Abstract:
An EMC (electromagnetic compatible) antenna having a shielding metal wall to effectively reduce the possible coupling with nearby electronic elements is presented. The antenna includes: a ground plane, a bent ground plate, and a radiating plate. The bent ground plate is vertically connected to the ground plane and functions as an effective shielding metal wall to eliminate or greatly reduce the possible EM coupling between the antenna and nearby electronic elements. The radiating plate is used to generate the operating resonant mode of the antenna and is generally parallel to the ground plane. The radiating plate is also electrically connected to and encircled by the bent ground plane.

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
       [0001]     This application claims the priority benefit of Taiwan application serial no. 94140042, filed on Nov. 15, 2005. All disclosure of the Taiwan application is incorporated herein by reference.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of Invention  
         [0003]     The present invention relates to an EMC (electromagnetic compatible) metal-plate antenna and a communication system using the same, and particularly to a built-in EMC antenna and a communication system using the same, which is capable of effectively reducing possible electromagnetic coupling between the antenna and other electronic elements without an isolation spacing.  
         [0004]     2. Description of Related Art  
         [0005]     Along with the thriving development of wireless communications, various communication products and communication technologies are being emerged in flourish, and the wireless communication products have gradually become an indispensable part in people&#39;s living. With drastic competitions in the market, a wireless communication apparatus is required to be lighter, thinner and smaller. Thus, a built-in antenna and the performance thereof play a significant role.  
         [0006]     Modern wireless communication products at least include an antenna, a battery, a RF circuit module (radio frequency circuit module) and other electronic components. High-level product even includes a digital camera lens of CCD (charge coupling device). Therefore, if the spacing between the antenna and other components is not large enough, a negative electromagnetic coupling occurs, which leads to the degradation in the antenna performance. Hence, to apply an antenna in a wireless communication apparatus, the EMC influence of the surroundings must be considered, which increases the difficulty of design.  
         [0007]     To reduce the electromagnetic coupling, an isolation spacing between the antenna and other components is preserved to sustain the antenna performance. However, the isolation spacing preservation reduces usable spaces inside the wireless communication apparatus, and also limits a wireless communication apparatus to be light and compact. Besides, since the electromagnetic coupling between the antenna and other components would be varied by the position change of other components, large effects on the antenna performance are expected.  
         [0008]     Some conventional arts, for example U.S. Pat. No. 6,856,294 (‘compact, lower profile, single feed, multi-band, printed antenna’) and U.S. Pat. No. 6,717,548 (‘dual- or multi-frequency planar inverted F-antenna’) disclose built-in antennas. In U.S. Pat. No. 6,856,294, a spacing of about 6 mm between an antenna and a shielding metal case of a RF circuit module is required to assure the circuit characteristics (frequency, impedance, efficiency) to be normal. In U.S. Pat. No. 6,717,548, a spacing of about 7 mm is required not only between an antenna and a shielding metal case of a RF circuit module, but also between an antenna and a shielding metal wall of a digital camera lens, such that normal circuit characteristics can be obtained.  
         [0009]     As a matter of fact, the above-mentioned antenna designs did not consider the shielding of an antenna itself yet. Therefore, when such kind of antennas is disposed near other electronic components, an extra spacing is required for reducing the electromagnetic coupling between the antenna and other electronic components, which results in an inefficient usage of the limited available space. If the spacing preserved is not sufficient, a frequency shift and an impedance change occur, which affect the signal quality and largely reduce the antenna performance due to the electromagnetic coupling.  
         [0010]     In high-level mobile communication products, components disposed near to an antenna are usually a digital camera lens, a RF circuit module and a battery. In general, the above-mentioned components have their own shielding metal cases. However, the conventional antenna does not have its own shielding. When the distance between the antenna and the shielded components is too small, the antenna performance would be degraded due to a strong electromagnetic coupling. To reduce the coupling, an extra spacing between the conventional antenna and the components is required, which leads to an inefficient usage of the avaiable space inside the mobile communication apparatus. Besides, when the position relation changes between the antenna and other components, the antenna performances would be varied, and the antenna needs to redesigned, leading to a labor waste.  
         [0011]     From the above description, an EMC (electromagnetic compatible) metal-plate antenna and a communication system using the same are demanded, which are capable of effectively reducing possible electromagnetic coupling between the antenna and other electronic components without an isolation spacing.  
       SUMMARY OF THE INVENTION  
       [0012]     An aspect of the present invention is to provide a built-in antenna, to which spacing from other major components is not needed while the antenna still possesses the electromagnetic compatible behavior to effectively decrease the influence on the antenna from other electronic components near to the antenna. Thus, the inside usable capacity of a wireless communication system is increased and the size of the wireless communication apparatus can be further compact.  
         [0013]     Another aspect of the present invention is to provide a built-in antenna of unified design by metal processing to reduce fabrication cost.  
         [0014]     Another aspect of the present invention is to provide an EMC (electromagnetic compatible) built-in antenna, capable of increasing the compatibility between the antenna and other components and adaptation in a wireless communication apparatus. In other words, the flexibility to dispose an antenna inside a wireless communication apparatus is increased.  
         [0015]     Another aspect of the present invention is to provide an EMC built-in antenna. The antenna can be applicable to different wireless communication products without modifying the antenna for wireless products standardizing.  
         [0016]     An embodiment of the present invention provides an EMC antenna, which includes: a ground plane, an antenna shielding metal wall and a radiator. The ground plane provides the signal ground. The antenna shielding metal wall roughly perpendicular to the ground plane. The antenna shielding metal wall is formed by bending a plate-like part once and is electrically connected to the ground plane. The radiator generates operating resonant modes of the antenna and is electrically connected to the antenna shielding metal wall. The radiator is parallel to the ground plane and encircled by the antenna shielding metal wall.  
         [0017]     Another embodiment of the present invention provides a wireless communication apparatus, which includes: an internal component; and an EMC built-in antenna. The EMC built-in antenna has an antenna shielding metal wall, capable of effectively reducing electromagnetic coupling between the antenna and the internal components and avoiding the antenna from the signal influence of the internal components. There is no spacing required between the antenna and the internal components.  
         [0018]     Another embodiment of the present invention provides a method for improving the receiving and transmitting quality of wireless signals in a wireless communication apparatus. The wireless communication apparatus includes a built-in antenna and a signal source. The method includes: providing the wireless communication apparatus with a common ground plane; providing the built-in antenna with an electromagnetic shielding metal wall electrically connected to the common ground plane. The electromagnetic shielding metal effectively encircles the built-in antenna and is capable of effectively protecting the built-in antenna from electromagnetic coupling of the signal source such to improve the receiving and transmitting operations of the wireless signals of the built-in antenna. There is no preserved spacing needed between the built-in antenna and the signal source. Even if other signal sources are added in the wireless communication apparatus, the whole behavior of the built-in antenna almost does not change. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0019]     The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.  
         [0020]      FIG. 1  shows an antenna structure according to a first embodiment of the present invention.  
         [0021]      FIG. 2  is an extended diagram of the bent ground plate and the radiating plate in an antenna of the first embodiment.  
         [0022]      FIG. 3  is a schematic drawing showing disposition relations between an antenna, a shielding metal wall of a digital camera lens and a shielding metal case of a RF circuit module according to a second embodiment of the present invention.  
         [0023]      FIG. 4  is an extended diagram of the bent ground plate and the radiating plate in an antenna of the second embodiment.  
         [0024]      FIG. 5  is a diagram showing the return loss results between the antenna and the shielding metal wall of the digital camera lens according to the second embodiment of the present invention.  
         [0025]      FIG. 6  is a diagram showing the return loss results between the antenna and the shielding metal case of the RF circuit module according to the second embodiment of the present invention.  
         [0026]      FIG. 7  is a diagram showing the return loss results between the antenna, the shielding metal wall of the digital camera lens and the shielding metal case of the RF circuit module according to the second embodiment of the present invention.  
         [0027]      FIG. 8  is a schematic showing an antenna structure according to a third embodiment of the present invention.  
         [0028]      FIG. 9  is a schematic showing an antenna structure according to a fourth embodiment of the present invention. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0029]     Reference will now be made in detail to the present preferred 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.  
         [0030]     Referring to  FIGS. 1 and 2  for showing an antenna according to a first embodiment of the present invention. The antenna mainly includes a ground plane  10 , a bent ground plate  12  and a radiating plate  13 . The ground plane  10  is for signal ground of the entire antenna and the communication system using the antenna.  
         [0031]     The bent ground plate  12  is perpendicular to the ground plane  10  and used as an electromagnetic shielding metal wall of the antenna for providing the antenna with a required shielding effect to effectively decrease the influence on the antenna from other electronic components (or signal sources) surrounding the antenna. The bent ground plate  12  is formed of a rectangle-like metal plate or a plate plated by metal or the equivalent. The bent ground plate  12  is formed by bending the rectangle-like metal plate or the plated plate at least once. In addition, the shape thereof after the bending is roughly of an L shape. The bent ground plate  12  has a first edge  121  and a second edge  122 . The second edge  122  is electrically connected to the ground plane  10 .  
         [0032]     The radiating plate  13  is for generating operating resonant modes of the antenna. The radiating plate  13  has a signal feeding point  131  and is parallel to the ground plane  10 . The radiating plate  13  is formed of a metal plate or a plate plated with metal or the equivalent. The radiating plate  13  is electrically connected to the first edge  121  of the bent ground plate. To effectively reduce electromagnetic coupling between the antenna and other components, the radiating plate  13  is encircled by the bent ground plate  12 .  
         [0033]      FIG. 2  is an extended diagram of the bent ground plate  12  and the radiating plate  13  in the antenna according to the first embodiment.  
         [0034]      FIGS. 3 and 4  are schematic showing an antenna structure according to a second embodiment of the present invention.  FIG. 3  illustrates the disposition relations between an antenna, a shielding metal wall  35  of a digital camera lens and a shielding metal case  36  of a RF circuit module according to the second embodiment of the present invention.  
         [0035]     The antenna architecture of the second embodiment mainly includes a ground plane  30 , a bent ground plate  32  and a radiating plate  33 . The bent ground plate  32  is perpendicular to the ground plane  30  and is formed of a rectangle metal plate or a plate plated with metal or the equivalent. The bent ground plate  32  is formed by bending the metal plate or the plated plate at least once. In addition, the shape thereof after the bending is roughly of an L shape. The bent ground plate  32  has a first edge  321  and a second edge  322 . The second edge  322  is electrically connected to the grounded plane  30 . The radiating plate  33  is for generating operating resonant modes of the antenna. The radiating plate  33  has a signal feeding point  331  and two gaps  341  and  342 , and is roughly parallel to the ground plane  30 . The radiating plate  33  is electrically connected to the first edge  321  of the bent ground plate and encircled by the bent ground plate  32 . The gap  341  makes two resonant paths in the radiating plate  33 . The two resonant paths have two resonant lengths close to each other for forming a wider operating band. The gap  342  is used for fine-adjusting the resonant paths of the antenna to slightly modify the center frequency of the antenna operating resonant modes. Number, shapes and sizes of the gaps are not limited by the figure, as long as the required functions are achieved.  
         [0036]     The above-described first embodiment and the second embodiment are suitable for the situation where at both the left side and the lower side (as shown by the orientations in the figures) of the antenna reside other interference components (such as a digital camera lens, a RF circuit module and other signal sources).  
         [0037]     In the tests of deciding whether the antenna of the second embodiment of the present invention is affected by other components or not, the distance between the shielding metal wall  35  of a digital camera lens and the bent ground plate  32  is defined as “t”; while the distance between the shielding metal case  36  of a RF circuit module and the bent ground plate  32  is defined as “d”.  FIG. 4  is an extended diagram of the bent ground plate  32  and the radiating plate  33  in the antenna of the second embodiment.  
         [0038]      FIG. 5  is a diagram showing the measured return loss between the antenna and the shielding metal wall of the digital camera lens according to the second embodiment of the present invention. In the experiment, the length of the ground plane  30  is about 100 mm and the width thereof is about 60 mm; the lengths of L-shape&#39;s two arms of the bent ground plate  32  are about 10 mm and 35 mm, respectively and the height thereof is about 7 mm; the length of the radiating plate  33  is about 34 mm and the width thereof is about 9 mm; the distance between signal feeding point  331  and the first edge  321  of the bent ground plate  32  is about 5 mm; the length of the gap  341  is about 31.5 mm and the length of the gap  342  is about 1.5 mm; the diameter of the shielding metal wall  35  of a digital camera lens is about 10 mm and the height thereof is 7 mm. In addition, a coaxial cable is used to feed signals for testing the antenna, wherein the central conductor of the coaxial cable is connected to the feeding point, while the grounding sheath thereof is connected to the bent ground plate.  
         [0039]     It is clear from the measured results that with the definition of 2.5:1 voltage standing wave ratio, the impedance bandwidth of the antenna covers the frequency band of 3G (the third generation) mobile communication, i.e. 1920˜21 70 MHz. Note that the impedance bandwidth is not varied by a variation of the distance t between the shielding metal wall  35  of the digital camera lens and the bent ground plate. That is to say the antenna is not influenced by the digital camera lens. Even if the antenna is contacted thereby (t=0), the antenna still meets the operation requirements. Thus, the antenna configuration shown by the second embodiment of the present invention can meet the operation frequency band requirement (1 920˜21 70 MHz) of the 3G mobile communication and is suitable for the mobile phone application.  
         [0040]      FIG. 6  is a diagram showing the measured return loss between the antenna and the shielding metal case of the RF circuit module according to the second embodiment of the present invention. Other parameters in  FIG. 6  are the same as  FIG. 5 , but the length, width and the height of the shielding metal case of a RF circuit module  36  are 60 mm, 60 mm and 7 mm, respectively. The measured results demonstrate that, with the definition of 2.5:1 voltage standing wave ratio, the impedance bandwidth covers the frequency band required by the 3G mobile communication. In addition, the impedance bandwidth of the antenna does not vary with a variation of the distance d between the shielding metal case of the RF circuit module and the bent ground plate. That is to say the antenna is not influenced by the RF circuit module. Even if the antenna is contacted thereby (d=0), the antenna still meets the operation requirement.  
         [0041]      FIG. 7  is a diagram showing the measured return loss between the antenna with and without other interference (signal) sources according to the second embodiment of the present invention. Other parameters are the same as the parameters in  FIGS. 5 and 6 ; except for t=d=0 (spaces between the antenna and other signal sources are zero), which indicates the interference sources (for example, the shielding metal case  36  of the RF circuit module and the shielding metal wall  35  of the digital camera lens) are in direct contact with the bent ground plate. In  FIG. 7 , “-” curve represents the measured results with the presence of an interference source, while “x” curve represents the measured results without the presence of an interference source. The measured results further prove that the interference sources have no influence on the impedance characteristic of the invented antenna. Besides, with the definition of 2.5:1 voltage standing wave ratio, the impedance bandwidth of the antenna of the second embodiment can cover the frequency band required by the 3G mobile communication, i.e. 1 920˜21 70 MHz. That is to say, the antenna of the embodiment can be disposed with other components without a spacing preserved and the antenna still meets the operation requirement.  
         [0042]      FIG. 8  is a schematic showing an antenna structure according to a third embodiment of the present invention. The antenna includes a ground plane  80 , a bent ground plate  82  and a radiating plate  83 . The bent ground plate  82  is formed of a rectangle-like metal plate or a plate plated with metal or the equivalent. The bent ground plate  82  is formed by bending the metal plate or the plate plated twice and has a U-like shape after the bending. Similarly, the bent ground plate  82  has a first edge  821  and a second edge  822 . The radiating plate  83  is for generating operating resonant modes of the antenna and has a signal feeding point  831 . The antenna structure enables the antenna to be easily disposed with other electronic components inside a wireless communication apparatus without any influence on the antenna performance under no space preserved. The third embodiment is suitable for the situation where the left side, the lower side and the right side (as shown by the orientations in the figures) of the antenna reside other interference components (such as a digital camera lens and a RF circuit module).  
         [0043]      FIG. 9  is a schematic showing an antenna structure according to a fourth embodiment of the present invention. The antenna includes a ground plane  90 , a bent ground plate  92  and a radiating plate  93 . The bent ground plate  92  is formed by a roughly rectangle-like metal plate or a plate-like part plating metal or the equivalent, needing multiple bending and having a C-like shape after the bending. Similarly, the bent ground plate  92  has a first edge  921  and a second edge  922 . The radiating plate  93  is for generating operating resonant modes of the antenna and has a signal feeding point  931 . The antenna structure enables the antenna to be easily disposed with other electronic components inside a wireless communication apparatus without any influence on the antenna performance under no space preserved. The fourth embodiment is suitable for the situation where at all of the left and right sides and the lower and right sides (as shown by the orientations in the figures) of the antenna reside other interference components (as above described, such as a digital camera lens and a RF circuit module).  
         [0044]     Although gaps are not shown in  FIG. 1 ,  FIG. 8  and  FIG. 9 , similarly with the second embodiment, the first, the third and the fourth embodiments further include gaps, respectively, to further intensify the efficiency thereof. In addition, the antennas of the embodiments are designed as built-in.  
         [0045]     From all the above described, the antennas disclosed by the aforesaid embodiments of the present invention have advantages of structure simplicity, low fabrication cost and tangible functions.  
         [0046]     The bent ground plate and the radiating plate are formed by cutting or punching a metal plate or a metal-plated plate. The radiating plate can be formed on a microwave substrate by printing or etching technology.  
         [0047]     In summary, the antenna architecture disclosed by the embodiments of the present invention enables to effectively reduce electromagnetic coupling between the antenna and other components without any space preservation. Therefore, the antenna architecture is able to advance available space usage of a wireless communication product having the antenna and further downsize the wireless communication product. Furthermore, a metal process can be used for the antenna to be a unified body such to further reduce the fabrication cost. Moreover, since such an antenna is used in a wireless communication apparatus, the flexibility for the wireless communication apparatus using the antenna is enhanced, and antennas of the same type allow to be used in different wireless products without any design modification, for antenna standardizing.  
         [0048]     Besides, a further embodiment of the present invention discloses a wireless communication apparatus, which uses a built-in antenna provided by the above-described embodiments and contains other signal sources.  
         [0049]     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 descriptions, it is intended that the present invention covers modifications and variations of this invention if they fall within the scope of the following claims and their equivalents.