Abstract:
Provided is an antenna. In one example, the antenna includes a base having a substantially planar upper surface with an axis perpendicular to the upper surface. The base forms a ground plane for the antenna. The antenna also includes at least three conductive planar elements that are substantially triangular and are electrically coupled to the base via a feed point. Each element has a vertical edge oriented parallel to the base&#39;s axis and a horizontal edge oriented parallel to the upper surface. An angle formed by the intersection of the vertical and horizontal edges of each element is located on the base&#39;s axis and is distal from the feed point. The elements are positioned equidistantly from the base and equiangularly from one another. The vertical edges of the elements are coupled along the base&#39;s axis to form a contiguous conductive surface that is a driven element of the antenna.

Description:
CROSS-REFERENCE  
       [0001]     This application claims priority from U.S. Provisional Patent Ser. No. 60/647,273, filed on Jan. 26, 2005, and hereby incorporated by reference. 
     
    
     BACKGROUND  
       [0002]     The rapid adoption of multiple wireless services operating at widely dispersed frequencies presents a challenge for conventional antenna designs, which typically focus on relatively narrowband characteristics in single, dual, or triple band configurations. Such designs are increasingly difficult to implement as existing frequency bands are expanded and new bands are made available to deliver new services. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0003]      FIG. 1  is a perspective view of one embodiment of an antenna having three antenna elements coupled to a base.  
         [0004]      FIG. 2  is side view of one embodiment of an antenna element that may be used in the antenna of  FIG. 1 .  
         [0005]      FIG. 3  is a perspective view of an embodiment of an antenna having two interlocking blades coupled to a base.  
         [0006]      FIGS. 4   a  and  4   b  are side views of one embodiment of the two interlocking blades that may be used in the antenna of  FIG. 3 .  
         [0007]      FIG. 5  is a perspective view of one embodiment of a base that may be used in the antenna of  FIG. 3 .  
         [0008]      FIG. 6   a  is a perspective view of an embodiment of the antenna of  FIG. 3  with a planar cover.  
         [0009]      FIG. 6   b  is a top view of one embodiment of a cover that may be used in the antenna of  FIG. 6   a.    
         [0010]      FIG. 7  is a perspective view illustrating an exemplary cover element attached to the base of the antenna of  FIG. 3  or  FIG. 6   a.    
         [0011]      FIG. 8  is another embodiment of an antenna having four triangular elements.  
         [0012]      FIG. 9  illustrates the antenna of  FIG. 8  with a planer cover.  
         [0013]      FIG. 10  illustrates the antenna of  FIG. 8  with one embodiment of a conductive ring.  
         [0014]      FIG. 11  illustrates the antenna of  FIG. 8  with another embodiment of a conductive ring.  
         [0015]      FIG. 12  illustrates an exemplary environment within which one of the antennas of  FIGS. 1, 3 ,  6   a,  or  8 - 11  may be used. 
     
    
     DETAILED DESCRIPTION  
       [0016]     The present disclosure is directed to an antenna for transmitting and receiving electromagnetic signals and, more specifically, to a low profile multi-octave omni-directional surface mountable antenna. It is understood that the following disclosure provides many different embodiments or examples. Specific examples of components and arrangements are described below to simplify the present disclosure. These are, of course, merely examples and are not intended to be limiting. In addition, the present disclosure may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed.  
         [0017]     Referring to  FIG. 1 , in one embodiment, an antenna  100  illustrates an antenna configuration using a broadband multi-octave radiation structure that balances antenna efficiency, bandwidth, polarization, gain, and directivity. The antenna  100  includes three substantially triangular antenna elements  102 ,  104 , and  106  connected to a base  108  (e.g., a disc) that is a contiguous conductive surface. As will be described below in greater detail, the base  108  is the ground plane and the antenna elements  102 ,  104 , and  106  provide a driven element that is a representation of a cone. The positioning of the base  108  as the ground plane and the antenna elements  102 ,  104 , and  106  as the driven element enables the feed point  110  to be inverted compared to a conventional discone antenna. This inversion makes the antenna  100  suitable for installation above an intended coverage area (e.g., surface mounted to ceiling) with the base  108  positioned above the antenna elements  102 ,  104 , and  106 . It is understood, however, that other mounting orientations may be used.  
         [0018]     The antenna elements  102 ,  104 , and  106  are electrically coupled to the base  108  via the feed point  110 . The antenna elements  102 ,  104 , and  106  are electrically also coupled to each other along their vertical edges to form a conductive surface. The antenna elements  102 ,  104 ,  106  are arranged for equiangular spacing around the feed point  110 , and are each offset from the base  108  by a predetermined distance spanned by the material forming the feed point.  
         [0019]     With additional reference to  FIG. 2 , the antenna element  102  is illustrated in greater detail and includes a vertical edge  202  and a horizontal edge  204 . The total length of the vertical edge  202  may be less than one quarter wavelength above the base  108  at the lowest frequency of operation of the antenna  100 . In the present example, the antenna element  102  is constructed of a metal or metal alloy, but it is understood that the antenna element may be formed using any suitable conductive material. Although not illustrated in detail, the antenna elements  104  and  106  are similar or identical in size and construction.  
         [0020]     In the present disclosure, the apex of a mathematical cone represented by the antenna elements  102 ,  104 , and  106  represents a truncated cross section of the cone, but optimizes the height above the disc  108  at which the truncation occurs. This aids, for example, in extending the high frequency response of the antenna  100 . Furthermore, impedance matching stubs (not shown) may be positioned on one or more of the antenna elements  102 ,  104 ,  106  at or near the point of truncation (illustrated by line  206  in  FIG. 2 ) to better match the feed-point impedance to the radiating impedance. This may further extend the high frequency operation of the antenna  100 , which improves the efficiency of the antenna over its entire operational frequency range.  
         [0021]     Unlike conventional discone antennas, the use of the antenna elements  102 ,  104 , and  106  extends the effective length of the conductor (e.g., adds perimeter length which is equivalent to adding length to the rods in conventional approximations) and partially closes the base of the mathematical cone. In the present embodiment, this effect may be used to reduce the total height of the cone above the disc  108 . For example, if the included half-angle of the cone is thirty degrees, the height of the cone may be reduced by thirty-three percent while achieving equivalent performance at the lowest frequency of operation. An additional benefit of reducing the total height of the cone may be that the inherent variation in elevation angle (theta) of peak directivity as a function of frequency (minimum to maximum) is correspondingly reduced.  
         [0022]     Referring to  FIG. 3  and with additional reference to  FIGS. 4   a,    4   b,  and  5 , in another embodiment, an antenna  300  includes two interlocking blades  302  and  304  coupled to a base  306 . As will be described in greater detail with respect to  FIG. 4 , conductive elements on the interlocking blades  302  and  304  form a representation of a cone, with the base  306  as a ground plane and the conductive elements as the driven element. As with the antenna  100  of  FIG. 1 , this enables a feed point  308  connecting the conductive elements to the base  306  to be inverted compared to a conventional discone antenna, which makes the antenna  300  suitable for installation above an intended coverage area.  
         [0023]     The use of blades  302  and  304  allows for ease in manufacture and also aids in the approximation of an omni-directional radiation characteristic. In addition, the use of blades  302  and  304  imparts structural integrity to the antenna  300  that provides flexibility in choosing design characteristics. For example, the tendency of conventional antennas to use the cone portion of a discone antenna as the ground is at least partly due to the practical need to maintain sufficient structural integrity. By truncating the apex of the cone, it is possible to use a sufficiently rigid feed point (center conductor) to sustain the mechanical loads of the disc. The use of printed circuit boards (discussed below with respect to  FIG. 4 ) as the blades  302 ,  304  enables a dielectric portion of each blade to directly contact the base  306 . This allows each blade to be mechanically secured to the base  306  independently from the connection of the feed point  308 . By freeing the feed point  308  from the mechanical constraint of supporting the blades  302  and  304 , the present embodiment is able to extend the high frequency operation of the antenna  300  to multi-octave capability.  
         [0024]     As illustrated in greater detail in  FIG. 4   a,  the blade  302  is formed on a dielectric printed circuit board. Two antenna elements  402  and  404 , which are substantially triangular in the present example, are formed on the circuit board  302  using techniques known to those of skill in the art (e.g., screening, etching, and plating processes). Although the blade  302  is described in terms of separate antenna elements  402  and  404  for purposes of clarity, it is understood that the two antenna elements may be formed as a single element. Additionally, although not shown, it is understood that the opposite surface of the blade  302  is similar or identical to that shown in  FIG. 4   a.  A slot  406  is formed in the circuit board  302  to allow the circuit board to engage an opposing slot in the blade  304  ( FIG. 4   b ).  
         [0025]     Each antenna element  402  and  404  includes a vertical edge  408 ,  410 , respectively, and a horizontal edge  412 ,  414 , respectively. The lower corner of each of the antenna elements  402  and  404  (e.g., the corner nearest the feed point  308 ) is truncated and is offset from the lower edge of the circuit board  302  (by about 0.125 inches in the present example). The blade  302  may also include one or more impedance matching stubs  416  at or near the point of truncation to better match the impedance of the feed point to the radiating impedance, which may serve to extend the high frequency operation of the antenna  300 . For purposes of example, the total width of the combined antenna elements  402 ,  404  is 4.0 inches and each element is 3.125 inches tall. The slot  406  is 0.04 inches wide and 1.675 inches high. The circuit board  302  includes one or more coupling means  418  (e.g., holes, protrusions, or brackets) by which the circuit board may be fastened to the base  306  ( FIG. 3 ).  
         [0026]     As illustrated in greater detail in  FIG. 4   b,  the blade  304  is substantially similar or identical to the blade  302  ( FIG. 4   a ) and includes antenna elements  422  and  424 . Although the blade  304  is described in terms of separate antenna elements  422  and  424  for purposes of clarity, it is understood that the two antenna elements may be formed as a single element. Additionally, although not shown, it is understood that the opposite surface of the blade  304  is similar or identical to that shown in  FIG. 4b . A slot  426  is formed in the circuit board  302  to allow the circuit board to engage the slot in the blade  302  ( FIG. 4   a ).  
         [0027]     Each antenna element  422  and  424  includes a vertical edge  428 ,  430 , respectively, and a horizontal edge  432 ,  434 , respectively. As in the blade  302 , the lower corner of each of the antenna elements  402  and  404  (e.g., the corner nearest the feed point  308 ) is truncated and is offset from the lower edge of the circuit board  304  (by about 0.125 inches in the present example). The blade  304  may also include one or more impedance matching stubs  436  at or near the point of truncation. For purposes of example, the total width of the combined antenna elements  422 ,  424  is 4.0 inches and each element is 3.125 inches tall. The slot  426  is 0.04 inches wide and 1.675 inches high. The circuit board  304  includes one or more coupling means  438  (e.g., holes, protrusions, or brackets) by which the circuit board may be fastened to the base  306  ( FIG. 3 ).  
         [0028]     As illustrated in  FIG. 5 , the base  306  in the present example is a metal disc. The disc  306  provides structural integrity to the antenna  300  and operates as a ground plane. While substantially planar, the disc  306  may include mounting means  502  (e.g., holes, protrusions, or brackets) positioned to correspond to the coupling means  418  and  438  of the blades  302  and  304 , as well as mounting means (not shown) for attaching the antenna to a surface. In addition, the feed point  308  may be elevated or otherwise physically differentiated from the remainder of the disc  306 .  
         [0029]     Referring to  FIG. 6   a,  in yet another embodiment, a planar cover  600  may be coupled to the upper edges of the blades  302  and  306  of  FIG. 3 . The cover  600 , which is electrically connected to the antenna elements of the blades  302 ,  304  and is parallel to the disc  306  (e.g., the ground plane), may aid in configuring the antenna  300  for broadband multi-octave operation. More specifically, the cover  600  may be used to alter the radiation impedance and have the effect of increasing the effective length of the conductor (and allowing a downward extension of operating frequency range). For example, the addition of the cover  600  results in a closed base for the mathematical cone represented by the antenna elements of the blades  302  and  304 , which allows a greater than fifty percent reduction in cone height above the disc  306  when compared to conventional practice. An additional benefit of reducing the total height of the mathematical cone is that when used as a multi-octave antenna, the inherent variation in elevation angle (theta) of peak directivity as a function of frequency (minimum to maximum) is correspondingly reduced.  
         [0030]     With additional reference to  FIG. 6   b,  in the present example, the cover  600  is a, disc formed using a printed circuit board. The cover  600  includes two grooves  602 ,  604  that are plated or lined with a conductive material. Each of the grooves  602 ,  604  have a width corresponding to a thickness of the blades  302 ,  304 . The upper edge of each blade  302 ,  304  (e.g., the horizontal edges  412 ,  414 ,  432 , and  344  of  FIGS. 4   a  and  4   b ) fits into one of the grooves  602 ,  604 . For purposes of example, the cover  308  is four inches in diameter (which is identical to the total width of the combined antenna elements  402 ,  404  and  432 ,  434  as illustrated in  FIGS. 4   a  and  4   b ).  
         [0031]     Referring to  FIG. 7 , in still another embodiment, the antenna  300  of  FIG. 3  is illustrated with a covering element  700 . The covering element  700  is attached to the disc  306  over the blades  302  and  304 . Additionally, a fastener  702  is coupled to the disc  306  for fastening the antenna  300  to a structure. For example, the antenna  300  may be surface mounted to a ceiling (see  FIG. 12 ). A transmission line (not shown) may attach to a connector  704  for receiving and/or transmitting signals via the antenna  300 .  
         [0032]     Referring to  FIG. 8 , in another embodiment, an antenna  800  includes four conductive elements  802 ,  804 ,  806 , and  808 . Each of the elements  802 ,  804 ,  806 , and  808  are coupled to form a contiguous conductive surface as previously described. The elements  802 ,  804 ,  806 , and  808  form a driven element of the antenna  800  and are electrically coupled to a base  810  that forms a ground plane for the antenna  800 . The elements  802 ,  804 ,  806 , and  808  are elevated from and electrically coupled to the base  810  via a feed point  812 .  
         [0033]     Referring to  FIG. 9 , in yet another embodiment, the antenna  800  of  FIG. 8  is illustrated with a cover element  900  that is at least partially conductive. As described previously, the cover element  900  alters the radiation impedance and effectively increases the length of the conductor and extends the operating frequency range of the antenna  800 .  
         [0034]     Referring to  FIG. 10 , in still another embodiment, the antenna  800  of  FIG. 8  is illustrated with a conductive ring  1000 . The ring  1000  is electrically coupled to each of the elements  802 ,  804 ,  806 , and  808 . In the present example, the ring  1000  is connected to the outer vertical edge of each of the elements  802 ,  804 ,  806 , and  808  to optimize the radiation impedance and to adjust the elevation angle peak directivity at specific frequencies. The ring  1000  may be positioned at selected heights above the base  810  to select the frequency at which the optimization occurs. It is understood that, although a single ring  1000  is illustrated, multiple rings may be used (e.g., at varying heights relative to the base  810 ) for selecting multiple frequencies.  
         [0035]     Referring to  FIG. 11 , in yet another embodiment, the antenna  800  of  FIG. 8  is illustrated with a conductive ring  1100 . In the present example, the ring  1100  represents a partial cylindrical shell that is centered on an axis  1102  that is perpendicular to the surface of the disc  810  and is parallel to the vertical edge of each of the elements  802 ,  804 ,  806 , and  808 . The ring  1100  is electrically coupled to each of the elements  802 ,  804 ,  806 , and  808 . The ring  1100  is connected to the outer vertical edge of each of the elements  802 ,  804 ,  806 , and  808  to optimize the radiation impedance and to adjust the elevation angle peak directivity at specific frequencies. The ring  1000  (or rings, if desired) may be positioned at selected heights above the base  810  to select the frequency (or frequencies) at which the optimization occurs. In the present example, each of the elements  802 ,  804 ,  806 , and  808  is formed on one of two printed circuit boards  814 ,  816 , as is described in greater detail with respect to  FIGS. 3 and 4 . Each of the circuit boards  814  and  816  include a notch that supports the ring  1100 .  
         [0036]     Referring to  FIG. 12 , one embodiment of an environment  1200  is illustrated within which one or more antennas  1206  (e.g., one of the antennas described in the preceding embodiments) may be used. The environment  1200  includes a multi-story building having a plurality of antennas (e.g., the antenna  300  of  FIG. 3 ) connected to radiating coaxial cables  1202 . The cables  1202  extend into a telecom room  1204  that provides connection to various external systems and networks (not shown), such as the internet. It is understood that the environment  1200  is merely one example of an environment that may utilize the antennas described in the present disclosure, and that many other environments are envisioned.  
         [0037]     The antennas described in the preceding embodiments may be used to ensure signal quality inside man-made structures such as buildings (e.g., the environment  1200 ). The complex signal propagation environment inside buildings dictates use of an antenna with well behaved polarization, true omni-directional patterns, and high efficiency. The aesthetics of, and limited available space for, in-building installation dictate a physical size less than a normally required quarter wavelength monopole above a ground plane (at the lowest frequency of operation). For example, a thin linear monopole operating at 450 MHz would generally require an 8.35 inch diameter ground plane and a 6.56 inch wire monopole. The multiplicity of frequencies to be transmitted and received strongly favors a physical structure inherently capable of contiguous frequency operation across multi-octaves. Accordingly, the antennas described herein may be used within the environment  1200  and similar environments.  
         [0038]     While the preceding description shows and describes one or more embodiments, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the present disclosure. For example, various portions of an antenna described in one embodiment may be used with an antenna described in another embodiment. Also, the shape of the conductive elements, base, and/or planar cover may vary. Furthermore, supplied measurements are for purposes of example, and antennas having different measurements may be constructed. Also, it is understood that the description of various elements as being separate (and having separate vertical and horizontal edges) is for purposes of convenience, and that elements described separately (e.g., the elements  402  and  404  of  FIG. 4   a ) may equally be described as a single element. In addition, various functions illustrated in the methods or described elsewhere in the disclosure may be combined to provide additional and/or alternate functions. Therefore, the claims should be interpreted in a broad manner, consistent with the present disclosure.