Patent Application
20080150831
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. For example, the Ka Band has an especially strict alignment requirement
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.
U.S. Pat. No. 7,046,210 “Precision Alignment Mount” by Brooker et al, issued May, 16, 2006, co-owned with the present invention by Andrew Corporation of Westchester, Ill., hereby incorporated by reference in the entirety, discloses an antenna mount with fine adjustment capabilities that applies bias springs and or belliview washers to minimize final tightening shift. However, these springs and or spring washers add complexity to the assembly operation, additional materials cost and over time the spring force of these elements may degrade, reducing their effect.
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.
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.
An exemplary embodiment of a fine adjusting antenna mount with improved final azimuth and elevation final lockdown pointing error characteristics is shown for example in
Fine azimuth adjustments are provided by a pivot action of the azimuth plate 12 with respect to the connecting surfaces 10 about an az-pivot fastener 16, such as a short neck coach bolt that couples the azimuth plate 12 to a connecting surface 10. Alternatively, the az-pivot fastener 16 may be a removable and or fastening force adjustable nut and bolt or a permanently connected fastener such as a rivet. A washer 18 (
Fine azimuth adjustment of the antenna mount may be driven by rotation of an azimuth bolt 26. For example, the azimuth bolt 26 may be rotatably retained at a fixed end 28 to the azimuth plate 12 via a pair of split inserts 32 keyed to and retained around a groove 34 of the azimuth bolt 26, the split inserts 32 held within a plummer pin 36 fixed to the azimuth plate 12. At a movable end 30 the azimuth bolt 26 threads into, for example, a threaded insert 38 seated in another plummer pin 36 formed in the head 40 of one of the az-lockdown fasteners 20. Incremental rotation of the azimuth bolt 26, rotatably fixed to the azimuth plate 12 and threadably connected to an az-lockdown fastener 20, the az-lockdown fastener 20 coupled to a connecting surface 10, operates to pivot the azimuth plate 12 about the az-pivot fastener 16 in fine increments proportional to the thread pitch of the azimuth bolt 26 threads.
Operator feedback indicia related to the azimuth fine adjustment may also be incorporated in the antenna mount. An az-thimble 42 with graduated indicia 44 of, for example, 0-100 graduations may be added to the azimuth bolt 26 to enable repeated fine tuning of known increments less than a full rotation of the azimuth bolt 26 with respect to a stationary reference point.
Elevation adjustment functionality may be added to the antenna mount via the addition of a generally U-shaped elevation bracket 46 with elevation angled ends 48 arranged to rotate around an elevation pivot formed by el-pivot fasteners 50 that couple the elevation angled end(s) 48 of the elevation bracket 46 to the azimuth angled ends 14 of the azimuth plate 12. For ease of rotation and a reduced manufacturing precision requirement, elevation pivot washers 52 may be applied to the el-pivot fasteners 50.
A selected elevation angle of the elevation bracket 46 about the elevation pivot may be locked by el-lockdown fasteners 54 coupling the elevation bracket 46 to the azimuth angled ends 14 through corresponding arc slots 56 formed in the elevation angled ends 48 having a radius of curvature generally about the elevation pivot.
The antenna may be directly coupled to the elevation bracket 46 via, for example, mounting tabs 58 (
The antenna (not shown) attachment typically results in a combined center of gravity that is located forward of the az-pivot fastener 16. Therefore, a cantilever effect acting on a fulcrum at the az-pivot fastener 16 will urge a gap to open between the azimuth plate 12 and the primary mount 2 connecting surfaces 10 at the az-lockdown fasteners 20 when the az-lockdown fasteners 20 are loosened for azimuth adjustment, thus causing a lockdown shift when the az-lockdown fasteners 20 are finally locked down. To counteract pointing errors arising from the cantilever effect and lockdown shift, the present invention, as best shown in
Alternatively, the retaining spacer 60 may be formed integral with the az-lockdown fastener 20 as a shoulder of the desired height below the az-lockdown fastener head 62. The shoulder having a diameter less than the diameter of the az-lockdown slot 22 but larger than the associated connecting surface 10 az-lockdown fastener 20 hole.
To finally lock down the azimuth plate 12 with respect to the connecting surfaces 20, an az-lockdown spacer 64 having at least one projection 66 that passes around the az-retaining nut 24 and through a corresponding projection hole 68 in the connecting surface 10 is retained at the bottom of the az-lockdown fasteners 20 by an az-lockdown nut 70. Preferably, at least two projections 66 are applied, so that the az-lockdown spacer 64 seats evenly via the projections 66 against the azimuth plate 12. Because the projections 66 pass through projection holes 68 of the connecting surfaces 10, a compression force is not applied between the azimuth plate 12 and the connecting surfaces 10 as the az-lockdown nut 70 is tightened against the azimuth lockdown spacer 64, driving the projections 66 to lock against the azimuth plate 12 to prevent further pivot of the azimuth plate 12 via the az-lockdown slots 22.
Similar to the azimuth fine adjustment, as best shown in
To minimize lockdown shift introduced with respect to the elevation adjustment, as best shown in
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 by high resolution of alignment adjustments enabled by the azimuth and or elevation bolts 26, 72, aided by the graduated indicia of the az-thimble 42 and el-thimble 80.
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'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.
