Abstract:
An antenna mount with a primary mount having a connecting surface(s) for an azimuth plate. The azimuth plate rotationally coupled to the connecting surface via an az-pivot fastener and rigidly connectable to the connecting surface via a pair of az-lockdown fasteners passing through az-lockdown slots in the azimuth plate. A pair of connection point(s) of the primary mount and the azimuth plate, respectively, movable towards and away from each other as an azimuth bolt coupling the connection points is threaded in or out of a threaded surface at one of the pair of connection points. The azimuth bolt carrying an az-bias spring compressed between the connection points biasing the connection points apart. Movement of the connection points towards and away from each other pivoting the azimuth plate with respect to the primary mount about the az-pivot fastener. Further pivot surfaces may also be added, providing an additional adjustment axis.

Description:
BACKGROUND 
     For optimal performance, a directional antenna such as a reflector antenna must be closely aligned with a target signal source. Alignment of a reflector antenna is typically performed via an adjustable antenna mount that, with respect to a fixed mounting point, is adjustable in azimuth and elevation to orient the antenna towards the target signal source. 
     Antenna mount coarse adjustment is often cost effectively incorporated into an antenna mount via a movable connection coupled to a fixed point, for example via one or more slot(s) and or a pivot point and a slot along which the pivot angle of the movable connection may be fixed by tightening one or more fasteners. Fine adjustments are difficult to make in these arrangements because the targeting resolution along the slot(s) is very low due to the free movement of the movable connection until the bolt(s) are tightened. Further, the weight of the antenna acts as a cantilever on the associated fasteners, distorting the selected alignment by biasing the fasteners towards an open rather than lock down fastener position. After the desired alignment has been achieved, for example by monitoring signal peaking, tightening these fasteners to the lock down position causes the alignment to shift back, causing a pointing error that cannot be readily compensated by the installer. Furthermore, when the fastener(s) are tightened, imperfect bearing and contact points between the adjusting surfaces can cause additional pointing error as the mechanism distorts. 
     Where multiple feeds are applied to a single reflector to simultaneously receive closely spaced beams from different satellites, precision alignment is critical to achieve acceptable signal performance with respect to each of the satellites. High resolution adjustment capability may also be used for a single feed reflector and or terrestrial applications where precision alignment is desired. 
     The adjustable antenna mount must support the entire antenna mass and also withstand any expected environmental factors such as wind shear and or ice loading. However, adjustable antenna mounts that are both sufficiently strong and easily adjustable with precision significantly increase the overall cost of the resulting antenna. 
     The conventional method for aiming an antenna is to adjust the azimuth and elevation mechanism until the maximum signal strength is received from the desired signal source, for example a satellite. In the presence of noise, random fluctuations in propagation loss, and other error, this method is not very accurate, because the gain of the antenna, as a function of pointing angle, varies only a small amount when it is close to boresight. 
     A better method is the so-called “bracketing” or “dither” technique, in which the amount of signal reduction is equalized for an equal positive and negative shift in pointing angle. This method generally requires an accurate calibrated scale of pointing angle and the corresponding mechanical accuracy of the mechanism. It also requires substantially more operator skill than the simple peaking method. 
     Neither of these prior methods allows for a final offset to account for factors such as circular polarization squint or satellite position offset. 
     The increasing competition for reflector antennas and associated mounting assemblies adapted for both industrial and high volume consumer applications such as data, VSAT, satellite tv and or internet communications has focused attention on cost reductions resulting from increased materials, manufacturing and service efficiencies. Further, reductions in required assembly operations and the total number of discrete parts are desired. 
     Therefore, it is an object of the invention to provide an apparatus that overcomes deficiencies in the prior art. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the general and detailed descriptions of the invention appearing herein, serve to explain the principles of the invention. 
         FIG. 1  is a schematic top view of an exemplary embodiment of the invention with the azimuth plate transparent for clarity. 
         FIG. 2  is a schematic side partial section view of  FIG. 1 . 
         FIG. 3  is a schematic side partial section view, including elevation adjustment features, parallel ends of the elevation bracket transparent for clarity. 
         FIG. 4  is an isometric angled side view of an embodiment including fine elevation adjustment. 
         FIG. 5  is a back view of  FIG. 4 . 
         FIG. 6  is a top view of  FIG. 4 . 
         FIG. 7  is an isometric side view of the elevation bracket and antenna mounting surface of  FIG. 4 . 
         FIG. 8  is an exploded isometric side view of the elevation bolt assembly of  FIG. 4 . 
     
    
    
     DETAILED DESCRIPTION 
     A first embodiment of a fine adjusting antenna mount is shown in  FIGS. 1 and 2 . A primary mount  2  is adapted to secure the antenna mount upon a desired mounting point. In the present embodiment, the primary mount  2  is a pipe clamp  4  adapted to mount upon the end of a cylindrical mounting pole or mast (not shown) via clamp fastener(s)  6  such as a nut and bolt through clamp fastening tab(s)  8 . Alternatively, the primary mount  2  may be any rigid connection to a desired mounting point. Coarse azimuth adjustment is effected by rotation of the primary mount  2  about the mounting point prior to final tightening of the, for example, clamp fastener(s)  6 . The top of the primary mount  2  is formed with a connecting surface(s)  10  for an azimuth plate  12 , such as integral front and rear mounting tabs  14 ,  16 . 
     Fine azimuth adjustments are obtained by pivoting the azimuth plate  12  about an az-pivot fastener  18  that couples the azimuth plate  12  to the front tab  14 . The az-pivot fastener  18  may be a removable and or fastening force adjustable nut and bolt or a permanently connected fastener such as a rivet. Az-lockdown fastener(s)  20  coupling the two rear tab(s)  16  to the azimuth plate  12  move through az-lockdown slots  22  in the azimuth plate  12  the extents of which define the range of available fine azimuth adjustment. An equivalent alternative structure being the location of the az-lockdown slot(s)  22  in the connecting surface(s)  10  of the primary mount  2 , in addition to or rather than in the azimuth plate  12 . 
     Where four or more contact points (including nominal surfaces) are present, imperfect tolerances between the points may cause gaps that close upon tightening of az-lock-down fastener(s)  20 , introducing alignment errors. Washer(s)  24 , for example slip washers may be placed around each of the az-pivot and the two az-lock-down fastener(s)  18 ,  20  to separate the azimuth plate  12  from the primary mount  2  thus enforcing contact there between at exactly three load contact points. Because the az-pivot and lock-down fastener(s)  18 ,  20  are concentric with the three washer(s)  24 , no distortion is introduced into the structures when these fastener(s) are tightened. In order to improve the performance of the azimuth motion, the washer(s)  24  could be made of, or coated with, a low-friction material such as nylon or PTFE. 
     Fine azimuth adjustment may be controlled by an azimuth bolt  26 , threaded rod or the like and a threaded surface  28  such as a nut operable by threading to adjust a distance between connection point(s)  30  on the primary mount  2  and the azimuth plate  12 , thereby introducing a pivot motion about the az-pivot fastener  18 . Alternatively, the threaded surface  28  may be integrated with one of the connection point(s)  30 . The connection point(s)  30  may be, for example, one or both of the clamp fastening tab(s)  8 , and a downward projecting adjustment tab  32  of the azimuth plate  12 . An az-bias spring  34  biased between the connection point(s)  30  urges a reverse azimuth pivot motion as the azimuth bolt  26  is loosened and also constantly biases the threading between the azimuth bolt  26  and the threaded surface  28  to absorb any threading slop or backlash that may be present. When fine adjustment is complete, the az-lock-down fastener(s)  20  and az-pivot fastener  18 , if applicable, are tightened, thus forming a rigid high-strength connection between the azimuth plate  12  and the primary mount  2  at the selected azimuth angle. 
     The antenna (not shown) may be attached via the azimuth plate  12 , commonly resulting in a combined center of gravity that is located forward of the az-pivot fastener  18 . Therefore, as shown in  FIG. 2 , a cantilever effect in the direction indicated by arrow CA acting on a fulcrum at the az-pivot fastener  18  will urge a gap  36  to open between the azimuth plate  12  and the primary mount  2  when the az-lock-down fastener(s)  20  are loosened for azimuth adjustment, thus causing an elevation shift. To counteract the cantilever effect, CA spring(s)  38 , such as a Belleville washer, may be positioned carried by the az-lockdown fastener(s)  20  to bias the connecting surface(s)  10  against the azimuth plate  12 . The CA spring  38  parameters would be adjusted such that when the az-lockdown fastener(s)  20  are loosened, the CA spring  38  force exceeds the cantilever torque, but not by so much that the static friction prevents the azimuth mechanism from being moved by the az-bias spring  34 . 
     The fine azimuth adjusting antenna mount of  FIGS. 1 and 2  may be enhanced to include elevation adjustment, as shown for example in  FIG. 3 . End tab(s)  40  are added to opposing sides of the azimuth plate  12 , angled upward normal to the azimuth plate  12 . A generally U-shaped elevation bracket  42  with parallel end(s)  44  rotates around an elevation pivot formed by el-pivot fastener(s)  45  that couple the parallel end(s)  44  of the elevation bracket  42  to the end tab(s)  40 . 
     A selected elevation angle of the elevation bracket  42  about the elevation pivot may be locked by dual el-lockdown fastener(s)  46  coupling the elevation bracket  42  to the end tab(s)  40  through corresponding arc slot(s)  48  formed in the elevation bracket  42  having a radius of curvature generally about the elevation pivot. 
     The antenna may be directly coupled to the elevation bracket  42  via, for example, mounting tab(s)  50  or to an antenna mounting surface  52  that then is coupled to the mounting tab(s)  50 . The antenna mounting surface  52  is useful where a further rotational tilt adjustment mechanism is desired between the antenna and the antenna mount. To reduce the number of discrete components, the antenna mounting surface  52  may be permanently coupled to the elevation bracket  42  via rivets, spot welding or the like. 
     Also demonstrated in  FIG. 3  is an alternative mechanism of compensating for cantilever load. A counterbalance spring  54  provides tension force between a central area  56  of the elevation bracket  42  and an extension  58  of the primary mount  2 . An advantage of this embodiment is that by determining the load geometry of the antenna over the range of movement of the elevation mechanism and selection of corresponding spring parameters, the torque imparted by the counterbalance spring  54  may be configured to change corresponding to the cantilever torque as the elevation bracket  42  moves through its range of motion, allowing the fine azimuth mechanism operation to be optimized over a wide range of elevation settings and also compensating for a significant portion of the antenna weight that must be supported prior to tightening of the el-lockdown fastener(s)  46  at the desired elevation angle. Because the azimuth fine adjustment range is small, aligning the antenna mount at either end of the fine azimuth adjustment range does not significantly change the required parameters of the counterbalance spring  54 . 
     In a further variation of the antenna mount, fine elevation adjustment functionality may be added to the general configuration of  FIG. 2  by the addition of a threaded elevation bolt  58  coupled between the central area  56  of the elevation bracket  42  and at least one of the el-lockdown fastener(s)  46 , as shown for example in  FIGS. 4–8 . As the elevation bracket  42  may be adapted to move though a wide angular range of movement, the threaded elevation bolt  58  connection to the elevation bracket  42  is arranged to allow a corresponding angular movement. As best viewed in  FIG. 7 , an aperture  60  in the elevation bracket may be formed with rounded edge(s) adapted to seat a ball  62  that the elevation bolt  58  passes through. The ball  62  is then retained in the aperture  60  between the elevation bracket  42  and a retaining plate  64  coupled to the elevation bracket  42 . An exploded view of the elevation bolt assembly appears in  FIG. 8 . An el-thimble  66  with graduated indicia  68  may be added, keyed to the elevation bolt  58 , between the ball  62  and the head of the elevation bolt  58  to provide high resolution operator feedback on the threading progress of the elevation bolt  58  to pivot the elevation bracket  42  to a desired angle about the elevation pivot. Angular changes occurring at the el-lockdown fastener  46  that the elevation bolt  58  threads into are compensated for by rotation of the el-lockdown fastener  46  within the associated end tab  40  el-lockdown hole. 
     Also shown in  FIGS. 4 and 5  are additional operator feedback indicia related to the azimuth fine adjustment that may also be incorporated in the antenna mount. An az-thimble  70  with graduated indicia  68  of, for example, 0–100 graduations may be similarly added to the azimouth bolt  26  to enable repeated fine tuning of known increments less than a full rotation of the azimuth bolt  26 . A graduated scale  72  showing, for example, plus or minus degree increments of azimuth plate  12  pivot relative to the primary mount  2  may also be easily added by adding a scale slot  74  to the azimuth plate  12  through which a stationary mark  76  of the primary mount  2  may be viewed. 
     In use, the az-thimble  70  and el-thimble  66  provide an operator reference gauge of, for example, 0 to 100 increments, marked around each thimble perimeter. Movable fiducial mark(s) proximate each of the az-thimble  70  and the el-thimble  66  may be applied to zero each scale before starting a measured rotation of the respective bolt (or vice versa). The operator can thus measure the rotation of the fastener as 100 units per turn. The antenna may also be supplied with a reference table, for example attached to the antenna, or on a data/configuration card supplied with the antenna. 
     An alignment procedure using the high resolution provided by the az-thimble and el-thimble is as follows: 
     1. Bring the signal to a certain level below peak, e.g. about 3–6 dB, note the signal meter or tone pitch, and zero the signal meter gauge or otherwise record the specific signal level. 
     2. Turn one of the az-thimble  70  and the el-thimble  66 , or their associated bolt head or threaded surface  28 , to bring the signal past its peak, then to the exact same signal level, meter reading and or tone pitch. The number of whole and fractional turns as indicated, for example, by the graduated indicia  68  on the az-thimble  70  and or el-thimble  66 . 
     3. Calculate a target number by either (a) dividing the number of whole and fractional turns from the previous step by two, or (b) using a supplied look-up table. In the latter case, the lookup table can include pre-calculated offsets to correct for cross polarization, squint, actual versus nominal spacecraft position, etc. The target number representing whole and fractional turns scaled to correspond with graduated indicia  68 . 
     3. Turn the nut back to unwind backlash, if any, then turn it forward to the starting point of step 2. Continue to turn forward by the number of whole turns (hundreds) in the target number, and stop at the corresponding target scale reading. 
     If required, repeat for the other of the az-thimble  70  and the el-thimble  66  not previously selected in step 2. 
     One skilled in the art will appreciate that the main components of the invention may be cost effectively fabricated by metal stamping. Alternatively, die casting and or injection molding may be applied. The specific exemplary embodiment of the invention described herein in detail is demonstrated with respect to a vertical pole mounting but may alternatively be readily adapted to a particular desired mounting surface and or mounting surface orientation. While the present invention has been demonstrated with mating u-brackets, equivalent elevation pivoting structures may be formed by mating angle or T-brackets having sufficient materials strength to withstand the expected weight and environmental stresses upon the antenna mount. 
     The present invention provides an antenna mount with precision alignment capability having significantly reduced complexity and manufacturing precision requirements, resulting in a significant reduction in overall cost. Also, the time required for installation and configuration of a reflector antenna incorporating an antenna mount according to the invention is similarly reduced using the invention&#39;s antenna alignment method enabled by high resolution of alignment adjustments enabled by the azimuth and or elevation bolts, aided by the graduated indicia  68  of the az-thimble  70  and el-thimble  66 . 
     
       
         
               
             
               
               
             
           
               
                   
               
               
                 Table of Parts 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 2 
                 primary mount 
               
               
                 4 
                 pipe clamp 
               
               
                 6 
                 clamp fastener 
               
               
                 8 
                 clamp fastening tab 
               
               
                 10 
                 connecting surface 
               
               
                 12 
                 azimuth plate 
               
               
                 14 
                 front tab 
               
               
                 16 
                 rear tab 
               
               
                 18 
                 az-pivot fastener 
               
               
                 20 
                 az-lockdown fastener 
               
               
                 22 
                 az-lockdown slot 
               
               
                 24 
                 washer 
               
               
                 26 
                 azimuth bolt 
               
               
                 28 
                 threaded surface 
               
               
                 30 
                 connection point 
               
               
                 32 
                 adjustment tab 
               
               
                 34 
                 az-bias spring 
               
               
                 36 
                 gap 
               
               
                 38 
                 CA spring 
               
               
                 40 
                 end tab 
               
               
                 42 
                 elevation bracket 
               
               
                 44 
                 parallel end 
               
               
                 46 
                 el-lockdown fastener 
               
               
                 48 
                 arc slot 
               
               
                 50 
                 mounting tab 
               
               
                 52 
                 antenna mounting surface 
               
               
                 54 
                 counterbalance spring 
               
               
                 56 
                 central area 
               
               
                 58 
                 elevation bolt 
               
               
                 60 
                 aperture 
               
               
                 62 
                 ball 
               
               
                 64 
                 retaining plate 
               
               
                 66 
                 el-thimble 
               
               
                 68 
                 graduated indicia 
               
               
                 70 
                 az-thimble 
               
               
                 72 
                 graduated scale 
               
               
                 74 
                 scale slot 
               
               
                 76 
                 mark 
               
               
                   
               
             
          
         
       
     
     Where in the foregoing description reference has been made to ratios, integers, components or modules having known equivalents then such equivalents are herein incorporated as if individually set forth. 
     While the present invention has been illustrated by the description of the embodiments thereof, and while the embodiments have been described in considerable detail, it is not the intention of the applicant to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications will readily appear to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details, representative apparatus, methods, and illustrative examples shown and described. Accordingly, departures may be made from such details without departure from the spirit or scope of applicant&#39;s general inventive concept. Further, it is to be appreciated that improvements and/or modifications may be made thereto without departing from the scope or spirit of the present invention as defined by the following claims.