Abstract:
The present invention relates to a multiband antenna specifically adapted for use with a Base Station Antenna (“BSA”). The present invention provides narrow azimuth or horizontal beamwidth (“HBW”) having 45 degrees and operational over four frequency bands. The composite antenna topology and associated circuitry described in embodiments achieves reduced antenna installation requirements and allows for ease of network deployment or reconfiguration at reduced cost. Embodiments employ an array of low band radiating elements and two sets of high band radiating elements. The first set is co-located within an array of low band radiating elements. The second set of is offset and outside the low band radiating elements. An RF feed network energizes the first and second set of high band radiating elements to compensate for interference between the high and low band elements.

Description:
RELATED APPLICATION INFORMATION 
       [0001]    The present application claims priority under 35 U.S.C. Section 119(e) to U.S. Provisional Patent Application Ser. No. 61/503,321 filed Jun. 30, 2011, 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 is related in general to radio communication systems and components. More particularly, the invention is directed to antenna arrays for wireless communication networks. 
         [0004]    2. Description of the Prior Art and Related Background Information 
         [0005]    Composite band antennas may be employed in multiband basestations for mobile communication systems to serve up to four different systems operating simultaneously on four different bands. For example, Global System for Mobile Communication (“GSM”), Digital Cellular Systems 1800 (“DCS1800”), and Universal Mobile Telecommunications System 2100 (“UMTS-2100”) systems currently coexist in Europe, and emerging fourth generation systems (e.g., Long Term Evolution (“LTE”)) will require separate antennas for communication with user equipment. Similarly in North America, Cellular 850 and Personal Communications Service 1900 (“PCS-1900”) systems are deployed with LTE-700 and 2100 systems will be deployed in near future. It is not uncommon to have separate antennas being used for two separate bands where antennas are stacked one above another or placed in a side-by-side arrangement. Alternatively, the antennas may be packaged as a single assembly. Conventional solutions may result in relatively large structures which are typically not favored by local municipalities. In general, base station structures should be as small and as inconspicuous as possible. 
         [0006]    Accordingly, a need exists to provide compact composite band antenna structures. 
       SUMMARY OF THE INVENTION 
       [0007]    In a first aspect, the present invention provides an antenna assembly. The antenna assembly comprises a reflector, an array of first frequency band radiating elements configured above the reflector, the elements arranged in one or more columns extending in a first direction, and a plurality of second frequency band radiating elements configured above the reflector including first and second sub groups, each of the first sub group of radiating elements essentially co-located with a corresponding first frequency band radiating element, and wherein the second sub group of radiating elements are configured outside of the first frequency band radiating elements, the second sub group offset with respect to the first sub group of radiating elements in the first direction. The antenna assembly further comprises an RF feed network coupled to each radiating element of the first and second sub groups, the RF feed network providing a first communication signal having a first power level to the first sub group, the RF feed network providing a second communication signal having a second power level differing from the first power level to the second sub group. The operating frequency of the first frequency band radiating elements is lower than the operating frequency of the second frequency band radiating elements. 
         [0008]    In a preferred embodiment, the first and second sub groups of radiating elements are arranged in three columns. The first power level is preferably greater than the second power level. The array of first frequency band radiating elements is preferably arranged in two columns. The first power level is preferably approximately −3.3 dB below an RF input level and the second power level is preferably approximately −6.7 dB below the RF input level. The RF feed network preferably further comprises a phase shifter receiving a first input signal and outputting a phase adjusted signal, and a plurality of first divider-combiner manifolds receiving the phase adjusted signal and outputting the first communication signal having the first power level to the first sub group, the first divider-combiner manifolds outputting the second communication signal having the second power level to the second sub group. The first and second sub groups of radiating elements are preferably each coupled to two independent high frequency radio frequency (“RF”) ports and the array of first frequency band radiating elements are each coupled to two lower frequency RF ports. The second sub group of radiating elements preferably form a series of radiating doublets having a radiating emission pattern narrower than that of the first sub group of radiating elements. The first and second sub groups of radiating elements preferably form a series of radiating triplets. The radiating elements of the first and second sub groups collectively provide a radiation pattern of about 40-50 degrees Half Power Beamwidth. 
         [0009]    In another aspect, the present invention provides an antenna assembly. The antenna assembly comprises a reflector and an array of first frequency band radiating elements configured above the reflector, the array arranged in pairs forming first and second columns both having lengths in a first direction. The antenna assembly further comprises a plurality of second frequency band radiating elements including a first sub group of radiating elements configured above the reflector, the first sub group of radiating elements arranged as a column having a length in the first direction, each of the first sub group of radiating elements essentially co-located with a corresponding radiating element of the first column of the array of first frequency band radiating elements, and a second sub group of radiating elements configured above the reflector arranged in pairs forming two columns on either side of the first sub group of radiating elements in a direction orthogonal to the first direction, the second sub group positioned outside corresponding radiating elements of the first column of the array of first frequency band radiating elements. The antenna assembly further comprises a plurality of third frequency band radiating elements including a third sub group of radiating elements configured above the reflector, the third sub group arranged as a column having a length in the first direction, each of the third sub group of radiating elements essentially co-located with a corresponding radiating element of the second column of the array of first frequency band radiating elements, and a fourth sub group of radiating elements configured above the reflector as an array arranged in pairs forming two columns on either side of the third sub group of radiating elements in a direction orthogonal to the first direction, the fourth sub group positioned outside corresponding radiating elements of the second column of the array of first frequency band radiating elements. The operating frequency of the second and third frequency band radiating elements is higher than the operating frequency of the first frequency band radiating elements. 
         [0010]    In a preferred embodiment, the antenna assembly further comprises an RF feed network coupled to each radiating element of the first, second, third, and fourth sub groups, the network providing a first communication signal having a first power level to the first sub group, the network providing a second communication signal having a second power level differing from the first power level to the second sub group, the network providing a third communication signal having a third power level to the third sub group, the network providing a fourth communication signal having a fourth power level differing from the third power level to the fourth sub group. The first power level is preferably greater than the second power level and the third power level is greater than the fourth power level. The operating frequency band of the first and second sub groups may be the same as the operating frequency band of the third and fourth sub groups or the operating frequency band of the first and second sub groups may differ from the operating frequency band of the third and fourth sub groups. The first and second sub groups of radiating elements and third and fourth sub groups of radiating elements each have collectively a radiating emission pattern of about 40-50 degrees Half Power Beamwidth. The second and fourth sub groups of radiating elements preferably form a series of radiating doublets having a radiating emission pattern narrower than that of the first and third sub groups of radiating elements. The first and second sub groups of radiating elements preferably form a first series of radiating triplets, wherein the third and fourth sub groups form a second series of radiating triplets. The radiating elements of the first, second, third, and fourth sub groups preferably comprise patch elements. 
         [0011]    In another aspect, the present invention provides a method of operating a multi band antenna comprising an array of low band radiating elements, a first set of high band radiating elements each co-located within a corresponding low band radiating element, and a second set of high band radiating elements positioned outside the low band radiating elements. The method comprises providing a first frequency RF communication signal to an array of low band radiating elements, providing a second higher frequency RF communication signal having a first power level to a first set of high band radiating elements each co-located with a corresponding low band radiating element, and providing the second higher frequency RF communication signal having a second power level to a second set of high band radiating elements positioned outside the low band elements, wherein the first power level differs from the second power level to compensate for increased beamwidth caused by co-location of the first set of high band radiating elements with corresponding low band radiating elements. 
         [0012]    Further features and aspects of the invention are set out in the following detailed description. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]      FIG. 1  is a front, boresight view of an exemplary dual broadband quad-port antenna. 
           [0014]      FIG. 2  is a front, boresight view of the dual broadband quad-port antenna showing only high band antenna elements and their arrangement. 
           [0015]      FIG. 3  is a block schematic diagram of a low band RF feed structure with the high band RF feed structure omitted for clarity. 
           [0016]      FIG. 4  is a block schematic diagram of a high band RF feed structure with the low band RF feed structure omitted for clarity. 
           [0017]      FIG. 5  is a block schematic diagram of a portion of the high and low band antenna element RF feed structure (from phase shifter to antenna element) shown together for a subset of antenna elements. 
           [0018]      FIG. 6A  is a representation of simulated performance of the HPBW as a function of horizontal spacing (lamba) for horizontal spacing of low band antenna elements in low band antenna array. 
           [0019]      FIG. 6B  is a representation of simulated performance for the HPBW as a function of horizontal spacing (lambda) for high band, horizontal doublet of antenna elements (i.e., for a pair). 
           [0020]      FIG. 6C  is a representation of simulated performance for the HPBW as a function of horizontal spacing (lambda) for high band antenna array, vertical spacing between co-located high band element and doublet of high band elements. 
           [0021]      FIG. 7  is a front, boresight view of an exemplary dual broadband antenna for Multiple Input Multiple Output (“MIMO”) applications. 
           [0022]      FIG. 7A  is a block schematic diagram of a portion of a high and low band antenna element RF feed structure arranged for high band MIMO (from phase shifter to antenna element) shown together for a subset of antenna elements. 
           [0023]      FIG. 7B  is a block schematic diagram of phase shifter networks used for beam tilting and main antenna ports. 
           [0024]      FIG. 8  is a front, boresight view of an exemplary triple-broadband embodiment of the dual broadband antenna. 
           [0025]      FIG. 8A  is a block schematic diagram of an exemplary triple band feed structure for the highest frequency band. 
           [0026]      FIG. 8B  is a block schematic diagram of exemplary triple band phase shifters for the Hex-Port antenna. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0027]    Embodiments of the invention provide a multiple frequency band, dual cross polarization base station antenna (“BSA”) arrangement exhibiting a narrow azimuth or horizontal plane beamwidth (“HPBW”) of approximately 45 degrees and an operable signal coverage in two non-overlapping frequency blocks. A block may include at least one or more communication bands. For example, a low frequency block may contain FB 1 =700 LTE and FB 2 =850 WCDMA, while a high frequency block may include FB 3 =1900 PCS, FB 4 =2100 AWS, and FB 5 =2600 LTE. While providing broadband operation, the antenna system shall be capable of low coupling between different frequency bands while at the same time minimizing the space needed as compared to conventional antennas. A first preferred embodiment of such an antenna may be provided with four RF feed ports. A second preferred embodiment may be capable of operation in a low frequency block and two independent high frequency blocks. It shall be understood that both the foregoing general description and the following detailed description are exemplary and are not restrictive of the present invention as claimed. 
         [0028]    Other objects, advantages, and novel features of one or more embodiments will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings. 
         [0029]    Embodiments seek to provide simultaneous quad frequency band operation for a cellular basestation antenna having a shared reflector and radome. Embodiments also seek to provide such an antenna which has minimum dimensions while providing 45 degree azimuth beamwidth for each band. Even though exemplary embodiments describe an antenna with 45 degree azimuth beamwidth, embodiments may be easily reconfigured to achieve azimuth beamwidth between 40 and 50 degrees. The desired azimuth beamwidth may be achieved by changing element spacing, altering power signal division, or as a combination of antenna element spacing and power signal division. 
         [0030]    Embodiments of a multiple frequency band antenna arrangement may be connected to a transceiver or a bank of transceivers for transmitting and receiving RF signals in at least four separate frequency bands. A first preferred antenna arrangement may have two sets of antenna elements arranged on a common reflector. A first set of antenna elements is arranged in a side-by-side column arrangement which operates in a first frequency region, whereas a second set of antenna elements is arranged in a tri-column arrangement and operates in a second frequency region. Embodiments may include first and second sets of antenna elements interleaved along and positioned on a first vertical axis parallel with the Z-axis so as to form a first column. 
         [0031]    Embodiments are described below with reference to the accompanying drawings. Specifically, the embodiments described below are exemplary only, without covering all possible embodiments. A person having ordinary skill in the art can derive other embodiments from the embodiments provided herein without making any creative effort, and all such embodiments are covered within the scope of the present invention. 
         [0032]    Referring to  FIGS. 1 and 2 , a structure of a multiband antenna  100  for transmitting and receiving electromagnetic signals is disclosed. The multiband antenna  100  includes a reflector  102  and a first band dual-polarized antenna elements group  104 , and a second band dual-polarized antenna elements group  106  arranged along reflector  102  outwardly positioned surface, generally in the direction of the main radiation beam of the antenna. In the embodiment shown, dual-polarized antenna elements groups  104  and  106  radiate in the two polarization planes P which are perpendicular with respect to one another and are perpendicular to the reflector plane and positioned longitudinally along major length alignment axes P 1a , P 1 , P 1b , and P 2  on the front surface of the radiator arrangement which is rectangular in a plan view. As such, each low frequency antenna element  110 ,  111 ,  112 ,  113 ,  114 ,  115 ,  116 ,  117 ,  118 , and  119  have two independent RF ports used for coupling RF signal to and from the antenna elements via suitably constructed RF wave guides. 
         [0033]    With regard to the construction and mode of functioning of such an antenna element type, reference is made, for example, to WO 2009108097 A1, incorporated herein by reference in its entirety. However, any radiator or radiator type can be used in the scope of the invention, in particular patch radiators, or dipole arrangements may be used as a suitable antenna element. 
         [0034]      FIG. 1  illustrates an antenna arrangement based on a rectangular reflector  102 . To facilitate ease of discussion, the outward pointing face of reflector  102  is oriented along the Z-axis, while the longitudinal or lengthwise dimension of the reflector  102  is set along the Y-axis with latitudinal or widthwise dimension is set along the X-axis. The reflector  102  can be constructed using conventional means such as by utilizing conductive materials such as aluminum or steel alloys. Alternatively, composite material construction can be implemented. As shown in the plan views of  FIGS. 1 and 2 , only antenna elements groups  104  and  106  can be viewed with the feed networks, to be discussed later, positioned on the back side of the reflector  102 . 
         [0035]    The first antenna element group  104  will now be described. The first antenna element group  104  is comprised of two columns of antenna elements  110 - 118 ,  111 - 119  arranged along the first P 1  and second P 2  vertical alignment axes. In the preferred embodiment, the first P 1  and second P 2  alignment axes are set equidistantly and parallel (i.e., C 1 =C 2 ) about the reflector  102  longitudinal center line (“CL”). However these dimensions can be altered to achieve performance goals (i.e. C 1 &lt; &gt;C 2 ). As viewed in  FIG. 1 , the first antenna element group  104  comprises a first subgroup  104   a  of antenna elements  110 ,  112 ,  114 ,  116 ,  118  positioned along first P 1  alignment axis, while second subgroup  104   b  of antenna elements  111 ,  113 ,  115 ,  117 , and  119  positioned along second P 2  alignment axis and paired along horizontal HA 1 , HA 2 , HA 3 , HA 4 , and HA 5  alignment axes. Within each antenna element sub group, adjacent antenna elements are spaced vertically along the Y-axis by distance V s1  +V s2  and horizontally along the X-axis by a distance C 1 +C 2 . In an embodiment, ten antenna elements  110  to  119  are employed, however the number of antenna elements can be increased or decreased without departing from the scope of the present invention. 
         [0036]    The second antenna element group  106  will now be described. The second antenna element group  106  comprises three columns of antenna elements  210 - 238  arranged along first P 1a , second P 1 , and third P 1b  vertical alignment axes. As illustrated in  FIGS. 1 and 2 , the second antenna element group  106  comprises a first subgroup  106   a  of antenna elements  212 ,  218 ,  224 ,  230 , and  236  positioned left along the P 1a  alignment axis. A second subgroup  106   b  of antenna elements  210 ,  216 ,  222 ,  228 , and  234  are positioned along the P 1  alignment axis. A third subgroup  106   c  of antenna elements  214 ,  220 ,  226 ,  232 , and  238  are positioned along the right P 1b  alignment axis. The second subgroup  106   b  antenna elements  210 ,  216 ,  222 ,  228 , and  234  are centrally co-located with first subgroup  104   a  of antenna elements  110 ,  112 ,  114 ,  116 , and  118  of the first antenna group  104  positioned along first vertical P 1  alignment axis, and along the horizontal HA 1 , HA 2 , HA 3 , HA 4 , and HA 5  alignment axes. 
         [0037]    With regard to the construction and mode of functioning of such co-located antenna element type, reference is made, for example, to WO 2007011295 A1, incorporated herein by reference in its entirety. As such, each high frequency antenna element such as antenna elements  210 ,  212 , and  214  have two independent RF ports used for coupling RF signals to or from the antenna elements via suitably constructed RF wave guides. In general, the co-located antenna elements  210 ,  216 ,  222 ,  228 , and  234  tend to have a HPBW of 65 degrees over a wide frequency range. Due to construction techniques used to co-locate antenna elements  210 ,  216 ,  222 ,  228 , and  234 , such placement may limit the degree of freedom afforded to those skilled in the art to alter basic antenna element design without affecting performance parameters of the lower frequency band antenna elements  110 ,  112 ,  114 ,  116 , and  118 . To achieve 45 degrees HPBW for high band antenna array, the HPBW of 65 degrees of the co-located antenna elements  210 ,  216 ,  222 ,  228 , and  234  must be compensated. In one or more embodiments, a doublet of horizontally positioned antenna elements such as antenna elements  212  and  214  each having HPBW of 65 degrees are placed along horizontal alignment axis HA 1a  below the co-located antenna elements such as antenna element  210  which is placed on the horizontal alignment axis HA 1 . Alignment axes HA 1  and HA 1a  are separated vertically by a distance V s1 . HA 1a  and HA 2  are separated by a vertical distance V s2 . The horizontally positioned antenna elements such as antenna elements  212  and  214  are equidistant from longitudinal alignment axis P 1  and separated from the P 1  axis by a distance HS 1  and HS 2 . The resultant antenna element doublet such as that formed by antenna elements  212  and  214  has a narrow HPBW of 26 to 38 degrees as shown in  FIG. 6B  over a wide frequency range. Effectively, the narrow HPBW of the high frequency antenna element doublet  212  and  214  is advantageously combined with HPBW of the co-located antenna elements  210  by altering RF feed network which results an antenna element group  106  array having a desired 45 degrees HPBW as shown in  FIG. 6C . 
         [0038]    The first and third subgroup  106   a  and  106   c  elements are positioned along horizontal alignment axes HA 1a , HA 2a , HA 3a , HA 4a , and HA 5a  generally vertically spaced from above alignment axes HA 1 , HA 2 , HA 3 , HA 4 , HA 5  by a distance V s1  such that the distance, for example, between HA 1  and HA 1a  is V s1  and HA 1a  and HA 2  is V s2 . It should be noted that V s1  and V s2  may be unequal to achieve performance goals or to further optimize antenna array performance parameters. 
         [0039]    In one preferred embodiment, a patch element may be employed as a unitary antenna element, but other suitable radiating structures such dipoles or horns may be employed. A wide bandwidth patch element is well known in the art and tends to exhibit a 65 degree azimuth beamwidth (HPBW) over a wide frequency range where approximately 40% of the bandwidth has been achieved at 1 dB directivity roll off with VSWR better than 1.8:1 over the same frequency span. Patch element design can be altered to exhibit azimuth beamwidth other than 65 degrees, but such a modification reduces the patch element useful frequency bandwidth over which the azimuth beamwidth remains nearly constant (i.e. within the design azimuth beamwidth). The problem is especially acute when antenna elements are combined into an array. The effective array antenna array beamwidth is also affected when multiple arrays share the same radiator structure to achieve a multi-band capable antenna. To solve the aforementioned problem, embodiments employ optimized patch elements exhibiting 65 degree azimuth beamwidth over a wide frequency range to achieve 45 degree azimuth beamwidth over nearly 40% bandwidth in two separate, non-overlapping frequency bands with an RF combining network providing RF signals with differing power levels which will be described later. It should be noted the embodiment of the present invention can be altered to provide an antenna array between 30 and 50 degrees. 
         [0040]    With respect to the low frequency antenna elements group  104  with horizontal element spacing C 1 +C 2 , a 45 degree HPBW is achieved when spacing is set at 0.54 lambda (i.e., the wavelength of the radiation) as depicted in  FIG. 6A  provided that broadside antenna element pairs such as pairs  110  and  111  are equally fed and in phase. Accordingly, in an exemplary antenna, there are five doublet groups of low band antenna elements as shown in Table I. 
         [0000]    
       
         
               
               
               
             
           
               
                   
                 TABLE I 
               
               
                   
                   
               
               
                   
                 Group 
                 Antenna Elements 
               
               
                   
                   
               
             
             
               
                   
                 1A 
                 110 and 111 
               
               
                   
                 2A 
                 112 and 113 
               
               
                   
                 3A 
                 114 and 115 
               
               
                   
                 4A 
                 116 and 117 
               
               
                   
                 5A 
                 118 and 119 
               
               
                   
                   
               
             
          
         
       
     
         [0041]    It has been determined that low band antenna elements do not suffer adverse radiation pattern affects from having high band elements positioned within. The same is not true for high band elements (e.g., antenna element  210 ) which are positioned centrally within larger low band elements (e.g., antenna element  110 ). 
         [0042]    With reference to  FIGS. 3 and 5 , two way −3 dB splitters  312 ,  313 ,  322 ,  323 ,  332 ,  333 ,  342 ,  343 ,  352 , and  353  are provided. An equal output RF splitter is well known in art—for example a Wilkinson divider/combiner - but other well know splitter combiners may be implemented. The two splitter output ports  312   a / 312   b ,  313   a / 313   b ,  322   a / 322   b , and  323   a / 323   b  are coupled to respective antenna elements  110 -  119  feed ports. The splitter common port is coupled to a designated phase shifter  52  and  53  ports via suitably constructive radio wave guides such as waveguides  62   a - 62   e  and  63   a - 63   e  known in the art. The phase shifter  52  and  53  are used as signal—divider combiners that provide controllable phase shift along its output ports relative to its input port (cp). The aforementioned phase shifters  52  and  53  are used to provide electrical beam tilt function and has been disclosed in WO 96/037922 and WO 02/03561 assigned to present assignee incorporated herein wholly by reference. 
         [0043]    As it was briefly mentioned above, high band antenna elements such as antenna elements  210  and  216  that are positioned within low frequency band elements such as antenna elements  110  and  112  have altered radiation patterns albeit slightly. Interposed high band element pattern augmentation is addressed by employing a paired high band antenna elements such as antenna elements  212  and  214  positioned below interposed high band element such as antenna element  210  forming a triplet group  261  or triangular arrangement of three high band elements such as antenna elements  210 ,  212 , and  214  that are commonly fed. In an exemplary antenna, there are five triplet groups of high band antenna elements as shown in Table II. The phase shifter common ports  52   cp  and  53   cp  are coupled to a corresponding antenna system having RF connectors  22  and  23  coupled to suitably constructed RF guides such as coaxes  32  and  33 . 
         [0000]    
       
         
               
               
               
             
           
               
                   
                 TABLE II 
               
               
                   
                   
               
               
                   
                 Group 
                 Antenna Elements 
               
               
                   
                   
               
             
             
               
                   
                 1B (261) 
                 210, 212, and 214 
               
               
                   
                 2B 
                 216, 218, and, 220 
               
               
                   
                 3B 
                 222, 224, and, 226 
               
               
                   
                 4B 
                 228, 230, and 232 
               
               
                   
                 5B 
                 234, 236, and 238 
               
               
                   
                   
               
             
          
         
       
     
         [0044]    To achieve the desired HPBW, such as 45 degrees for example, from the triplet group  261  of antenna elements  210 ,  212 , and  214 , it is necessary to provide an un-equal signal combining—dividing distribution network between the phase shifters  50  and  51  and the respective triplet groups. 
         [0045]    With reference to  FIGS. 4 and 5 , a high band feed network will be described. The triplet group  261  comprises antenna elements  210 ,  212 , and  214 . Together, five of such antenna elements groups or triplets are used to form a broadband antenna. The centrally located high band antenna element such as radiating element  210  has HPBW pattern altered due to its placement within the perimeter of the low band antenna element  110 . In general, design of stacked, dual band patch based antenna elements involves techniques which result in HPBW augmentation that single band patch antenna elements do not experience. Further modifications of high band antenna elements such as antenna element  210  may impact performance of the low band antenna elements such as antenna element  110  which may require additional design constraints. To overcome performance constraints, a pair of high band antenna elements  212  and  214  spaced vertically V s1  (i.e., parallel with the Y axis) below centrally located high band antenna element  210  and horizontally (i.e., parallel with the X axis) spaced H s1  and H s2  apart from the common alignment axis P 1 . The spacing H s1  and H s2  horizontal spacing define high band antenna elements vertical alignment axes P 1   a  and P 1b  respectively. The combination of vertical V s1  and horizontal spacing H s1  and H s2  define relative position of two high band antenna elements  212 ,  214 . To achieve desired HPBW, for example 45 degrees the antenna elements  210 ,  212 ,  214  of the triplet group  261  are provided with unequal signal split provided by divider—combiner manifolds  310 ,  311 ,  320 ,  321 ,  330 ,  331 ,  340 ,  341 ,  350 , and  351 . 
         [0046]    As shown in  FIGS. 4 and 5 , there are ten manifolds  310 ,  311 ,  320 ,  321 ,  330 ,  331 ,  340 ,  341 ,  350 ,  351  with five manifolds for each polarization ( 310 ,  320 ,  330 ,  340 , and  350 ;  311 ,  321 ,  331 ,  341 , and  351 ). The common port of the aforementioned manifolds are coupled to phase shifters  50  and  51  distribution ports via suitably constructed RF wave guides  60   a  to  60   e ;  61   a , to  61   e . In addition to a common port, each divider—combiner manifold such as  310  is constructed to have one −3.35 dB and two −6.7 dB distribution ports relative to the common port. For example, manifold ports  310   a ,  311   a ,  320   a , and  321   a  are −3.35 dB distribution ports, and manifold output ports  310   b ,  310   c ,  311   b ,  311   c ,  320   b ,  320   c ,  321   b  and  321   c  are −6.7 dB distribution ports. 
         [0047]    In a preferred embodiment, the two lower antenna elements such as antenna elements  212  and  214  are provided with signal level −6.7 dB below input signal levels. The upper element such as antenna element  210  is coupled to the −3.35 distribution ports of the manifold  310  and  311 . 
         [0048]    A combination of RF signal distribution and relative antenna elements result in broadband antenna having multi band elements having a HPBW from 40 to 50 degrees. Many variations of the invention will occur to those skilled in the art. All such variations are intended to be within the scope and spirit of the invention. 
         [0049]    Multiband antennas as described above may be modified for multiple input multiple output (“MIMO”) applications for transmitting and receiving RF signals. With reference to  FIGS. 7 ,  7 A, and  7 B, a multiband antenna  400  tailored for MIMO will now be described. In an embodiment, dual-polarized, dual band antenna elements groups  108   a  and  108   b  are arranged to radiate in two polarization planes P which are perpendicular with respect to one another and perpendicular to the reflector plane  102  and are positioned longitudinally along major length alignment axes P 1 , P 1 , P 1b , P 2a , P 2 , and P 2b  on the front surface of the radiator arrangement which is rectangular in a plan view. The first antenna element group  108   a  may be similarly configured as elements groups  104   a  and  106   a  as described above. However, for the MIMO configuration, the two columns of antenna elements  108  comprising the previously described first antenna element group  108   a  are used in combination with six antenna ports  20  to  25  and six paired phase shifters  50  to  55  to allow MIMO functionality in the high frequency band forming MIMO capable antenna array arrangement. 
         [0050]    As depicted in  FIGS. 7A and 7B , each low frequency antenna element such as antenna elements  110 - 119  have two independent RF ports designated herein as having a suffix “a” or “b” used for coupling the low frequency band RF signals to or from said antenna elements via suitably constructed RF wave guides  62   a - 62   e  and  63   a - 63   e  via two-way RF −3 dB manifolds or splitters  312 ,  313 ;  322 ,  323 ;  332 ,  333 ;  342 ,  343 ; and  352 ,  353 . An equal output RF manifold or splitter-combiner networks are well known in art, such as, for example, a Wilkinson divider—combiner, but other well know splitter-combiners can be implemented. The two splitter output ports such as splitter output ports  312   a ,  312   b ,  313   a ,  313   b ,  322   a ,  322   b ,  323   a , and  323   b  are coupled to the respective antenna elements  110  to  119  feed ports. The two way splitters such as splitters  312 ,  313 ;  322 ,  323 ; to  352 ,  353  each have a common port that is coupled to a designated phase shifters  52  and  53  output ports via wave guides  62   a - 62   e  and  63   a - 63   e . The phase shifters  52  and  53  are preferably adjusted in unison so as to provide identical phase shift to RF signals in wave guides  62   a - 62   e  and  63   a - 63   e  relative to the input and output RF signal at the phase shifter common port  52   cp  and  53   cp . The phase shifter common ports  52   cp  and  53   cp  are coupled to a corresponding antenna system having RF connectors  22  and  23  coupled to suitably constructed RF guides such as coaxes  32  and  33 . 
         [0000]    
       
         
               
               
               
               
             
           
               
                 TABLE III 
               
               
                   
               
               
                 Group 
                 Antenna Elements 
                 2-way manifold 
                 Phase shifter ports 
               
               
                   
               
             
             
               
                 1C 
                 110 and 111 
                 312 and 313 
                 62a and 63a 
               
               
                 2C 
                 112 and 113 
                 322 and 323 
                 62b and 63b 
               
               
                 3C 
                 114 and 115 
                 332 and 333 
                 62c and 63c 
               
               
                 4C 
                 116 and 117 
                 342 and 343 
                 62d and 63d 
               
               
                 5C 
                 118 and 119 
                 352 and 353 
                 62e and 63e 
               
               
                   
               
             
          
         
       
     
         [0051]    The first antenna system RF connector  22  is referenced as having a +45 degree polarization and the second antenna system RF connector  23  is referenced as having a −45 degree polarization for the low frequency band together providing polarization diversity. 
         [0052]    In an embodiment, an antenna assembly adapted for MIMO systems may use antenna diversity to improve data throughput in multi-path environment. Numerous techniques can be applied to take advantage of MIMO capable antenna systems to improve data throughput such as precoding, spatial multiplexing and diversity coding. One preferred embodiment allows for MIMO operation in the high frequency band by taking advantage of two sets of high frequency antenna elements in element groups  108   a  and  108   b  arranged along two spaced apart longitudinal axes P 1  and P 2 . 
         [0053]    The first column of antenna elements group  108   a  comprises dual band antenna elements  110 ,  210 ;  112 ,  216 ; to  118 ,  234  arranged along first main longitudinal axis P 1 . A first group of high frequency antenna elements  212 ,  218 , to  236  are aligned along longitudinal sub-axis P 1a  to the left of the first main axis P 1 . A second group of high frequency antenna elements  214 ,  220 , to  238  are aligned along longitudinal sub-axis P 1b  to the right of the first main axis P 1 . 
         [0054]    The horizontal dual band antenna elements  110 ,  111 ;  112 ,  113 ; to  118 ,  119  are arranged along horizontal alignment axes HA 1 −HA 5  spaced by distance V s1 +V s2  as presented Table IV below. 
         [0000]    
       
         
               
               
               
               
             
           
               
                   
                 TABLE IV 
               
               
                   
                   
               
               
                   
                 Axis 
                 P 1   
                 P 2   
               
               
                   
                   
               
             
             
               
                   
                 HA 1   
                 110 and 210 
                 111 and 410 
               
               
                   
                 HA 2   
                 112 and 216 
                 113 and 416 
               
               
                   
                 HA 3   
                 114 and 222 
                 115 and 422 
               
               
                   
                 HA 4   
                 116 and 228 
                 117 and 428 
               
               
                   
                 HA 2   
                 118 and 234 
                 119 and 434 
               
               
                   
                   
               
             
          
         
       
     
         [0055]    An identical arrangement may be used for the second column of antenna elements group  108   b , with elements  111 ,  410 ;  113 ,  416 ;  115 ,  422 ;  117 ,  428 ; and  119 ,  434  arranged along second main longitudinal axis P 2 . A third group of high frequency antenna elements  412 ,  418 ,  424 ,  430 , and  436  are aligned along longitudinal sub-axis P 2b  to the right of the second main axis P 2 . A fourth group of high frequency antenna elements ( 414 ,  420 ,  426 ,  432 , and  438 ) are aligned along longitudinal sub-axis P 2a  to the left of the second main axis P 2 . 
         [0056]    The first main axis P 1  is offset from reflector center line CL by a distance C 1  and the second main axis P 2  is offset from reflector center line CL by a distance C 2 . It has been determined that, in most cases, the C 1  and C 2  dimensions may be the same, but if required, due to a combination of low and high frequency bands, it may be advantageous to have C 1 ≠C 2  and/or H s1 ≠H s2  and H s1 ≠H s4  to achieve desired antenna system performance characteristics. 
         [0057]    The first and second MIMO antenna sub-array generally comprises of first and second columns of antenna elements groups  108   a  and  108   b . The first column of antenna elements group  108   a  comprises five triplet antenna elements  210 ,  212 ,  214 ;  216 ,  218 ,  220 ; to  234 ,  236 ,  238  groups each having antenna element feed port coupled to three way RF divider/combiner  310 ,  311  and  320 ,  321  pairs. Table V summarizes element groupings used for first column of antenna elements group  108   a  sub-array. 
         [0000]    
       
         
               
               
               
               
             
           
               
                 TABLE V 
               
               
                   
               
               
                 Group 
                 Antenna Elements 
                 3-way manifold 
                 Phase shifter ports 
               
               
                   
               
             
             
               
                 1A 
                 210, 212, and 214 
                 310 and 311 
                 60a and 61a 
               
               
                 2A 
                 216, 218, and 220 
                 320 and 321 
                 60b and 61b 
               
               
                 3A 
                 222, 224, and 226 
                 330 and 331 
                 60c and 61c 
               
               
                 4A 
                 228, 230, and 232 
                 340 and 341 
                 60d and 61d 
               
               
                 5A 
                 234, 236, and 238 
                 350 and 351 
                 60e and 61e 
               
               
                   
               
             
          
         
       
     
         [0058]    Table VI summarizes element groupings used for second column of antenna elements  108   b  sub-array. 
         [0000]    
       
         
               
               
               
               
             
           
               
                 TABLE VI 
               
               
                   
               
               
                 Group 
                 Antenna Elements 
                 3-way manifold 
                 Phase shifter ports 
               
               
                   
               
             
             
               
                 1B 
                 410, 412, and 414 
                 314 and 315 
                 64a and 65a 
               
               
                 2B 
                 416, 418, and 420 
                 324 and 325 
                 64b and 65b 
               
               
                 3B 
                 422, 424, and 426 
                 334 and 335 
                 64c and 65c 
               
               
                 4B 
                 428, 430, and 432 
                 344 and 345 
                 64d and 65d 
               
               
                 5B 
                 434, 436, and 438 
                 354 and 355 
                 64e and 65e 
               
               
                   
               
             
          
         
       
     
         [0059]    The beam tilt for the first column high frequency band antenna elements group  108   a  sub-array is controlled with a first and second phase shifters  60  and  61  coupled to the first and second antenna system RF ports  20  and  21  respectively. The beam tilt for second column high frequency band antenna elements group  108   b  sub-array is controlled with fifth and sixth phase shifters  64  and  65  coupled to fifth and sixth antenna system RF ports  24  and  25  respectively. Each pair of phase shifters may have a remotely controllable motor drive mechanism to alter phase shift to provide remote beam tilt control. 
         [0060]    The multiband antennas  100  and  400  as described above may be modified for triple band operation for transmitting and receiving RF signals. With reference to  FIGS. 8 ,  8 A, and  8 B, the tri-band adaptation multiband antenna  500  will now be described. In the embodiment shown, dual-polarized, dual band antenna elements groups  109   a  and  109   b  are arranged to radiate in two polarization planes P perpendicular with respect to one another and perpendicular to the reflector plane  102  and positioned longitudinally along major length alignment axes P 1 , P 1 , P 1b , P 2a , P 2 , and P 2b  on the front surface of the radiator arrangement which is rectangular in a plan view. The first antenna element group  109   a  may be configured similar to that of antenna elements groups  104   a  and  106   a  described before and to provide HPBW 40 to 50 degrees in the two frequency bands FB 2  and FB 3 . 
         [0061]    However the two column antenna array element arrangement can be used in three separate bands, for example FB 2 =850 MHz, FB 3 =1900 MHz, and FB 5 =2600 MHz. An antenna capable of such frequency coverage is referred to as a tri-band antenna and has six antenna RF ports  20 ,  21 ,  26 ,  27 ,  22 , and  23  for ±45 degree polarization. The left most group of antenna element group  109   a  is aligned along axis P 1 . In the right most column of antenna element group  109   b  positioned along P 2 , the dual band antenna elements  111 ,  511 ,  113 ,  515 , to  119 ,  525  have been adapted to provide desired antenna pattern characteristics in FB 2  and FB 5  bands. In addition to FB 5  band paired antenna elements, antenna elements  512 ,  513 ;  516 ,  517 ;  520 ,  521 ;  523 ,  524 ;  526 ,  527  interposed between the dual band elements  111 ,  511 ;  113 ,  515 ; to  119 ,  525  and below the last dual band  119  and  525  antenna elements. 
         [0062]    A single FB 5  band antenna element  514  is placed on the P 2  axis between second dual band antenna element  113  and  515  and first FB 5  band paired antenna elements  512  and  513 . Another single FB 5  band antenna element  519  is placed above the third FB 5  band paired antenna elements  520 ,  521  and below the third dual band antenna elements  115  and  518 . The five horizontally paired FB 5  band antenna elements  512 ,  513 ;  516 ,  517 ;  520 ,  521 ;  523 ,  524 ; and  561 ,  562  provide narrow HPBW (i.e., 26 to 38 degrees for example) beamwidth. When combined with non horizontally paired antenna elements  511 ,  514 ,  515 ,  518 ,  519 ,  522 , and  525  each having 65 degree HPBW results in an antenna array that has 45 degree HPBW. Inclusion of the aforementioned two single FB 5  band antenna elements  514  and  519  improves HPBW over the FB 5  band without effecting performance of the low frequency antenna array (i.e. elements  110  to  119 ) while providing excellent vertical sidelobe control. However, these additional FB 5  band antenna elements  514  and  519  introduce somewhat of unique feed structure as shown in  FIG. 8A  and summarized in a Table VII below. 
         [0000]    
       
         
               
               
               
               
               
             
           
               
                 TABLE VII 
               
               
                   
               
               
                   
                   
                 2-way 
                 3-way 
                 Phase shifter 
               
               
                 Group 
                 Antenna Elements 
                 manifold 
                 manifold 
                 ports 
               
               
                   
               
             
             
               
                 1C 
                 511, 512, 513, 
                 561 and 562 
                 551 and 552 
                 66a and 67a 
               
               
                   
                 and 514 
               
               
                 2C 
                 515, 516, and 517 
                   
                 553 and 554 
                 66b and 67b 
               
               
                 3C 
                 518 and 519 
                 563 and 564 
                   
                 66c and 67c 
               
               
                 4C 
                 520, 521, and 522 
                   
                 555 and 556 
                 66d and 67d 
               
               
                 5C 
                 523, 524, 525, 
                 565, 561, 566, 
                 558 and 559 
                 66e and 67e 
               
               
                   
                 526, and 527 
                 562 
               
               
                   
               
             
          
         
       
     
         [0063]    Five antenna element groups are used along horizontal alignment axes HA 1 −HA 5 . For dual band antenna elements  111 ,  511 ;  113 ,  515 ; to  119 ,  525 , the low frequency FB 2  feed structure was previously discussed in above with respect to multiband antenna  100  illustrated in  FIGS. 3 and 5  and may be retained in a third preferred embodiment. Since the right most column compromises of new set of dual band (i.e., FB 2 , FB 5 ) elements  111 ,  511 ;  113 ,  515 ; to  119 ,  525 , the feed structure for the FB 5  band antenna elements  511 ,  512  to  527  is modified slightly to take advantage of additional antenna elements  514 ,  519 . 
         [0064]    For tri-band beam tilt control in each of the respective frequency bands (i.e., FB 2 , FB 3 , and FB 5 ), phase shifter pairs  52 ,  53 ;  50 ,  51 ; and  56 ,  57  may be controlled independently from each other. RF signals to and from the tri-band antenna system for each respective frequency band FB 2 , FB 3 , and FB 5  are coupled from RF common ports  22 ,  23 ;  20 ,  21 ;  26 ,  27  respectively. 
         [0065]    Although some embodiments are shown to include certain features, the applicant(s) specifically contemplate that any feature disclosed herein may be used together or in combination with any other feature on any embodiment of the invention. It is also contemplated that any feature may be specifically excluded from any embodiment of an invention. 
         [0066]    The present invention has been described primarily as methods and structures for antenna systems. Furthermore, the description is not intended to limit the invention to the form disclosed herein. Accordingly, variants and modifications consistent with the following teachings, 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.