Abstract:
An antenna adapted for wireless networks and having a variably controlled stagger antenna array architecture is disclosed. The antenna array contains 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 so as to provide a controlled variation of the antenna array&#39;s azimuth radiation pattern.

Description:
RELATED APPLICATION INFORMATION 
       [0001]    The present application claims priority under 35 USC section 119(e) to U.S. provisional patent application Ser. No. 60/922,130 filed Apr. 6, 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 antennas for wireless networks. 
         [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 beamwidth and azimuth scan angle. Azimuth antenna beamwidth can be advantageously modified by varying amplitude and phase of an RF signal applied to respective radiating elements. Azimuth antenna beamwidth has been conventionally defined by Half Power Beam Width (HPBW) of the azimuth beam of relative to a bore sight of such 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 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. 
         [0006]    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 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 system and method to adjust antenna beamwidth control. 
       SUMMARY OF THE INVENTION 
       [0008]    In a first aspect the present invention provides an antenna for a wireless network. The antenna comprises a generally planar reflector, a first plurality of radiators and a second plurality of radiators, wherein at least one of the first plurality of radiators and the second plurality of radiators are movable relative to the reflector in a direction generally parallel to the reflector plane, wherein the radiators are movable from a first configuration where the radiators are all aligned to a second configuration where the radiators are staggered relative to each other, to provide variable signal beamwidth. 
         [0009]    In one preferred embodiment of the antenna the first and second plurality of radiators may comprise vertically polarized radiating elements. Alternatively, the first and second plurality of radiators may comprise dual polarization radiating elements arranged in groups of plural elements for each radiator. Alternatively, the first and second plurality of radiators may comprise dual polarization cross over dipole radiating elements. 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. The reflector preferably has a plurality of orifices and the first and second plurality of radiator mount plates are configured behind the orifices. The first and second plurality of radiator mount plates preferably comprise reflective material on the portion thereof facing the orifice. The antenna may further comprise one or more actuators coupled to the first and second plurality of radiator mount plates to slide the mount plates and attached radiators relative to the reflector. The antenna may further comprise a first and second plurality of guide frames coupled to the reflector adjacent the orifices and receiving the respective first and second plurality of radiator mount plates. The generally planar reflector may be 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 one or more actuators are configured to adjust Y-axis position of the first plurality of radiators and the second plurality of radiators in opposite directions. The reflectors in the first configuration may be aligned along a center line of the reflector parallel to the Z-axis of the reflector and spaced apart a distance VS in the Z direction, providing a relatively wide beamwidth setting. The reflectors in the second configuration may be offset in opposite Y directions from the center line of the reflector by a distance HS, to provide a narrower beamwidth, the offset defining a stagger distance (SD) defined by the following relationship: 
         [0000]        SD= √{square root over (4 HS   2   +VS   2 )} 
         [0010]    The distance SD is preferably less than about 1 λ, where λ is the wavelength of the RF operating frequency of the antenna. The antenna may further comprise a multipurpose control port receiving azimuth beamwidth control signals provided to the one or more actuators. 
         [0011]    In another aspect the present invention provides a mechanically variable azimuth beamwidth and electrically variable elevation beam tilt antenna. The antenna comprises a reflector, a first plurality of slidably mounted radiators adjacent the reflector, a second plurality of slidably mounted radiators adjacent the reflector, and at least one actuator coupled to the first and second radiators, wherein signal azimuth beamwidth is variable based on positioning of the first plurality of radiators and the second plurality of radiators relative to each other in the sliding direction. The antenna further comprises an input port coupled to a radio frequency (RF) power signal dividing-combining network for providing RF signals to the first plurality of radiators and the second 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. 
         [0012]    In a preferred embodiment, the antenna further comprises a multipurpose port coupled to the actuator and signal dividing-combining network to provide beamwidth and beam tilt control signals to the antenna. 
         [0013]    In another aspect the present invention provides a method of adjusting signal beamwidth 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 adjusting the radiators in a direction generally parallel to the plane of the reflector to a first configuration relative to the reflector and each other to provide a first signal beamwidth and adjusting the radiators in a direction generally parallel to the plane of the reflector to a second configuration relative to the reflector and each other to provide a second signal beamwidth. 
         [0014]    In a preferred embodiment the method further comprises providing at least one beamwidth control signal for remotely controlling the position setting of the radiators. In the first configuration all radiators may be 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. 
         [0015]    Further features and advantages of the present invention will be appreciated from the following detailed description of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]      FIG. 1  is front view of a vertically polarized antenna array in wide azimuth beamwidth setting. 
           [0017]      FIGS. 2A and 2B  are cross sectional views along A-A datum detailing the motion of a vertically polarized antenna element in wide ( FIG. 2A ) and narrow ( FIG. 2B ) azimuth beamwidth setting. 
           [0018]      FIG. 2C  is a back side view of the area immediate about the fourth radiating element with movable plate positioned as depicted in  FIG. 2B . 
           [0019]      FIG. 3  is a front view of a vertically polarized antenna array in narrow azimuth beamwidth setting. 
           [0020]      FIG. 4  is an RF circuit diagram of an antenna array equipped with a Phase Shifter and Power Divider. 
           [0021]      FIGS. 5A and 5B  together present a front view of a dual polarized antenna array configured for wide ( FIG. 5   a ) azimuth beamwidth setting and narrow ( FIG. 5B ) azimuth beamwidth setting. 
           [0022]      FIGS. 6A and 6B  together present a front view of a dual polarized antenna array employing crossover dipole elements configured for wide ( FIG. 6A ) azimuth beamwidth setting and narrow ( FIG. 6B ) azimuth beamwidth setting. 
           [0023]      FIG. 7  depicts a wide azimuth radiation pattern corresponding to the  FIG. 1  configuration (the radiation pattern for the embodiment of  FIGS. 5A ,  6 A is similar). 
           [0024]      FIG. 8  depicts narrow azimuth radiation pattern corresponding to the  FIG. 3  configuration (the radiation pattern for the embodiment of  FIGS. 5B ,  6 B is similar). 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0025]    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 beamwidth control is required or desired. In this regard, the following description of a twin offset stagger, vertically and dually polarized antenna array equipped with shiftable 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. 
         [0026]      FIG. 1  shows a front view of a vertically polarized antenna array,  100 , 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, reflector  105 , plane is shown as a featureless rectangle, but in actual practice additional features (not shown) may be added to aid reflector performance. 
         [0027]    Continuing with reference to  FIG. 1  an antenna array,  100 , contains a plurality of RF radiators ( 110 ,  120 ,  130 ,  140 ) preferably arranged both vertically and horizontally in a single column arrangement along primary vertical axis disposed on shift-able  114 ,  124 ,  134 ,  144  plates below the forward facing surface of the reflector  105  in the corresponding reflector orifices ( 113 ,  123 ,  133 ,  143 ). In particular, each RF radiator ( 110 ,  120 ,  130 , and  140 ) is mounted on a feed-through ( 112 ,  122 , 132 ,  142 ) mount centrally disposed on a top surface of a shiftable foundation mount plate ( 114 ,  124 ,  134 ,  144 ) capable of controllable orthogonal movement relative to the main vertical axis limited by the peripheral dimensions of the corresponding reflector orifices ( 113 ,  123 ,  133 ,  143 ). Details pertaining to movable foundation mount plates ( 114 ,  124 ,  134 ,  144 ) and relating structures will become apparent upon examination of  FIG. 2A  and  FIG. 2B . 
         [0028]    Generally, in a broad beamwidth radiation pattern configuration RF radiators are preferably aligned along the common vertical axis labeled P 0  and are separated vertically by a distance VS. In one embodiment of the invention the plurality of RF radiators are separated by a distance VS in the range of ½λ-λ from one another where λ is the wavelength of the RF operating frequency. Examples of frequencies of operation in a cellular network system are well known in the art. For example, one range of RF frequencies may be between 806 MHz and 960 MHz. Alternative frequency ranges are possible with appropriate selection of frequency sensitive components. Preferably, the common axis P 0  is the same as center vertical axis of the reflector  105 , plane. As illustrated in  FIG. 1  common 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 
         [0029]    For a narrow azimuth radiation pattern RF radiator ( 110 ,  120 ,  130 , and  140 ) are alternatively positioned as shown in  FIG. 3 . 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 (4 HS   2   +VS   2 )} 
         [0030]    SD should preferably be less than 1 λ. Through computer simulations and direct EM field measurement it was determined that azimuth radiation beam pattern can be deduced from the above formula. By varying HS dimensions desired azimuth beamwidth settings can be attained. VS dimension is typically fixed by the overall length of the reflector  105  plane which defines the effective antenna aperture. In the illustrative non-limiting implementation shown, RF reflector,  105 , together with a plurality of vertically polarized dipole elements forms 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. 
         [0031]    A cross section datum A-A 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. 2A  and  FIG. 2B   
         [0032]      FIGS. 2A and 2B  provide a cross sectional view along A-A datum. A-A datum, as shown in  FIG. 1 , bisects fourth  140  radiating element and associated mechanical structures.  FIG. 2C  provides a back side view of the area immediate of the fourth radiating  140  element. It shall be understood that all radiating elements share similar construction features, details being omitted for clarity. As shown in  FIG. 2A  a vertically polarized radiating element  140  is mounted with a feed-through  142  mount. A feed through  142  mount is preferably constructed out of a dielectric material and provides isolation means between radiating element  140  and movable  144  plate. Movable  144  plate is preferably constructed utilizing a rigid material as long as 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 for each radiating  110 ,  120 ,  130 ,  140  element is individually supplied from a power dividing-combining  190  network with a suitable flexible radio wave  149  guide, such as flexible coaxial cable, and coupled to conventionally constructed feed through  142  mount terminals (details are not shown). 
         [0033]    Movable foundation mount plate  144  is recessed and mounted immediately below the bottom surface of reflector  105  plane and supported with a pair of sliding  147  guide frames, on each side reflector orifice  143 , having U-shaped slots  148  which provide X dimensional stability while providing Y dimensional movement to the movable foundation mount plate  144 . As shown In  FIG. 2C  the back side of the movable foundation mount plate  144  and associated sliding  147  guide frames which are used for support are enclosed with a suitably constructed cover  145  to prevent undesirable back side radiation and to improve the front to back signal ratio. 
         [0034]    Actuator  180  provides mechanical motion means to the jack screw  141 . Jack screw rotation is coupled to a mechanical coupler  146  attached to the back side movable foundation mount plate  144 . By controlling direction and duration of rotation of the jack screw  141  subsequently provides Y dimensional movement to the movable foundation mount plate  144 . As it is well known in the art jack screw  141  is one of many possible means to achieve Y dimensional movement to the movable foundation mount plate  144 . The mechanical actuator  180 , or other well known means, may be extended to provide mechanical motion means to other or preferably all other jack screws  111 ,  121 ,  131  used to control motion of respective radiating  110 ,  120 ,  130 ,  140  elements. 
         [0035]    The above description outlines basic concepts covering one radiating element, but it shall be understood that basic building elements can be replicated for each radiating element. In some instances it may be advantageous to combine or perhaps mirror mount mechanical assemblies into a single device as deemed appropriate for the application as will be appreciated by one skilled in the art. 
         [0036]    With reference to  FIG. 4  RF radiator ( 110 ,  120 ,  130 ,  140 ) elements may be fed from a master RF input port,  210 , with the same relative phase angle RF signal through a conventionally designed RF power signal dividing-combining  190  network. RF power signal dividing-combining  190  network output-input  190 ( a - d ) ports are coupled with a suitable radio wave  119 ,  129 ,  139 ,  149  guides, such as coaxial cable to corresponding radiating elements  110 ,  120 ,  130 ,  140 . In some operational instances such RF power signal  190  dividing-combining network may include 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 implementation is shown in  FIG. 4  wherein RF signal dividing-combining  190  network provides electrically controlled beam down-tilt capability. Phase shifting function of the power dividing network  190  may be remotely controlled via multipurpose control port  200 . Similarly, azimuth beamwidth control signals are coupled via multipurpose control port  200  to a mechanical actuator(s)  180 . 
         [0037]    As described hereinabove a plurality of vertically polarized dipole  110 ,  120 ,  130 ,  140  elements together form an antenna array useful for RF signal transmission and reception. However, vertically polarized dipole  110 ,  120 ,  130 ,  140  elements can be replaced with a dual polarization radiating elements groups  310 ,  320 ,  330 ,  340  which may utilize discrete radiating elements such as patches, taper slot, horn, folded dipole, and etc. One such implementation using dipoles is shown in  FIG. 5A  and  FIG. 5B  wherein radiating elements groups  310 ,  320 ,  330 ,  340  are respectively mounted on movable foundation mount plates  314 ,  324 ,  334 ,  344 . Movable foundation mount plates  314 ,  324 ,  334 ,  344  are recess mounted in corresponding radiator  105  plane orifices  313 ,  323 ,  333 ,  343 . As shown in  FIG. 5B  movable foundation mount plates  314 ,  324 ,  334 ,  344  can be alternatively shifted relative to radiating elements groups  310 ,  320 ,  330 ,  340  center. For this configuration stagger distance (SD) is defined by the following relationship: 
         [0000]        SD= √{square root over (4 HS   2   +VS   2 )} 
         [0038]    Conventional dipole radiating elements  310 ( a - d ) as shown in  FIG. 5A  and  FIG. 5B  can be replaced with cross over dipole pairs wherein radiating elements groups  310 ,  320 ,  330 ,  340  are equivalently replaced with crossover dipole radiating elements groups  410 ,  420 ,  430 ,  440  respectively mounted on movable foundation mount plates  314 ,  324 ,  334 ,  344 . The resulting configuration, as depicted in  FIG. 6   a  and  FIG. 6B  generally operates in nearly identical manner as described hereinabove. 
         [0039]    Consider the following two operational conditions (a-b): 
         [0040]    Operating condition (a) wherein all RF radiators ( 110 ,  120 ,  130 ,  140 ), as depicted in  FIG. 1 , are aligned about P 0  axis which is proximate to vertical center axis of the reflector  105  plane. Such alignment setting will result in relatively wide azimuth beamwidth as shown in the simulation of  FIG. 7 . 
         [0041]    Operating condition (b) wherein RF radiators ( 110 ,  120 ,  130 ,  140 ) as depicted in  FIG. 3 , are positioned in the following configuration: 
         [0042]    The first group of RF radiators  120 ,  140  is positioned along P 1  axis and the second group of RF radiators  110 ,  130  is positioned along P 2  axis. Once all RF radiators ( 110 ,  120 ,  130 ,  140 ) are positioned the resultant azimuth radiation beamwidth will be narrower. Such alignment setting will result in a relatively narrow azimuth beamwidth as shown in the simulation of  FIG. 8 . Obviously, HS can be varied continuously from minimum (0) to a maximum value to provide continuously variable azimuth variable beamwidth between two extreme settings described hereinabove. 
         [0043]    It will be appreciated from the foregoing that one embodiment of the invention includes a method for providing variable signal beamwidth by controlling positioning of the slidably mounted radiators relative to the reflector and each other. For example, the method may control beamwidth by setting the radiator positioning to a first position corresponding to operating condition (a) above wherein all RF radiators ( 110 ,  120 ,  130 ,  140 ), as depicted in  FIG. 1 , are aligned to obtain a relatively wide beamwidth setting. The method may further control beamwidth by setting the radiator positioning to a second position where the radiators are staggered, for example corresponding to operating condition (b) above to obtain a relatively narrow beamwidth. These first and second settings may of course be varied in between the example settings (a) and (b) in accordance with the beamwidth control signals to provide the desired beamwidth. The method of the invention may also provide variable beam tilt. In this embodiment of the invention variable beam tilt is provided by controlling the phase of the RF signals applied to the radiators through a remotely controllable phase shifting network such as described above in relation to  FIG. 4 . 
         [0044]    Numerous modifications of the above described illustrative embodiments will be apparent to those skilled in the art, including alternative radiator position settings and frequency ranges of operation. 
       REFERENCE DESIGNATOR LIST 
       [0045]    Ref Des Description 
         [0046]      100  Vertical polarization movable stagger antenna array 
         [0047]      101  Dual polarization movable stagger antenna array 
         [0048]      102  Dual polarization movable stagger antenna array equipped with crossover dipole radiating elements 
         [0049]      105  Antenna Reflector 
         [0050]      110  First Radiating Element (in this case a dipole) 
         [0051]      111  First jack screw 
         [0052]      112  Feed-through mount 
         [0053]      113  First Radiating Element Reflector orifice 
         [0054]      114  First movable plate 
         [0055]      115  First back cover 
         [0056]      116  First mechanical coupler cover 
         [0057]      117  Sliding guide frames 
         [0058]      118  Sliding guide slot in a sliding guide frames 
         [0059]      119  First Radiating Element feed line (coax) to RF power dividing and combining network 
         [0060]      120  Second Radiating Element (in this case a dipole) 
         [0061]      129  Second Radiating Element feed line (coax) to RF power dividing and combining network 
         [0062]      130  Third Radiating Element (in this case a dipole) 
         [0063]      139  Third Radiating Element feed line (coax) to RF power dividing and combining network 
         [0064]      140  Fourth Radiating Element (in this case a dipole) 
         [0065]      141  Fourth mechanical actuator coupling 
         [0066]      142  Fourth pivoting joint 
         [0067]      143  Fourth Radiating Element feed line to RF power dividing and combining network 
         [0068]      140  Fourth Radiating Element (in this case a dipole) 
         [0069]      141  Fourth jack screw 
         [0070]      142  Fourth Feed-through mount 
         [0071]      143  Fourth Radiating Element Reflector orifice 
         [0072]      144  Fourth movable plate 
         [0073]      145  Fourth back cover 
         [0074]      146  Fourth mechanical coupler cover 
         [0075]      147  Sliding guide frames 
         [0076]      148  Sliding guide slot in a sliding guide frames 
         [0077]      149  Fourth Radiating Element feed line (coax) to RF power dividing and combining network 
         [0078]      180  Mechanical Azimuth Actuator 
         [0079]      190  RF power dividing and combining network with integrated remote electrical tilt capability 
         [0080]      190 ( a - d ) RF power dividing and combining network to antenna coupling ports. 
         [0081]      200  Multipurpose communication port 
         [0082]      210  Common RF port 
         [0083]      310  First dual polarization radiating element grouping. 
         [0084]      310 ( a - b ) Radiation elements used in first dual polarization radiating element group 
         [0085]      313  First Radiating Element Reflector orifice for dual polarization group 
         [0086]      314  First movable plate for dual polarization group 
         [0087]      320  Second dual polarization radiating element grouping. 
         [0088]      320 ( a - b ) Radiation elements used in second dual polarization radiating element group 
         [0089]      323  Second Radiating Element Reflector orifice for dual polarization group 
         [0090]      324  Second movable plate for dual polarization group 
         [0091]      330  Third dual polarization radiating element grouping. 
         [0092]      330 ( a - b ) Radiation elements used in third dual polarization radiating element group 
         [0093]      333  Third Radiating Element Reflector orifice for dual polarization group 
         [0094]      334  Third movable plate for dual polarization group 
         [0095]      340  Fourth dual polarization radiating element grouping. 
         [0096]      340 ( a - b ) Radiation elements used in fourth dual polarization radiating element group 
         [0097]      343  Fourth Radiating Element Reflector orifice for dual polarization group 
         [0098]      344  Fourth movable plate for dual polarization group 
         [0099]      410  First dual polarization radiating element grouping utilizing crossover dipoles. 
         [0100]      420  Second dual polarization radiating element grouping utilizing crossover dipoles. 
         [0101]      430  Third dual polarization radiating element grouping utilizing crossover dipoles. 
         [0102]      440  Fourth dual polarization radiating element grouping utilizing crossover dipoles.