Abstract:
A single pole antenna array architecture provides an azimuth variable beamwidth. The array includes a number of driven radiating elements that are spatially arranged having a pivoting actuator so as to provide a controlled variation of the antenna array&#39;s radiation pattern.

Description:
The present application claims priority under 35 USC section 119(e) to U.S. Provisional Patent Application Ser. No. 60/905,202, filed Mar. 5, 2007, the disclosure of which is herein incorporated by reference in its entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates in general to communication systems and components. More particularly the present invention is directed to antennas for wireless networks. 
     2. Description of the Prior Art and Related Background Information 
     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 scan angle. Azimuth antenna beamwidth can be advantageously modified by varying amplitude and phase of a Radio Frequency (RF) signal applied to respective radiating elements. Azimuth antenna beamwidth has been conventionally defined by Half Power Beam Width (HPBW) of the azimuth beam relative to a bore sight of an antenna array. In such an antenna array structure, radiating element positioning is critical to the overall beamwidth control as such antenna systems rely on accuracy of amplitude and phase angle of an RF signal supplied to each radiating element. This places a great deal of tolerance and accuracy on a mechanical phase shifter to provide required signal division between various radiating elements over various azimuth beamwidth settings. 
     Real world applications often call for an antenna array with beam down tilt and azimuth beamwidth 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 utilize lower cost materials may fail to provide adequate passive intermodulation suppression under high power RF signal levels. 
     Consequently, there is a need to provide a simpler method to adjust antenna beamwidth control. 
     SUMMARY OF THE INVENTION 
     One aspect of the invention provides an antenna for a wireless network. The antenna comprises a reflector, a plurality of radiators pivotally connected along a common axis and movable relative to the reflector, and an input port configured to feed a radio frequency (RF) signal to the radiators. The radiators are configurable at different adjustable angles relative to the reflector and to each other to provide variable signal beamwidth. 
     In a preferred embodiment of the invention, the radiators comprise vertically polarized radiator elements. The antenna preferably further comprises a plurality of actuator couplings coupled to the plurality of pivotal radiators and an actuator coupled to the plurality of actuator couplings. The input port is coupled to an RF power signal combining-divider network. The antenna preferably further comprising a multipurpose control port coupled to the RF power signal combining-divider network. The antenna may further comprise means for providing a plurality of azimuth beamwidth control signals coupled to an actuator via the multipurpose control port. The reflector is generally planar defined by a Y-axis, a Z-axis and an X-axis extending out of the plane of the reflector, wherein the actuator is configured to adjust positive and negative X-axis orientation of the plurality of radiators. The plurality of radiators are preferably spaced apart along the Z-axis direction and the plurality of radiators are pivotally adjustable about the Z-axis of the reflector. The plurality of radiators may be aligned vertically at a predetermined distance in the range of 1/2 λ-1λ from one another in the Z-axis direction of the reflector where λ is the wavelength corresponding to the operational frequency of the antenna. The plurality of radiators are pivotally adjustable between 0°-120° apart. 
     In another aspect the invention provides a vertically polarized variable azimuth beamwidth antenna, comprising a plurality of actuator couplings coupled to respective pivoting points, a plurality of vertically polarized radiators coupled to corresponding actuator couplings, and an actuator coupled to the plurality of actuator couplings. Signal beamwidth is adjusted based on positioning of the plurality of vertically polarized radiators to different relative angular orientations. 
     In a preferred embodiment of the invention, the antenna further comprises a reflector coupled to the plurality of aligned radiator dipoles, wherein the plurality of aligned radiator dipoles are positioned to adjust positive and negative X-axis orientation relative to a Z-axis of the reflector. The antenna may further comprise a signal-dividing-combining network coupled to the plurality of aligned radiator dipoles. The signal dividing-combining network may include a remotely controllable phase shifting network configured to provide elevation beam tilting. The actuator may be configured to move each radiator of the plurality of radiator dipoles. The antenna may further comprise a multipurpose port coupled to the actuator and a signal dividing-combining network to provide beamwidth control signals to the actuator. The plurality of radiators are preferably pivotally adjustable between 0°-120° apart. 
     In another aspect the invention provides a method of adjusting signal beamwidth in a wireless antenna having a plurality of radiators pivotally coupled along a common axis relative to a reflector. The method comprises adjusting the plurality of radiators to a first angle relative to the reflector and to each other to provide a first signal beamwidth. The method further comprises adjusting the plurality of radiators to a second angle relative to the reflector and to each other to provide a second signal beamwidth. 
     In a preferred embodiment, the method further comprises providing at least one beamwidth control signal for remotely controlling the plurality of radiators with an actuator responsive to the at least one beamwidth control signal. The method may further comprise moving the plurality of radiators in one of a positive and negative X-axis direction relative to the reflector via the actuator. The plurality of radiators may be pivotally adjusted between 0°-120° apart. 
     Further features and advantages of the present invention will be appreciated from the following detailed description of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  illustrates a front view of a single column antenna array in a wide azimuth beamwidth setting. 
         FIG. 1B  illustrates a front view of a single column antenna array in narrow azimuth beamwidth setting. 
         FIG. 2A  illustrates a cross section along line C-C in Z-view of a single column antenna array in wide azimuth beamwidth setting. 
         FIG. 2B  illustrates a cross section along line D-D in Z-view of a single column antenna array in a narrow azimuth beamwidth setting. 
         FIG. 3A  illustrates a RF circuit diagram of a single column antenna array equipped with fixed down angle tilt and remotely controllable mechanically adjustable azimuth beamwidth. 
         FIG. 3B  illustrates a RF circuit diagram of a single column antenna array equipped with down angle tilt and remotely controllable mechanically adjustable azimuth beamwidth. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     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 a plurality of mechanical phase shifters. It should be expressly understood that the present invention may be applicable in other applications wherein beamwidth control is required or desired. In this regard, the following description of a single pole, antenna array equipped with pivotable radiating elements 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. 
       FIG. 1A  shows a front view of an antenna array  101 , according to an exemplary implementation, which 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, the plane of reflector  105  is shown as a featureless rectangle, but in actual practice additional features (not shown) may be added to aid reflector performance. 
     The antenna array  101  contains a plurality of RF radiators ( 110 ,  120 ,  130 ,  140 ) arranged vertically and preferably proximate to the vertical center axis of the reflector  105  plane and are vertically offset from one another. In one embodiment of the invention the plurality of RF radiators are aligned vertically at a predetermined distance in the range of ½λ-1λ from one another in the Z-axis direction on the reflector where λ is the wavelength of the RF operating frequency. Examples of frequencies of operation in a cellular network system are provided in table I. In one embodiment, the preferred number of vertically aligned RF radiators ranges between 2-15. In the illustrative non-limiting implementation shown, RF reflector  105 , together with a plurality of vertically polarized dipole elements forms one embodiment of 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. 
     As illustrated in  FIG. 3A-3B , RF radiator ( 110 ,  120 ,  130 ,  140 ) elements are fed from a single RF input port  210  with the same relative phase angle through a conventionally designed RF power signal dividing-combining  190  network. RF power signal dividing-combining  190  network output ports  113 ,  123 ,  133 ,  143  are coupled to corresponding radiating elements  110 ,  120 ,  130 ,  140 . In some operational instances such an RF power signal dividing-combining network  190  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 the current assignee and incorporated herein by reference in its entirety. Phase shifting functionality of the RF power signal dividing-combining network  190  may be remotely controlled via a multipurpose control port  200 . Similarly, azimuth beamwidth control signals are coupled via multipurpose control port  200  to a mechanical actuator  180 . Mechanical actuator  180  is rigidly attached to the back plate  185  of the antenna array  101  which is used for antenna array attachment (see also  FIG. 2A-2B ). 
     Each RF radiator ( 110 ,  120 ,  130 ,  140 ) element is mechanically attached to the reflector  105  plane with a corresponding, suitably constructed pivoting joint ( 112 ,  122 ,  132 ,  142 -only  142  being shown but the other radiator elements  110 ,  120 ,  130  having corresponding structures  112 ,  122  and  132 , respectively) which allows for both positive and negative X-dimension declination relative to the reflector  105  plane aligned along the vertical axis. As shown in  FIGS. 2A and 2B  each radiating element ( 110 ,  120 ,  130 ,  140 ) X-dimension angle, relative to the reflector  105  plane, is altered via mechanical actuator couplings ( 111 ,  121 ,  131 ,  141 -only  131  and  141  are shown in  FIG. 2B , corresponding to radiator elements  130 ,  140 , respectively, but elements  110 ,  120  have identical structures  111 ,  121 , respectively) mechanically controllable by actuator  180 . 
     Consider an operational condition wherein RF radiators ( 110 ,  120 ,  130 ,  140 ) are aligned at 90 degrees relative to the reflector  105  plane. Such alignment setting will result in wide azimuth beamwidth. Conversely, if each RF radiator alternatively ( 110 ,  120 ,  130 ,  140 ) has its X-dimension orientation angle altered (relative to 90 degree) in the |+, −, +, −| sequence, for example 100, 80, 100, 80 degree orientation will result in narrower azimuth beamwidth. Additional examples are shown in Table I below, along with associated beamwidths (based on simulations). 
     Table I provides a listing of beamwidth for RF radiators adjusted apart from each other by 0°, 30°, 60°, 90° and 120° for an antenna array designed for continuous operation between 806 MHz and 960 MHz. Alternative frequency ranges are possible with appropriate selection of frequency sensitive components. 
     
       
         
               
               
               
               
               
               
             
           
               
                 TABLE I 
               
               
                   
               
               
                   
                 Beamwidth 
                   
                   
                   
                   
               
               
                   
                 θ = 0° apart 
               
               
                   
                 (all 
                 Beamwidth 
                 Beamwidth 
                 Beamwidth 
                 Beamwidth 
               
               
                 RF 
                 elements 
                 θ = 30° 
                 θ = 60° 
                 θ = 90° 
                 θ = 120° 
               
               
                 Freq. (MHz) 
                 are in line) 
                 Apart 
                 Apart 
                 Apart 
                 Apart 
               
               
                   
               
             
             
               
                 806 
                 90° 
                 84° 
                 79° 
                 69° 
                 58° 
               
               
                 883 
                 87° 
                 80° 
                 76° 
                 65° 
                 54° 
               
               
                 960 
                 86° 
                 77° 
                 73° 
                 62° 
                 50° 
               
               
                   
               
             
          
         
       
     
     One embodiment of the invention includes a method for providing variable signal beamwidth by actuating RF radiators. In this embodiment of the invention, phase shifting functionality of the RF power signal dividing-combining network  190  is remotely controlled via a multipurpose control port  200 . Azimuth beamwidth control signals are coupled via multipurpose control port  200  to a mechanical actuator  180  to align the RF radiators to adjust beamwidth. 
     In this embodiment of the invention each RF radiator ( 110 ,  120 ,  130 ,  140 ) element is mechanically attached to the reflector  105  plane with a corresponding, suitably constructed pivoting joint ( 112 ,  122 ,  132 ,  142 -only  142  being shown but the other radiator elements  110 ,  120 ,  130  having corresponding structures  112 ,  122  and  132 , respectively) which allows for both positive and negative X-axis movement relative to the reflector  105  plane aligned along the vertical axis. In this method, each radiating element ( 110 ,  120 ,  130 ,  140 ) X-axis angle, relative to the reflector  105  plane, is altered via mechanical actuator couplings ( 111 ,  121 ,  131 ,  141 -only  131  and  141  are shown in  FIG. 2B , corresponding to radiator elements  130 ,  140 , respectively, but elements  110 ,  120  have identical structures  111 ,  121 , respectively) mechanically controllable by actuator  180  (e.g., a stepper motor, etc.). It should be noted in other embodiments that more than one actuator can be used to adjust the radiating elements. 
     In one embodiment, RF radiators ( 110 ,  120 ,  130 ,  140 ) are mechanically aligned at 90 degrees relative to the reflector  105  plane resulting in a wide azimuth beamwidth. Conversely, each RF radiator is alternatively ( 110 ,  120 ,  130 ,  140 ) adjusted to have its X-dimension orientation angle altered (relative to 90 degree) in the |+, −, +, −| sequence, for example 100, 80, 100, 80 degree orientation, resulting in a narrower azimuth beamwidth. Also, the alignment control may be set to any of the values in Table I as further examples. 
     Numerous modifications, alternative frequency range of operation of the above described illustrative embodiments will be apparent to those skilled in the art. 
     
       
         
               
             
               
               
               
             
           
               
                   
               
               
                 Reference Designator Listing 
               
             
          
           
               
                   
                 Ref Des 
                 Description 
               
               
                   
                   
               
               
                   
                 101 
                 Vertical polarization single pole antenna array 
               
               
                   
                 105 
                 Antenna Reflector 
               
               
                   
                 110 
                 First Radiator Element (in this case a dipole) 
               
               
                   
                 111 
                 First mechanical actuator coupling 
               
               
                   
                 112 
                 First pivoting joint 
               
               
                   
                 113 
                 First Radiator Element feed line to RF power 
               
               
                   
                   
                 dividing and combining network 
               
               
                   
                 120 
                 Second Radiator Element (in this case a dipole) 
               
               
                   
                 121 
                 Second mechanical actuator coupling 
               
               
                   
                 122 
                 Second pivoting joint 
               
               
                   
                 123 
                 Second Radiator Element feed line to RF power 
               
               
                   
                   
                 dividing and combining network 
               
               
                   
                 130 
                 Third Radiator Element (in this case a dipole) 
               
               
                   
                 131 
                 Third mechanical actuator coupling 
               
               
                   
                 132 
                 Third pivoting joint 
               
               
                   
                 133 
                 Third Radiator Element feed line to RF power 
               
               
                   
                   
                 dividing and combining network 
               
               
                   
                 140 
                 Fourth Radiator Element (in this case a dipole) 
               
               
                   
                 141 
                 Fourth mechanical actuator coupling 
               
               
                   
                 142 
                 Fourth pivoting joint 
               
               
                   
                 143 
                 Fourth Radiator Element feed line to RF power 
               
               
                   
                   
                 dividing and combining network 
               
               
                   
                 180 
                 Mechanical Actuator 
               
               
                   
                 185 
                 Antenna back mounting plane 
               
               
                   
                 190 
                 RF power dividing and combining network 
               
               
                   
                 200 
                 Multipurpose communication port 
               
               
                   
                 210 
                 Common RF port