second extensions  112  can also slightly adjust the central frequency point of the first frequency band, the isolation of the first frequency band, the matching characteristic of the first frequency band, the isolation of the second frequency band and the matching characteristic of the second frequency band. Moreover, the length L 2  of the second extensions  112  is also related to the resonance between the second extension  112  and the radiators  12 ; the length L 2  should be higher than a certain value, or the resonance between the second extensions  112  and the radiators will not occur. 
     The width W 2  of the second extensions  112  is related to at least the matching characteristic of the second frequency band. The width W 2  of the second extensions  112  should be proper; if the width W 2  of the second extensions  112  is too wide, the matching bandwidth becomes narrower. Besides, adjusting the width W 2  of the second extensions  112  can also slightly adjust the central frequency point of the first frequency band, the isolation of the first frequency band, the matching characteristic of the first frequency band and the isolation of the second frequency band. 
     Please refer to  FIG. 6 , which is a schematic view of the high-isolation dual-band antenna in accordance with a fourth embodiment of the present disclosure. As shown in  FIG. 6 , the size of the radiators  12  of the dual-band antenna  1  can be adjusted to change the antenna characteristics of the dual-band antenna  1  so as to conform to different requirements. The width W 3  of the radiators  12  is related to at least the matching characteristic of the first frequency band and the matching characteristic of the second frequency band. Adjusting the width W 3  of the radiators  12  can change the distance D 1  between the radiators  12  and the first extensions  111  to change the matching characteristic of the first frequency band. Adjusting the width W 3  of the radiators  12  can change the distance D 2  between the radiators  12  and the ground zone  11  on the feed points  14  side to adjust the matching characteristic of the second frequency band. Besides, adjusting the width W 3  of the radiators  12  can also slightly adjust the central frequency point of the first frequency band, the central frequency point of the isolation of the first frequency band, the central frequency point of the second frequency band and the central frequency point of the isolation of the second frequency band. 
     Please refer to  FIG. 7 , which is a schematic view of the high-isolation dual-band antenna in accordance with a fifth embodiment of the present disclosure. As shown in FIG.  7 , the size of the radiators  12  of the dual-band antenna  1  can be adjusted to change the antenna characteristics of the dual-band antenna  1  so as to conform to different requirements. The length L 3  of the radiators  12  is related to at least the matching characteristic of the first frequency band and the matching characteristic of the second frequency band. Adjusting the length L 3  of the radiators  12  can change the distance D 3  between the tops of the radiators  12  and the second extensions  112  to change the matching characteristic of the first frequency band. Adjusting the length L 3  of the radiators  12  can change the distance D 4  between the bottoms of the radiators  12  and the ground zone  11  to adjust the matching characteristic of the second frequency band. Besides, adjusting the length L 3  of the radiators  12  can also slightly adjust the bandwidth of the second frequency band and the isolation of the second frequency band. 
     As described above, as the dual-band antenna  1  has a special structure design, the antenna characteristics of the dual-band antenna  1  can be directly adjusted just by changing the size of each part thereof; thus, the dual-band antenna  1  can achieve all desired antenna characteristics, so is applicable to different frequency bands, such as 802.11a (5150˜5850 MHz), 802.11b (2400˜2500 MHz), 802.11g (2400˜2500 MHz) and 802.11n (2.4 GHz or 5 GHz Band). Accordingly, antenna designers can easily satisfy different requirements just by slightly adjusting the structure of the dual-band antenna  1  instead of re-designing the whole structure of the dual-band antenna  1  according to different requirements. Therefore, the application of the dual-band antenna  1  according to the embodiments of the present disclosure can be more comprehensive. 
     To sum up, according to one embodiment of the present disclosure, the dual-band antenna has a special structure design, so antenna designers do not need to spend a lot of time on adjusting the structure of the antenna according to different requirements but can directly realize the desired antenna characteristics just by adjusting the size of each part of the antenna; therefore, antenna designers can more efficiently design the antennas able to conform to their requirements. 
     Besides, according to one embodiment of the present disclosure, the dual-band antenna has a special structure design, so antenna designers can directly realize the desired antenna characteristics meeting different requirements just by adjusting the size of each part of the antenna; therefore, the application of the dual-band antenna can be more comprehensive. 
     Moreover, according to one embodiment of the present disclosure, the isolation zone of the dual-band antenna has a special structure design, so the isolation zone can achieve higher isolation; therefore, the performance of the dual-band antenna can be optimized to significantly better the performance of the dual-band antenna. 
     It will be apparent to those skilled in the art that various modifications and variations can be made to the disclosed embodiments. It is intended that the specification and examples be considered as exemplary only, with a true scope of the disclosure being indicated by the following claims and their equivalents.