Patent Publication Number: US-7212171-B2

Title: Dipole antenna

Description:
BACKGROUND OF THE INVENTION 
   1. Field of Invention 
   The invention relates to an antenna, and more particularly to a dipole antenna with an effectively reduced dimension. 
   2. Related Art 
   The rapidly developed radio transmission has brought various products and technologies applied in the field of multi-band transmission, such that many new products have the performance of radio transmission to meet the consumer&#39;s requirement. The antenna is an important element for transmitting and receiving electromagnetic wave energy in the radio transmission system. If the antenna is lost, the radio transmission system cannot transmit and receive data. Thus, the antenna plays an indispensable role in the radio transmission system. Selecting a proper antenna can match the feature of the product, enhance the transmission property, and further reduce the product cost. Different methods and different materials for manufacturing the antennas are used in different application products. In addition, considerations have to be taken when the antenna is designed according to different frequency bands used in different countries. The commonly used specifications of frequency band include IEEE 802.11, the most popular bluetooth communication (IEEE 802.15.1), and the like. The bluetooth works at the frequency band of 2.4 GHz. IEEE 802.11 is further divided into 802.11a, 802.11b and 802.11g, wherein the 802.11a specification corresponds to the frequency band of 5 GHz, and the 802.11b and 802.11g specifications correspond to the frequency band of 2.4 GHz. 
   The most-frequently used antennas in the industry include a monopole antenna, an inverted-F antenna, and a dipole antenna. Because the dipole antenna can effectively radiate and receive the electromagnetic wave, it is widely used in various communication fields. However, if the conventional dipole antenna wants to reach the better polarization effect, its dimension cannot be effectively reduced, and the product dimension has to be increased and cannot meet the miniaturization trend of the current electrical device. 
   Therefore, it is an important subject of the invention to design a dipole antenna with an effectively reduced dimension such that the product can be minimized. 
   SUMMARY OF THE INVENTION 
   In view of the foregoing, the invention is to provide a dipole antenna with an effectively reduced dimension so that the product can be minimized. 
   To achieve the above, a dipole antenna of the invention includes a substrate, a first radiating member and a second radiating member. The first radiating member and the second radiating member are disposed symmetrically. In this invention, the substrate has a first surface and a second surface opposite to the first surface. The first radiating member has a first radiating part, a second radiating part and a third radiating part. The first radiating part is disposed on the first surface and electrically connected to a grounding point. The second radiating part is disposed on the first surface. The third radiating part is disposed on the second surface and electrically connected to the first radiating part and the second radiating part. The second radiating member has a fourth radiating part, a fifth radiating part and a sixth radiating part. The fourth radiating part is disposed on the second surface and electrically connected to a feeding point. The fifth radiating part is disposed on the second surface. The sixth radiating part is disposed on the first surface and electrically connected to the fourth radiating part and the fifth radiating part. 
   As mentioned above, the third radiating part of the first radiating member and the first and second radiating parts of the first radiating member are on opposite surfaces, and the sixth radiating part of the second radiating member and the fourth and fifth radiating parts of the second radiating member are disposed on opposite surfaces. Thus, it is possible to effectively reduce the dimension of the dipole antenna, such that the application product of the dipole antenna may be minimized, and the trend of miniaturized electrical devices can be met. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will become more fully understood from the detailed description given herein below illustration only, and thus is not limitative of the present invention, and wherein: 
       FIG. 1  is a side view showing a dipole antenna according to a preferred embodiment of the invention; 
       FIG. 2  is another side view showing the dipole antenna according to the preferred embodiment of the invention; 
       FIG. 3  is a schematic illustration showing a measured result of a voltage standing wave ratio of the dipole antenna according to the embodiment of the invention; 
       FIG. 4  is a schematic illustration showing a measured result of a radiation pattern on an E-Plane when the dipole antenna of this embodiment is operating at 2.45 GHz; 
       FIG. 5  is a schematic illustration showing another measured result of the radiation pattern on an E-Plane when the dipole antenna of this embodiment is operating at 2.45 GHz; and 
       FIG. 6  is a schematic illustration showing a measured result of the radiation pattern on an H-Plane when the dipole antenna of this embodiment is operating at 2.45 GHz. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   The present invention will be apparent from the following detailed description, which proceeds with reference to the accompanying drawings, wherein the same references relate to the same elements. 
   Referring to  FIGS. 1 and 2 , a dipole antenna  1  according to the preferred embodiment of the invention includes a substrate  11 , a first radiating member  12  and a second radiating member  13 . The first radiating member  12  and the second radiating member  13  are symmetrically disposed on the substrate  11  with a center axis C serving as a symmetrical axis. The dipole antenna  1  may have a length L ranging from about 0.6 cm to 0.9 cm, and a width W ranging from about 1.5 cm to 2.3 cm. 
   The substrate  11  has a first surface  111 , a second surface  112 , a first through hole  113 , a second through hole  114 , a third through hole  115  and a fourth through hole  116 . The first surface  111  and the second surface  112  are opposite to each other. In this embodiment, the material of the substrate  11  may be a printed circuit board made of a Bismaleimide-triazine (BT) resin or a fiberglass reinforced epoxy resin (FR4). Alternatively, the substrate  11  may be a flexible film substrate made of polyimide. Moreover, it may be integrated in one part of the circuit layout of an electronic device so that the occupied space may be reduced. 
   The first radiating member  12  has a first radiating part  121 , a second radiating part  122  and a third radiating part  123 . The first radiating part  121  is disposed on the first surface  111  and connected to the first through hole  113 . In addition, the first radiating part  121  is also electrically connected to a grounding point  2 . The second radiating part  122  is disposed on the first surface  111  and connected to the second through hole  114 . The third radiating part  123  is disposed on the second surface  112  and electrically connected to the first radiating part  121  and the second radiating part  122  through the first through hole  113  and the second through hole  114 , respectively. 
   The second radiating member  13  has a fourth radiating part  131 , a fifth radiating part  132  and a sixth radiating part  133 . The fourth radiating part  131  is disposed on the second surface  112  and connected to the third through hole  115 . The fifth radiating part  132  is disposed on the second surface  112  and electrically connected to the fourth through hole  116 . In addition, the fourth radiating part  131  may also be electrically connected to a feeding point  3 . The sixth radiating part  133  is disposed on the first surface  111  and electrically connected to the fourth radiating part  131  and the fifth radiating part  132  through the third through hole  115  and the fourth through hole  116 , respectively. 
   In this embodiment, the first to third radiating parts  121  to  123 , and the fourth to sixth radiating parts  131  to  133  may be disposed symmetrically. 
   In addition, the first radiating part  121  and the fourth radiating part  131  may be configured to have an L-shape, the second radiating part  122  and the fifth radiating part  132  may be configured to have an L-shape, the third radiating part  123  and the sixth radiating part  133  may be configured to have a U-shape, as shown in  FIGS. 1 and 2 , according to different requirements in this embodiment. 
   Furthermore, an electroconductive material or electroconductive materials may be formed in the first through hole  113 , the second through hole  114 , the third through hole  115  and the fourth through hole  116  according to the actual requirement in this embodiment. Accordingly, the third radiating part  123  is electrically connected to the first radiating part  121  and the second radiating part  122  through the first through hole  113  and the second through hole  114  with the electroconductive material(s), respectively, and the sixth radiating part  133  is electrically connected to the fourth radiating part  131  and the fifth radiating part  132  through the third through hole  115  and the fourth through hole  116  with the electroconductive material(s), respectively. 
   In addition, the dipole antenna  1  may further include a first impedance matching unit  14  disposed on the first surface  111  of the substrate  11  and a second impedance matching unit  15  disposed on the second surface  112  of the substrate  11 . 
   In this embodiment, the first radiating part  121  is electrically connected to the grounding point  2  through the first impedance matching unit  14 , and the fourth radiating part  131  is electrically connected to the feeding point  3  through the second impedance matching unit  15 . In addition, the first impedance matching unit  14  and the second impedance matching unit  15  may be configured to have a continuously curved shape according to the actual requirements such as for saving the space. 
   Furthermore, it is also possible to add a first short-circuit member  141  to the first impedance matching unit  14  and a second short-circuit member  151  to the second impedance matching unit  15  according to the experimental or simulated result, such that the dipole antenna  1  may be adjusted to have a better impedance matching condition. In this embodiment, in order to make the dipole antenna  1  operate at the frequency band of about 2.4 GHz and have the better impedance matching effect, the first short-circuit member  141  and the second short-circuit member  151  are disposed as shown in  FIG. 1 . 
   As shown in  FIG. 3 , the vertical axis represents the static voltage standing wave ratio (VSWR), and the horizontal axis represents the frequency. According to the definition of the VSWR smaller than 2, it can be observed that the dipole antenna  1  according to the preferred embodiment of the invention can operate at the frequency band ranging from about 2.33 GHz to 2.56 GHz. 
     FIGS. 4 to 6  show measured results of a radiation pattern on an E-Plane and an H-Plane when the dipole antenna of this embodiment is operating at 2.45 GHz. It is observed that the polarization effect of the dipole antenna  1  of the invention is not worse than the prior art dipole antenna and can meet the commercial standard. 
   In summary, the third radiating part of the first radiating member and the first and second radiating parts of the first radiating member are on opposite surfaces and the third radiating part is electrically connected to the first and second radiating parts through the first and second through holes, respectively, in the dipole antenna of the invention. In addition, the sixth radiating part of the second radiating member and the fourth and fifth radiating parts of the second radiating member are disposed on opposite surfaces, and the sixth radiating part is electrically connected to the fourth and fifth radiating parts through the third and fourth through holes, respectively. Thus, it is possible to effectively reduce the dimension of the dipole antenna, and the power gain and bandwidth may be increased such that the application product of the dipole antenna may be minimized, and the trend of miniaturized electrical devices can be met. 
   Although the invention has been described with reference to specific embodiments, this description is not meant to be construed in a limiting sense. Various modifications of the disclosed embodiments, as well as alternative embodiments, will be apparent to persons skilled in the art. It is, therefore, contemplated that the appended claims will cover all modifications that fall within the true scope of the invention.