Abstract:
Disclosed is a high performance, low cost antenna for wireless communication applications which benefit from a dual feed diversity antenna. The antenna device can be fabricated from a single layer of conductive material, thus allowing easy, low cost manufacture of a high gain antenna. Antenna embodiments may provide both spatial and polarization diversity. The antenna need not be planar, but rather may be bent or formed, such as to provide an antenna which is conformal with the shape of a wireless communication device. Furthermore, other embodiments of the present invention may be made of thin film, conductive foil, vapor deposition, or could be made of a flexible conductive material, such as metallized MYLAR. Each of the slot elements may be linear or may be formed in a meander shape or other shape to reduce size. The slot elements may be provided within an antenna array useful for beam scanning applications.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of priority of U.S. Ser. No. 60/287,185, filed Apr. 27, 2001, pursuant to 35 U.S.C. §119, the disclosure of which is incorporated in its entirety by reference herein. 
    
    
     BACKGROUND OF THE INVENTION 
     Other diversity antenna devices have typically used two separate antennas. Previous related diversity antennas, such as taught in U.S. Pat. No. 6,031,503 and 6,052,093 (both incorporated in their entireties by reference herein) typically include one or more circuit board type dielectric substrate layers with one or more layers of conductive material such as plated copper, which is then processed to create the desired features in the conductive layers, such as by photolithography followed by etching in a corrosive acid bath. These related antenna methods are somewhat expensive to produce as requiring the use of expensive processing equipment and harsh chemicals for lithography, plating and etching. Furthermore, related antenna types typically employ multiple layers of conductive material. U.S. Pat. Nos. 5,717,410; 5,166,697; 5,943,020; and 5,406,292 are incorporated in their entireties by reference herein. 
     One object of the present invention is to provide a high performance, low cost antenna which is easily manufactured. 
     Another object of the present invention is to provide a flat, compact, diversity antenna without the use of harsh chemicals for plating, lithography and etching. 
     Another object of the invention is to provide a high performance, low cost diversity antenna from a single layer of conductive material. 
     Another object of the invention is to provide an antenna with spatial diversity. 
     Another object of the invention is to provide an antenna with both spatial and polarization diversity. 
     Another object of the invention is to provide slot elements within an antenna array useful for beam scanning applications. 
     Another object of the invention is to provide a high performance, low cost antenna which uses separate feed lines to each of the diversity antenna segments. 
     Another object of the invention is to provide a high performance, low cost diversity antenna which can further include a through-hole or crimp to mark the location of the 50 ohm feed point and to easily and inexpensively ensure proper location of the feedline(s) for impedence matching during mass assembly. An antenna with uniform performance is provided for wireless communication devices. 
     SUMMARY OF THE INVENTION 
     The present invention provides for a high performance, low cost diversity antenna which can be produced as a one-piece, single layer of conductive material. The conductive material may be stamped from sheet metal, foil or the like, to form the appropriate features required to produce the desired frequency band response. Numerous means of manufacturing can be employed to produce the invention. Manufacturing processes of particular significance include metal stamping process. Stamped metal embodiments of an antenna structure according to the present invention may be efficiently and economically produced. Descriptions of these embodiments are in no way meant to limit the scope of the invention, as any number of manufacturing methods known or developed by those skilled in the art can be employed. Such methods may include but are not limited to stamping, etching or milling of conductive sheets, thin conductive foil, milled, stamped or cut to specification, such as copper or aluminum foil. The invention may also be produced by deposited as a thin film, such as copper vapor deposition directly onto the housing of the wireless communication device, as well as other methods known or developed by those skilled in the art 
    
    
     BRIEF DESCRIPTION OF THE FIGURES 
     FIG. 1 illustrates a substantially planar embodiment of a single layer spatial diversity antenna. 
     FIG. 2 illustrates the dimensions to produce an antenna embodiment of FIG. 2, which is tuned to operate on the IEEE 802.11 wireless data transfer protocol at 2.4 GHz. 
     FIG. 3 illustrates a substantially planar embodiment of a dual frequency single layer spatial diversity antenna. 
     FIG. 4 illustrates a substantially planar embodiment of another dual frequency single layer spatial diversity antenna. 
     FIG. 5 illustrates a substantially planar embodiment of another dual frequency single layer spatial diversity antenna. 
    
    
     DETAILED DESCRIPTION 
     FIG. 1 illustrates a substantially planar embodiment of a single layer spatial diversity antenna device  10 . As previously stated, the antenna device can be fabricated using thin sheet metal such as copper, brass, or tin-plated steel, or other conductive materials as would be known to those skilled in the art. In a preferred embodiment, tin-plated steel having steel thickness on the order of 0.010 inch and tin plating thickness on the order of 0.001 inch is used. The conductive sheet  11  can be shaped and the proper features produced using common manufacturing techniques known in the art. Two such manufacturing methods which are commonly know in the art would be milling and stamping, although other methods which are capable of producing the desired features could also be employed. The primary features which are needed to produce the antenna device  10  from a conductive sheet  11  are the driven slots  12  and  22 . The frequency band is primarily controlled by the electrical length of the slots  12  and  22  which are cut, stamped, or formed out of, or otherwise defined upon the sheet of conductive material  11 . 
     In the illustrated embodiment which is designed for the IEEE 802.11 wireless communication protocol with the frequency band centered around 2.4 GHz, the slots  12  and  22  would, if created as simple straight slots, be too long for the antenna device  10 . Thus the rounded, oversized ends  14  and  16  for slot  12  and the rounded, oversized ends  24  and  26  of the slot  22  have the function of increasing the effective electrical length of the slots  12  and  22 . Thus, in this embodiment, a reduced size of conductive sheet can be employed to produce the antenna device  10  which features a frequency band lower than would normally be enabled by simple straight oval or rectangular slots. These rounded end features  14 ,  16 ,  24  and  26  as described can be used to reduce the overall size of the antenna device  10 . The width, “w,” of the slots  12  and  22  can be adjusted for tuning the performance of the antenna device  10  which may be necessary due to variations in the size dimensions and material makeup of components of a particular wireless communication device in which the antenna device  10  is to be employed. In the illustrated embodiment depicted in FIG. 1, the cut out features  32  and  34  are not necessary for the operation of the antenna device  10 , but are merely a non-functional feature to coincide with cutouts in the housing of the wireless communication device (not shown) used in conjunction with the depicted embodiment of FIG.  1 . 
     The feed systems employed in the preferred embodiment depicted in FIG. 1 can be coaxial feedline cables, attached at on end to the rf signal source  19  having a radio transceiver  21  and a ground plane  23  and connected at the opposite end to the antenna device  10  at feed points  18  and  20  for slot  12  and at feed points  28  and  30  for slot  22 . The center portion of the coaxial cable for slot  12  is operatively connected at feedpoint  18 , and the grounded outer shield of the coaxial cable is operatively attached at feedline grounding point  20  such as by soldering. Similarly, for driven slot  22 , the center portion of the coaxial feedline cable is attached to feedpoint  28 , and the outer shield attached to feedline grounding point  30 . These feedpoint pairs,  18 ,  20  and  28 ,  30  are placed so as to create a feedpoint with 50 ohm impedence. Crimps, bends, notches, holes or other features (not shown) produced in the conductive sheet  11  can be used to accurately mark the 50 ohm feedpoints, enabling fast, accurate placement of feedlines during mass production assembly. Alternative feed approaches may also be utilized, including but not limited to micro-strip transmission line(s). 
     In yet another embodiment of the present invention, additional slot features (not shown in the illustrations) can be made on the antenna device  10 . A corresponding additional slot feature can be incorporated along with each of the previously described slot features  12  and  22 . The additional corresponding slot features can be coupled to the same feed lines as are used to service the slots  12  and  22  respectively. In one such embodiment, the IEEE 802.11 wireless protocol using the frequency band centered ground 5.8 GHz can be useful, thus allowing such an embodiment of the antenna device  10  to serve as a multi-band antenna for multiple frequency response capability. The additional corresponding slot features for the additional frequency bands may have substantially similar shape as the primary slots  12  and  22 , yet are scaled in dimensions to match the frequency band desired. Such scaling of dimensions can be readily accomplished by one skilled in the art, within a reasonable amount of experimentation, in order to enable the proper tuned response of the multiple frequencies. The slots fed as shown are electrically ½ wavelength long. In another embodiment (not shown), the slots may have a ¼ wavelength slot length. 
     In additional embodiments, the driven slots,  12  and  22  can also be constructed as an arcuate shaped slot or a meander shaped slot to conserve space and reduce the overall size of the wireless communication device, although such shapes may reduce the performance of the antenna device. 
     FIG. 2 illustrates a substantially planar embodiment of a single layer diversity antenna device  40 , which features both spatial and polarization diversity. As previously stated, the antenna device can be fabricated using thin sheet metal such as copper, brass, or tin-plated steel, or other conductive materials as would be known to those skilled in the art. In a preferred embodiment, tin-plated steel can be used having a steel thickness on the order of 0.010 inch and tin plating thickness on the order of 0.001 inch. The conductive sheet  41  can be shaped and the proper features produced using common manufacturing techniques known in the art. Two such manufacturing methods which are commonly know in the art would be milling and stamping, although other methods which are capable of producing the desired features could also be employed. The primary features which are needed to produce the antenna device  40  from a conductive sheet  41  are the driven slots  42  and  52 . In this particular embodiment, featuring polarization diversity, the slots  42  and  52  are substantially perpendicular. The frequency band is primarily controlled by the electrical length of the slots  42  and  52  which are defined out of the sheet of conductive material  41 . 
     In the illustrated embodiment which is designed for the IEEE 802.11 wireless communication protocol with the frequency band centered ground 2.4 GHz, the slots  42  and  52  are created as simple straight slots, without the rounded ends shown in the embodiment  10  of FIG. 1, although rounded ends (not shown) could certainly be employed to reduce size of the antenna  40  shown in FIG.  2 . 
     The width, “w,” of the slots  42  and  52  can be adjusted for tuning the performance of the antenna device  40  which may be necessary due to variations in the size dimensions and material makeup of components of a particular wireless communication device in which the antenna device  40  is to be employed. In the illustrated embodiment depicted in FIG. 2 the cut out features  62  and  64  are not necessary for the operation of the antenna device  40 , but are merely a decorative feature to coincide with cutouts in the housing of the wireless communication device (not shown) which was used in conjunction with the depicted embodiment of FIG.  2 . 
     The feed systems employed in the preferred embodiment depicted in FIG. 2 can be coaxial feedline cables, attached at on end to the radio transceiver (not shown), and connected at the opposite end, to the antenna device  40  at feed points  48  and  50  for slot  42  and at feed points  58  and  60  for slot  52 . The center portion of the coaxial cable for slot  42  is operatively connected at feedpoint  48 , and the grounded outer shield of the coaxial cable is operatively attached at feedline grounding point  50  such as by soldering. Similarly, for driven slot  52 , the center portion of the coaxial feedline cable is attached to feedpoint  58 , and the outer shield attached to feedline grounding point  60 . These feedpoint pairs,  48 ,  50  and  58 ,  60  are placed so as to create a feedpoint with 50 ohm resistance. Crimps, bends, notches, holes or other features (not shown) produced in the conductive sheet  41  can be used to accurately mark the 50 ohm feedpoints, enabling fast, accurate placement of feedlines during mass production assembly. The cutout features  66  and  68  on antenna device  40 , are optional decoupling elements, used in this particular type of embodiment to decouple the slot  52  from the cutout features  62  and  64  and are optional features for other embodiments which do not have cutout features such as  62  and  64 . Alternative feed approaches may also be utilized, including but not limited to micro-strip transmission line(s). 
     In yet another embodiment of the present invention, multi-band operation can be realized, by providing additional slot features as illustrated in one such possible embodiment in FIG.  3 . The antenna device embodiment  70  retains all of the basic features of antenna device  10  plus additional features to create a dual band diversity antenna. The additional features depicted in FIG. 3 to create antenna device embodiment  70  are as follows. Additional slot features  72  and  82  are cut into the conductive sheet  11 , where the effective electrical length of the slots  72  and  82  correspond to ½ wavelength of the desired operating frequency of said second frequency band. As with embodiment  10 , the features  32  and  34  of embodiment  70  are not necessary, and merely facilitate the physical form factor of a particular wireless device. The rounded oversized end features  74 ,  76 ,  84  and  86  are optional features which serve to shorten the physical length of the slots  72  and  82  respectively, in the same manner as described above for the rounded ends  14 ,  16 ,  24  and  26 , of antenna device embodiment  10 . As will be obvious to those skilled in the art, the rounded ends  14 ,  16   24  and  26  are optional, and would not be needed if the antenna has slots with actual length in the range of ½ wavelength of the desired frequency. Furthermore, other end-loading shapes could be employed to produce the invention in embodiments desiring physically smaller features than ½ wavelength. Likewise, additional embodiments of the invention may also be produced which feature multiband operation including a plurality of slot features to produce the plurality of desired frequency bands of operation, as would be known or could be built by those skilled in the art within the scope of the invention, without requiring an undue amount of experimentation. The antenna device embodiment  70  may employ additional separate feedlines (not shown) to be operatively connected to points  78  and  80  for slot feature  72 , and connected to points  88  and  90  for slot feature  82 . However, the dual band antenna device embodiment  70  may also be built using only the two feed lines described in antenna device  10 , where the additional slots  72  and  82  would be fed through parasitic coupling from the slots  12  and  22 , along with their corresponding feedlines, connected at feed points  18 ,  20 ,  28  and  30  respectively. Additionally, other embodiments within the scope of the invention, could use alternative feeding systems as are known or would be developed by those skilled in the art. 
     An example of an alternate multi-band embodiment of the invention is depicted in FIG. 4, where only a single feedline is used for each pair of dual band antenna slots comprising the diversity antenna system of the present invention. In the antenna device embodiment  100  depicted in FIG. 4, the primary frequency band slots  12  and  22  are supplemented with second frequency band slot features  102  and  104  respectively. In this present antenna device embodiment  100  the feed points  18  and  20  can be used to service both frequencies, as provided by slot features  12  and  102 . Likewise, the feedpoints  28  and  30  as depicted in the FIG. 1 can be used to service to bath frequencies as provided by slot features  22  and  104 . As will be obvious to those skilled in the art, other slot shapes and configurations capable of providing multi-frequency bands of operation, would also fall within the scope of the present invention. Thus, additional slot features can also be incorporated along with each of the previously described slot features  12 ,  22 ,  102  and  104 . The additional corresponding slot features can be coupled to the same feed lines, or can be fed by separate feed lines (not shown). The additional corresponding slot features for the additional frequency bands may have substantially similar shape as the primary slots  12  and  22 , yet are scaled in dimensions to match the frequency band desired. Such scaling of dimensions can be readily accomplished by one skilled in the art, within a reasonable amount of experimentation, in order to enable the proper tuned response of the multiple frequencies. The longest dimension of the additional slots could have an effective electrical length on the order of either ¼ or ½ wavelength. 
     Another embodiment of a multi-band antenna according to the present invention is illustrated in FIG.  5 . The primary frequency band slots  122  and  124  are supplemented with second frequency band slot features  126  and  128 , respectively. In this present antenna device embodiment  120  the feed points  18  and  20  can be used to service both frequencies, as provided by slot features  122  and  126 . Likewise, the feedpoints  28  and  30  as depicted in the FIG. 5 can be used to service to both frequencies as provided by slot features  124  and  128 . As will be obvious to those skilled in the art, other slot shapes and configurations capable of providing multi-frequency bands of operation, would also fall within the scope of the present invention. Thus, additional slot features can also be incorporated along with each of the previously described slot features  122 ,  124 ,  126 ,  128 . The additional corresponding slot features can be coupled to the same feed lines, or can be fed by separate feed lines (not shown). The additional corresponding slot features for the additional frequency bands may have substantially similar shape as the primary slots  122  and  124 , yet are scaled in dimensions to match the frequency band desired. Such scaling of dimensions can be readily accomplished by one skilled in the art, within a reasonable amount of experimentation, in order to enable the proper tuned response of the multiple frequencies. The longest dimension of the additional slots could have an effective electrical length on the order of either ¼ or ½ wavelength. 
     In additional embodiments (not shown), the driven slots,  122  and  124  can also be constructed as arcuate-shaped slots or as meander-shaped slots to conserve space and reduce the overall size of the wireless communication device, although such shapes may reduce the performance of the antenna device. Although the invention has been described in connection with particular embodiments thereof other embodiments, applications, and modifications thereof which will be obvious to those skilled in the relevant arts are included within the spirit and scope of the invention.