Abstract:
A variably controlled stagger antenna array architecture is disclosed. The array employs a plurality of driven radiating elements that are spatially arranged having each radiating element or element groups orthogonally movable relative to a main vertical axis. This provides a controlled variation of the antenna array&#39;s azimuth radiation pattern without excessive side lobe radiation over full range of settings.

Description:
RELATED APPLICATION INFORMATION 
       [0001]    The present application claims priority under 35 USC section 119(e) to U.S. provisional patent application Ser. No. 60/934,371 filed Jun. 13, 2007, the disclosure of which is incorporated herein by reference in its entirety. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates in general to communication systems and components. More particularly the present invention is directed to antenna arrays for cellular communications systems. 
         [0004]    2. Description of the Prior Art and Related Background Information 
         [0005]    Modern wireless antenna implementations generally include a plurality of radiating elements that may be arranged over a reflector plane defining a radiated (and received) signal beam width and azimuth scan angle. Azimuth antenna beam width can be advantageously modified by varying amplitude and phase of an RF signal applied to respective radiating elements. Azimuth antenna beam width has been conventionally defined by Half Power Beam Width (HPBW) of the azimuth beam relative to a bore sight of such antenna array. In such an antenna array structure radiating element positioning is critical to the overall beam width control as such antenna systems rely on accuracy of amplitude and phase angle of the RF signal supplied to each radiating element. This places severe constraints on the tolerance and accuracy of a mechanical phase shifter to provide the required signal division between various radiating elements over various azimuth beam width settings. 
         [0006]    Real world applications often call for an antenna array with beam down tilt and azimuth beam width control that may incorporate a plurality of mechanical phase shifters to achieve such functionality. Such highly functional antenna arrays are typically retrofitted in place of simpler, lighter and less functional antenna arrays while weight and wind loading of the newly installed antenna array can not be significantly increased. Accuracy of a mechanical phase shifter generally depends on its construction materials. Generally, highly accurate mechanical phase shifter implementations require substantial amounts of relatively expensive dielectric materials and rigid mechanical support. Such construction techniques result in additional size and weight not to mention being relatively expensive. Additionally, mechanical phase shifter configurations that have been developed utilizing lower cost materials may fail to provide adequate passive intermodulation suppression under high power RF signal levels. 
         [0007]    Consequently, there is a need to provide a simpler method to adjust antenna beam width control. 
       SUMMARY OF THE INVENTION 
       [0008]    In a first aspect the present invention provides an antenna for a wireless network comprising a generally planar reflector, a plurality of radiators, and one or more actuators coupled to at least some of the radiators. The radiators are reconfigurable from a first configuration where the radiators are all aligned to a second configuration where the radiators are configured in three columns, each column having plural radiators generally aligned. 
         [0009]    In a preferred embodiment of the antenna the plurality of radiators comprise a first and second plurality of radiators which are movable and a third plurality of radiators which are fixed. The first and second plurality of radiators are preferably movable in opposite directions. In a preferred embodiment a first plurality of radiator mount plates are coupled to the first plurality of radiators and slidable relative to the reflector and a second plurality of radiator mount plates are coupled to the second plurality of radiators and slidable relative to the reflector. The reflector preferably has a plurality of orifices and the first and second plurality of radiator mount plates are configured behind the orifices. The reflector is preferably generally planar and is defined by a Y-axis and a Z-axis parallel to the plane of the reflector and an X-axis extending out of the plane of the reflector, and the radiators are spaced apart a distance VS in the Z direction. The reflectors in the first configuration are preferably aligned along a center line parallel to the Z-axis of the reflector. The reflectors in the second configuration are offset in opposite Y directions from the center line by a distance HS 1  and HS 2  respectively. The radiators are spaced apart by a stagger distance (SD) defined by the following relationship: 
         [0000]        SD =√{square root over ( HS   2   +VS   2 )} 
         [0000]    where 
         [0000]        HS=HS   1   +HS   2 . 
         [0010]    The antenna may further comprise a multipurpose port coupled to the one or more actuators to provide beam width control signals to the antenna. The antenna may further comprise a signal dividing-combining network for providing RF signals to the plurality of radiators wherein the signal dividing-combining network includes a phase shifting network for controlling elevation beam tilt by controlling relative phase of the RF signals applied to the radiators. 
         [0011]    In another aspect the present invention provides a mechanically variable beam width antenna comprising a generally planar reflector, a first plurality of radiators configured in a first column adjacent the reflector, a second plurality of radiators configured in a second column adjacent the reflector, a third plurality of radiators configured in a third column adjacent the reflector, and at least one actuator coupled to the first and second plurality of radiators. The first plurality of radiators and the second plurality of radiators are movable relative to each other in a direction generally parallel to the plane of the reflector from a first configuration wherein the first and second columns are spaced a first distance apart to a second configuration wherein the first and second columns are spaced a second distance apart. 
         [0012]    In a preferred embodiment the antenna further comprises a multipurpose port coupled to the at least one actuator to provide beam width control signals to the antenna. The antenna may further comprise a signal dividing-combining network for providing RF signals to the plurality of radiators wherein the signal dividing-combining network includes a phase shifting network for controlling elevation beam tilt by controlling relative phase of the RF signals applied to the radiators. The first and second plurality of radiators are preferably configured in rows aligned perpendicularly to the columns and the third plurality of radiators are offset from the rows of the first and second plurality of radiators. More specifically, the columns comprising the first and second plurality of radiators are spaced apart a distance HS and the orthogonal offset between the first and second plurality of radiators and the third plurality of radiators is VS. A stagger distance (SD) between the first and second plurality of radiators and the third plurality of radiators is defined by the following relationship: 
         [0000]    
       
         
           
             
               S 
                
               
                   
               
                
               D 
             
             = 
             
               
                 
                   
                     
                       ( 
                       
                         HS 
                         2 
                       
                       ) 
                     
                     2 
                   
                   + 
                   
                     VS 
                     2 
                   
                 
               
               . 
             
           
         
       
     
         [0013]    The antenna may further comprise a first plurality of radiator mount plates coupled to the first plurality of radiators and slidable relative to the reflector and a second plurality of radiator mount plates coupled to the second plurality of radiators and slidable relative to the reflector, wherein pairs of first and second mount plates are coupled to a common actuator. 
         [0014]    In another aspect the present invention provides a method of adjusting signal beam width in a wireless antenna having a plurality of radiators, at least some of which are movable in a direction generally parallel to a plane of the reflector. The method comprises providing the radiators in a first configuration where the radiators are all aligned in a single column generally parallel to the reflector axis to provide a first signal beam width. The method further comprises adjusting at least some of the radiators in a direction generally orthogonal to the axis of the column to a second configuration wherein the radiators are configured in at least three separate columns of plural radiators to provide a second signal beam width. 
         [0015]    In a preferred embodiment the method further comprises providing at least one beam width control signal for remotely controlling the position setting of the radiators. In the first configuration all radiators are preferably aligned with a center line of the reflector and in the second configuration alternate radiators are offset from the center line of the reflector in opposite directions. The method may further comprise providing variable beam tilt by controlling the phase of the RF signals applied to the radiators through a remotely controllable phase shifting network. 
         [0016]    In another aspect the present invention provides a method of adjusting signal beam width in a wireless antenna having a plurality of radiators at least some of which are movable in a direction generally parallel to a plane of the reflector. The method comprises providing the radiators in a first configuration wherein the radiators are aligned in at least three separate columns of plural radiators to provide a first signal beam width. The method further comprises adjusting at least some of the radiators in a direction generally orthogonal to the axis of the columns to a second configuration, wherein the radiators are configured in at least three separate columns of plural radiators and wherein at least two of the columns have a different spacing between the axes of the columns than in the first configuration, to provide a second signal beam width. 
         [0017]    In a preferred embodiment of the method the at least three separate columns of plural radiators comprise first and second columns configured with rows of radiators aligned generally orthogonal to the axis of the columns. The at least three separate columns of plural radiators further comprise a third column of radiators with radiators offset in a direction orthogonal to the rows of radiators comprising the first and second columns. The radiators comprising the first and second columns are movable relative to each other in the direction of the rows. 
         [0018]    Further features and aspects of the invention are set out in the following detailed description of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0019]      FIG. 1A  is a front view of a dual polarization, triple column antenna array in narrow azimuth beam width setting in accordance with a first embodiment of the invention. 
           [0020]      FIG. 1B  is a front view of a dual polarization, triple column antenna array in narrow azimuth beam width setting in accordance with a second embodiment of the invention. 
           [0021]      FIG. 2A  is a front view of a dual polarization, triple column antenna array in wide azimuth beam width setting in accordance with a first embodiment of the invention. 
           [0022]      FIG. 2B  is a front view of a dual polarization, triple column antenna array in wide azimuth beam width setting in accordance with a second embodiment of the invention. 
           [0023]      FIG. 3A  and  FIG. 3B  provide cross sectional view details along A-A datum detailing the motion of a dual polarized antenna element corresponding to a wide ( FIG. 2A ) and narrow ( FIG. 1A ) azimuth beam width setting, respectively. 
           [0024]      FIG. 3C  is a back side view of the area immediate about the third radiating element with movable plate positioned as depicted in  FIG. 3B . 
           [0025]      FIG. 4A  and  FIG. 4B  provide cross sectional view details along B-B datum detailing the motion of a dual polarized antenna element corresponding to a wide ( FIG. 2A ) and narrow ( FIG. 1A ) azimuth beam width setting, respectively. 
           [0026]      FIG. 4C  is a back side view of the area immediate about the fifth radiating element with movable plate positioned as depicted in  FIG. 4B . 
           [0027]      FIG. 5  is an RF circuit diagram of an antenna array equipped with a Phase Shifter and Power Divider. 
           [0028]      FIG. 6A  and  FIG. 6B  provide cross sectional view details along C-C datum detailing the motion of a dual polarized (second embodiment) antenna element corresponding to a wide ( FIG. 2B ) and narrow ( FIG. 1B ) azimuth beam width setting, respectively. 
           [0029]      FIG. 7  is a simulated azimuth radiation pattern of an antenna (first embodiment) configured for narrow azimuth beam width ( FIG. 1A ). 
           [0030]      FIG. 8  is a simulated azimuth radiation pattern of an antenna (first embodiment) configured for wide azimuth beam width ( FIG. 2A ). 
           [0031]      FIG. 9  is a simulated azimuth radiation pattern of an antenna (second embodiment) configured for narrow azimuth beam width ( FIG. 1B ). 
           [0032]      FIG. 10  is a simulated azimuth radiation pattern of an antenna (second embodiment) configured for wide azimuth beam width ( FIG. 2B ). 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0033]    Reference will be made to the accompanying drawings, which assist in illustrating the various pertinent features of the present invention. The present invention will now be described primarily in solving aforementioned problems relating to use of plurality of mechanical phase shifters, it should be expressly understood that the present invention may be applicable in other applications wherein azimuth beam width control is required or desired. 
       First Embodiment 
       [0034]      FIG. 1A  shows a front view of a dual polarization, triple column antenna array,  100 , according to a first exemplary implementation of the invention. The array utilizes a conventionally disposed reflector  105 . Reflector,  105  is oriented in a vertical orientation (Z-dimension) of the antenna array. The reflector,  105 , may, for example, consist of an electrically conductive plate suitable for use with Radio Frequency (RF) signals. Further, reflector  105 , plane is shown as a featureless rectangle, but in actual practice additional features (not shown) may be added to aid reflector performance. 
         [0035]    Continuing with reference to  FIG. 1A  an antenna array,  100 , contains a plurality of RF radiating ( 110 ,  120 ,  130 ,  140 -to- 250 ) elements preferably arranged both vertically and horizontally in a triple column arrangement along three operationally defined vertical axis. The left most axis, P 1 , provides horizontal alignment movement limit to shiftable plates  154 , ( 114 ,  194 ,  234  are not shown) operationally disposed below the forward facing surface of the reflector  105  in the corresponding reflector orifices  153 , ( 113 ,  193 ,  233  are not shown). The right most axis, P 2 , provides horizontal alignment movement limit to shiftable plates  134 , ( 174 ,  214 ,  254  not shown) operationally disposed below the forward facing surface of the reflector  105  in the corresponding reflector orifices  133 , ( 173 ,  213 ,  253  not shown). Centrally disposed axis, P 0 , is co-aligned with vertical center line CL of the reflector  105 . In this particular embodiment RF radiating elements ( 120 ,  140 ,  160 ,  180 ,  200 ,  220 ,  240 ) are vertically aligned about P0 axis and are not equipped with horizontal movement capability. It is possible to implement the antenna array wherein centrally disposed radiating elements ( 120 ,  140 ,  160 ,  180 ,  200 ,  220 ,  240 ) can be horizontally moveable thus allowing enhanced beam width shape control. 
         [0036]    Referring to  FIGS. 3A-3C , right most RF radiating  130  element (or RF radiator for short) is mounted on corresponding feed-through mount  132  centrally disposed on a top surface of a shiftable foundation mount plate  134  capable of controllable orthogonal (horizontal) movement relative to the main vertical axis P 0  limited by the peripheral dimensions of the corresponding reflector orifices  133 . The maximum right most displacement of the radiating element  130  is defined by limit axis P 2  and traversal distance HS 2 . In addition to radiator  130 , radiators  170 ,  210 , and  250  are similarly equipped and are mounted on corresponding feed-through mounts (not shown  172 ,  212 ,  252 ) centrally disposed on a top surface of a shiftable foundation mount plate (not shown  174 ,  214 ,  254 ,  234 ) exhibiting identical controllable orthogonal movement relative to the main vertical axis limited by the peripheral dimensions of the corresponding reflector orifices (not shown  173 ,  213 ,  253 ). Details pertaining to movable foundation mount plate  114  and relating structures will become apparent upon examination of  FIGS. 3A , B and C. 
         [0037]    Referring to  FIGS. 4A-4C , left most RF radiator  150  is similarly mounted on corresponding feed-through mount  152  centrally disposed on a top surface of a shiftable foundation mount plate  154  capable of controllable orthogonal movement relative to the main vertical axis limited by the peripheral dimensions of the corresponding reflector orifices  153 . The maximum left most displacement of the radiating element  150  is defined by limit axis P 1  and traversal distance HS 1 . In addition to radiator  150  radiators  110 ,  190 , and  230  are similarly equipped and are mounted on corresponding feed-through mounts (not shown  112 ,  192 ,  232 ) centrally disposed on a top surface of a shiftable foundation mount plate (not shown  114 ,  194 ,  234 ) exhibiting identical controllable orthogonal movement relative to the main vertical axis limited by the peripheral dimensions of the corresponding reflector orifices (not shown  113 ,  293 ,  233 ). Details pertaining to movable foundation mount plate  154  and relating structures will become apparent upon examination of  FIGS. 4A , B and C. 
         [0038]    In an antenna system  100  configured for a broad beam width radiation pattern, the RF radiators are preferably aligned along the common vertical axis labeled P 0  and are separated vertically by a distance VS. Preferably, the common axis P 0  is the same as center vertical axis of the reflector  105 , plane. Such a broad beam width configuration is illustrated in  FIG. 2A . Alignment axis P 0  is equidistant from the vertical edges of the of the reflector  105 , plane. For this nominal configuration stagger distance (SD) is defined by the following relationship: 
         [0000]      SD=VS 
         [0039]    For a narrow beam width azimuth radiation pattern left group RF radiators ( 110 ,  150 ,  190 , and  230 ) are positioned at leftmost alignment position and right group ( 130 ,  170 ,  210 , and  250 ) are positioned as shown in  FIG. 1A . This position is characterized by stagger distance (SD) which for a particular setting can be defined by the following relationship: 
         [0000]        SD =√{square root over ( HS   2   +VS   2 )} where  HS=HS   1   =HS   2    
         [0040]    Through computer simulations and direct EM field measurement it was determined that the azimuth radiation beam pattern can be deduced from the above formula. By varying HS dimension desired azimuth beam width settings can be attained. VS dimension is defined by the overall length of the reflector  105  plane which defines the effective antenna aperture. In the illustrative non-limiting implementation shown, RF radiator,  105 , together with a plurality of folded dipole ( 110 ,  120 ,  130 ,  140 -to- 250 ) radiating elements form an antenna array useful for RF signal transmission and reception. However, it shall be understood that alternative radiating elements, such as taper slot, horn, aperture coupled patches (APC), and etc, can be used as well. 
         [0041]    A cross section datum A-A and B-B will be used to detail constructional and operational aspects relating to radiating elements relative movement. Drawing details of A-A datum can be found in  FIG. 3A  and  FIG. 3B . 
         [0042]      FIGS. 3A and 3B  provide cross sectional views along A-A datum. A-A datum, as shown in  FIG. 1A , bisects right side movable radiating element  130  and associated mechanical structures.  FIG. 3C  provides a back side view of the area immediate of the third radiating element  130 . It shall be understood that all right side movable radiating elements share similar construction features, details being omitted for clarity. As shown in  FIG. 3A  a vertically polarized radiating element  130  is mounted with a feed-through mount  132 . A feed through mount  132  is preferably constructed out of a dielectric material and provides isolation means between radiating element  130  and movable plate  134 . Movable plate  134  is preferably constructed utilizing a rigid material as long as the plate&#39;s top surface is comprised of highly conductive material, but alternatively can be constructed from aluminum plate and the like. The RF signal is individually supplied from a power dividing-combining network  310  with a suitable flexible radio wave guide  139 , such as flexible coaxial cable, and coupled to conventionally constructed feed through mount terminals  132  (details are not shown). 
         [0043]    Movable foundation mount plate  134  is recessed, and mounted immediately below the bottom surface of radiator  105  plane and supported with a pair of sliding  137  guide frames, on each side reflector orifice  133 , having u-shape slots  138  which provide X (vertical) dimensional stability while providing Y (horizontal when viewed from front of the antenna) dimensional movement for the movable foundation mount plate  134 . As shown in  FIG. 3C  the back side of the movable foundation mount plate  134  and associated sliding guide frames  137  which are used for support are enclosed with a suitably constructed cover  135  to prevent undesirable back side radiation and to improve the front to back signal ratio. Actuator  300  provides mechanical motion means to the jack screw  131 . Jack screw rotation is coupled to a mechanical coupler  136  attached to the back side movable foundation mount plate  134 . By controlling direction and duration of rotation of the jack screw  131  subsequently provides Y dimensional movement to the movable foundation mount plate  134 . As will be appreciated by those skilled in the art jack screw  131  is one of many possible means to achieve Y-dimensional movement to the movable foundation mount plate  134 . The mechanical actuator  300 , or other well known means, may be extended to provide mechanical motion means to other or preferably all other right side jack screws  131 ,  171 ,  211 , and  251  used to control motion of respective radiating elements  130 ,  170 ,  210 , and  250 . 
         [0044]    The above description outlines basic concepts covering right side radiating element group ( 130 ,  170 ,  210  &amp;  250 ), but it shall be understood that basic building elements are replicated for left hand side radiating element group ( 110 ,  150 ,  190 ,  230 ) as well, while incorporating appropriate directional changes to accommodate element movement relative to the centerline P 0 . In some instances it maybe advantageous to combine or perhaps mirror mount mechanical assemblies into a single device as deemed appropriate for the application. 
         [0045]    It is also possible to provide an antenna element position configuration such that HS 1 ≠HS 2 . Such configuration is possible since right side jack screw  300  and left side jack screw  305  are independently controlled. Resultant antenna array azimuth pattern may exhibit a desirable pattern skew which can be altered based on operational requirements. 
         [0046]    With reference to  FIG. 5  RF radiator elements ( 110 ,  120 ,  130 ,  140 , -to- 250 ) are fed from a master RF input port,  315 , with the same relative phase angle RF signal through a conventionally designed RF power signal dividing-combining network  310 . RF power signal dividing-combining network  310  output-input ports  310 ( a - o ) are coupled via suitable radio wave guides ( 119 ,  129 ,  139 ,  149 -to- 259 ), such as coaxial cable to corresponding radiating elements ( 110 ,  120 ,  130 ,  140 -to- 250 ). In some operational instances such RF power signal  310  dividing-combining network may include a remotely controllable phase shifting network so as to provide beam tilting capability as described in U.S. Pat. No. 5,949,303 assigned to current assignee and incorporated herein by reference. An example of such an implementation is shown in  FIG. 5  wherein RF signal dividing-combining network  310  provides an electrically controlled beam down-tilt capability. Phase shifting function of the power dividing network  310  may be remotely controlled via multipurpose control port  320 . Similarly, azimuth beam width control signals are coupled via multipurpose control port  320  to left  300  and right  305  side mechanical actuators. Since each side mechanical actuators are individually controlled it possible to set the amount of element displacement differently. This provides advantageous means for radiation pattern skewing and azimuth beam width control. 
         [0047]    As was described hereinabove a plurality of radiating elements ( 110 ,  120 ,  130 ,  140 , -to- 250 ) together form an antenna array useful for RF signal transmission and reception. 
         [0048]    Consider the following two operational conditions (a-b): 
         [0049]    Operating condition (a) wherein all RF radiators ( 110 ,  120 ,  130 ,  140 -to- 250 ), as depicted in  FIG. 2A , are aligned about P 0  axis which is proximate to vertical center axis of the reflector  105  plane. Such alignment setting will result in a relatively wide azimuth beam width as shown in the simulated pattern of  FIG. 7 . 
         [0050]    Operating condition (b) wherein RF radiators ( 110 ,  120 ,  130 ,  140 ) as depicted in  FIG. 1A , are positioned in the following configuration: The left side group of RF radiators  110 ,  150 ,  190 , and  230  are positioned along P 1  axis and right group of RF radiators  130 ,  170 ,  210 ,  250  are positioned along P 2  axis. The resultant azimuth radiation beam width will be narrower when compared to (a). Such alignment setting will result in a relatively wide azimuth beam width as shown in the simulated pattern of  FIG. 8 . Obviously, HS 1  and HS 2  can be varied continuously from a minimum (0) to a maximum value to provide continuously variable azimuth variable beam width between two extreme settings described hereinabove. It is possible to achieve azimuth HBW from 30 to 90 degrees while utilizing relatively small sized reflector width commonly used with non adjustable antennas. Narrower HBW azimuths can be achieved with wider size reflector  105  and increased HS1 and HS2 dimensions. 
       Second Embodiment 
       [0051]      FIG. 1B  shows a front view of a dual polarization, triple column antenna array,  101 , according to an exemplary implementation of the invention in accordance with a second embodiment. The array utilizes a conventionally disposed reflector  105 . Reflector,  105  is oriented in a vertical orientation (Z-dimension) of the antenna array. The reflector,  105 , may, for example, comprise an electrically conductive plate suitable for use with RF signals. Further, reflector  105 , plane is shown as a featureless rectangle, but in actual practice additional features (not shown) may be added to aid reflector performance. 
         [0052]    Continuing with reference to  FIG. 1B  an antenna array,  101 , contains a plurality of horizontally displaceable RF radiating element pairs ( 110 A- 110 B,  130 A- 130 B, -to- 250 A- 250 B) preferably arranged both vertically and horizontally, in a dual column arrangement along operationally defined vertical axis P 1  and P 2 . In between horizontally moveable element pairs, fixed radiating elements  120 ,  140 ,  160 ,  180 ,  200 ,  220 ,  240  are placed along vertical centerline axis P 0 . Each horizontally displaceable RF radiating element pair ( 110 A- 110 B,  130 A- 130 B, -to- 250 A- 250 B) is provided with displacement means to provide equidistant motion for its individual radiating elements  110 A and  110 B. 
         [0053]    In reference to  FIGS. 6A and 6B  right mounted RF radiating element  110 A is mounted with feed-through mount  411  on top of right moveable plate  413 . Similarly, right mounted RF radiating element  110 B is mounted with feed-through mount  412  on top of right moveable plate  414 . Both left  413  and right  414  plates are operationally disposed below the forward facing surface of the reflector  105  in the reflector orifice  113 . Electrically conductive filler panel  410  is used to bridge variable gap between the left  413  and right  414  moveable plates to prevent ground discontinuity as the two moveable plates are moved apart or toward each other horizontally and equidistantly about the center axis P 0 . A suitable mechanical actuator  302  is provided to provide equidistant horizontal displacement about antenna array center axis P 0 . 
         [0054]    Movable foundation mount left  413  and right  414  plates are recessed, and mounted immediately below the bottom surface of radiator  105 ′ plane and supported with a pair of sliding  117  guide frames, on top and bottom sides of reflector orifice  133 , having u-shape slots  118  which provide X (vertical) dimensional stability while providing Y (horizontal when viewed from front of the antenna) dimensional movement for the movable foundation mount plates  413  and  414 . In  FIG. 6C  the back side of the movable foundation plates and associated sliding guide frames  117  are covered with suitably constructed back cover  115  to prevent undesirable back side radiation and to improve the front to back signal ratio. 
         [0055]    Mechanical actuator  302  is equipped with left  415  and right  416  jack screws to provide equidistant displacement about center axis to corresponding left  413  and right  414  moveable plates. Left  415  and right  416  jack screws are operationally coupled via left  419  and right  420  rotation to linear displacement couplers that are attached to corresponding left  413  and right  414  moveable plates. Altering jack screw rotation effectively changes the direction of travel for both RF radiating element  110 A-B in unison such that both RF radiating elements  110 A and  110 B are equidistant about center axis P 0 . It should be readily apparent to those skilled in the art that the jack screw arrangement can be replaced with any alternative mechanical actuator suitably adapted for this purpose. 
         [0056]    Net horizontal displacement of RF radiating elements  110 A-B is measured between feed through ( 411 ,  412 ) centerlines min≦H s ≦max where, for antenna system design to operate between 1.7 to 2.1 GHz min=90 mm and max=190 mm. Movable RF radiating elements stagger distance (SD) for a particular setting can be defined by the following relationship: 
         [0000]    
       
         
           
             
               S 
                
               
                   
               
                
               D 
             
             = 
             
               
                 
                   
                     ( 
                     
                       HS 
                       2 
                     
                     ) 
                   
                   2 
                 
                 + 
                 
                   VS 
                   2 
                 
               
             
           
         
       
     
         [0057]    Through computer simulations and direct EM field measurement it was determined that the azimuth radiation beam pattern can be deduced from above formula. 
         [0058]    RF radiating elements  110 A-B are provided with corresponding RF feed lines  417  and  418 . In downlink transmission mode the RF signal, from power combiner-divider network  310 , is delivered from port  310   a  to a conventional in phase 3 dB divider (not shown) network having its first output port coupled left side feed line  417  and second output port coupled right side feed line  418 . In uplink receiving mode RF signals from RF radiating elements  110 A-B are delivered to corresponding −3 dB ports of a conventional in phase 3 dB divider (not shown) network having its common port coupled to port  310   a  of the power combiner-divider network  310 . Alternatively, combiner-divider network  310  can be modified to provide required coupled ports with necessary networks. 
         [0059]    Consider the following two operational conditions (c-d): 
         [0060]    Operating condition (c) wherein all RF radiators ( 110 A-B,  130 A-B, -to- 250 A-B), as depicted in  FIG. 2B , are aligned about corresponding P 1  and P 2  axis such that HS=minimum. Such an alignment setting will result in a relatively wide azimuth beam width as shown in the simulated pattern of  FIG. 9 . 
         [0061]    Operating condition (d) wherein all RF radiators ( 110 A-B,  130 A-B, -to- 250 A-B), as depicted in  FIG. 1B , are aligned about corresponding P 1  and P 2  axis such that HS=maximum. Such an alignment setting will result in a relatively narrow azimuth beam width as shown in the simulated pattern of  FIG. 10 . The resultant azimuth radiation beam width will be narrower when compared to (c). Obviously, HS can be varied continuously from a minimum to a maximum value to provide continuously variable azimuth variable beam width between the two extreme settings described hereinabove. It is possible to achieve azimuth HBW from 30 to 90 degrees. As in the first embodiment it is possible to achieve azimuth HBW from 30 to 90 degrees while utilizing relatively small sized reflector width commonly used with non adjustable antennas. Further narrowing of the HBW azimuth angle can be achieved with wider size reflector  105  and increased HS dimension. 
         [0062]    The foregoing description is presented for purposes of illustration and description. Furthermore, the description is not intended to limit the invention to the form disclosed herein. Accordingly, variants and modifications consistent with the following teachings, and skill and knowledge of the relevant art, are within the scope of the present invention. The embodiments described herein are further intended to explain modes known for practicing the invention disclosed herewith and to enable others skilled in the art to utilize the invention in equivalent, or alternative embodiments and with various modifications considered necessary by the particular application(s) or use(s) of the present invention.