Abstract:
A broadband multi-signal loop antenna used in a mobile terminal comprises a conductive part and a supporter supporting the conductive part. The said conductive part is electrically connected to the substrate of the mobile terminal. The said conductive part includes at least two signal loops which start at a common feed point and end at the ground points, wherein at least two signal loops each has a ground point and the ground points are located at different physical positions. The antenna can resonate at multi-band.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of Invention 
         [0002]    The invention relates to antenna for hand-held telecommunication devices and more particularly to a broadband multi-loop antenna mounted in a mobile communication device (e.g., cellular phone). 
         [0003]    2. Description of Related Art 
         [0004]    The development trend of antenna for a hand-held telecommunication device (e.g., cellular phone) is an antenna capable of operating in multi-band (e.g., GSM 800/900/1800/1900 Hz, and/or WLAN 2.4 GHz/5.1 GHz/5.8 GHz), being high in gain, and working well in one of a plurality of states of the cellular phone (e.g., folding, open, hand-held, waist hanging, or resting upon a desk). Moreover, antennas for cellular phone are typically mounted therein (i.e., internal antennas) for purposes including aesthetics, durability, portability, etc. Such internal antenna is typically capable of operating in dual-band (i.e., GSM 900 Hz and GSM 1800 Hz; GSM 850 Hz and GSM 1900 Hz); or tri-band (i.e., GSM 900 Hz, GSM 1800 Hz and GSM 1900 Hz; or GSM 850 Hz, GSM 1800 Hz and GSM 1900 Hz). It is desired by the cellular phone manufacturers to produce a cellular phone having an antenna capable of operating in four different bands so as to reduce the manufacturing cost, be more competitive in the market, and have other beneficial advantages. 
         [0005]    United States Patent Application Number 2004/0075610 discloses a PIFA antenna apparatus for mobile communications terminals as shown in  FIG. 1A . The PIFA antenna comprises an HF input/output and two antenna surfaces respectively having a connecting point to the ground plane of a mobile communication terminal. The first antenna surface is configured for two independent frequencies and the second antenna surface  1000  is configured for a third independent frequency. Only the first antenna surface is connected to the HF input/output and the second antenna surface is arranged in a non-contact manner with respect to the first antenna surface, whereby an electromagnetic coupling occurs between both antenna surfaces. 
         [0006]    United States Patent Application Number 2003/0052824 discloses an internal multi-band antenna with improved radiation efficiency as shown in  FIG. 1B  in which a third radiating element  1000  is provided for effecting multi-band operation. 
         [0007]    Another conventional proposal for effecting a multi-band antenna is characterized by increasing the number of loops as shown in  FIG. 1C . However, grounding points  1  and  2  are common for a plurality of loops. Thus, it is low in performance. 
         [0008]    All of the above prior art failed to effect an antenna capable of operating in quad-band. Thus, the need for innovative improvement still exists. 
       SUMMARY OF THE INVENTION 
       [0009]    It is therefore one object of the invention to provide a broadband multi-loop antenna mountable in a mobile communication device having a chassis, comprising a conductor assembly electrically connected to the chassis and including a plurality of loops each starting at a common feed point and ending at respective grounding points; and a mounting member for mounting the conductor assembly thereon. 
         [0010]    In a first aspect of the invention at least one of the loops comprises at least one conductive branch having one end connected to a predetermined location of the loop other than the grounding point of the loop and the other end open. 
         [0011]    In a second aspect of the invention a length from the feed point of the loop to the grounding point thereof is longer than 20 mm. 
         [0012]    In a third aspect of the invention the loops comprise a first loop and a second loop, and the first and the second loops have a common conductor. 
         [0013]    In a fourth aspect of the invention the loops comprise a first loop, a second loop, and a third loop, and the first, the second, and the third loops have a common conductor. 
         [0014]    In a fifth aspect of the invention the first loop is either completely surrounded by the second loop or partially surrounded by the second loop, or the first loop and the second loop are located at each side of the common conductor. 
         [0015]    In a sixth aspect of the invention the first loop comprises at least one conductive branch and the second loop comprises at least one conductive branch, each of the conductive branches has a length in a range of about 0.1 mm to about 80 mm, a length from a connecting point of the conductive branch and the loop to an end of the feed point is about 10% to 90% of a total length of the first loop, and a length from a connecting point of the conductive branch and the loop to an end of the feed point is about 10% to 90% of a total length of the second loop. 
         [0016]    In a seventh aspect of the invention further comprises a conductive connection for interconnecting portions of the first loop and the second loop other than the common conductor. 
         [0017]    In an eighth aspect of the invention further comprises a conductive connection for interconnecting the first loop and the second loop. 
         [0018]    In a ninth aspect of the invention the first loop comprises a conductive branch, the second loop comprises a conductive branch, and the third loop comprises a conductive branch, each of the conductive branches has a length in a range of about 0.1 mm to about 80 mm, a length from a connecting point of the conductive branch and the loop to an end of the feed point is about 10% to 90% of a total length of the first loop, a length from a connecting point of the conductive branch and the loop to an end of the feed point is about 10% to 90% of a total length of the second loop, and a length from a connecting point of the conductive branch and the loop to an end of the feed point is about 10% to 90% of a total length of the third loop. 
         [0019]    In a tenth aspect of the invention at least one of the first, the second, and the third loops comprises two conductive branches, at least one of the first, the second, and the third loops comprises a conductive branch, each of the conductive branches has a length in a range of about 0.1 mm to about 80 mm, a length from a connecting point of the conductive branch and each of the first, the second, and the third loops to an end of the feed point is about 10% to 90% of a total length of each of the first, the second, and the third loops. 
         [0020]    In an eleventh aspect of the invention further comprises a first conductive connection for interconnecting portions of the first loop and the second loop other than the common conductor, and a second conductive connection for interconnecting portions of the second loop and the third loop other than the common conductor. 
         [0021]    In a twelfth aspect of the invention further comprises a first conductive connection for interconnecting the first loop and the second loop, and a second conductive connection for interconnecting the second loop and the third loop. 
         [0022]    In a thirteenth aspect of the invention a projection of the antenna relative to a normal of the chassis is completely out of the projection of the chassis. 
         [0023]    In a fourteenth aspect of the invention a projection of the antenna relative to a normal of the chassis is either completely within the projection of the chassis or partially within the projection of the chassis, and further comprises a recess on a ground plane of the chassis at the projection superposition portion of the antenna and the chassis. 
         [0024]    In a fifteenth aspect of the invention each of the first and the second loops has a shape of a zigzag line, a curve line, a tooth-shaped line, a line having a width gradually increased, or a hollow line. 
         [0025]    In a sixteenth aspect of the invention each of the first, the second, and the third loops has a shape of a zigzag line, a curve line, a tooth-shaped line, a line having a width gradually increased, or a hollow line. 
         [0026]    In a seventeenth aspect of the invention the loops comprise a first loop, a second loop, a third loop, and a fourth loop, and each of the first, the second, the third, and the fourth loops has a grounding point and a conductive branch. 
         [0027]    In an eighteenth aspect of the invention the loops comprise a first loop, a second loop, a third loop, and a fourth loop, each of the first and the second loops has a common grounding point, and each of the first, the second, and the fourth loops has a conductive branch. 
         [0028]    The above and other objects, features and advantages of the invention will become apparent from the following detailed description taken with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0029]      FIG. 1A  is a schematic top view of a PIFA antenna according to United States Patent Application Number 2004/0075610; 
           [0030]      FIG. 1B  is a schematic top view of an internal multi-band antenna according to United States Patent Application Number 2003/0052824; 
           [0031]      FIG. 1C  is a schematic top view of a conventional multi-band antenna; 
           [0032]      FIG. 2A  is a schematic top view of a first preferred embodiment of broadband multi-loop antenna for use in a mobile communication device according to the invention; 
           [0033]      FIG. 2B  is a perspective view of the antenna of  FIG. 2A  mounted on a chassis of the mobile communication device; 
           [0034]      FIG. 2C  is a schematic top view of the antenna of  FIG. 2A  where portions of two loops other than common conductor are connected together by a conductive connection; 
           [0035]      FIG. 3  is a schematic top view of a second preferred embodiment of broadband multi-loop antenna for use in a mobile communication device according to the invention; 
           [0036]      FIG. 4  is a schematic top view of a third preferred embodiment of broadband multi-loop antenna for use in a mobile communication device according to the invention; 
           [0037]      FIG. 5A  is another schematic top view of the antenna of  FIG. 4  where two loops have no common part other than common feed point and each loop has a conductive branch; 
           [0038]      FIG. 5B  is a view similar to FIG.  FIG. 5A  where a conductive connection is interconnected the loops and each loop has a conductive branch; 
           [0039]      FIG. 6  is a schematic top view of a fifth preferred embodiment of broadband multi-loop antenna for use in a mobile communication device according to the invention; 
           [0040]      FIG. 7  is a schematic top view of a sixth preferred embodiment of broadband multi-loop antenna for use in a mobile communication device according to the invention; 
           [0041]      FIG. 8A  is a schematic top view of a seventh preferred embodiment of broadband multi-loop antenna for use in a mobile communication device according to the invention; 
           [0042]      FIG. 8B  is a first configuration of the antenna of  FIG. 8A  where each loop has a conductive branch; 
           [0043]      FIG. 8C  is a second configuration of the antenna of  FIG. 8A  where a conductive connection is interconnected the first and second loops and another conductive connection is interconnected the second and third loops respectively; 
           [0044]      FIG. 9  is a schematic top view of an eighth preferred embodiment of broadband multi-loop antenna for use in a mobile communication device according to the invention; 
           [0045]      FIG. 10  is a schematic top view of a ninth preferred embodiment of broadband multi-loop antenna for use in a mobile communication device according to the invention; 
           [0046]      FIG. 11  is a schematic top view of a tenth preferred embodiment of broadband multi-loop antenna for use in a mobile communication device according to the invention; 
           [0047]      FIG. 12A  is a first configuration of the antenna of  FIG. 2A  where the conductor forming the loop is a curve and the conductive branch of the loop is zigzag; 
           [0048]      FIG. 12B  is a second configuration of the antenna of  FIG. 2A  where the conductors forming the loop and the conductive branch are lines having an increased width; 
           [0049]      FIG. 12C  is a third configuration of the antenna of  FIG. 2A  where the loop is formed by forming a groove on the conductor; 
           [0050]      FIG. 13  is a first schematic view of the antenna according to the invention mounted on a chassis of a mobile communication device where projection of the antenna is completely out of that of the chassis; 
           [0051]      FIG. 14  is a second schematic view of the antenna according to the invention mounted on a chassis of a mobile communication device where projection of the antenna is completely within that of the chassis; 
           [0052]      FIG. 15A  is a third schematic view of the antenna according to the invention mounted on a chassis of a mobile communication device where a portion of projection of the antenna is within that of the chassis, another portion thereof is out of the projection of the chassis, and there is a gap on a ground plane of the chassis; 
           [0053]      FIG. 15B  is a view similar to FIG.  FIG. 15A  where a grid structure is formed at the ground plane as a variation of the antenna shown in  FIG. 15A ; 
           [0054]      FIG. 16A  is a graph showing a curve drawn by testing the antenna of the invention in a first application; and 
           [0055]      FIG. 16B  is a graph showing a curve drawn by testing the antenna of the invention in a second application. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0056]    Term Definitions 
         [0057]    “Feed point” means a connecting point of an antenna and a chassis of a mobile communication device. That is, a point of radio frequency (RF) input and output of the chassis. The feed point is a starting point of a loop of the invention. 
         [0058]    “Grounding point” means a physical connecting point of the antenna and a ground plane of the chassis of a mobile communication device (e.g., cellular phone), that is, at an end of the loop of the invention. The grounding point is electrically connected to a grounding point of the feed point so as to form a loop. There are a plurality of grounding points at different physical locations electrically connected to a conductor (i.e., ground plane) according to the invention. 
         [0059]    “Loop” means a conductive loop starts at the feed point and terminates at one of the grounding points. 
         [0060]    “Relations between the loops including completely surrounding and partially surrounding” means location relationships between the loops after spreading the loops on a plane. 
         [0061]    Referring to  FIGS. 2A and 2B , a broadband multi-loop antenna for mobile communication device in accordance with the invention comprises conductors (indicated by bold lines) and a mounting member for mounting the conductors thereon. The mounting member can be an FPC (flexible printed circuit board), a PCB (printed circuit board), a plastic member, a housing of a mobile communication device, etc. The conductor can be a copper membrane, a plated or printed metal, etc. These are well known in the art and a detailed description thereof is therefore deemed unnecessary. 
         [0062]    As shown in  FIG. 2B , the conductor is electrically connected to a chassis  100  of a mobile communication device. The chassis  100  is the main-board of the mobile communication device and is formed thereon with transmission circuits, receiving circuits, and control circuits by printing. 
         [0063]    Referring to  FIG. 2A , a first preferred embodiment of the invention is shown. The conductor comprises a first loop  10  and a second loop  20 . The loops  10  and  20  starts at a common feed point  1  and ends at grounding points  2  and  3  respectively. The first loop  10  is completely surrounded by the second loop  20 . The first and second loops  10  and  20  have a common conductor  5  having a length in a range of 0.001 mm to 80 mm. 
         [0064]    Referring to  FIG. 3 , a second preferred embodiment of the invention is shown. The conductor comprises a first loop  10  and a second loop  20 . The second embodiment is identical to the first embodiment, except that the first loop  10  is partially surrounded by the second loop  20 . 
         [0065]    Referring to  FIG. 4 , a third preferred embodiment of the invention is shown. The third embodiment is identical to the first embodiment, except that the first loop  10  and the second loop  20  are located at both sides of the common conductor  5  respectively. 
         [0066]    Referring to  FIG. 5A , a fourth preferred embodiment of the invention is shown. The fourth embodiment is identical to the first embodiment, except that the common feed point  1  is the only common part of the first loop  10  and the second loop  20 . In each of the above embodiments, bands for the loops  10  and  20  are different each other due to their different location relationships. Thus, the antenna of the invention can be implemented in different applications. 
         [0067]    Referring to  FIGS. 3 to 5  in conjunction with  FIG. 2A , the first loop  10  comprises a conductive branch  12  and the second loop  20  comprises a conductive branch  22  respectively. Each of the conductive branches  12  and  22  has a length about 0.1 mm to about 80 mm. A length from a connecting point  11  of the conductive branch  12  and the first loop  10  to the end of the feed point  1  is about 10% to 90% of the total length of the first loop  10  and a length from a connecting point  21  of the conductive branch  22  and the second loop  20  to the end of the feed point  1  is about 10% to 90% of the total length of the second loop  20  respectively. 
         [0068]    Referring to  FIG. 6 , a fifth preferred embodiment of the invention is shown. The characteristics of the fifth preferred embodiment are detailed below. The first loop  10  does not have any conductive branches. The second loop  20  has two conductive branches  22 . 
         [0069]    Referring to  FIG. 7 , a sixth preferred embodiment of the invention is shown. The characteristics of the sixth preferred embodiment are detailed below. The first loop  10  has two conductive branches  12  and the second loop  20  has a conductive branch  22 . 
         [0070]    It is possible of forming additional loops by shorting the loops with a conductive connection. For example, in each of the first, second and third preferred embodiments a conductive connection  9  is employed to interconnect portions of the first loop  10  and the second loop  20  other than the common conductor  5 . In the fourth preferred embodiment, a conductive connection  9  is employed to interconnect the first loop  10  and the second loop  20  as shown in  FIGS. 2C and 5B . 
         [0071]    Referring to  FIG. 8A , a seventh preferred embodiment of the invention is shown. The conductor comprises a first loop  10 , a second loop  20  and a third loop  30 . The loops  10 ,  20  and  30  start at a common feed point  1  and end at grounding points  2 ,  3  and  8  respectively. The first, second and third loops  10 ,  20  and  30  have a common conductor  5 . The first loop  10  does not have any conductive branches. The second loop  20  comprises a conductive branch  22  and the third loop  30  comprises a conductive branch  32  respectively.  FIG. 8B  shows a first configuration of the antenna of  FIG. 8A  where each of the loops  10 ,  20  and  30  has a conductive branch  12 ,  22 , or  32 . 
         [0072]    Referring to  FIG. 9 , an eighth preferred embodiment of the invention is shown. The conductor comprises a first loop  10 , a second loop  20  and a third loop  30 . The characteristics of the eighth preferred embodiment are detailed below. The common feed point  1  is the only common part of the loops  10 ,  20  and  30 . Each of the loops  10 ,  20  and  30  ends at grounding points  2 ,  3  and  8  respectively. The first loop  10  comprises a conductive branch  12  and the third loop  30  comprises a conductive branch  32  respectively. Alternatively, one or two of the loops  10 ,  20  and  30  has (or have) two conductive branches and the remaining loops have a conductive branch. Each of the conductive branches  12 ,  22  and  32  has a length about 0.1 mm to about 80 mm. A length from a connecting point  11  of the conductive branch  12  and the first loop  10  to the end of the feed point  1  is about 10% to 90% of the total length of the first loop  10 , a length from a connecting point  21  of the conductive branch  22  and the second loop  20  to the end of the feed point  1  is about 10% to 90% of the total length of the second loop  20 , and a length from a connecting point  31  of the conductive branch  32  and the third loop  30  to the end of the feed point  1  is about 10% to 90% of the total length of the third loop  30  respectively. 
         [0073]    Referring to  FIG. 8C , a second configuration of the antenna of  FIG. 8A  is shown. A conductive connection  9  is employed to interconnect portions of the first loop  10  and the second loop  20  other than the common conductor  5 . A conductive connection  9 ′ is employed to interconnect portions of the second loop  20  and the third loop  30  other than the common conductor  5 . 
         [0074]    Likewise, as shown in  FIG. 9 , a conductive connection  9  is employed to interconnect the first loop  10  and the second loop  20 . A conductive connection  9 ′ is employed to interconnect the second loop  20  and the third loop  30 . Alternatively, a plurality of conductive connections are employed to interconnect two loops. 
         [0075]    Referring to  FIG. 10 , a ninth preferred embodiment of the invention is shown. The conductor comprises a first loop  10 , a second loop  20 , a third loop  30 , and a fourth loop  40 . The characteristics of the ninth preferred embodiment are detailed below. Each of the loops  10 ,  20 ,  30 , and  40  has a grounding point  2 ,  3 ,  8 , or  8 ′ and a conductive branch  12 ,  22 ,  32 , or  42 . 
         [0076]    Referring to  FIG. 11 , a tenth preferred embodiment of the invention is shown. The conductor comprises a first loop  10 , a second loop  20 , a third loop  30 , and a fourth loop  40 . The tenth embodiment is identical to the ninth embodiment, except that there are only three grounding points  2 ,  3  and  8  in which grounding point  8  is common to the third and fourth loops  30  and  40 , the third loop  30  does not have any conductive branch, and each of the first, second and fourth loops  10 ,  20  and  40  has a conductive branch  12 ,  22 , or  42 . 
         [0077]    In each of the above embodiments, each loop including its conductive branch can be a zigzag line, a curve line, a tooth-shaped line, a line having width gradually increased, a hollow line, or the like. For example,  FIG. 12A  shows a first configuration of the antenna of  FIG. 2A  in which the first loop  10  including its conductive branch  12  is zigzag. In  FIG. 12B , the second loop  20  including its conductive branch  22  is a line having a gradually increased width. In  FIG. 12C , the second loop  20  is formed by forming a groove on the conductor. 
         [0078]    For the antenna of the invention mounted on the chassis  100  of the mobile communication device, location relationship of the antenna with respect to the chassis  100  and ground plane of the chassis  100  both affect the band features of the antenna. 
         [0079]      FIG. 13  shows a first schematic view of the antenna according to the invention mounted on a chassis  100  of a mobile communication device (e.g., cellular phone) and electrically connected thereto. A projection of the antenna relative to a normal of the chassis  100  (i.e., a direction perpendicular to the plane of the chassis  100 ) is completely out of the projection of the chassis  100 . Part A of  FIG. 13  shows in perspective the antenna mounted on the chassis  100  and part B thereof shows in elevation of the same. 
         [0080]      FIG. 14  shows a second schematic view of the antenna according to the invention mounted on a chassis  100  of a mobile communication device (e.g., cellular phone) and electrically connected thereto. A projection of the antenna relative to a normal of the chassis  100  is completely within the projection of the chassis  100 . Part A of  FIG. 14  shows in perspective the antenna mounted on the chassis  100  and part B thereof shows in elevation of the same. 
         [0081]      FIG. 15A  shows a third schematic view of the antenna according to the invention mounted on a chassis  100  of a mobile communication device (e.g., cellular phone) and electrically connected thereto. A portion of projection of the antenna relative to a normal of the chassis  100  is within the projection of the chassis  100 , another portion thereof is out of the projection of the chassis  100 , and there is a recess  101  on a ground plane of the chassis  100  at the superposition portion of the antenna and the chassis  100 . Part A of  FIG. 15A  shows in perspective the antenna mounted on the chassis  100  and part B thereof shows in elevation of the same. 
         [0082]      FIG. 15B  shows a fourth schematic view of the antenna according to the invention mounted on a chassis  100  of a mobile communication device (e.g., cellular phone) and electrically connected thereto. Similar to the structure shown in  FIG. 15A , a portion of projection of the antenna relative to a normal of the chassis  100  is within the projection of the chassis  100 , another portion thereof is out of the projection of the chassis  100 , and there is a recess  101  on a ground plane of the chassis  100 . Part A of  FIG. 15B  shows in perspective the antenna mounted on the chassis  100  and part B thereof shows in elevation of the same. The only difference is that a grid structure  102  is formed at the ground plane of the chassis  100 . 
         [0083]    Referring to  FIG. 16A , it is a graph showing a curve drawn by testing the antenna of the invention in a first application in which the antenna is capable of operating in one of five bands including GSM 800 Hz, GSM 900 Hz, GSM 1800 Hz, GSM 1900 Hz, and UMTS. 
         [0084]    Referring to  FIG. 16B , it is a graph showing a curve drawn by testing the antenna of the invention in a second application in which the antenna is capable of operating in one of four bands including GSM 850 Hz, GSM 900 Hz, GSM 1800 Hz, and GSM 1900 Hz. 
         [0085]    While the invention herein disclosed has been described by means of specific embodiments, numerous modifications and variations could be made thereto by those skilled in the art without departing from the scope and spirit of the invention set forth in the claims.