Patent Publication Number: US-7592966-B2

Title: Broadband antenna and assembly combination thereof

Description:
FIELD OF THE INVENTION 
   The present invention relates to a broadband antenna, especially to a compact broadband antenna and an assembly combination thereof. 
   DESCRIPTION OF RELATED ART 
   Due to system integration for wireless communication is in progress, the broadband antenna has been an essential requirement for communication systems. 
   Conventionally, a discone antenna of the broadband antenna has been disclosed. Refer to U.S. Pat. No. 4,851,859, the discone antenna provides optimal performance at microwave frequencies. Though, the conventional discone antenna can receive signals in broadband, its structure is not only too large but also quite heavy. It&#39;s not practical and not able to meet requirements of compact size and light weight as desired for the market. 
   Moreover, the structure of the conventional antenna is shaped in conical, and the desired radiation pattern can&#39;t be controlled according to such structure. 
   In order to solve above problems, the present invention provides a broadband antenna and an assembly combination thereof. 
   SUMMARY OF THE INVENTION 
   It is a primary objective of the present invention to provide a compact broadband antenna. Another objective of the present invention is to provide a broadband antenna assembly combination that includes at least two antennas. Further objective of the present invention is to provide a broadband antenna and a broadband antenna assembly combination that both are able to control the radiation pattern. 
   An embodiment of the broadband antenna according to the present invention includes a first radiation element, a second radiation element, a substrate, and a reflector. The first radiation element comprising a first trapezoid portion. The first radiation element and the second radiation element are disposed on the substrate. 
   The first radiation element further comprises a second trapezoid portion, and the first trapezoid portion and the second trapezoid portion connect with each other to form an integral. Both the first trapezoid portion and the second trapezoid portion have an upper base and a lower base, and the length of the lower base of the first trapezoid portion is substantially equal to that of the upper base of the second trapezoid portion. Moreover, the length of the lower base of the second trapezoid portion is larger than that of the lower base of the first trapezoid portion. 
   It is preferable that the distance between the first radiation element and the second radiation element is smaller than or substantially equal to 5 mm while the distance between the first radiation element and a soldering part is larger than or substantially equal to 0.3 mm. In an embodiment, the substrate is arranged perpendicular to the reflector. In another embodiment, the substrate and the reflector may be on the same plane. The first radiation element and the second radiation element are excited so as to reflect the energy by the radiator. 
   The first trapezoid portion of the first radiation element is an isosceles trapezoid with congruent legs and an angle formed by an intersection of the two legs of the first trapezoid portion ranges substantially from 50 to 80 degrees. 
   Furthermore, the second trapezoid portion of the first radiation element is also an isosceles trapezoid with congruent legs. In the first trapezoid portion, the absolute values of slopes of the two legs are the same and are larger than or substantially equal to that of the second trapezoid portion. 
   It is preferable that the length of the second radiation element is larger than or equal to ¼ wavelength of the center frequency at low frequency band, and the width of the second radiation element is smaller than or substantially equal to 1/16 wavelength of the center frequency at low frequency band. 
   In another embodiment of the present invention, the second radiation element comprises a first part, a second part, and a connecting part that connects the first part and the second part. The first part is n-shaped and the width of the first part is smaller than or substantially equal to 1/16 wavelength of center frequency at the low frequency band. The midpoint of the second part of the second radiation element is a feeding point for current. 
   The total length of the first part and the second part is about ¼ wavelength of the center frequency at low frequency band while the length of the second part is substantially ¼ wavelength of the center frequency at high frequency band. 
   In a further embodiment of the present invention, the first radiation element includes an upper base, a lower base, and two legs, wherein the lower base has an opening. It is preferable that a length of the upper base is substantially about ¼ wavelength of the center frequency at high frequency band. The width of the two legs of the first radiation element substantially ranges from 1/16 to ⅛ of the length of lower base. Also, the length of the opening is substantially about 1/16 to ⅛ of the length of lower base. 
   In addition, the present invention also provides a broadband antenna assembly combination comprising a first antenna, a second antenna, a radiation plate, and a reflector. 
   The first antenna and/or the second antenna may utilize the first radiation element and substrate mentioned above, and the first antenna and the second antenna intersect with each other at an angle such as 90 degrees. The radiation plate is perpendicular to both of the first antenna and the second antenna. Moreover, the radiation plate includes a first side, a second side, a third radiation element disposed on the first side, and a fourth radiation element disposed on the second side. By current passing through the first antenna, the second antenna, and the radiation plate, radiation energy is excited and then reflected by the reflector. 
   Other objectives, advantages, and novel features of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and other features, aspects, and advantages of the present invention will become better understood with regard to the following description, appended claims, and accompanying drawings, in which: 
       FIG. 1A  is a perspective view of a broadband antenna of an embodiment in accordance with the present invention; 
       FIG. 1B  is a front view of a broadband antenna of an embodiment in accordance with the present invention; 
       FIG. 1C  is a broadband antenna of an embodiment in accordance with the present invention with a first radiation element and a reflector arranged on the same plane; 
       FIG. 2A  and  FIG. 2B  respectively show a perspective view and a front view of a broadband antenna of another embodiment in accordance with the present invention; 
       FIG. 3A  and  FIG. 3B  respectively show a perspective view and a front view of a broadband antenna of a further embodiment in accordance with the present invention; 
       FIG. 4  is a perspective view of a broadband antenna of a further embodiment in accordance with the present invention; 
       FIG. 5  is a perspective view of a broadband antenna assembly combination of an embodiment in accordance with the present invention; 
       FIG. 6  shows Voltage Standing Wave Ratio (VSWR) of a broadband antenna of the embodiment in  FIG. 1A  at different frequencies; 
       FIG. 7A  and  FIG. 7B  respectively show the E-plane pattern and the H-plane pattern of a broadband antenna of the embodiment in  FIG. 1A  at different frequencies; 
       FIG. 8  shows efficiencies of a broadband antenna of the embodiment in  FIG. 1A  at different frequencies; 
       FIG. 9  shows Voltage Standing Wave Ratio (VSWR) of a broadband antenna of the embodiment in  FIG. 3A  detected at different frequencies; 
       FIG. 10A  and  FIG. 10B  show the E-plane pattern of a broadband antenna of the embodiment in  FIG. 3A  at 2.5 GHz (low frequency) and at 5.25 GHz (high frequency) respectively; and 
       FIG. 11  shows Voltage Standing Wave Ratio (VSWR) of a broadband antenna of the embodiment in  FIG. 4  at different frequencies. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   The present invention discloses a broadband antenna and an assembly combination thereof. Referring to  FIG. 1A  and  FIG. 1B  of a perspective view and a front view of a broadband antenna of an embodiment, a broadband antenna  1  according to the present invention comprises a first radiation element  11 , a second radiation element  12 , a substrate  13 , and a reflector  14 . The first radiation element  11  comprises a first trapezoid portion  11   a  and a second trapezoid portion  11   b  that connected with each other to form an integral. The first trapezoid portion  11   a  and the second trapezoid portion  11   b  have an upper base  111 ,  119   b  and a lower base  119   a ,  112  respectively. The length of the lower base  119   a  of the first trapezoid portion  11   a  is substantially equal to that of the upper base  119   b  of the second trapezoid portion  11   b . In this embodiment, the second radiation element  12  is shaped in string while it can be varied in other embodiment. Moreover, the first radiation element  11  can also be varied in different arrangements, which will be described more detail in below. 
   The first radiation element  11  and second radiation element  12  are preferred to be disposed on the substrate  13 . In a preferred embodiment, the distance D 1  between the first radiation element  11  and the second radiation element  12  is smaller than or substantially equal to 5 mm. 
   The reflector  14  and the substrate  13  are secured with each other. For example, a soldering part S can be used to connect and fix the substrate  13  with the reflector  14 . It is preferably that distance D 2  between the first radiation element  11  and the soldering part S is larger than or substantially equal to 0.3 mm. In this embodiment, the substrate  13  is arranged perpendicular to the reflector  14 , while in other embodiment, the substrate  13  and the reflector  14  may, for example, lie on the same plane, as shown in  FIG. 1C . The first radiation element  11  and the second radiation element  12  radiate energy by current passing through, the reflector  14  reflects the radiation energy to generate the radiation pattern for signal transmission of the broadband antenna  1 . 
   The reflector  14  can be a metal plate or a metal layer coated on the substrate  13 . As skilled in the present art will be appreciated, there is no limitation on shape or material for the reflector  14  shown in Figs. 
   It is preferable that the first radiation element  11  and the second radiation element  12  respectively include a first feeding point F 1  and a second feeding point F 2 . The first feeding point F 1  is located at the midpoint of a upper base  111  of the first trapezoid portion  11   a  on the first radiation element  11  while the second feeding point F 2  is at the midpoint of the second radiation element  12 . 
   The first radiation element  11  having a feeding part  110  that projects a bit beyond the upper base  111  of the first trapezoid portion  11   a . It is preferable that the first feeding point F 1  is located at the feeding part  110 . 
   In this embodiment, an angle formed by an intersection of two legs  113  on the first trapezoid portion  11   a  of the first radiation element  11  substantially ranges from 50 to 80 degrees. In other words, the angle θ 1 , in  FIG. 1B , substantially ranges from 25 to 40 degrees. 
   It is preferable that, in the first trapezoid portion  11   a , the absolute vales of the slopes of the two legs  113  are the same and larger than or substantially equal to that of the two legs  114  of the second trapezoid portion  11   b . For example, the slope is larger than or substantially equal to 0 to 20 degrees. That means the angle θ 2  is larger than the angle θ 1  substantially about 0 to 20 degrees. 
   One of the key points of the present invention is in the shape of the first radiation element  11 . That is, it is about the slope of the two legs  113  of the first trapezoid portion  11   a  and the slope of the two legs  114  of the first trapezoid portion  11   b . Although in the embodiment mentioned above and below, the trapezoid shape is taken as an example, there is no limitation on that shape. For example, the upper base  111  of the first trapezoid portion  11   a  and the lower base  112  of the second trapezoid portion  11   b  may be parallel with each other or not. Moreover, the upper base  111  and/or the lower base  112  may not be a linear line. 
   The length L 1  of the second radiation element  12  is larger than or substantially equal to ¼ wavelength at the lower operating frequency such as the center frequency at the low frequency band. The width W 1  of the second radiation element  12  is smaller than or substantially equal to 1/16 wavelength of the center frequency at low frequency band. 
   The substrate  13  can be a non-conducting substrate or a multilayer circuit board. Once the substrate is a non-conducting substrate, the broadband antenna  1  further includes a coaxial cable  15  that electrically connects with the first radiation element  11  and the second radiation element  12  for feeding current. For example, the first feeding point F 1  can be a positive electrode while the second feeding point F 2  is a negative electrode or vice versa so as to make the first radiation element  11  and the second radiation element  12  radiate energy through current excitation. 
   If the substrate  13  is a multilayer circuit board, there is no need to use the coaxial cable  15  for feeding current. By means of circuit design in the multilayer, the first radiation element  11  and the second radiation element  12  are electrically connected with each other. For example, the first radiation element  11  and the second radiation element  12  can be located on different layers of the circuit board respectively. Thus the alternating current is fed into the first radiation element  11  and the second radiation element  12  for radiating energy. 
     FIG. 2A  and  FIG. 2B  showing a perspective view and a front view of a broadband antenna of another embodiment in accordance with the present invention respectively. The second radiation element  12  disclosed in  FIG. 2A  differs from that in  FIG. 1A . In order to reduce the size of the broadband antenna, a second radiation element  22  of a broadband antenna  2  includes a first part  221 , a second part  222 , and a connecting part  223  that connects the first part  221  and the second part  222 . The first part  221  is in n-shaped and the width W 1  of the first part  221  is smaller than or substantially equal to 1/16 wavelength of the center frequency at low frequency band. Moreover, the width W 1  of the second radiation element  22  in  FIG. 2B  is substantially equal to that of the second radiation element  12  in  FIG. 1B . The midpoint of the second part  222  of the second radiation element  22  is a feeding point for current. 
   In this embodiment, the total length of the first part  221  and the second part  222 , L 1   a  plus L 1   b , is about ¼ wavelength of the center frequency at low frequency band, and the length L 1   b  of the second part  222  is about ¼ wavelength of the center frequency at high frequency band. Thus the size of the second radiation element  22  is minimized so that the volume of the broadband antenna  2  can be reduced notably. 
   Referring to  FIG. 3A  and  FIG. 3B , which show a perspective view and a front view of a broadband antenna of a further embodiment in accordance with the present invention respectively. A first radiation element  31  of a broadband antenna  3  includes an upper base part  315 , a lower base part  316 , and two legs  311  that connect the upper base part  315  and the lower base part  316  thereby a hollowed area  313  is formed therein. 
   The first radiation element  31  comprises a feeding part  310  that projects a bit over beyond the upper base  315 . The lower base  316  includes an opening  312  that connects with the hollow area  313 . 
   It is preferable that length L 4   c  of the upper base  315  is about ¼ of the wavelength at high frequency band. The length L 4   b  of two legs  311  of the first radiation element  31  ranges substantially from 1/16 to ⅛ length L 4  of the lower base  316 . And the length L 4   a  of the opening  312  is about from 1/16 to ⅛ length L 4  of the lower base  316 . 
   Referring to  FIG. 4 , except utilizing the soldering part S, in an embodiment of a broadband antenna  4 , the substrate  13  is connected with the reflector  14  by the second radiation element  12 . And the first radiation element  11  of this embodiment is arranged opposite to that of the embodiment in  FIG. 1A . 
   Refer to  FIG. 5 , a broadband antenna assembly combination  5  is disclosed, which comprises of a first antenna  50 , a second antenna  50 ′, a radiation plate  56 , and a reflector  54 . 
   The first antenna  50  and/or the second antenna  50 ′ respectively includes a first radiation element  51 ,  51 ′ and a substrate  53 ,  53 ′. The substrate  53  of the first antenna  50  and the substrate  53 ′ of the second antenna  50 ′ intersect with each other at an angle such as 90 degrees. The radiation plate  56  is perpendicular to the substrate  53  of the first antenna  50  and the substrate  53 ′ of the second antenna  50 ′. Moreover, the radiation plate  56  includes a third radiation element  57  and a fourth radiation element  58  that are disposed at a first side  56   a  and a second side  56   b  of the radiation plate  56  respectively. By current passing through the first radiation element  51  of the first antenna  50 , the first radiation element  51 ′ of the second antenna  50 ′, and the third radiation element  57  as well as the fourth radiation element  58  of the radiation plate  56 , radiation energy is excited and then reflected by the reflector  54 . 
   Furthermore, the broadband antenna assembly combination  5  further includes a cable duct  59  that is disposed on an intersection of the substrate  53  of the first antenna  50  and the substrate  53 ′ of the second antenna  50 ′ and is extending to the radiation plate  56  for feeding current. 
   By a first soldering part S and a second soldering part S 1 , the reflector  54  is fixed with the substrate  53  of the first antenna  50  and the substrate  53 ′ of the second antenna  50 ′ by soldering respectively. 
   Referring to  FIG. 6 , it shows Voltage Standing Wave Ratio (VSWR) of the broadband antenna  1  in  FIG. 1A  at different frequencies.  FIG. 7A  shows the E-plane pattern at different frequencies while  FIG. 7B  shows the H-plane pattern at different frequencies.  FIG. 8  shows efficiency of the broadband antenna  1  in  FIG. 1A  at different frequencies. 
   Referring to  FIG. 9 , it shows Voltage Standing Wave Ratio (VSWR) of the broadband antenna  3  in  FIG. 3A  at different frequencies.  FIG. 10A  and  FIG. 10B  respectively show the E-plane pattern at 2.5 GHz (low frequency) and at 5.25 GHz (high frequency). 
   Referring to  FIG. 11 , it shows Voltage Standing Wave Ratio (VSWR) of the broadband antenna  4  in  FIG. 4  at different frequencies. 
   In accordance with above embodiments, it should be noted that by adjusting width, length, angle and distance of the radiation element such as parameter W 1 , L 1 , L 1   a , L 1   b , L 4 , L 4   a , L 4   b , L 4   c , D 1 , D 2 , θ, θ 1 , θ 2  mentioned above, a better impedance match can be achieved. Moreover, the radiation pattern can be controlled in accordance with different shapes of the radiation elements. 
   Furthermore, the positions of the elements mentioned above can be varied, as skilled persons in this art will be appreciated. For example, as the second radiation element  22  shown in  FIG. 2B  is n-shaped, but not limited to. It can also be U-shaped. That means the second part  222  is on above the first part  221  (not shown in figures). 
   Additional advantages and modifications will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details, and representative devices shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.