Abstract:
An inverted-F antenna is disclosed including: a radiating body including a plurality of radiating portions, and some of the radiating portions located on a same plane; a shorting element extending outward from the radiating body and forming a first predetermined included angle with one of the radiating portions; a feeding element extending outward from the radiating body and forming a second predetermined included angle with one of the radiating portions; and a protrusion extending outward from the radiating body and forming a third predetermined included angle with one of the radiating portions; wherein at least one of the first, second, and third predetermined included angles is substantially a right angle.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based upon and claims the benefit of priority to Taiwanese Patent Application No. 099122701, filed on Jul. 9, 2010; the entire content of which is incorporated herein by reference for all purpose. 
     BACKGROUND 
     The present disclosure generally relates to an antenna, and more particularly, to an inverted-F antenna for use in a wireless communication apparatus. 
     Antenna is an important component for a wireless communication apparatus, but it often occupies considerable area and volume of the circuitry module. With the increasing demand on lighter, thinner, and smaller wireless communication devices, the volume of the antenna has to be further reduced for meeting the trend of device miniaturization. 
     In related art, an inverted-F antenna (IFA) is widely utilized in many network cards, mobile phones, and other portable wireless devices due to it possesses good omnidirectional radiation patterns. 
     However, the radiating body length of the inverted-F antenna has to be one quarter wavelength of the radio signal to be received/transmitted by the antenna. It is thus difficult to reduce the overall volume of the circuitry module because of the above restriction on the radiating body length of the inverted-F antenna. 
     SUMMARY 
     In view of the foregoing, it is appreciated that a substantial need exists for antenna structure that possesses good radiation characteristic, compact in size, and has merit of lower cost. 
     An exemplary embodiment of an inverted-F antenna is disclosed comprising: a radiating body comprising a plurality of radiating portions, and some of the radiating portions located on a first plane; a shorting element extending outward from the radiating body and forming a first predetermined included angle with one of the radiating portions; a feeding element extending outward from the radiating body and forming a second predetermined included angle with one of the radiating portions; and a protrusion extending outward from the radiating body and forming a third predetermined included angle with one of the radiating portions; wherein at least one of the first, second, and third predetermined included angles is substantially a right angle. 
     An exemplary embodiment of a wireless communication apparatus is disclosed comprising: a circuit board comprising a first connection portion, a second connection portion, and a grounded plane; and an inverted-F antenna comprising: a radiating body comprising a plurality of radiating portions, some of the radiating portions located on a first plane, and at least one of the radiating portions not located on the first plane; a shorting element extending outward from the radiating body, the shorting element contacting with the first connection portion and the grounded plane, and forming a first predetermined included angle with one of the radiating portions; a feeding element extending outward from the radiating body, the feeding element contacting with the second connection portion and forming a second predetermined included angle with one of the radiating portions; and a protrusion extending outward from one of the radiating portions, the protrusion forming a third predetermined included angle with one of the radiating portions, and not contacting with the grounded plane. 
     It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a simplified schematic diagram of a planar inverted-F antenna according to an exemplary embodiment. 
         FIG. 2  is a schematic diagram illustrating the fabrication of the antenna of  FIG. 1  according to an exemplary embodiment. 
         FIG. 3  is a simplified schematic diagram of a wireless communication device using the antenna of  FIG. 1  according to an exemplary embodiment. 
         FIG. 4  is a top-view of the wireless communication device of  FIG. 3 . 
         FIG. 5  is a schematic diagram of operating characteristics of the antenna of  FIG. 1  with the use of the protrusion and without the use of the protrusion. 
         FIG. 6  and  FIG. 7  are simplified schematic diagrams of wireless communication devices according to other exemplary embodiments. 
         FIG. 8  and  FIG. 9  are simplified schematic diagrams of planar inverted-F antennas according to other exemplary embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to embodiments of the invention, which are illustrated in the accompanying drawings. The same reference numbers may be used throughout the drawings to refer to the same or like parts or components. 
     Certain terms are used throughout the description and following claims to refer to particular components. As one skilled in the art will appreciate, vendors may refer to a component by different names. This document does not intend to distinguish between components that differ in name but not in function. In the following description and in the claims, the terms “include” and “comprise” are used in an open-ended fashion, and thus should be interpreted to mean “include, but not limited to . . . .” 
     Please refer to  FIG. 1 , which shows a simplified schematic diagram of a planar inverted-F antenna (PIFA)  10  according to an exemplary embodiment. The antenna  10  comprises a radiating body, and a shorting element  110 , a feeding element  120 , and a protrusion  170  which extend outward from the radiating body. The protrusion  170  comprises a positioning member  172  extending outward therefrom. In this embodiment, the radiating body of the antenna  10  comprises a first radiating portion  130 , a second radiating portion  140 , a third radiating portion  150 , and a fourth radiating portion  160 . In  FIG. 1 , a virtual path  180  schematically illustrates the equivalent current path of the radiating body of the antenna  10 , and the length of the virtual path  180  may represent the length of the equivalent current path of the radiating body, or may be regarded as the total length of the radiating body of the antenna  10 . 
     In implementations, the gap between the shorting element  110  and the feeding element  120  may be manipulated to adjust the input impendence of the antenna  10  in order to achieve better impendence matching. 
     The respective parts of the antenna  10  described above may be formed separately by conductive materials and then assembled with together. Alternatively, respective parts of the antenna  10  may be made integrally by stamping or cutting a single metal sheet so as to reduce the complexity and cost of manufacture. 
     Before assembling the antenna  10  with the circuit board of a wireless communication apparatus, the antenna  10  may be bent to an appropriate shape to increase its structural rigidity. 
       FIG. 2  is a schematic diagram illustrating the fabrication of the antenna  10  according to an exemplary embodiment. As shown in  FIG. 2 , the shorting element  110 , the feeding element  120 , and the second radiating portion  140  of the antenna  10  may be respectively bent to have a predetermined included angle (e.g., an angle between 80˜100 degrees) with the first radiating portion  130 , or to be substantively perpendicular to the first radiating portion  130 . Then, the protrusion  170  is bent to have a predetermined included angle (e.g., an angle between 80˜100 degrees) with the second radiating portion  140 , or to be substantively perpendicular to the second radiating portion  140 . 
     In this embodiment, the second radiating portion  140 , the third radiating portion  150 , and the fourth radiating portion  160  are located on the same plane under normal operating condition, and substantively parallel to both the shorting element  110  and the feeding element  120 . That is, the shorting element  110  and the feeding element  120  are not located on the plane on which the second radiating portion  140 , the third radiating portion  150 , and the fourth radiating portion  160  are located. On the other hand, the first radiating portion  130  of this embodiment is not located on the plane on which the second radiating portion  140 , the third radiating portion  150 , and the fourth radiating portion  160  are located under normal operating condition. Instead, the first radiating portion  130  is substantially perpendicular to the second radiating portion  140 , the third radiating portion  150 , and the fourth radiating portion  160 . As a result, the antenna  10  has a three-dimensional structure under normal operating condition to greatly enhance its structural rigidity and stability, so that the antenna  10  would not deform during assembling and operation. 
     Please refer to  FIG. 3  and  FIG. 4 .  FIG. 3  shows a simplified schematic diagram of a wireless communication device  300  using the antenna  10  according to an exemplary embodiment.  FIG. 4  illustrates a top-view of the wireless communication device  300 . In addition to the antenna  10 , the wireless communication device  300  further comprises a circuit board  310 , three connection portions  320 ,  330 , and  340 , and a button socket  350 . The circuit board  310  further comprises a grounded plane  412 , and the button socket  350  is provided with a push-button  352 . For the sake of brevity, other components of the circuit board  310  are omitted in  FIG. 3  and  FIG. 4 . 
     The connection portions  320 ,  330 , and  340  of the circuit board  310  may be implemented with openings for positioning the antenna  10  firmly on the circuit board  310 . In one embodiment, the opening  320  is a through hole and its interior surface is not conductive. There is a gap between the opening  320  and the grounded plane  412  so that the positioning member  172  of the protrusion  170  is not conductive with the grounded plane  412  when the positioning member  172  is inserted into or soldered with the opening  320 . The interior surface of the opening  330  is coated with conductive materials, such as copper, and there is a gap between the opening  330  and the grounded plane  412  of the circuit board  310 . When the feeding element  120  of the antenna  10  is inserted into or soldered with the opening  330 , the feeding element  120  transmits the radio signals received by the antenna  10  to appropriated components for further processing. The interior surface of the opening  340  is also coated with conductive materials and connected with the grounded plane  412  of the circuit board  310 . Accordingly, when the shorting element  110  of the antenna  10  is inserted into or soldered with the opening  340 , the shorting element  110  is conductive with the grounded plane  412 . 
     In one embodiment, when the antenna  10  is assembled with the circuit board  310 , the second radiating portion  140 , the third radiating portion  150 , and the fourth radiating portion  160  of the antenna  10  is substantively perpendicular to the edges of the circuit board  310 . 
     In addition, the position of the fourth radiating portion  160  located in the end of the antenna  10  corresponds to the push-button  352  on the button socket  350 . Therefore, when a user wants to press the push-button  352  to activate a particular function of the wireless communication device  300 , such as the WPS setting, the user could press the fourth radiating portion  160  of the antenna  10  to indirectly press the push-button  352 . In a preferred embodiment, the area of the fourth radiating portion  160  is more than twice of the area of the push-button  352 . As a result, the user is able to easily press the push-button  352  indirectly through the fourth radiating portion  160  even if the dimensions of the push-button  352  shrink due to device miniaturization. 
     In one embodiment, the end of the shorting element  110  and the end of the feeding element  120  are both dimensioned to be ladder-shaped, enabling the antenna  10  to have a predetermined height when assembled with the circuit board  310 . In addition, the end of the protrusion  170  may be dimensioned to be ladder-shaped for maintaining the height of the antenna  10  and for increasing the structural stability of the antenna  10  when assembled with the circuit board  310 . 
     In addition to the merit of increasing structural stability, the use of the protrusion  170  also effectively reduces the required size or radiating body length of the antenna  10  under a given operating frequency. 
     Please refer to  FIG. 5 , which shows the operating characteristics of the antenna  10  with the use of the protrusion  170  and without the use of the protrusion  170 . In this embodiment, if the antenna  10  is without the protrusion  170 , the operating frequency of the antenna  10  is about 2.58 GHz. On the other hand, if the antenna  10  is with the protrusion  170 , e.g., as illustrated in the embodiment of  FIG. 1 , the operating frequency of the antenna  10  would be reduced to about 2.44 GHz from 2.58 GHz due to the parasitical capacitor effect between the protrusion  170  and the grounded plane  412  of the circuit board  310 . In other words, the use of the protrusion  170  reduces the operating frequency of the antenna  10  without substantively changing the total length of equivalent current path (or the total length of the radiating body). 
     From another aspect, the use of the protrusion  170  effective reduces the required size or radiating body length of the antenna  10  without substantively changing a predetermined operating frequency. Accordingly, the total length of equivalent current path or the total length of the radiating body of the antenna  10  can be designed to be less than one quarter wavelength of the radio signal to be received/transmitted by the antenna  10 . For example, in the previous embodiment where the antenna operating frequency is 2.44 GHz, the total length of the radiating body of the antenna  10  (i.e., the length of the virtual path  180  shown in  FIG. 1 ) could be only 25 mm. This is about 16% less than 30 mm, which is the minimum required length in the conventional art. In other words, the total length of equivalent current path of the antenna  10  could be 85%˜90% of one quarter wavelength of the radio signal to be received/transmitted by the antenna  10 . 
     In the conventional art, the antenna may encounter the over-bending problem due to the space restriction, which inevitably deteriorates the antenna radiation characteristic. The above drawback in the conventional art could be avoided in this invention as the required size or radiating body length of the antenna  10  can be reduced. 
     In implementations, by reducing the gap between the grounded plane  412  of the circuit board  310  and the positioning member  172  of the protrusion  170 , the parasitical capacitor effect can be increased, enabling the antenna  10  to have a lower operating frequency without changing the total length of the equivalent current path. In addition, if the gap between the grounded plane  412  and the positioning member  172  is given, the parasitical capacitor effect can be increased by increasing the width of the positioning member  172 . In this way, the antenna  10  is also allowed to have a lower operating frequency without changing the total length of the equivalent current path. Therefore, the operating frequency of the antenna  10  can be effectively reduced by adjusting the gap between the grounded plane  412  and the positioning member  172  of the protrusion  170 , or by changing the width of the positioning member  172 . Similarly, the required radiating body length of the antenna  10  under a given operating frequency can be effectively reduced by adjusting the gap between the grounded plane  412  and the positioning member  172  of the protrusion  170 , or by changing the width of the positioning member  172 . 
     Additionally, the radiation characteristic of the antenna  10  can be improved by positioning the protrusion  170  on the side of the radiating body where there corresponds to the middle 70% of the equivalent current path of the radiating body. Thus, depending on the length of respective radiating portions of the antenna  10 , the protrusion  170  may be positioned on one side of the second radiating portion  140 , on one side of the first radiating portion  130 , or on one side of the third radiating portion  150 . Preferably, the protrusion  170  is positioned on the side of the radiating body where there corresponds to the middle one-third of the equivalent current path of the radiating body of the antenna  10 . 
       FIG. 6  shows a simplified schematic diagram of a wireless communication device  600  according to another exemplary embodiment. The wireless communication device  600  is similar to the wireless communication device  300  of  FIG. 3 , but the bending direction of the radiating body of an antenna  60  of the wireless communication device  600  differs from the bending direction of the antenna  10  of  FIG. 3 . In the embodiment of  FIG. 3 , the shorting element  110 , the feeding element  120 , and the second radiating portion  140  of the antenna  10  are bent upward with respect to the first radiating portion  130 . In the embodiment of  FIG. 6 , the shorting element  110 , the feeding element  120 , and the second radiating portion  140  of the antenna  60  are bent downward with respect to the first radiating portion  130 . The operating mechanism of the antenna  60  is the same as that of the antenna  10 . 
       FIG. 7  shows a simplified schematic diagram of a wireless communication device  700  according to yet another exemplary embodiment. The wireless communication device  700  and wireless communication device  300  of  FIG. 3  differ in the protrusion structure of their antenna. The protrusion  170  of the antenna  10  shown in  FIG. 3  has the positioning member  172  extending outward thereform, but a protrusion  770  of an antenna  70  shown in  FIG. 7  has no similar structure. When assembling a circuit board  710  and the antenna  70  of the wireless communication device  700 , the protrusion  770  of the antenna  70  may be simply placed on the circuit board  710 , or soldered on the circuit board  710  without using any additional opening (such as the opening  320  of  FIG. 3 ) as a connecting medium. The protrusion  770  of the antenna  70  is not conductive with the grounded plane  412 , but parasitical capacitor effect occurs between the protrusion  770  and the grounded plane  412 . Accordingly, similar to the previous embodiment, the antenna structure of  FIG. 7  can also reduce the antenna operating frequency or required antenna length under a given operating frequency. 
     As described previously, the antenna radiation characteristic can be improved by positioning the protrusion  770  on the side of the radiating body where there corresponds to the middle 70% of the equivalent current path of the radiating body. In addition, depending on the length of respective radiating portions of the antenna  70 , the protrusion  770  may be positioned on one side of the first radiating portion  130 , on one side of the second radiating portion  140 , or on one side of the third radiating portion  150 . 
     For example, the protrusion  770  in the embodiment of  FIG. 7  is positioned on one side of the second radiating portion  140  where there is away from the feeding element  120 . In the embodiment of  FIG. 8 , a protrusion  870  of an antenna  80  is positioned on one side of the second radiating portion  140  where there corresponds to the middle 70% of the equivalent current path of the radiating body and opposes to the first radiating portion  130 . In  FIG. 8 , a virtual path  880  illustrates the equivalent current path of the radiating body of the antenna  80  and its length may be regarded as the total length of the radiating body of the antenna  80 . 
     In other embodiments, the protrusion may be positioned on the side of the radiating body where there corresponds to the middle one-third of the equivalent current path of the radiating body of the antenna. For example, in the embodiment shown in  FIG. 9 , a protrusion  970  of an antenna  90  is positioned on the side of the first radiating portion  130  where there corresponds to the middle one-third of the equivalent current path of the radiating body of the antenna  90  and opposes to the second radiating portion  140 . In  FIG. 9 , a virtual path  980  illustrates the equivalent current path of the radiating body of the antenna  90  and its length may be regarded as the total length of the radiating body of the antenna  90 . 
     Each of the disclosed antennas could be formed integrally, and thus the disclosed antenna may be realized by bending a single metal sheet with appropriate shape. In addition, the disclosed antennas have the merits of low cost and easy to manufacture and assemble as they could be directly inserted into or soldered with the circuit board of an electronic device. 
     Other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the invention being indicated by the following claims.