Patent Publication Number: US-9837716-B2

Title: Multiband antenna

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to antennas and, more particularly, to an antenna that supports multiple frequency bands. 
     Description of the Prior Art 
     Antennas have to change with communication-related technological advancements in order to meet frequency band requirements for the latest generation of communication technology. LTE (Long-Term Evolution), a major standard for 4G (fourth generation) wireless communication technology, surpasses 3G mobile communication technology in bandwidth and data transmission speed. However, antenna design is confronted with a challenge, that is, complying simultaneously with the requirements of conventional communication electronic devices for being lightweight, thin and compact, the requirements of 4G wireless communication technology in terms of frequency bands, and the limitation of communication electronic device on antenna size. 
     SUMMARY OF THE INVENTION 
     The present invention provides a multiband antenna that supports frequency bands required by 4G wireless communication technology and is advantageously compact to therefore suit lightweight, thin and compact communication electronic devices. 
     The multiband antenna of the present invention comprises a short-circuit element, feed element, first connection segment and low-frequency radiating element. The first end of the short-circuit element has a grounding point. The short-circuit element is connected to the ground through the grounding point. The first end of the feed element has a feed point. The feed element has a second end connected to the short-circuit element. The feed element receives a feed signal through the feed point. The first connection segment has a first end connected to a second end of the short-circuit element. The low-frequency radiating element has a closed pattern. The closed pattern has a first side and a second side opposing the first side. The first side is of a larger width than the second side. The second side is connected to the second end of the first connection segment. 
     In an embodiment of the present invention, the closed pattern comprises a second connection segment, a third connection segment and a fourth connection segment. The fourth connection segment, second connection segment and third connection segment together form the triangular closed pattern. A common connection end of the second connection segment and fourth connection segment functions as the second side of the closed pattern. The third connection segment functions as the first side of the closed pattern. The first, the second, the third and the fourth connection segments provide a resonance path whereby the multiband antenna supports low frequency bands. 
     In an embodiment of the present invention, the low frequency band ranges from 690 MHz to 960 MHz. 
     In an embodiment of the present invention, the first, second, the third and the fourth connection segments provide the resonance path whereby the multiband antenna supports a multiplied frequency band. 
     In an embodiment of the present invention, the multiplied frequency band ranges from 2400 MHz to 2600 MHz. 
     In an embodiment of the present invention, the multiband antenna further comprises a first grounding surface coupled to the first end of the short-circuit element, parallel to the low-frequency radiating element, and separated from the low-frequency radiating element by a first distance. 
     In an embodiment of the present invention, an area of projection of the closed pattern upon a plane of the first grounding surface falls within the first grounding surface. 
     In an embodiment of the present invention, the multiband antenna further comprises a first high-frequency radiating element connected to the first connection segment to provide a first resonance path whereby the multiband antenna supports a first high frequency band. 
     In an embodiment of the present invention, the multiband antenna further comprises a second connection segment and a second grounding surface. The second connection segment has a first end connected to the first grounding surface. The second grounding surface is connected to a second end of the second connection segment, parallel to the first high-frequency radiating element, and separated from the first high-frequency radiating element by a second distance. The first distance is larger than the second distance. 
     In an embodiment of the present invention, the multiband antenna further comprises a second high-frequency radiating element connected to the first connection segment to provide a second resonance path whereby the multiband antenna supports a second high frequency band, with the second high-frequency radiating element separated from the second grounding surface by the second distance. 
     In an embodiment of the present invention, the first high frequency band and the second high frequency band support a frequency band of 1710 MHz through 2200 MHz. 
     In an embodiment of the present invention, the first resonance path is of a larger length than the second resonance path. 
     In conclusion, in the embodiments of the present invention, resonance paths provided by a first connection segment and a low-frequency radiating element with a closed pattern enable the multiband antenna to support a low frequency band and a multiplied frequency band, whereas a resonance path provided by high-frequency radiating elements enables the multiband antenna to support high frequency bands, so as for the multiband antenna to meet the requirements of 4G wireless communication technology in terms of various frequency bands and effectively reduce the required size of the antenna, thereby allowing the multiband antenna to be easily disposed in various communication electronic device. The closed pattern has a first side and a second side. The first side is of a larger width than the second side. The second side is connected to a second end of the first connection segment. 
     To render the above technical features and advantages of the present invention obvious and comprehensible, the prevent invention is illustrated with embodiments, depicted with drawings, and described below. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic view of a multiband antenna according to an embodiment of the present invention; 
         FIG. 2  is a graph of antenna efficiency of the multiband antenna operating at a low frequency band according to the embodiment shown in  FIG. 1 ; 
         FIG. 3  is a graph of antenna efficiency of the multiband antenna operating at a high frequency band according to the embodiment shown in  FIG. 1 ; and 
         FIG. 4  is a schematic view of the multiband antenna according to another embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
       FIG. 1  is a schematic view of a multiband antenna according to an embodiment of the present invention. As shown in  FIG. 1 , a multiband antenna  100  comprises a short-circuit element  102 , a feed element  104 , a first connection segment  106 , a low-frequency radiating element  108 , a high-frequency radiating element  110  and a first grounding surface  112 . The first end of the short-circuit element  102  has a grounding point G 1 . The short-circuit element  102  is connected to the first grounding surface  112  through the grounding point G 1 . The first grounding surface  112  is parallel to the first connection segment  106  and the low-frequency radiating element  108  and is separated from the low-frequency radiating element  108  by a first distance d 1 . The first end of the feed element  104  has a feed point F 1 . The first end of the feed element  104  is connected to the first grounding surface  112  through a feed signal source (not shown). The feed element  104  receives a feed signal through the feed point F 1 . The second end of the short-circuit element  102  and the second end of the feed element  104  are connected to the first end of the first connection segment  106 . The second end of the first connection segment  106  is connected to the low-frequency radiating element  108 . In this embodiment, the first connection segment  106  is an L-shaped connection segment. The low-frequency radiating element  108  has a closed pattern. The area of projection of the closed pattern upon the plane of the first grounding surface  112  falls within the first grounding surface  112 . The closed pattern has a first side and a second side opposing the first side. The width W 1  of the first side is larger than the width W 2  of the second side. The second side is connected to the second end of the first connection segment  106 . 
     Referring to  FIG. 1 , in this embodiment, the closed pattern is a triangle. The first side of the closed pattern is one of the three sides of the triangle, and the second side of the closed pattern is a vertex of the triangle. Furthermore, the low-frequency radiating element  108  comprises a second connection segment  108 - 1 , a third connection segment  108 - 2  and a fourth connection segment  108 - 3 . The second connection segment  108 - 1 , the third connection segment  108 - 2  and the fourth connection segment  108 - 3  together form the triangular closed pattern. A common connection end of the second connection segment  108 - 1  and the fourth connection segment  108 - 3  functions as the second side of the closed pattern. The third connection segment  108 - 2  functions as the first side of the closed pattern. The first connection segment  106 , the second connection segment  108 - 1 , the third connection segment  108 - 2  and the fourth connection segment  108 - 3  provide resonance path whereby the multiband antenna  100  supports a low-frequency band, and the low frequency band ranges from 690 MHz to 960 MHz to meet the requirements of 4G wireless communication technology in terms of low-frequency bands. 
     Furthermore, the high-frequency radiating element  110  is connected to the first connection segment  106 . Referring to  FIG. 1 , one end of the high-frequency radiating element  110  is connected to a bend of the first connection segment  106 , but the present invention is not limited thereto. The other end of the high-frequency radiating element  110  is an open circuit end. The first connection segment  106  and the high-frequency radiating element  110  provide the resonance path (which begins at the first end of the first connection segment  106  and ends at the open circuit end of the high-frequency radiating element  110 ) whereby the multiband antenna  100  supports a high-frequency band, and the high-frequency band ranges from 1710 MHz to 2200 MHz. Moreover, the resonance path provided by the second connection segment  108 - 1 , the third connection segment  108 - 2  and the fourth connection segment  108 - 3  of the low-frequency radiating element  108  and the first connection segment  106  enables the multiband antenna  100  to support a multiplied frequency band by frequency multiplication such that multiplied frequencies, such as 1600 MHz, 2400 MHz, which are two times, three time or multiple times higher than the central operating frequency, such as 800 Hz, of the low-frequency radiating element  108 , are generated. In this embodiment, the multiplied frequency band ranges from 2400 MHz to 2600 MHz. Therefore, the high-frequency radiating element  110  provides the resonance path whereby the multiband antenna  100  supports high-frequency bands, whereas the first connection segment  106  and the low-frequency radiating element  108  provide the resonance path whereby the multiband antenna  100  supports a multiplied frequency band, to meet the requirements of 4G wireless communication technology in terms of high-frequency bands. 
       FIG. 2  is a graph of antenna efficiency of the multiband antenna operating at a low frequency band according to the embodiment shown in  FIG. 1 .  FIG. 3  is a graph of antenna efficiency of the multiband antenna operating at a high-frequency band according to the embodiment shown in  FIG. 1 . Referring to  FIG. 2 , the multiband antenna  100  of the embodiment shown in  FIG. 1  markedly surpasses a conventional 4G antenna in antenna efficiency, when operating at a low frequency band, where the solid curve indicates the multiband antenna  100 , and the dashed curve indicates the conventional 4G antenna. Referring to  FIG. 2 , for example, the multiband antenna  100  achieves an antenna efficiency of 62% approximately, whereas the conventional 4G antenna achieves an antenna efficiency of 52% approximately, at 800 Hz. Referring to  FIG. 3 , the multiband antenna  100  of the embodiment shown in  FIG. 1  markedly surpasses the conventional 4G antenna in antenna efficiency, when operating at high-frequency bands, where the solid curve indicates the multiband antenna  100 , and the dashed curve indicates the conventional 4G antenna. Referring to  FIG. 3 , for example, the multiband antenna  100  achieves an antenna efficiency of 68% approximately, whereas the conventional 4G antenna achieves an antenna efficiency of 50% approximately, at 1800 Hz. 
     In this embodiment, the multiband antenna  100  is characterized in that: the resonance path provided by the first connection segment  106  and the low-frequency radiating element  108  with a closed pattern enables the multiband antenna  100  to support a low frequency band and multiplied frequency band; and the resonance path provided by the high-frequency radiating element  110  enables the multiband antenna  100  to support high frequency bands, thereby allowing the multiband antenna  100  to meet the requirements of 4G wireless communication technology in terms of various frequency bands. Moreover, in this embodiment, the structure of the multiband antenna  100  effectively reduces the required size of the antenna. In the embodiment shown in  FIG. 1 , the multiband antenna  100  is of a length L 1  as small as 7 cm such that the multiband antenna  100  can be easily disposed in various communication electronic devices. 
       FIG. 4  is a schematic view of the multiband antenna according to another embodiment of the present invention. As shown in  FIG. 4 , a multiband antenna  200  of this embodiment differs from the multiband antenna  100  of the embodiment shown in  FIG. 1  in that the multiband antenna  200  of this embodiment comprises a first grounding surface  202 , second grounding surface  204  and connection segment  206  for connecting the first grounding surface  202  and second grounding surface  204 . The first grounding surface  202 , second grounding surface  204  and connection segment  206  differ in height. The multiband antenna  200  further comprises two high-frequency radiating elements  208 ,  210 . The first grounding surface  202  is similar to the first grounding surface  112  of the embodiment shown in  FIG. 1 . The first grounding surface  202  is connected to the short-circuit element  102  and the feed element  104  and separated from the low-frequency radiating element  108  by a first distance d 1 . The second grounding surface  204  is parallel to the high-frequency radiating elements  208 ,  210  and separated from the high-frequency radiating elements  208 ,  210  by a second distance d 2 . The first distance d 1  is larger than the second distance d 2 . Furthermore, the first end and second end of the connection segment  206  are connected to the first grounding surface  202  and second grounding surface  204 , respectively. Therefore, the high-frequency radiating elements are closer to the grounding surface to enhance the energy of the coupling of the high-frequency radiating elements  208 ,  210  to the second grounding surface  204  and thereby enhance the quality of signal reception of the multiband antenna  200 . Moreover, in this embodiment, the high-frequency radiating elements  208 ,  210  provide resonance paths. The resonance path provided by the high-frequency radiating element  208  is longer than the resonance path provided by the high-frequency radiating element  210 . The resonance paths provided by the high-frequency radiating elements  208 ,  210  enable the multiband antenna  200  to support two high frequency bands. The two high frequency bands range from 1710 MHz to 2200 MHz, thereby allowing the multiband antenna  200  to meet the requirements of 4G wireless communication technology in terms of high frequency bands. 
     In conclusion, in the embodiments of the present invention, resonance paths provided by a first connection segment and a low-frequency radiating element with a closed pattern enable the multiband antenna to support a low frequency band and a multiplied frequency band, whereas a resonance path provided by high-frequency radiating elements enables the multiband antenna to support high frequency bands, so as for the multiband antenna to meet the requirements of 4G wireless communication technology in terms of various frequency bands and effectively reduce the required size of the antenna, thereby allowing the multiband antenna to be easily disposed in various communication electronic device. The closed pattern has a first side and a second side. The first side is of a larger width than the second side. The second side is connected to a second end of the first connection segment. 
     Although the present invention is disclosed above by embodiments, the embodiments are not restrictive of the present invention. Any persons skilled in the art can make some changes and modifications to the embodiments without departing from the spirit and scope of the present invention. Accordingly, the legal protection for the present invention should be defined by the appended claims.