Abstract:
An antenna array employing a combined azimuth and elevation beam angle adjustment electromechanical system is disclosed. The system employs a dual purpose remotely controllable actuator. The actuator is used to adjust azimuth angle of the antenna array and radiation beam tilt of the same. An antenna array employing a combined azimuth, beamwidth and elevation beam angle adjustment electromechanical system is also disclosed.

Description:
RELATED APPLICATION INFORMATION 
       [0001]    The present application claims priority under 35 USC section 119(e) to U.S. Provisional Patent Application Ser. No. 61/004,242, filed Nov. 26, 2007, the disclosure of which is herein incorporated 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 antennas and antenna arrays employed in wireless 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 ground plane defining a radiated (and received) signal beamwidth and azimuth angle relative to a defined bore sight. The azimuth radiation pattern of the antenna (in horizontal plane) can be advantageously moved to provide different geographic coverage by rotating the antenna assembly about a vertical axis. In the past such movement has been achieved by implementing electro mechanical rotors and the like. In addition to azimuth radiation shifting, modern wireless antennas may employ remote electrical tilt (RET) to control antenna beam tilt which allows real time augmentation of cell coverage due to topography and traffic density. RET allows wireless network operators to alter vertical radiation pattern, i.e. the pattern&#39;s cross-section in the vertical plane, as there is a need to alter the vertical angle of the antenna&#39;s main beam (also known as the “tilt”), in order to adjust the coverage area of the antenna. RET can be readily achieved by providing accurate phase control over signals fed to different antenna elements. 
         [0006]    An example of RET implementation can be found in R. C. Johnson, Antenna Engineers Handbook, 3rd Ed 1993, McGraw Hill, ISBN 0-07-032381-X, Ch 20,  FIG. 20-2  discloses a method for locally (or possibly remotely) adjusting the angle of electrical tilt of a phased array antenna. In this method, a radio frequency (RF) transmitter carrier signal is fed to through a power distribution network before being coupled to individually controllable phase shifters. Each antenna element is coupled to its associated phase shifter. RET is achieved when signal phase is adjusted as a function of antenna aperture (reflector length). 
         [0007]    This prior art method antenna has a number of disadvantages due to high cost involved in implementing individual phase shifters. These circuit costs may be offset by using a single common phase shifter for a group of antenna elements instead of per antenna element are previously known from the documents WO96/37922, corresponding to U.S. Pat. No. 5,949,303, and WO002/35651 A1 assigned to current assignee and incorporated wholly herein by reference. 
         [0008]    Real world applications often call for an antenna array having remotely controllable “azimuth” antenna gain pattern (the pattern in the horizontal plane) and the “elevation” pattern (the pattern in the vertical plane)—RET, as well as having a variable Half Power Band Width (HPBW) adjustment capability. 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. Generally, to provide above mentioned functionality remote actuators utilize electromechanical control systems which may add substantial weight, size and complexity to an antenna assembly. Consequently, there is a need to provide a simpler remote means to adjust antenna “azimuth” pattern and the “elevation” pattern—RET. 
       SUMMARY OF THE INVENTION 
       [0009]    In a first aspect the present invention provides a mechanically variable azimuth and beam tilt antenna, comprising a reflector, a plurality of radiators coupled to the reflector, a first mechanical drive element coupled to the reflector, a mechanically controlled phase shifter, a second mechanical drive element coupled to the phase shifter, and a single actuator selectively coupled to the first and second mechanical drive elements. Signal azimuth direction is variable based on positioning of the reflector by the actuator in a first control mode and elevation beam tilt is controlled by adjusting the phase adjuster by the actuator in a second control mode. 
         [0010]    In a preferred embodiment of the antenna, the actuator is coupled to the first and second mechanical drive elements by a transfer module and the transfer module receives a control signal to selectively couple the actuator to the first and second mechanical drive elements. The actuator preferably comprises a motor and the first and second mechanical drive elements preferably comprise first and second rotatable shafts. The second rotatable shaft is preferably coupled to the phase shifter by a linear actuator and a coupling for creating linear motion from rotation of the second shaft. The antenna preferably further comprises a fixed azimuth ring gear extending through an azimuth arcuate range and the first rotatable shaft is coupled to the azimuth ring gear by an azimuth cog gear. The antenna preferably further comprises an azimuth position indicator coupled to the first rotatable shaft. The antenna preferably further comprises a motor control module and a feedback coupling from the azimuth position indicator to the motor control module. The antenna preferably further comprises a phase shifter position indicator coupled to the linear actuator and a feedback coupling from the phase shifter position indicator to the motor control module. The antenna preferably further comprises a radome and the reflector is configured inside the radome and rotates within the radome. 
         [0011]    In another aspect the present invention provides a mechanically variable azimuth, beamwidth and beam tilt antenna. The antenna comprises an antenna array including a reflector and a plurality of radiators coupled to the reflector, a first mechanical drive element coupled to the reflector, a mechanically controlled phase shifter, a second mechanical drive element coupled to the phase shifter, a third mechanical drive element coupled to the antenna array, and a single actuator selectively coupled to the first, second and third mechanical drive elements. Signal azimuth direction is variable based on positioning of the reflector by the actuator in a first control mode, elevation beam tilt is controlled by adjusting the phase adjuster by the actuator in a second control mode and beamwidth is controlled by adjusting relative radiator positioning in a third control mode. 
         [0012]    In a preferred embodiment of the antenna, the radiators are movable relative to the reflector in response to the second actuator motion to alter beamwidth. The single actuator preferably comprises a motor and the first, second and third mechanical drive elements preferably comprise rotatable shafts. The antenna preferably further comprises a transfer module selectively coupling the motor and the rotatable shafts. 
         [0013]    In another aspect the present invention provides an antenna electromechanical system, comprising a motor control module including a single motor and a motor control processor, a selective transfer coupling mechanism coupled to the motor, a first rotatable drive element coupled to the motor via the selective transfer coupling mechanism and to an antenna reflector coupling, and a second rotatable drive element coupled to the motor via the selective transfer coupling mechanism and to a mechanical phase shifter coupling. The selective coupling mechanism receives a control signal from the motor control processor to control selective coupling of the motor to the first and second rotatable drive elements. 
         [0014]    In a preferred embodiment of the antenna electromechanical system the first and second rotatable drive elements each comprise a rotatable shaft. The antenna electromechanical system preferably further comprises first and second position detectors for sensing position of the first and second rotatable drive elements, respectively, and providing detected position signals to the motor control processor. The motor control processor preferably has an input for receiving remotely provided antenna azimuth and antenna beam tilt adjustment control signals. 
         [0015]    In another aspect the present invention provides a method of adjusting signal azimuth direction and beam tilt in a wireless antenna having a reflector, a plurality of radiators coupled to the reflector, and a mechanically adjustable phase shifter. The method comprises receiving a remotely provided antenna azimuth adjustment control signal, operatively coupling a motor to a first drive element coupled to the reflector, and adjusting the reflector azimuth pointing direction using the first drive element driven by the motor to move the reflector. The method further comprises receiving a remotely provided antenna beam tilt adjustment control signal, decoupling the motor from the first drive element and operatively coupling the motor to a second drive element coupled to the phase shifter, and adjusting the beam tilt using the second drive element driven by the motor to move the phase shifter. 
         [0016]    The method may further comprise receiving a remotely provided antenna beamwidth adjustment control signal, operatively coupling the motor to a third drive element coupled to the radiators, and adjusting signal beamwidth using the third drive element driven by the motor to move the radiators. 
         [0017]    Further features and advantages of the present invention will be appreciated from the following detailed description of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]      FIG. 1  is a block diagram for an antenna array employing a combined azimuth and elevation beam angle adjustment electromechanical system, in accordance with a preferred embodiment of the present invention, as viewed from the back of the antenna (back side partial view). 
           [0019]      FIG. 2A  is a top view of a partially assembled antenna array in accordance with a preferred embodiment of the present invention. 
           [0020]      FIG. 2B  is a block diagram of the Motor Control Module (MCM) in accordance with a preferred embodiment of the present invention. 
           [0021]      FIG. 3A ,  3 B and  3 C are top view schematic drawings showing azimuth rotation of the antenna array. 
           [0022]      FIG. 4  is a block diagram for an antenna array employing a combined azimuth, beamwidth and elevation beam angle adjustment electromechanical system in accordance with a second preferred embodiment of the present invention (including optional manual transfer case function selector), as viewed from the back of the antenna. 
           [0023]      FIG. 5  is a front view of an antenna system in accordance with the first and second preferred embodiments of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0024]    It is an object of the present invention to provide a combined remotely controllable azimuth (and/or HPBW adjustment) and elevation beam angle adjustment. In carrying out these and other objectives, features, and advantages of the present invention, an azimuth (and/or HPBW adjustment) and elevation beam angle antenna array is provided for a wireless network system. Reference will be made to the accompanying drawings, which assist in illustrating the various pertinent features of the present invention. 
         [0025]      FIG. 1  shows a front view of antenna electromechanical actuator system,  10 , according to an exemplary implementation, which is enclosed within a conventionally constructed radome  14 . In a first preferred embodiment electromechanical actuator system,  10  is positioned at the bottom of the antenna array  12  for ease of field servicing if such need may arise. To avoid potential interference to antenna radiation pattern the electromechanical actuator system,  10  is positioned on the back side of the antenna reflector  16 .  FIG. 1  shows the non radiating (back side) side of antenna in a vertical orientation (Z-dimension) in a conventional installation configuration and  FIG. 5  shows the front side. The reflector,  16 , may, for example, consist of an electrically conductive plate (or extruded material) suitable for use with Radio Frequency (RF) signals. Furthermore, reflector  16 , plane is shown in a ‘gull’ wing configuration, but in actual practice additional features (not shown) or alternative configurations may be added to aid reflector performance. 
         [0026]    As shown in  FIG. 5 , the antenna array,  12 , contains a plurality of RF radiators  18  arranged vertically and preferably proximate to the vertical center axis of the reflector  16 , plane and are vertically offset from one another. In the illustrative non-limiting implementation shown, reflector  16  plane, together with a plurality of dipole elements  18  form an antenna array useful for RF signal transmission and reception. However, it shall be understood that alternative radiating elements, such as taper slot antenna, horn, folded dipole, etc., can be used as well. Alternative radiating element  18  placements can be also used, including multi column arrangements. 
         [0027]    Antenna array  12  is supported with a simple pivot arrangement utilizing a bottom support pivot  52  and top pivot  62 . Alternative pivoting structures are possible. A form shaped bracket  54  is used to attach antenna array  12  at the bottom and a similar bracket (not shown) provides top support. Bottom support pivot  52  is positioned on a stationary bottom plate  56  which is attached to the fixed backbone brace  60  used for antenna array mounting to a suitable support structure, for example a tower or a side of building. 
         [0028]    Attached to the bottom of the antenna reflector  16  plane is a bottom end cap  20  used as bulkhead for RF and control cables (not shown) as well as providing overall structural rigidity. Complimentary top end cap (not shown) provides overall rigidity to the antenna reflector  16  by reducing longitudal twisting. 
         [0029]    Placed just above bottom end cap  20  is a Motor Control Module (MCM)  22 . Details pertaining to MCM are shown in  FIG. 2B  and will be described later. MCM  22  houses an electrical motor and control circuitry which is remotely controllable via a suitable interface, such as Antenna Interface Standards Group (AISG). 
         [0030]    MCM motor output shaft  24  is coupled to a transfer case  28  input drive shaft. It is highly desirable to construct MCM  22  module to be field serviceable—so as to provide minimum disassembly required to replace a failed module without removing the antenna from service. Accordingly, well known quick disconnect electrical and mechanical connectors are preferably used to couple MCM motor output shaft  24  to transfer case  28  input drive shaft. 
         [0031]    Transfer case  28  is used to redirect MCM  22  motor output to selectively provide dimensional displacement where needed. In an exemplary non limiting embodiment, transfer case  28 , under one control mode, may be configured to drive a jack screw  32  used to control RET phase shifter  70  (details are provided in the above noted WO96/37922 and WO02/35651 published applications and &#39;303 patent incorporated by reference herein; additional mechanical phase shifter implementations are known to those skilled in the art). If so required, actuating solenoid  30  under MCM control  30 c operating in another control mode, is used to redirect MCM  22  motor output to provide rotational drive to azimuth rotator shaft  34 . Since MCM motor output may have limited torque capabilities on its own gear reduction can be used within transfer case  28  to provide torque multiplication and speed reduction. In addition to torque multiplication and speed reduction transfer case  28  may incorporate lockouts or parking brakes to prevent unintended output shaft displacement when disconnected from MCM  22  drive shaft. 
         [0032]    In a dynamically re-configurable antenna system it is important to know current displacement vs. commanded displacement. Consider a RET adjustment, wherein transfer case  28  is configured to direct MCM motor  91  output  24  shaft rotation to RET jack shaft  32  which is coupled via coupling nut  38  to a displacement rod  40 . Rotation of the jack shaft  32  is converted into linear displacement useful for adjusting phase shifter  70 . Coupled to a displacement rod  40  is displacement detector  58  which provides feedback  58   c  back to MCM  22 . For azimuth positional feedback, rotational indicator  36  is used to provide azimuth  34  shaft rotation feedback  36   c  to MCM  22 . Alternative displacement indicators, their positioning within antenna assembly and alternative feedback techniques can be used to provide displacement feedback means to MCM  22 . For azimuth angle adjustments azimuth  34  shaft is passed through a support bearing  46  to a cog gear  48  coupled to a stationary ring gear  50 , which is attached to a bottom plate  56 . Since bottom plate  56  is fixed and the antenna array is rotatable about pivot axis  52  controlled rotation of the azimuth  34  shaft provides azimuth angle adjustment of the antenna array. 
         [0033]      FIG. 4  and  FIG. 2B  include provisions for manual operation. Fully manual operation can be readily accomplished by providing MCM motor  91  with a through shaft extension  24   a  which can be reachable through a service hole (not shown) in the bottom plate  56 . Transfer case  28  may include manual selector control rod  68  extended to and reachable through a service hole (not shown) in the bottom plate  56 , as well as addition of manual position indicators and the like. Manual operation may be desirable during commissioning when remote control capabilities are not fully functional. 
         [0034]    MCM  22  will now be described with reference to  FIG. 2B . MCM  22  includes electrical motor  91  which is controlled by a power supply module  93 . Since it is desired to reverse direction of rotation and control initiation and the amount of rotation, microprocessor board  95  provides control inputs to motor power supply module  93 . Motor power supply circuit may provide feedback to microprocessor board  95  to indicate excessive loads due to mechanical travel limit or mechanical binding. Microprocessor board  95  serves as a local area controller by monitoring AISG I/O and responding to AISG commands by controlling motor  91  rotation, if needed, while monitoring antenna element position ( 36   c  &amp;  58   c ). Transfer case  28  output shaft control is accomplished by applying desired control signal  30 C to shaft selector actuator  30 . 
         [0035]    In a second preferred embodiment shown in  FIG. 4 , transfer case  28  is equipped with three selectable output shafts ( 32 ,  34 ,  64 ). As described hereinabove RET shaft  32  and azimuth adjustment shafts  34  can be selected while the other is locked. Additionally an azimuth beamwidth adjustment is possible under a third operational control mode which actuates shaft  64  and coupler  66 . Azimuth beamwidth adjustment is described in detail in provisional application Ser. No. 60/906,161 filed Mar. 8, 2007, and utility application Ser. No. 12/074,980 filed Mar. 7, 2008, the disclosure of which is incorporated herein by reference in its entirety, wherein radiating elements are moved about a center line of the reflector plate. Accordingly, MCM  22  can adapted to receive additional position sensor inputs (not shown) similar to RET  58   c  and azimuth position  36   c,  whilst transfer case output select actuator  30  can be adapted to have three selector positions and associated control modes. 
         [0036]    The present invention has been described primarily in solving the aforementioned problems relating to use of employing combined azimuth and elevation beam angle adjustment systems. However, it should be expressly understood that the present invention may be applicable in other applications wherein employing combined azimuth and elevation beam angle adjustment control is required or desired. In this regard, the foregoing description of a single panel antenna array equipped with combined azimuth and elevation beam angle adjustment system 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. 
       REFERENCE DESIGNATORS  
       [0037]      10  First preferred embodiment of the electro mechanical actuator system 
         [0038]      12  Antenna Array Assembly 
         [0039]      14  Antenna radome 
         [0040]      16  Antenna reflector plate 
         [0041]      18  Antenna radiating element (for example dipole, etc) 
         [0042]      20  Antenna bottom end cap 
         [0043]      21  Antenna top end cap 
         [0044]      22  Motor control module (MCM) 
         [0045]      24  MCM motor output shaft with a quick disconnect coupling 
         [0046]      24   a  MCM motor output shaft assessable from outside for manual rotation 
         [0047]      26  Transfer case input shaft 
         [0048]      28  Transfer case module 
         [0049]      30  Transfer case output select actuator 
         [0050]      30   c  MCM control signal to transfer case actuator—selector 
         [0051]      32  Output jack shaft for RET control 
         [0052]      34  Output shaft for Azimuth adjustment 
         [0053]      36  Azimuth shaft turn counter—position indicator 
         [0054]      36   c  Signal output from azimuth shaft turn counter - position indicator 
         [0055]      38  Jack screw coupling nut 
         [0056]      40  RET phase shift linear actuator rod 
         [0057]      42  Jack shaft support bearing 
         [0058]      44  Bearing support bracket 
         [0059]      46  Azimuth shaft support bearing 
         [0060]      48  Azimuth cog gear 
         [0061]      50  Azimuth ring gear 
         [0062]      52  Bottom support bearing 
         [0063]      54  Bottom support bracket 
         [0064]      56  Stationary bottom plate 
         [0065]      58  Displacement detector (RET) 
         [0066]      58   c  Signal from displacement detector (RET)—position indicator 
         [0067]      60  Backbone brace (used to provide antenna system rigidity) 
         [0068]      62  Top pivot support 
         [0069]      64  Azimuth beam width adjustment drive shaft 
         [0070]      66  Azimuth beam width adjustment coupler to shaft 
         [0071]      68  Optional manual transfer case override selector rod. 
         [0072]      70  Mechanical phase adjuster 
         [0073]      91  Electrical motor 
         [0074]      93  Electrical motor power supply circuit 
         [0075]      95  Microprocessor Board