Abstract:
The invention discloses a slot antenna having a pair of orthogonally oriented front and rear reflector panels. In one embodiment, the antenna assembly includes first and second front panels oriented approximately orthogonally to each other, said first and second front panels being coupled together and having a substantially elongate slot defined upon at least a portion of each of the first and second front panels, and first and second rear reflector panels oriented approximately orthogonally to each other, and disposed proximate the first and second front panels, and a feed terminal coupled to one of the first or second front panels, said feed terminal being coupled to an input/output RF connection point. The slot antenna according to the present invention may be disposed within an associated wireless communications device relative to a ground plane element of a printed wiring board, or may be disposed separately away from the associated wireless communications device.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates generally to antenna assemblies for wireless communication devices and systems, and in particular to multiple band antenna assemblies. The invention provides particular utility to multiple polarization antennas for with telecommunications devices, or other wireless devices.  
         BACKGROUND OF THE INVENTION  
         [0002]    There is a need for a multiple band, isolated feed antenna assembly for efficient operation over a variety of frequency ranges. A further need exists for such an antenna to be suitable for mounting within a communication device and yet have little or no operational interference from other internal components of the device. In addition, there is a need for such antennas to provide polarization diversity, useful for reducing the effects of multipath.  
           [0003]    Existing antenna structures for wireless devices include both external and internal structures. External single or multi-band wire dipole antennas are half wave antennas operating over one or more frequency ranges. The typical gain is +2 dBi. These antennas have no front to back ratio and therefore radiate equally toward and away from the user of the wireless device without Specific Absorption Rate (SAR) reduction. LC (inductor and capacitor) traps may be used to achieve multi-band resonances. The bandwidth near the head is limited to 80 degrees nominal.  
           [0004]    Another external antenna structure is a single or multi-band asymmetric wire dipole. This antenna is a quarter wave antenna operating over one or more frequency ranges. The typical gain is +2 dBi. There is no front to back ratio or SAR reduction. LC traps may be used to achieve multi-band resonances. An additional quarter wave conductor is needed to achieve additional resonances. The beamwidth near the head is limited to 80 degrees nominal.  
           [0005]    Internal single or multi-band antennas include asymmetric dipole antennas. These antennas include quarter wave resonant conductor traces, which may be located on a planar, printed circuit board. These antennas operate over one or more frequency ranges with a typical gain of +1 to +2 dBi, and have a slight front to back ratio and reduced SAR. These antenna structures may have one or more feedpoints, and require a second conductor for a second band resonance.  
           [0006]    Another internal antenna structure is a single or multi-band planar inverted F antenna, or PIFA. These are planar conductors that may be formed by metallized plastics. PIFA operate over a second conductor or a ground plane. The typical gain for such antennas is +1.5 dBi. The front to back ratio and SAR values are dependent of frequency.  
           [0007]    Yet other known antenna structures include quadrifilar helix and turnstile antenna structures providing circular polarization.  
         SUMMARY OF THE INVENTION  
         [0008]    A multiple band antenna for internal installation in wireless communications devices is described. The antenna includes a plurality of feed points, one each for an associated transmission and reception band. Importantly, the antenna provides enhanced isolation between the plurality of feed points. Additionally, the antenna assembly may be incorporated within such devices with minimal operational interference.  
           [0009]    Another object of the invention is to provide an antenna integrated upon a transceiver board for ease and economy of manufacture. The antenna assembly is of a compact size suitable for mounting directly on the printed wiring board of a wireless communications device. The antenna is preferably positioned at an upper rear side of the device.  
           [0010]    The antenna assembly of the present invention also preferably provides a dual band antenna for wireless communications devices having separated feeds for each band and isolation between feed points in the range of 10-24 dB.  
           [0011]    Other objects and advantages include the provision of: a dual band antenna that exhibits elliptical polarization in at least one of the bands; a relatively high bandwidth; and amenability to efficient mass production processes.  
           [0012]    In one embodiment, the antenna assembly may be disposed away from the ground plane of an associated wireless communications device and coupled via a pair of signal transmission lines such as RF coax lines, microstrip transmission lines, coplanar wave guides, or other known signal transmission approaches as appreciated by those skilled in the arts. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]    [0013]FIG. 1 is a perspective view of a wireless communications device incorporating an antenna assembly according to the present invention;  
         [0014]    [0014]FIG. 2 is a detailed perspective view of the antenna assembly of FIG. 1;  
         [0015]    [0015]FIG. 3 illustrates various view of the antenna assembly of FIGS. 1 and 2;  
         [0016]    [0016]FIG. 4 is a perspective view of a wireless communications device incorporating another embodiment of an antenna assembly according to the present invention;  
         [0017]    [0017]FIG. 5 is a detailed perspective view of the antenna assembly of FIG. 4; and  
         [0018]    [0018]FIG. 6 is a data plot of isolation versus frequency between feed ports of antenna assembly  20  of FIGS. 1 and 2.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0019]    Referring now to the drawings, wherein like numerals depict like parts throughout, FIGS. 1 and 2 illustrate an antenna assembly  20  according to the present invention disposed near the upper rear portion of a hand-held wireless communications device  22 . The antenna  20  is disposed within the housing  24  of the wireless communications device  22 . The antenna assembly  20  according to the present invention includes a resonator structure  26  disposed relative to a ground plane  28  of the wireless communications device  22 . As depicted, the resonator structure  26  of the antenna assembly  20  is disposed at an upper end portion of a printed wiring board (PWB)  30  and is operatively coupled to the PWB  30  by a pair of signal feed elements  40 ,  42 , including a high frequency feed element  40  and a lower frequency feed element  42 . The resonator structure  26  is illustrated as conductive sections disposed upon a dielectric substrate element  50 . Alternatively, the resonator structure  26  may be formed from bent metal elements or plated plastic components (not shown).  
         [0020]    The resonator structure  26  includes a high frequency resonator  52  and a low frequency resonator  54 , each separately coupled to the ground plane  28  and respective input/output ports  56 ,  58  on the printed wiring board 30, and each sized to resonate at the respective frequency bands.  
         [0021]    Referring to FIGS. 1 and 2, the resonator structure  26  includes an upper face surface  60 , a top surface  62 , a bottom surface  64  and left and right surfaces  66 ,  68 . The upper face surface  60 , top surface  62 , and bottom surface  64 , each include portions of both high and low frequency resonator elements  52 ,  54 . The left surface  66  includes a portion  82  of the low frequency resonator element  54 . The right surface  68  includes portions  92 ,  94  of the high frequency resonator surface  52 .  
         [0022]    The upper face surface  60  includes portions  70 ,  72  of both the high and low frequency resonator elements  52 ,  54 . The portion  70  of the high frequency resonator element  52  extends to the top, bottom, and right surfaces  62 ,  64 ,  68 . The portion  72  of the low frequency resonator element  54  extends between the top, bottom, and left surfaces  62 ,  64 ,  66 .  
         [0023]    As shown in FIG. 1, the top surface  62  of the resonator includes a portion  74  of the high frequency resonator element  52  defining a high frequency feed point  76 . The high frequency feed point  76  is coupled via the high frequency feed element  40  to the high frequency input/output RF port  56  of the PWB  30 . The portion  74  extends between the upper face surface  60  and the right surface  68 . The top surface  62  further includes a portion  78  of the low frequency resonator element  54  defining a ground connection point  80 . As described in more detail hereinafter, the ground connection point  80  is coupled to the ground plane  28  of the PWB  30  via a low frequency grounding element  96 . The portion  78  extends between the upper face surface  60  and the left surface  66 .  
         [0024]    As further shown in FIGS. 1 and 2, the left surface  66  of the resonator  26  includes a portion  82  of the low frequency resonator element  54 . The portion  82  extends between the upper face surface  60 , the top surface,  62  and the bottom surface  64 . The portion  82  is coupled to portions  72 ,  78 , and  86 .  
         [0025]    As shown in FIG. 2, the bottom surface  64  of the resonator includes a portion  84  of the high frequency resonator element  52 . The portion  84  extends to the upper face surface  60  and is coupled with portion  70 . The bottom surface further  64  includes a portion  86  of the low frequency resonator element  54  defining a low frequency feed point  88 . The low frequency feed point  88  is coupled to the low frequency input/output RF port  58  via the low frequency feed element  42 . The portion  86  extends between the upper face surface  60  and the left surface  66  and is coupled to portions  72  and  82 .  
         [0026]    As further shown in FIGS. 1 and 2, the right surface  68  of the resonator includes a portion  90  of the high frequency resonator element  52  defining a high frequency ground connection point  92 . As described in more detail hereinafter, the high frequency ground connection point  92  is coupled to the ground plane  28  of the PWB  30  via a high frequency grounding element  98 . The portion  90  extends between the upper face surface  60  and the top surface  62  and is coupled to portions  70  and  74 . The right surface  68  further includes a portion  94  of the high frequency resonator element  52  which extends to the upper face surface  60  and surface  64  and is coupled to portion  70 .  
         [0027]    Referring to FIG. 1, high frequency feed element  40  includes a first end which is operatively connected to the resonator structure  26  at feed point  76 , or portion  74  and a second end which is operatively connected to the PWB  30  at a high frequency RF  50  ohm input/output terminal or port  90 .  
         [0028]    Referring to FIG. 2, low frequency feed element  42  includes a first end which is operatively connected to the resonator structure  26  at feed point  88  on portion  86 , and a second end which is operatively connected to the PWB  30  at a low frequency RF 50 ohm input/output terminal or port  92 .  
         [0029]    High frequency grounding element  98  has two ends, one end of which is operatively coupled to portion  90  of the high frequency resonator element  52 . The other end of the high frequency grounding element  96  is operatively connected near the top of the PWB  30  to the ground plane  28  in a conventional manner. Low frequency grounding element  96  has two ends, one end of which is operatively coupled to portion  78  of the resonator element  54 . The other end of the low frequency grounding element  96  is operatively connected near the top of the PWB  30  to the ground plane  28  in a conventional manner.  
         [0030]    The antenna assemblies  20  of FIGS. 1 and 2 are sized to function over two different frequency bands, such as 880-960 MHz and 1710-1880 MHz or 824-894 MHz and 1850-1990 MHz. FIG. 3 illustrates views of the resonator element  26  of the antenna assembly  20  of the present invention. Dimensions of the features of the components indicated in FIG. 3 are as follows:  
                                                                 Item   Dimension (in.)                                        a   1.47           b   1.34           c   1.24           d   .792           e   .774           f   .655           g   .363           h   .278           i   .276           j   .148           k   1.47           l   .159           m   .250           n   .281           o   .315           p   .79           q   .459           r   .558           s   .79           t   .315           u   .505           v   .666           w   .79           x   .437           y   .315           z   .299           aa   .126           bb   .588           cc   .427           dd   .280           ee   .208           ff   .078           gg   .227           hh   .240           ii   .355           jj   .576           kk   .248           ll   .446                      
 
         [0031]    [0031]FIGS. 4 and 5 illustrate another embodiment of the antenna assembly  120  according to the present invention. The resonator structure  126  includes a high frequency resonator  152  and a low frequency resonator  154 , each separately coupled to the ground plane  128  and respective input/output ports  156 ,  158  on the printed wiring board  130 , and each sized to resonate at the respective frequency bands.  
         [0032]    The resonator structure  126  includes an upper face surface  160 , a top surface  162 , a bottom surface  164 , and left and right surfaces  166 ,  168 . The upper face surface  160 , top surface  162 , and bottom surface  164 , each include portions of both high and low frequency resonator elements  152 ,  154 . The left surface  166  includes a portion  190  of the high frequency resonator element  152 . The right surface  168  includes a portion  182  of the low frequency resonator surface  154 .  
         [0033]    The upper face surface  160  includes portions of  170 ,  172  both the high and low frequency resonator elements  152 ,  154 . The portion  170  of the high frequency resonator element  152  extends to the top, bottom, and left surfaces  162 ,  164 ,  166 . The portion  170  is coupled to portions  174 ,  184 ,  190 . The portion  172  of the low frequency resonator element  154  extends between the top, bottom, and right surfaces  162 ,  164 ,  168 . The portion  172  is coupled to portions  178 ,  182 ,  186 .  
         [0034]    As shown in FIG. 4, the left surface  166  of the resonator includes a portion  190  of the high frequency resonator element  152  defining the high frequency feed point  176 . The high frequency feed point  176  is coupled via the high frequency feed element  140  to the high frequency input/output RF port  156  of the PWB  130 . The portion  190  of the high frequency resonator element  154  further defines a ground connection point  192 . As described in more detail hereinafter, the ground connection point  192  is coupled to the ground plane  128  of the PWB  130  via a high frequency grounding element  198 .  
         [0035]    As further shown in FIGS. 4 and 5, the right surface  168  of the resonator  126  includes a portion  182  of the low frequency resonator element  154 . The portion  182  extends between the upper face surface  160 , the top surface  162 , and the bottom surface  164 . The portion  182  is coupled to portions  172 ,  178 , and  186 .  
         [0036]    As shown in FIG. 5, the bottom surface  164  of the resonator includes a portion  184  of the high frequency resonator element  152 . The portion  184  extends to the upper face surface  160  and left surface  166 , and is coupled to portions  170  and  190 . The bottom  164  further includes a portion  186  of the low frequency resonator element  154 . The portion  186  extends between the upper face surface  160  and the right surface  166  and is coupled to portions  172  and  182 . A tuning capacitor  202  may be coupled between the conductive portion  186  and the ground plane circuit  130 .  
         [0037]    The top surface  162  of the resonator includes a portion  178  of the low frequency resonator element  154  defining a low frequency ground connection point  180 . As described in more detail hereinafter, the low frequency ground connection point  180  is coupled to the ground plane  128  of the PWB  130  via a low frequency grounding element  196 . The portion  178  extends between the upper face surface  160  and the right surface  168  and is coupled to portions  172  and  182 . The portion  178  further defines a low frequency feed point  178 . A low frequency feed element  142  includes a first end which is operatively connected to the resonator structure  126  at feed point  178 , and a second end which is operatively connected to the PWB  130  at a low frequency RF  150  ohm input/output port  158 .  
         [0038]    High frequency feed element  140  includes a first end which is operatively connected to the resonator structure  126  at feed point  176  on portion  174  and a second end which is operatively connected to the PWB  130  at a high frequency RF  150  ohm input/output terminal or port  156 .  
         [0039]    The resonator structure  126  includes high and low frequency grounding points  192 ,  180 , and high and low frequency grounding elements  198 ,  196 . High frequency grounding element  198  has two ends, one end of which is operatively coupled to portion  190  of the high frequency resonator element  152 . The other end of the high frequency grounding element  198  is operatively connected near the top of the PWB  130  to the ground plane  128  in a conventional manner. Low frequency grounding element  196  has two ends, one end of which is operatively coupled at ground point  180 . The other end of the low frequency grounding element  196  is operatively connected near the top of the PWB  130  to the ground plane  128  in a conventional manner.  
         [0040]    [0040]FIG. 6 is a data plot of isolation versus frequency between feed ports of antenna assembly  20  of FIGS. 1 and 2. The view of FIGS. 1, 2,  4 , and  5  are not necessarily to scale, but illustrate possible orientations and components of a wireless communications device including an antenna assembly according to the present invention.  
         [0041]    It should be noted that the drawings may indicate proportions and dimensions of components of the antenna device. However, e.g., thickness of conductive layers have been exaggerated for clarity. Although, in many embodiments conductive layers have been mentioned, it is understood that it includes the use of conductive plates, foils, etc., possibly attached, secured, or otherwise disposed upon dielectric substrate(s).  
         [0042]    With knowledge of the present disclosure, other modifications will be apparent to those persons skilled in the art. Such modifications may involve other features which are already known in the design, manufacture and use of antennas and component parts thereof and which may be used instead of or in addition to features already described herein. Such modifications may include alternative manufacturing processes to form the various antenna portions, e.g., for example, conductive material selectively plated over dielectric substrate or dielectric materials, and plated plastic components and conductive foil elements. In an alternative, the antenna assembly  120  may be operatively coupled to the PWB  30 ,  130  via a coaxial RF cable, a strip line feed, a ground portion of a coplanar wave guide, or other methods as known to those skilled in the relevant arts. Additionally, while the preferred embodiments have been described herein as applying to the wireless local area network frequencies, operation in alternative bandwidths may also be feasible. Those skilled in the relevant arts will appreciate the applicability of the antenna assembly of the present invention to alternative bandwidths by proper scaling of the antenna components, etc. Still other changes may be made without departing from the spirit and scope of the present invention.