Patent Publication Number: US-9893422-B2

Title: Antenna with the eighth of the wavelength

Description:
RELATED APPLICATIONS 
     This application claims priority to Taiwanese Application Serial Number 102136603, filed Oct. 9, 2013, which is herein incorporated by reference. 
     BACKGROUND 
     Field of Invention 
     The present invention relates to an antenna. More particularly, the present invention relates to an antenna with the eighth of the wavelength. 
     Description of Related Art 
     A space available to an antenna and the wavelength of the antenna are mutually related. With the limitation of the space, the antenna is designed to fit into the limited space. In general, the antenna is designed as the one with a quarter wavelength. The efficiency of the quarter wavelength antenna is better, and the distance of the wireless transmission can achieve over 200 meters (e.g., Wi-Fi). However, the space needed by the quarter wavelength antenna is relatively larger. Concerning the present compact electronic devices, it has been a challenge to arrange a space of accommodating the quarter wavelength antenna. 
     As far as the efficiency is concerned, the antenna now must be designed as the quarter wavelength, and the accommodation space therefore becomes a pressing challenge. Therefore, it is one of the important objectives to dispose an antenna with the one-eighth wavelength, under the condition of an interferential source of the antenna being controllable, so as to reduce the required accommodation space and operate the antenna under a working frequency. 
     SUMMARY 
     An antenna is provided to resolve the problems met in the art. 
     According to an embodiment of the present invention, the antenna includes a grounding conductor, a feed conductor, a resonant conductor, and a radiation conductor. The feed conductor is disposed apart from the grounding conductor, and one end of the feed conductor has a feed node configured to feed a signal. The resonant conductor has a resonant width, is disposed along the grounding conductor and disposed apart from the grounding conductor by a resonant-ground distance. One end of the resonant conductor is connected to another end of the feed conductor opposite to the feed node. The radiation conductor has a radiation width. One end of the radiation conductor is connected to the one end of the resonant conductor connected to the feed conductor, and another end of the radiation conductor is disposed apart from the grounding conductor. The radiation conductor comprises a deformable section and a plurality of extension sections extended from two opposing sides of the deformable section, and the plurality of extension sections are disposed along the resonant conductor and disposed apart from the resonant conductor by a resonant-radiation distance. The resonant conductor is positioned between the radiation conductor and the grounding conductor. A proportion of the resonant-ground distance, the resonant width, the resonant-radiation distance, and the radiation width is a fixed proportion. 
     In an embodiment, the grounding conductor has a slot, and the end of the feed conductor with the feed node is disposed toward the slot. 
     In an embodiment, the feed conductor is an elongated element. 
     In an embodiment, the grounding conductor comprises a protrusive part. 
     In an embodiment, the resonant conductor comprises at least one resonant bending part so that the resonant conductor is bent along the protrusive part and disposed apart from the protrusive part by the resonant-ground distance. 
     In an embodiment, the plurality of extension sections includes at least one radiation bending part so that the extension section is bent along the resonant conductor and disposed apart from the resonant conductor by the resonant-radiation distance. 
     In an embodiment, the proportion of the resonant-ground distance, the resonant width, the resonant-radiation distance, and the radiation width is 1:1:1:1. 
     In an embodiment, each of the resonant-ground distance and the resonant-radiation distance is 1 mm, and each of the resonant width and the radiation width is 1 mm. 
     In an embodiment, a range of an utility frequency of the antenna is 2.4 GHz-2.5 GHz. 
     In an embodiment, a total length of the resonant conductor and the radiation conductor connected together is an one-eighth wavelength related to the utility frequency of the antenna. 
     In an embodiment, a length of the resonant conductor is longer than an one-sixteenth wavelength related to the utility frequency of the antenna. 
     In an embodiment, the deformable section is a U-shaped element. 
     In summary, the technical solutions of the present invention have obvious advantages and beneficial effects over the prior art. With the above technical solutions, considerable advances of technology and extensive utilization in industry can be achieved. The present invention has an advantage in that disposing the antenna with the one-eighth wavelength to reduce the used space and make the antenna work on the utility frequency if the interferential source related to the antenna is controllable. 
     It is to be understood that both the foregoing general description and the following detailed description are by examples, and are intended to provide further explanation of the invention as claimed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention can be more fully understood by reading the following detailed description of the embodiment, with reference made to the accompanying drawings as follows: 
         FIG. 1  is a schematic diagram of an antenna according to an embodiment of the present invention; 
         FIG. 2  is a structure diagram of an antenna according to an embodiment of the present invention; 
         FIG. 3  is another structure diagram of an antenna according to an embodiment of the present invention; 
         FIG. 4  is a return loss diagram of an antenna according to an embodiment of the present invention; 
         FIG. 5A-5C  are radiation pattern diagrams of an antenna according to an embodiment of the present invention; 
         FIG. 6  is a maximum gain curve diagram of an antenna according to an embodiment of the present invention; and 
         FIG. 7  is an efficiency diagram of an antenna according to an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to the present embodiments of the invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers are used in the drawings and the description to refer to the same or like parts. In addition, the well-known components and steps are not described in the embodiments to avoid unnecessary limitations to the present invention. 
     An antenna is used to transmit or receive the radio wave and electromagnetic wave, and it may be applied to the system such as the radio, the television, the wireless electronic device, the point-to-point radio communications device, the radar, the space exploration, etc.  FIG. 1  is a schematic diagram of an antenna  11  according to an embodiment of the present invention. As shown in  FIG. 1 , a circuit board  1  is disposed on the wireless electronic device. For example, a wireless measuring instrument that is configured to measure the heartbeat of human transmits the result to a computer device with a bluetooth receiver module through the bluetooth transmission. The layout related to the circuit of the wireless electronic device is within the area of a circuit board edge  12  in the circuit board  1 , and the antenna  11  that is configured to transmit the wireless signal may be disposed at a corner of the circuit board  1 . 
       FIG. 2  is a structure diagram of an antenna  11  according to an embodiment of the present invention. As shown in  FIG. 2 , in an embodiment, the antenna  11  of the present invention includes a grounding conductor  111 , a feed conductor  112 , a resonant conductor  113 , and a radiation conductor  114 . The grounding conductor  111  may be connected to a system ground terminal of the circuit board  1  through layout or via. The feed conductor  112  is disposed apart from the grounding conductor  111 . One end of the feed conductor  112  has a feed node  112   a  that is configured to feed a signal. In a physical circuit, the feed node  112   a  is connected to a circuit module through a section of a micro wire and π circuit. A current of the circuit module will flow into the feed node  112   a  to cause the radiation conductor  114  of the antenna  11  generating the resonance radiation that is excited by the current. The current of the circuit module will also flow into the resonant conductor  113  from the feed conductor  112  through the feed node  112   a  then into the grounding conductor  111  and generate the resonance radiation on the grounding conductor  111 . So the size or the shape of the grounding conductor  111  will influence the whole radiation pattern and the mode of the antenna. The position of the feed node  112   a  may be designed and further adjusted the impedance of the resonance point of the antenna  11  to meet a specified value (e.g., 50 Ohm) and thereby excite the radiation of the electromagnetic wave to transmit the signal due to the good impedance matching. The resonant conductor  113  has a resonant width W1, and it is disposed along the grounding conductor  111  and disposed apart from the grounding conductor  111  by a resonant-ground distance D1. One end of the resonant conductor  113  is connected to another end of the feed conductor  112  opposite to the feed node  112   a.    
     The radiation conductor  14  has a radiation width W2. One end of the radiation conductor  114  is connected to the one end of the resonant conductor  113  that is connected to the feed conductor  112 , i.e., one end of the feed conductor  112 , one end of the resonant conductor  113 , and one end of the radiation conductor  114  are connected together, and another end of the radiation conductor  114  is disposed apart from the grounding conductor  111 . The radiation conductor  114  is resonated as an utility frequency (e.g., 2.4 GHz-2.5 GHz) to shoot or receive the electromagnetic signal. The radiation conductor  114  includes a deformable section  114   a  and extension sections  114   b ,  114   c  extended from two opposing sides of the deformable section  114   a , and the extension sections  114   b ,  114   c  are disposed along the resonant conductor  113  and disposed apart from the resonant conductor  113  by a resonant-radiation distance D2. When the antenna  11  is disposed at the corner of the circuit board  1 , the radiation conductor  114  is a part of the antenna  11  that is nearest to the circuit board edge  12 . In order to achieve the more radiation effect on the radiation conductor  114 , the deformable section  114   a  of the radiation conductor  114  may be changed its shape based on the size of the layout space, but its width is still kept the radiation width W2. For example, the deformable section  114   a  is a U-shaped element, and the closed end of the U-shaped element is toward the circuit board edge  12  to cause the deformable section  114   a  extended outward and strengthen the radiation effect. The resonant conductor  113  is positioned between the radiation conductor  114  and the grounding conductor  111 , and a proportion of the resonant-ground distance D1, the resonant width W1, the resonant-radiation distance D2, and the radiation width W2 is a fixed proportion. 
     In an embodiment, the grounding conductor  111  has a slot S, the one end of the feed conductor  112  with the feed node  112   a  is disposed toward the slot S, and a part of the feed conductor  112  is disposed apart from the grounding conductor  111  inside the slot S. The position of the slot S should be adjusted based on the actual circuit layout. Those skilled in the art may specifically implement the slot S, feed conductor  112 , and the feed node  112   a  with flexibility according to the requirements then. 
     In an embodiment, the feed conductor  112  is an elongated element. One end of the feed conductor  112  is connected to both the resonant conductor  113  and the radiation conductor  114 , and another end of the feed conductor  112  is connected to the feed node  112   a . It should be understood that the shape of the feed conductor  112  may not influence the radiation effect of the antenna  11 , and the embodiment is not limit the scope of the invention. Those skilled in the art may specifically implement the feed conductor  112  with flexibility according to the requirements then. 
       FIG. 3  is another structure diagram of an antenna  11  according to an embodiment of the present invention. Because the size or the shape of the grounding conductor  111  may also influence the radiation pattern and the mode of the antenna, the edge of the grounding conductor  111  approached the resonant conductor  113  may be a line type or a protruded type. As shown in  FIG. 3 , in an embodiment, the grounding conductor  111  includes a protrusive part  111   a  that causes the edge of the grounding conductor  111  to protrude toward the resonant conductor  113 . When the grounding conductor  111  includes the protrusive part  111   a , the resonant conductor  113  must be disposed along the grounding conductor  111  and disposed apart from the grounding conductor  111  by the resonant-ground distance D1 so that the shape of the resonant conductor  113  is also changed due to the protrusive part  111   a.    
     As shown in  FIG. 2 - FIG. 3 , in an embodiment, the resonant conductor  113  includes resonant bending parts  113   a ,  113   b . When the grounding conductor  111  includes the protrusive part  111   a , the resonant bending parts  113   a ,  113   b  are configured to make the resonant conductor  113  bend along the protrusive part  111   a  and disposed apart from the protrusive part  111   a  by the resonant-ground distance D1 because the resonant conductor  113  must be disposed along the grounding conductor  111  and disposed apart from the grounding conductor  111  by the resonant-ground distance D1. It should be understood that the resonant bending parts  113   a ,  113   b  may be decided to dispose simultaneously or alternatively based on the shape of the protrusive part  111   a  because the shape of the protrusive part  111   a  may be depended on the circumstances. For example, when the protrusive part  111   a  protrudes only one angle, the resonant bending parts  113   a ,  113   b  exist alternatively. When the protrusive part  111   a  protrudes three angles, not only the resonant bending parts  113   a ,  113   b  is disposed simultaneously but also the other resonant bending parts is additionally disposed so that the resonant conductor  113  is bent and disposed apart from the protrusive part  111   a  by the resonant-ground distance D1. Furthermore, the position of the resonant bending parts  113   a ,  113   b  should be decided to disposed according to the shape of the protrusive part  111   a.    
     In the same way, because the radiation conductor  114  must be disposed along the resonant conductor  113  and disposed apart from the resonant conductor  113  by the resonant-radiation distance D2, the shape of the radiation conductor  114  is also changed due to the resonant conductor  113  if the protrusive part  111   a  included in the grounding conductor  111  causes the shape of the resonant conductor  113  changing. In an embodiment, the plurality of the extension sections  114   c ,  114   b  include radiation bending parts  114   d ,  114   e  so that the extension sections  114   c ,  114   b  is bent along the resonant conductor  113  and disposed apart from the resonant conductor  113  by the resonant-radiation distance D2. It should be understood that the radiation bending parts  114   d ,  114   e  should be decided to dispose simultaneously, alternatively, or add the other radiation bending parts so that the radiation conductor  114  is bent and disposed apart from the resonant conductor  113  by the resonant radiation distance D2 because the shape of the protrusive part  111   a  will influence the shape of the resonant conductor  113  then influence the shape of the extension section  114   c ,  114   b . Besides, the position of the radiation bending parts  114   d ,  114   e  should be decided to dispose according to the shape of the resonant conductor  113 . 
     As shown in  FIG. 2 , in an embodiment, the proportion of the resonant-ground distance D1, the resonant width W1, the resonant-radiation distance D2, and the radiation width W2 is 1:1:1:1, i.e., each of the resonant-ground distance D1, the resonant width W1, the resonant-radiation distance D2, and the radiation width W2 is the same measured value. The proportion disclosed in this embodiment of the resonant-ground distance D1, the resonant width W1, the resonant-radiation distance D2, and the radiation width W2 is the best proportion gotten from the physical circuit after experimental testing. In an embodiment, each of the resonant-ground distance D1 and the resonant-radiation distance D2 is 1 mm, and each of the resonant width W1 and the radiation width W2 is 1 mm. It should be understood that none of the above examples is more preferable than any of the other examples, nor are they intended to limit the scope of the invention. Those skilled in the art may specifically implement the resonant-ground distance D1, the resonant width W1, the resonant-radiation distance D2, and the radiation width W2 with flexibility according to the requirements then, however the proportion of the resonant-ground distance D1, the resonant width W1, the resonant-radiation distance D2, and the radiation width W2 must be 1:1:1:1. 
     The antenna  11  as shown in  FIG. 2 - FIG. 3  is measured through a network analyzer. Each of the feed node  112   a  and the grounding conductor  111  is connected by coaxial cables to transmit the signal to the network analyzer, and a return loss of the antenna  11  that is called S 11  can be known. The return loss S 11  is a parameter elated to the reflection returned to the transmission signal terminal after the transmission signal terminal transmits the signal. It is better that the value of the return loss S 11  is lower (e.g. −25 dB-−40 dB), and it means the reflection fewer; the return loss S 11  is called Input Reflection Coefficient.  FIG. 4  is a return loss diagram of an antenna according to an embodiment of the present invention. As shown in  FIG. 4 , in an embodiment, a range of the utility frequency of the antenna is 2.4 GHz-2.5 GHz. 
       FIG. 5A-5C  are radiation pattern diagrams of an antenna according to the embodiment of the present invention.  FIG. 5A  is a radiation pattern diagram when the utility frequency of the antenna is 2.4 GHz.  FIG. 5B  is a radiation pattern diagram when the utility frequency of the antenna is 2.45 GHz.  FIG. 5C  is a radiation pattern diagram when the utility frequency of the antenna is 2.5 GHz. According to the specific three dimensions (e.g., horizontal, vertical) plane, the antenna can be classified as two types. The first type is omni-directional antenna, and its characteristic is homogeneous radiation in the plane. The second type is directional antenna, and it has greater radiation intensity in specific plane. A radiation pattern diagram may describe the relative electric field intensity related to the antenna shooting or receiving. Because the antenna radiates to three dimensions, the radiation of the antenna needs a plurality of radiation pattern diagrams to describe. In the past, the designer of the antenna designed the antenna based on a quarter wavelength commonly. The antenna with the quarter wavelength is belong to the directional antenna that has greater radiation intensity in specific plane, so the radiation pattern diagram of the antenna with the quarter wavelength is directional. As shown in  FIG. 5A-5C , the antenna disclosed in the present invention is an antenna with the one-eighth wavelength, and it is belong to the omni-directional antenna because the radiation pattern diagram is homogeneous radiation in the plane. 
     In the small area space, it is a good design method to use the antenna with the one-eighth wavelength if an interferential source is controllable; wherein the interferential source may be a radiation interference caused by the grounding conductor  111  (drawn in  FIG. 2 ) connected to the antenna or caused by an electronic device with the antenna when humans use. It should be understood that the method for controlling the interferential source could be considered by the designer skilled in the art according to the requirements. As shown in  FIG. 2 , the application of the antenna  11  may achieved through the total length and each length of the two structure bodies (i.e., the resonant conductor  113 , the radiation conductor  114 ). In an embodiment, if the antenna  11  is applied to wifi or bluetooth and acted on the utility frequency 2.4 GHz-2.5 GHz, the one-eighth wavelength is about 15 mm. Because the antenna with the one-eighth wavelength can be disposed in the narrow space, the radiation conductor  114  must be extended as the direction that is parallel with the resonant conductor  113  to make the radiation conductor  114  achieve the radiation function efficiently. 
     In an embodiment, the range of the utility frequency of the antenna  11  may be 2.4 GHz-2.5 GHz if the total length of the connection with the resonant conductor  113  and the radiation conductor  114  together. Because the design of the planar inverted F antenna (PIFA) structure must be effectively achieved the oscillated radiation of the utility frequency within the resonant area that is also the active point for the radiation efficiency, the length of the resonant conductor  113  is longer than an one-sixteenth wavelength related to the utility frequency 2.4 GHz-2.5 GHz of the antenna  11 , i.e., 8-9 mm. 
       FIG. 6  is a maximum gain curve diagram of an antenna according to an embodiment of the present invention.  FIG. 7  is an efficiency diagram of an antenna according to an embodiment of the present invention. As shown in  FIG. 6  and  FIG. 7 , the antenna  11  has good gain and radiation efficiency in a frequency band related to the utility frequency 2.4 GHz-2.5 GHz of the antenna  11 . 
     It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the present invention without departing from the scope or spirit of the invention. In view of the foregoing, it is intended that the present invention cover modifications and variations of this invention provided they fall within the scope of the following claims.