Abstract:
An antenna apparatus includes: (a) A radial waveguide parallel with a reference plane and having a first conductive element in parallel spaced relation with a second conductive element. The radial waveguide has a first signal coupling locus for coupling signals with a host unit and a plurality of second signal coupling loci. The radial waveguide distributes signals between the first signal coupling locus and the second signal coupling loci. (b) Signal coupling elements, each presenting a respective signal coupling path for effecting signal coupling association with a respective second signal coupling locus. Each signal coupling path is perpendicular with the reference plane. (c) Antenna elements, each associated with a signal coupling element, each a polygonal element parallel with the reference plane. The radial waveguide element, the signal coupling elements and the antenna elements cooperate to transfer electromagnetic signals between the host unit and a medium adjacent to the antenna elements.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     The following applications contain subject matter similar to the subject matter of this application. 
     U.S. Pat. Ser. No. 10/199,266, filed Jul. 19, 2002 U.S. Pat. No. 6,642,890, entitled “APPARATUS FOR COUPLING ELECTROMAGNETIC SIGNALS”; 
     U.S. Pat. Ser. No. 10/199,724, filed Jul. 19, 2002, entitled “A TUNABLE ELECTROMAGNETIC TRANSMISSION STRUCTURE FOR EFFECTING COUPLING OF ELECTROMAGNETIC SIGNALS”; and 
     U.S. Pat. Ser. No. 10/199,732, filed Jul. 19, 2002 U.S. Pat. No. 6,642,810, entitled “WAVEGUIDE APPARATUS”. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention is directed to electromagnetic antennas, and especially to electromagnetic antenna arrays employing a plurality of antenna elements known as patch antenna elements. Such patch antenna construction is advantageous in constructing antenna arrays that are known as steerable beam antennas. Steerable beam antennas employ fixed antenna elements, such as patch antenna elements, to “steer” loci of sensitivity (i.e., transmitting beams or bearings of reception) by establishing predetermined interference patterns among the various patch antenna elements. The desired predetermined interference patterns are commonly effected by imposing phase differences among the various patch antenna elements. 
     In today&#39;s marketplace it is desirable that a small compact steerable beam and antenna device be available for communication, locating (e.g., radar) and other applications. 
     It is desirable that patch antenna elements in steerable beam antennas be closely or densely situated in order that maximum interaction among the various patch antenna elements may be realized to “steer” loci of sensitivity (i.e., transmitting beams or bearings of reception) by establishing predetermined interference patterns among the various patch antenna elements. Prior art coupling structures employed for coupling the respective patch antenna elements with a signal coupling locus (e.g., a transmission line leading to a host device such as a transceiver for radio or radar operations) have heretofore occupied an undesirable lateral expanse about the respective antenna patch elements. As a result, antenna patch elements have not been as densely situated as desired. One solution has been to provide larger antenna patch elements. Installing an antenna patch element that occupies a larger area provides a larger available expanse in the vicinity of that patch element for effecting the requisite electromagnetic coupling and phase shifting of electromagnetic signals. However, the larger the respective patch elements, the less resolution that can be established in steering beam operations. That is, larger patch elements yield coarser beam patterns that result in coarser control of beam steering operations. 
     Another desired feature for steerable beam antenna device is that electromagnetic signals transferred between the various antenna patch elements and a signal coupling locus (e.g., coupling with a host device) be of equal strength. That is, it is desired that the structure or device that effects the desired distribution does not itself impart a variance to the signals being distributed. 
     There is a need for a steerable beam antenna device that is small, compact and densely populated with respective antenna patch elements. 
     SUMMARY OF THE INVENTION 
     An antenna apparatus includes: (a) A radial waveguide parallel with a reference plane and having a first conductive element in parallel spaced relation with a second conductive element. The radial waveguide has a first signal coupling locus for coupling signals with a host unit and a plurality of second signal coupling loci. The radial waveguide distributes signals between the first signal coupling locus and the second signal coupling loci. (b) Signal coupling elements, each presenting a respective signal coupling path for effecting signal coupling association with a respective second signal coupling locus. Each signal coupling path is perpendicular with the reference plane. (c) Antenna elements, each associated with a signal coupling element, each a polygonal element parallel with the reference plane. The radial waveguide element, the signal coupling elements and the antenna elements cooperate to transfer electromagnetic signals between the host unit and a medium adjacent to the antenna elements. 
     It is, therefore, an object of the present invention to provide a steerable beam antenna device that is small, compact and densely populated with respective antenna patch elements. 
    
    
     Further objects and features of the present invention will be apparent from the following specification and claims when considered in connection with the accompanying drawings, in which like elements are labeled using like reference numerals in the various figures, illustrating the preferred embodiments of the invention. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic perspective view of a prior art electromagnetic signal coupling arrangement with an antenna element. 
     FIG. 2 is a schematic section view of the antenna apparatus of the present invention. 
     FIG. 3 is a schematic perspective view of an electromagnetic signal coupling arrangement with an antenna element employed with the preferred embodiment of the present invention. 
     FIG. 4 is a schematic section view of the coupling arrangement illustrated in FIG. 3, taken along Section  4 — 4  in FIG.  3 . 
     FIG. 5 is a schematic perspective view of a signal coupling element employed in the preferred embodiment of the present invention. 
     FIG. 6 is a schematic perspective view of an electromagnetic signal coupling arrangement with a radial waveguide element employed in the present invention. 
     FIG. 7 is a top plan schematic view illustrating details relating to construction of the preferred embodiment of selected portions of the antenna apparatus of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1 is a schematic perspective view of a prior art electromagnetic signal coupling arrangement with an antenna element. In FIG. 1, an antenna element  10  and a slot line electromagnetic coupling structure  12  are illustrated in an installed orientation. Antenna element  10  is illustrated in a partially exploded view in order to simplify FIG.  1 . Antenna element  10  includes a first dielectric substrate  20  with a first conductive element  22  on first substrate  20 . Antenna element  10  further includes a second dielectric substrate  24  with a second conductive element  26  on second substrate  24 . First conductive element  22  is separated from second conductive element  26  by second substrate  24 . First substrate  20 , first conductive element  22 , second substrate  24  and second conductive element  26  are all substantially planar. In an assembled orientation, first substrate  20 , first conductive element  22 , second substrate  24  and second conductive element  26  are in a substantially parallel abutting relationship and substantially in register, as indicated by dotted lines  28 ,  29 . 
     An aperture  30  traverses first conductive element  22 . Antenna element  10  is designed for efficient performance at an operating frequency f 0 . Dimensions of aperture  30  are determined for efficient operation as a function of operating frequency f 0 . Aperture  30  is preferably substantially rectangular oriented about a major axis  32 . 
     Slot line coupling structure  12  includes a first dielectric slot line substrate  40  with a first transmission conductive layer  42  on a side of first slot line substrate  40  that is distal from antenna element  10 , and a second transmission conductive layer  44  on a side of first slot line substrate  40  that is proximal to antenna element  10 . Second transmission conductive layer  44  has a slot  50  traversing second transmission conductive layer  44 . Slot  50  extends from a first edge  46  toward a second edge  48  opposing first edge  46  to a slot termination locus  51 . Slot  50  is oriented about an axis  52 . Axes  32 ,  52  are substantially perpendicular. 
     Thus, electromagnetic signals are transmitted, for example, from a signal coupling locus (not shown in FIG. 1) along slot  50  toward slot termination locus  51 . As the transmitted signals pass aperture  30 , electromagnetic coupling occurs through aperture  30  to establish a transmission path with respect to antenna element  10 . That is, the coupled signals are transmitted by cooperation of first conductive element  22  and second conducive element  24 . In such manner, signals from a host device (not shown in FIG. 1) are transmitted to antenna element  10  for transmission via slot  50  and via signal coupling via aperture  30 . 
     One skilled in the art of antenna design will recognize that receive operations by antenna element  10  will be carried out in substantially the same manner to couple signals received by antenna element  10 , via aperture  30  to slot  50  and thence via slot  50  to a host device (not shown in FIG.  1 ). Transmitting operations of antenna elements, including the antenna apparatus of the present invention, are used frequently throughout this specification as illustrative of the operation of antenna apparatuses in either transmission or reception operations. 
     A significant shortcoming of the prior art coupling arrangement illustrated in FIG. 1 is the parallel relationship of antenna element  10  and slot line coupling structure  12 . One must provide sufficient expanse for antenna element  10 , or provide sufficient space between adjacent antenna elements  10  (i.e., in an array of a plurality of antenna elements  10 ), to accommodate the lateral room required by slot line coupling structure  12  to reach its host device (not shown in FIG.  1 ). This requirement for lateral room by slot line coupling structure  12  is a drawback in antenna devices using a plurality of antenna elements  10 , such as by way of example and not by way of limitation an array of antenna patch elements configured for operation as a steerable beam antenna device. The lateral room requirement for slot line coupling structure  12  limits how close adjacent antenna patch elements (e.g., antenna element  10 ; FIG. 1) can be placed, and may also limit how small each respective antenna element  10  may be. 
     FIG. 2 is a schematic section view of the antenna apparatus of the present invention. In FIG. 2, an antenna apparatus includes a radial waveguide  102  coupled with a signal transfer structure  104  at a signal transfer locus  106 . Signal transfer structure  104  is representatively illustrated in FIG. 2 as a coaxial cable  108  borne in a grounded sheath  110 . Other signal transfer structures, such as a waveguide, a two-line transmission line, a slot line or another signal transmission structure may be employed within the intended scope of the invention. 
     Coaxial cable  108  is coupled with a transition element  112 . Transition element  112  facilitates substantially even distribution of energy coupled from coaxial cable  108  to radial waveguide  102 . Radial waveguide  102  includes a first conductive member  120  and a second conductive member  122 . Conductive members  120 ,  122  are preferably metal, preferably substantially circular and centered on a common axis  116 , preferably planar and preferably parallel. FIG. 2 illustrates radial waveguide  102  in a section view taken substantially along a diameter of conductive members  120 ,  122 . Signal transfer locus  106  is substantially at axis  116 . A dielectric material may be introduced between conductive members  120 ,  122  if desired (not shown in FIG.  2 ). Grounded sheath  110  is connected with conductive member  120 . A wall  118  of signal absorbing material preferably establishes an outer boundary for radial waveguide  102 . 
     Second conductive member  122  is provided with a plurality of signal coupling loci embodied in a plurality of signal coupling apertures, or slots  130 ,  132 ,  134 ,  136 . Signal coupling slots  130 ,  132 ,  134 ,  136  traverse second conductive member  122 . 
     A plurality of signal coupling elements  140 ,  142 ,  144 ,  146  are provided. Each respective signal coupling element  140 ,  142 ,  144 ,  146  is substantially in register with a respective signal coupling slot  130 ,  132 ,  134 ,  136 . Each respective signal coupling element  140 ,  142 ,  144 ,  146  is embodied in a slot line signal transmission structure having one side of a substrate clad or covered in a conductive, preferably metal, layer, and an opposing side of the substrate bearing two conductive, preferably metal, lands with a narrow substantially linear slot separating the two lands. Antenna apparatus  100  is designed for efficient performance at an operating frequency f 0 . The width of the slot that separates the two conductive lands on one side of each respective signal coupling element  140 ,  142 ,  144 ,  146  is a function of operating frequency f 0 . 
     Thus, signal coupling element  140  has two metal lands  150 ,  152  separated by a slot  154 . A substrate  156  is visible in FIG. 2 between lands  150 ,  152 . Another conductive land on the opposing side of substrate  156  is not visible in FIG.  2 . Signal coupling element  142  has two metal lands  160 ,  162  separated by a slot  164 . A substrate  166  is visible in FIG. 2 between lands  160 ,  162 . Another conductive land on the opposing side of substrate  166  is not visible in FIG.  2 . Signal coupling element  144  has two metal lands  170 ,  172  separated by a slot  174 . A substrate  176  is visible in FIG. 2 between lands  170 ,  172 . Another conductive land on the opposing side of substrate  176  is not visible in FIG.  2 . Signal coupling element  146  has two metal lands  180 ,  182  separated by a slot  184 . A substrate  186  is visible in FIG. 2 between lands  180 ,  182 . Another conductive land on the opposing side of substrate  186  is not visible in FIG.  2 . 
     A plurality of antenna elements  190 ,  192 ,  194 ,  196  are couplingly provided electromagnetic signals by signal coupling elements  140 ,  142 ,  144 ,  146 . Each respective antenna element  190 ,  192 ,  194 ,  196  is substantially in register with a respective signal coupling element  140 ,  142 ,  144 ,  146 . Each respective antenna element  190 ,  192 ,  194 ,  196  is embodied in a substrate clad or covered in a conductive, preferably metal, layer on each of two opposing faces, or sides. Thus, antenna element  190  is embodied in a substrate  200  with conductive, preferably metal, layers  202 ,  204  on opposing faces of substrate  200 . Preferably metal layer  202  occupies a smaller area than is occupied by metal layer  204 . Antenna element  192  is embodied in a substrate  210  with conductive, preferably metal, layers  212 ,  214  on opposing faces of substrate  210 . Preferably metal layer  212  occupies a smaller area than is occupied by metal layer  214 . Antenna element  194  is embodied in a substrate  220  with conductive, preferably metal, layers  222 ,  224  on opposing faces of substrate  220 . Preferably metal layer  222  occupies a smaller area than is occupied by metal layer  224 . Antenna element  196  is embodied in a substrate  230  with conductive, preferably metal, layers  232 ,  234  on opposing faces of substrate  230 . Preferably metal layer  232  occupies a smaller area than is occupied by metal layer  234 . 
     Coupling apertures are provided in each respective antenna element metal layer adjacent with a respective coupling element for effecting coupling between a respective signal coupling element—antenna element pair. Thus, metal layer  204  of antenna element  190  is provided with an aperture  203  substantially in register with slot  154  of signal coupling element  140 . Metal layer  214  of antenna element  192  is provided with an aperture  213  substantially in register with slot  164  of signal coupling element  142 . Metal layer  224  of antenna element  194  is provided with an aperture  223  substantially in register with slot  174  of signal coupling element  144 . Metal layer  234  of antenna element  196  is provided with an aperture  233  substantially in register with slot  184  of signal coupling element  146 . 
     Energy is couplingly provided from coaxial cable  108  at signal transfer locus  106 . Transition element  112  assists in substantially evenly distributing electromagnetic energy in the form of electromagnetic waves  126 . Energy embodied in electromagnetic waves  126  is couplingly transferred with signal coupling elements  140 ,  142 ,  144 ,  146  via signal coupling slots  130 ,  132 ,  134 ,  136 . Signal coupling elements  140 ,  142 ,  144 ,  146  couplingly transfer electromagnetic energy via slots  154 ,  164 ,  174 ,  184  and apertures  203 ,  213 ,  223 ,  233  with antenna elements  190 ,  192 ,  194 ,  196 . Orientation of each respective signal coupling slot  130 ,  132 ,  134 ,  136  determines the portion of the respective electromagnetic wave  126  traversing a respective signal coupling slot  130 ,  132 ,  134 ,  136 . It is by selectively orienting respective signal coupling slots  130 ,  132 ,  134 ,  136  that one may assure that respective electromagnetic signals  126  arriving at respective signal coupling elements  140 ,  142 ,  144 ,  146  are substantially of equal signal strength. This aspect of the antenna apparatus of the present invention is discussed in greater detail in connection with FIG.  7 . 
     FIG. 3 is a schematic perspective view of an electromagnetic signal coupling arrangement with an antenna element employed with the preferred embodiment of the present invention. Elements illustrated in FIG. 2 are indicated with like reference numerals in FIG.  3 . In FIG. 3, signal coupling element  140  has two conductive, preferably metal lands  150 ,  152  on one face, or side of a substrate  156 . A slot  154  extends to substrate  156  and separates metal lands  150 ,  152 . Another metal land  151  is borne upon an opposing face of substrate  156 . Antenna element  190  is embodied in a substrate  200  with conductive, preferably metal layers  202 ,  204  on opposing faces of substrate  200 . Preferably metal layer  202  occupies a smaller area than is occupied by metal layer  204 . Antenna element  190  is in substantially abutting relationship with signal coupling element  140 . Antenna element  190  includes a coupling aperture  203  traversing metal layer  204 . Preferably coupling aperture  203  abuts substrate  200  and does not traverse any portion of substrate  200 . Signal coupling element  140  is illustrated in phantom to clearly indicate its relationship with coupling aperture  203 . Coupling aperture  203  is substantially in register with slot  154 . Electromagnetic signals are conveyed or transmitted by slot  154  to be coupled via coupling aperture  203  with antenna element. Signal coupling element  140  is substantially planar. Antenna element  190  is substantially planar. Signal coupling element  140  is substantially perpendicular with antenna element  190 . In the substantially perpendicular arrangement between signal coupling element  140  and antenna element  190  there is little lateral space required by signal coupling element  140  for delivering electromagnetic signals to antenna element  190 . The advantageous structure illustrated in FIG. 3 permits using smaller antenna elements  190  in denser, more closely juxtaposed arrays of antenna elements than is feasible using the prior art coupling arrangement illustrated in FIG.  1 . 
     FIG. 4 is a schematic section view of the coupling arrangement illustrated in FIG. 3, taken along Section  4 — 4  in FIG.  3 . Elements illustrated in FIG. 3 are indicated with like reference numerals in FIG.  4 . In FIG. 4, signal coupling element  140  has two conductive, preferably metal lands  150 ,  152  on one face, or side of a substrate  156 . A slot  154  extends to substrate  156  and separates metal lands  150 ,  152 . Another metal land (metal land  151 ; FIG. 3) that is borne upon an opposing face of substrate  156  is not visible in FIG.  4 . Antenna element  190  is embodied in a substrate  200  with conductive, preferably metal layers  202 ,  204  on opposing faces of substrate  200 . Preferably metal layer  202  occupies a smaller area than is occupied by metal layer  204 . Antenna element  190  is in substantially abutting relationship with signal coupling element  140 . Antenna element  190  includes a coupling aperture  203  traversing metal layer  204 . Preferably coupling aperture  203  abuts substrate  200  and does not traverse any portion of substrate  200 . Coupling aperture  203  is substantially in register with slot  154 . Electromagnetic signals are conveyed or transmitted by slot  154  to be coupled via coupling aperture  203  with antenna element. Signal coupling element  140  is substantially planar. Antenna element  190  is substantially planar. Signal coupling element  140  is substantially perpendicular with antenna element  190 . An additional feature that may be employed in connection with antenna element  190  is illustrated in FIG. 4 in dotted line format to indicate the alternate nature of the additional structure. That is, in an alternate embodiment of the antenna apparatus of the present invention, an additional substrate  215  may be borne upon metal layer  202 , and an additional conductive, preferably metal layer  217  may be borne upon substrate  215  on a face distal from conductive layer  202 . Preferably metal layer  217  occupies a smaller area than is occupied by metal layer  202 . Providing an additional metal layer  217  within electromagnetic coupling range of metal layer  202  permits operation of antenna element  190  as a broadband antenna. 
     FIG. 5 is a schematic perspective view of a signal coupling element employed in the preferred embodiment of the present invention. In FIG. 5, a signal coupling element  240  is configured substantially as described earlier in connection with FIGS. 2-4, with the additional feature that signal coupling element  240  is configured for phase shifting operation. Thus, signal coupling element  240  has two conductive, preferably metal lands  250 ,  252  on one face, or side of a substrate  256 . Another metal land  251  is borne upon an opposing face of substrate  256 . A slot  254  extends to substrate  256  and separates metal lands  250 ,  252 . 
     Slot  254  is filled with a dielectric phase shifting material  258 . Phase shifting material  258  may somewhat overfill slot  254 , so long as an electrical potential may be applied across phase shifting material  258 , as by applying a voltage across metal lands  250 ,  252  from terminals  260 ,  262  via electrical leads  264 ,  266 . Phase shifting material  258  can be tuned at room temperature to alter the phase of electromagnetic signals traversing phase shifting material  258  in slot  254  by controlling an electric field across phase shifting material  258 . Such tuning may be effected, for example, by altering electrical potential across metal lands  250 ,  252  via terminals  260 ,  262  and electrical leads  264 ,  266 . Phase shifting material  258  is preferably substantially the same material as is described in U.S. patent application Ser. No. 09/838,483, filed Apr. 19, 2001, by Louise C. Sengupta and Andrey Kozyrev, for “WAVEGUIDE-FINLINE TUNABLE PHASE SHIFTER”, assigned to the assignee of the present invention. That is, the preferred embodiment of phase shifting material  258  is comprised of Barium-Strontium Titanate, Ba x Sr 1−x TiO 3  (BSTO), where x can range from zero to one, or BSTO-composite ceramics. Examples of such BSTO composites include, but are not limited to: BSTO—MgO, BSTO—MgAl 2 O 4 , BSTO—CaTiO 3 , BSTO—MgTiO 3 , BSTO—MgSrZrTiO 6  and combinations thereof. Other materials suitable for employment as phase shifting material  258  may be used partially or entirely in place of barium strontium titanate. An example is Ba x Ca 1−x TiO3, where x ranges from 0.2 to 0.8, and preferably from 0.4 to 0.6. Additional alternate materials suitable for use as phase shifting material  258  include ferroelectrics such as Pb x Zr 1−x TiO3 (PZT) where x ranges from 0.05 to 0.4, lead lanthanum zirconium titanate (PLZT), lead titanate (PbTiO 3 ), barium calcium zirconium titanate (BaCaZrTiO 3 ), sodium nitrate (NaNO 3 ), KNbO 3 , LiNbO 3 , LiTaO 3 , PbNb 2 O 6 , PbTa 2 O 6 , KSr(NbO 3 ) and NaBa 2 (NbO 3 ) 5  and KH 2 PO 4 . In addition, phase shifting material  258  may include electronically tunable materials having at least one metal silicate phase. The metal silicates may include metals from Group  2 A of the Periodic Table, i.e., Be, Mg, Ca, Sr, Ba, and Ra, preferably Mg, Ca, Sr and Ba. Preferred metal silicates include Mg 2 SiO 4 , CaSiO 3 , BaSiO 3  and SrSiO 3 . In addition to Group  2 A metals, metal silicates in phase shifting material  258  may include metals from Group  1 A, i.e., Li, Na, K, Rb, Cs and Fr, preferably Li, Na and K. For example, such metal silicates may include sodium silicates such as Na 2 SiO 3  and NaSiO 3 -5H 2 O, and lithium-containing silicates such as LiAlSiO 4 , Li 2 SiO 3  and Li 4 SiO 4 . Metals from Groups  3 A,  4 A and some transition metals of the Periodic Table may also be suitable constituents of the metal silicate phase of phase shifting material  258 . Additional metal silicates may include Al 2 Si 2 O 7 , ZrSiO 4 , KAlSi 3 O 8 , NaAlSi 3 O 8 , CaAl 2 Si 2 O 8 , CaMgSi 2 O 6 , BaTiSi 3 O 9  and Zn 2 SiO 4 . 
     FIG. 6 is a schematic perspective view of an electromagnetic signal coupling arrangement with a radial waveguide element employed in the present invention. Elements illustrated in FIGS. 2-4 are indicated with like reference numerals in FIG.  6 . In FIG. 6, conductive member  122  is provided with a signal coupling aperture, or slot  130 . Signal coupling slot  130  traverses second conductive member  122 . Signal coupling element  140  is substantially in register with signal coupling slot  130 . Signal coupling element  140  is embodied in a slot line signal transmission structure having one side of a substrate clad or covered in a conductive, preferably metal, layer, and an opposing side of the substrate bearing two conductive, preferably metal, lands with a narrow substantially linear slot separating the two lands. Antenna apparatus  100  (FIG. 2) is designed for efficient performance at an operating frequency f 0 . The width of the slot that separates the two conductive lands on one side of signal coupling element  140  is a function of operating frequency f 0 . Thus, signal coupling element  140  has two metal lands  150 ,  152  on one side or face of a substrate  156  separated by a slot  154 . Another conductive land  151  is on the opposing face of substrate  156 . 
     FIG. 7 is a top plan schematic view illustrating details relating to construction of the preferred embodiment of selected portions of the antenna apparatus of the present invention. In FIG. 7, a circular conductive member  322  of an antenna apparatus has two signal coupling elements  340 ,  342 . Conductive member  322  is similar to second conductive member  122  (FIG.  2 ); signal coupling elements  340 ,  342  are similar to signal coupling elements  140 ,  142  (FIG.  2 ). Signal coupling apertures, or slots  330 ,  332  traverse conductive member  322 . Signal coupling slots  330 ,  332  are similar to signal coupling slots  130 ,  132  (FIG.  2 ). 
     Signal coupling element  340  has two metal lands  350 ,  352  on one side or face of a substrate  356  separated by a slot  354 . Another conductive land  351  is on the opposing face of substrate  356 . Signal coupling element  342  has two metal lands  360 ,  362  on one side or face of a substrate  366  separated by a slot  364 . Another conductive land  361  is on the opposing face of substrate  366 . Signal coupling elements  340 ,  342  are oriented on conductive member  322  with their respective substrates  356 ,  366  parallel with a radius  301  from center  300  of conductive member  322 . A second radius  302  is substantially perpendicular with radius  301  so that substrate  356  is substantially perpendicular with radius  302 . A coupling element angle φ defines the angle established between the planar face of a respective signal coupling element and a radius substantially bisecting a coupling slot in the respective signal coupling element. Thus, angle φ 1  is established for signal coupling element  340  with respect to radius  302  at substantially 90 degrees. Angle φ 2  is established for signal coupling element  342  with respect to radius  301  at substantially 0 degrees. The antenna apparatus of the present invention typically employs a greater number of signal coupling elements (and associated antenna elements) in a more closely packed, denser distribution on conductive member  322  than are shown in FIG.  7 . Only signal coupling elements  340 ,  342  are shown in FIG. 7 in order to simplify the drawing to facilitate understanding the invention. It is preferred, but not required that the various signal coupling elements  340 ,  342  be oriented parallel with a common radius, as illustrated in FIG.  7 . However, also in the interest of simplifying FIG. 7 to facilitate understanding the invention, signal coupling elements  340 ,  342  are both parallel with radius  301 . 
     Signal coupling slot  330  is substantially rectangular having a major axis  333  and a minor axis  331  substantially perpendicular with major axis  333 . Energy is transferred across signal coupling slot  330  substantially parallel with minor axis  331  for effecting electromagnetic signal coupling with signal coupling element  340 . Major axis  333  establishes a coupling slot angle θ 1  with radius  302 . Energy transferred across signal coupling slot  330  parallel with minor axis  331  is a vector component of signals propagated from center  300  (described in connection with FIG.  2 ). If minor axis  331  is perpendicular with radius  302 , then no component of energy will be available for transfer across signal coupling slot  330  parallel with minor axis  331 . Signal coupling slot  332  is substantially rectangular having a major axis  335  and a minor axis  337  substantially perpendicular with major axis  335 . Energy is transferred across signal coupling slot  332  substantially parallel with minor axis  337  for effecting electromagnetic signal coupling with signal coupling element  342 . Major axis  335  establishes a coupling slot angle θ 2  with radius  301 . Energy transferred across signal coupling slot  332  parallel with minor axis  337  is a vector component of signals propagated from center  300  (as described in connection with FIG.  2 ). If minor axis  337  is perpendicular with radius  301 , then no component of energy will be available for transfer across signal coupling slot  332  parallel with minor axis  337 . 
     The inventor has discovered that it is preferable for coupling element angle φ and coupling slot angle θ to be related according to the following expression in order to assure effective coupling across respective coupling slots to respective coupling elements: 
     
       
         φ=180−2θ  [1] 
       
     
     Given such a relation between coupling element angle φ and coupling slot angle θ it may be observed that the respective angles may range among the following values: 
     
       
         φ→0 degrees to 90 degrees  [2] 
       
     
     
       
         θ→90 degrees to 45 degrees  [3] 
       
     
     By arranging the dimensions of signal coupling slots, such as signal coupling slots  330 ,  332 , to accommodate a desired operating frequency f 0  and by adjusting the attitude (manifested in respective coupling slot angles θ and coupling element angles φ) of respective signal coupling slots, such as signal coupling slots  330 ,  332 , one can control the amount of energy couplingly transferred between a respective signal coupling slot and its associated signal coupling element for further transfer with a respective antenna element (not shown in FIG. 7; see FIG.  2 ). This capability to control the mount of energy couplingly transferred permits a designer to assure that varying distance from a signal transfer locus (e.g., signal transfer locus  106 ; FIG. 2) at center  300  of conductive member  322  may be accommodated to ensure that signals couplingly provided to respective signal coupling elements via respective signal coupling slots will be of substantially equal signal strength. Thus, coupling slot angles θ 1 , θ 2  may be individually selected for signal coupling slots  330 ,  332  to assure that signals couplingly transferred with signal coupling elements  340 ,  342  have substantially equal signal strength despite signal coupling slots  330 ,  332  being at different distances from center  300 , and despite coupling element angles φ 1 , φ 1  being different for respective signal coupling elements  340 ,  342 . 
     The antenna apparatus of the present invention permits denser juxtaposition of smaller individual antenna patch elements than is permitted using prior art coupling technology (FIG.  1 ). Moreover, the antenna apparatus of the present invention is particularly well suited for steerable beam antenna arrays because it provides a compact phase adjusting structure and a design facility for equalizing signal strengths of various signals couplingly provided to respective antenna patch elements. 
     It is to be understood that, while the detailed drawings and specific examples given describe preferred embodiments of the invention, they are for the purpose of illustration only, that the apparatus of the invention is not limited to the precise details and conditions disclosed and that various changes may be made therein without departing from the spirit of the invention which is defined by the following claims: