Patent Publication Number: US-11664607-B2

Title: Integrated filter radiator for a multiband antenna

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. application Ser. No. 16/753,377, filed Apr. 3, 2020, which is a National Phase of U.S. Application No. PCT/US2018/054321, filed Oct. 4, 2018, which claims priority to U.S. Provisional Application No. 62/567,809, filed Oct. 4, 2017, and U.S. Provisional Application No. 62/587,926, filed Nov. 17, 2017, the disclosures of which are incorporated hereby by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to antennas for wireless communications, and more particularly, to multiband antennas that have low band and high band dipoles located in close proximity. 
     Related Art 
     There is considerable demand for cellular antennas that can operate in multiple bands and at multiple orthogonal polarization states to make the most use of antenna diversity. A solution to this is to have an antenna that operates in two orthogonal polarization states in the low band (LB) (e.g., 496-690 MHz) and in two orthogonal polarization states in the high band (HB) 1.7-3.3 GHz). There is further demand for the antenna to have minimal wind loading, which means that it must be as narrow as possible to present a minimal cross-sectional area to oncoming wind. 
     The need for a compact array face for an antenna that operates in both the low band and the high band presents challenges. Specifically, the more closely LB and HB dipoles are spaced on a single array face, the more they suffer from interference whereby transmission in either the HB and harmonics of the LB is respectively picked up by the dipoles of the other band, causing coupling and re-radiation that contaminates the gain pattern of the transmitting band. 
     This problem can be solved with dipoles that are designed to be “cloaked”, whereby they radiate and receive in the band for which they are designed yet are transparent to the other band that is radiated by the other dipoles sharing the same compact array face. However, it can be costly to manufacture cloaked dipoles, which may require additional layers of components and rather complex structures. 
       FIGS.  1   a  and  1   b    illustrate an antenna array face  100  with a plurality of HB dipoles  110  and an LB dipole  120 . As illustrated, both LB and HB dipoles may both operate in +/−45° polarizations, enabling two HB signals and two LB signals to operate simultaneously. As may be inferred from  FIGS.  1   a  and  1   b   , LB dipole  120  may physically obstruct one or more HB dipoles  110 , leading to cross band contamination and degrading the HB gain pattern. 
     Further, there is also demand for cellular antennas that are capable of operating in circular polarization in the low band. This offers greatly improved performance, but generally requires completely different dipole hardware in order to implement it, making a full scale deployment of a circular polarized low band communication scheme cost prohibitive. 
     Accordingly, what is needed is a low band dipole configuration that minimizes physical interference and cross coupling with nearby high band dipoles, is capable of being operated simultaneously in +/−45° polarization states, is capable of being operated in a circular polarization mode without requiring hardware modifications, and is inexpensive and easy to manufacture. 
     SUMMARY OF THE INVENTION 
     Accordingly, the present invention is directed to an integrated filter radiator for multiband antenna that obviates one or more of the problems due to limitations and disadvantages of the related art. 
     An aspect of the present invention involves an antenna dipole that comprises a first dipole arm that extends from a dipole center in a positive direction along a first axis; a second dipole arm that extends from the dipole center in a negative direction along the first axis; a third dipole arm that extends from the dipole center in a positive direction along a second axis, wherein the second axis is orthogonal to the first axis; and a fourth dipole arm that extends from the dipole center in a negative direction along the second axis. The antenna further comprises a dipole stem on which the first, second, third, and fourth dipole arms are disposed. The dipole stem has a first dipole stem plate oriented along the first axis and a second dipole stem plate oriented along the second axis, the first and second dipole stem plates mechanically coupled in a cross arrangement having a center corresponding to the dipole center, the cross arrangement defining a first quadrant, a second quadrant, a third quadrant, and a fourth quadrant. The antenna also has and a feedline network having a +45° feedline and a −45° feedline. The +45° feedline has a +45° feedline power divider, a first +45° trace coupled to the +45° feedline power divider, and second +45° trace coupled to the +45° feedline power divider. the second +45° trace corresponding to a 180° phase delay relative to the first +43° trace. The −45° feedline has a −45° feedline power divider, a first −45° trace coupled to the −45° feedline power divider, and second −45° trace coupled to the −45° feedline power divider, the second −45° trace corresponding to a 180° phase delay relative to the first −45° trace, wherein the first +45° trace is coupled to a first balun disposed on the first stem plate in the fourth quadrant, the second +45° trace is coupled to a second balun disposed on the first stem plate in the first quadrant, the first −45° trace is coupled to a third balun disposed on the second stem plate in the third quadrant, and the second −45° trace is coupled to a fourth balun disposed on the second stem plate in the second quadrant. 
     Another aspect of the present invention involves a dipole that comprises four dipole arms arranged in a cross configuration, and a dipole stem having a plurality of microstrip baluns and microstrip ground plates disposed thereon, wherein each of the microstrip ground plates is coupled to a corresponding dipole arm, wherein the microstrip baluns and microstrip ground plates are arranged such that each microstrip ground plate receives a directly coupled RF signal corresponding to one of a +45° polarization signal and a −45° polarization signal and a capacitively coupled RF signal corresponding to the other of the +45° polarization signal and the −45° polarization signal. 
     Yet another aspect of the present invention involves a dipole that comprises a PCB substrate; a first plurality of cloaking elements disposed on a first side of the PCB substrate: and a second plurality of cloaking elements disposed on a second side of the PCB substrate, wherein the first plurality of cloaking elements and the second plurality of cloaking elements are respectively formed from a single conductive layer respectively disposed on the first and second side of the PCB substrate. Further embodiments, features, and advantages of the integrated filter radiator for multiband antenna, as well as the structure and operation of the various embodiments of the integrated filter radiator for multiband antenna, are described in detail below with reference to the accompanying drawings. 
     It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only, and are not restrictive of the invention as claimed 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, are incorporated in and constitute a part of this specification, illustrate embodiment(s) of the integrated filter radiator for multiband antenna described herein, and together with the description, serve to explain the principles of the invention. 
         FIGS.  1   a  and  1   b    illustrate an antenna array face having diagonally oriented HB and LB dipoles for operation in +/−4.5° polarizations. 
         FIGS.  2   a  and  2   b    illustrate an exemplary antenna array face in which the LB dipole is oriented in a vertical and horizontal orientation yet operates in +/−4.5° polarizations. 
         FIG.  3   a    illustrates a top or front surface of an exemplary LB dipole according to the disclosure. 
         FIG.  3   b    illustrates a bottom or back surface of an exemplary LB dipole according to the disclosure. 
         FIG.  3   c    illustrates the top or front surface of the LB dipole, showing exemplary dimensions. 
         FIG.  3   d    illustrates the bottom or back surface of the LB dipole, showing exemplary dimensions. 
         FIG.  4    illustrates a side view of an exemplary LB dipole according to the disclosure, revealing the arrangement of conductive elements on the top and bottom surfaces of a PCB substrate. 
         FIG.  5    illustrates an exemplary LB dipole according to the disclosure, including its dipole stem and portions of the feedline network. 
         FIG.  6   a    illustrates the LB dipole stem from a “top-down” perspective, along with the balun circuit and relevant feedlines for an exemplary +45° polarization LB dipole component. 
         FIG.  6   b    illustrates the LB dipole stem from a “top-down” perspective, along with the balun circuit and relevant feedlines far an exemplary −45° polarization LB dipole component. 
         FIG.  6   c    illustrates the LB dipole stem, similarly to  FIGS.  6   a  and  6   b   , with the balun circuitry for both +45° and −45° polarizations present on the dipole stem. 
         FIG.  7   a    is a different perspective view of the feedlines and balun circuit for the +45° polarization LB dipole component 
         FIG.  7   b    is a different perspective view of the feedlines and balun circuit for the −45° polarization LB dipole component. 
         FIG.  8    illustrates the balun circuitry for both the +45 and −45° polarization components of the LB dipole, with the dipole stem plates removed from view. 
         FIG.  9    illustrates the balun circuitry of  FIG.  8   , but with the dipole stem plates in view. 
         FIG.  10   a    illustrates the top and bottom sides of an additional exemplary LB dipole. 
         FIG.  10   b    illustrates the exemplary LB dipole of  FIG.  10   a   , along with a depiction of the capacitive and inductive structures embedded within the dipole structure 
         FIG.  11    illustrates the top and bottom sides of another exemplary LB dipole, having a reduced LB dipole span. 
         FIG.  12    plots S-parameter performance of the LB dipole illustrated in  FIG.  11   . 
     
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     Reference will now be made in detail to embodiments of the integrated filter radiator for multiband antenna with reference to the accompanying figures 
       FIGS.  2   a  and  2   b    illustrate an exemplary antenna array face in which the HB dipoles  110  are oriented diagonally, and the LB dipole  210  is oriented in a vertical and horizontal direction yet is configured top radiate and receive in +/−45° polarizations. As illustrated, having the LB dipole  210  oriented vertically and horizontally substantially mitigates the physical obstruction present in the antenna array face of  FIGS.  1   a  and  1   b   . As is described below, LB dipole  210  has a vertically-oriented LB dipole and a horizontally-oriented dipole. The vertically-oriented dipole has a radiator component extending “upward” from center that is fed by an individual LB RF feed (not shown), and a counterpart radiator component extending “downward” from center that is fed by another LB RF feed (also not shown). Similarly, the horizontally-oriented LB dipole has a radiator component extending “leftward” from center that is fed by an individual LB RF feed (not shown), and a counterpart radiator component extending “rightward” from center that is fed by another LB RF feed (also not shown). These dipole structures are described in further detail a  FIGS.  3   a    and  3   b.    
     It will be understood that the terms “upward” and “downward” are used for convenience in reference to the drawings, and do not refer to the actual orientation of the LB dipole  210 . 
       FIGS.  3   a  and  3   b    respectively illustrate a front or “top” face  210   a  of LB dipole  210 , and a back or “bottom” face  210   b  of LB dipole  210 . Both figures illustrate a first horizontal dipole arm  310   a  that extends “rightward” from the dipole center, second horizontal dipole arm  310   b  that extends “leftward” from the dipole center, a first vertical dipole arm  320   a  that extends “upward” from the dipole center, and second vertical dipole arm  320   b  that extends “downward” from the dipole center. As illustrated, the shaded portions of front face  210   a  and back face  210   b  correspond to PCB substrate or an otherwise non-conducting, surface, and the non-shaded portions correspond to metal conductor, such as copper. 
     Referring to  FIG.  3   a   , at the center region of the cross shape of front dipole face  210   a  are four solder pads  305   a  to which corresponding microstrip ground plates (described later) are conductively coupled, and which are surrounded by non-conductive surface. Moving outward from center along each dipole arm, the next component in each dipole arm is a conductive element  340   a , coupled to which is an “outward” facing inductor trace  350   a  to which is coupled a “diamond” shaped capacitive element  360   a . Conductive element  340   a , inductor trace  350   a , and capacitive element  360   a  may be formed of a simile piece of metal, such as copper. Located further “outward” is a distal conductive element  330   a , which is separated from its corresponding diamond shaped capacitive element  360   a  by a gap. Exemplary dimensions are shown in  FIG.  3     c.    
     Referring to  FIG.  3   b   , at the center region of the cross shape of back dipole face  210   b  are four “arrowhead” conductive elements  305   b , each corresponding to an arm of the back dipole face  210   b . Within each arrowhead conductive element  305   b  is a via  370   b , through which microstrip ground plates (described later) pass without making conductive contact to arrowhead conductive element  305   b . This may be accomplished whereby the conductive portion of the microstrip ground plate has disposed on it a solder mask, which prevents electrically conductive contact between microstrip ground plate and arrowhead conductive element  305   b . Moving outward from center along each dipole arm, each arrowhead conductive element  305   a  is coupled to an inductor trace  350   b , which is in turn coupled to a “diamond” shaped capacitive element  360   b . Located further outward is conductive element  340   b , which is separated from diamond shaped capacitive element  360   b  by a gap and which is coupled to further inductor trace  350   b , to which is coupled a further diamond shaped capacitive element  360   b.    
     Although capacitive element  360   a/b  has a “diamond” shape in this example, other shapes (e.g., rectangular, triangular, circular, etc.) are possible and within the scope of the disclosure, as long as the volume of the capacitive element is the same. 
       FIGS.  3   c  and  3   d    respectively illustrate front face  210   a  and back face  210   b  of LB dipole  210 , including exemplary dimensions. It will be readily understood that these dimensions are examples, and that varying dimensions are possible and within the scope of the disclosure. 
       FIG.  4    illustrates a side view of an exemplary LB dipole  210  according to the disclosure, revealing the arrangement of conductive elements on the top and bottom surfaces (respectively, front face  210   a  and back face  210   b ). LB dipole  210  includes a PCB substrate  410 , and a conductive surface on the top and bottom that may be etched to form the components of front face  210   a  and back face  210   b . As illustrated, dipole stem  400  engages LB dipole  210  by mechanically coupling directly to back face  210   b , and microstrip ground plates (described later) electrically and mechanically couple to front face  210   a  by being passed through via  370  (of back face  210   b ) and soldered to solder pad  305   a  (of front face  210   a ). Further illustrated in  FIG.  4    are the alternating combinations of conductive elements  340   a  and  330   a  (on front face  210   a ) in back-to-back configurations with corresponding diamond shaped capacitive elements  360   b  (on back face  210   b ), as well as conductive elements  340   b  (on back face  210   b ) in a back-to-back configuration with diamond shaped capacitive element  360   a  (on back face  210   a ). Accordingly, a plurality of capacitors are formed. A first capacitor is formed of conductive element  340   a  and its corresponding capacitive element  360   b , with the PCB substrate  410  serving as the dielectric; a second capacitor is formed of conductive element  340   b  and its corresponding capacitive element  360   a ; with the PCB substrate  410  serving as its dielectric; and a third capacitor is formed of conductive element  330   a  and its corresponding capacitive element  360   b , with the PCB substrate  410  serving as its dielectric. Accordingly, each dipole arm assembly  310   a/b  and  320   a/b  comprises a succession of capacitors and inductors, providing a cloaking function whereby RF energy radiated by the LB dipoles are effectively transparent to the LB dipole, and induced currents are suppressed, thus mitigating interference between the HB and LB dipoles. 
     Exemplary materials or the LB dipole  210  may include the following. Substrate  410  may be a standard PCB material, such as 0.0203″ Rogers 4730J1XR, and the conductive material disposed on the top and bottom surfaces of substrate  410  (which may be etched to form the illustrated components) may by 1 oz. copper. It will be understood that variations to these materials are possible and within the scope of the disclosure. 
     The structure of LB dipole  210  offers an advantage in that it comprises a single PCB substrate on which a conductive layer is disposed. The conductive layer on the front and back faces of the dipole may be etched to form the structure disclosed. Accordingly, the structure of LB dipole  210  is extremely simple and inexpensive to manufacture, unlike other cloaked dipole configurations. 
       FIG.  5    illustrates exemplary LB dipole  210 , mounted on dipole steal  400 , and a portion of the feed network disposed on a feedboard to which the dipole stem  400  is mounted. The feed network includes RF feedlines corresponding to the +45° signal and the −45° signal. Illustrated is +45° feedline  510   a , which includes a power divider  520   a , and two traces coupled to the power divider  520   a : first +45° trace  540   a , and second −45° trace  530   a . First +45° trace  340   a  couples directly to a microstrip balun that feeds corresponding dipole arm  310   a . Second +45° trace  530   a  takes a longer path to couple with a microstrip balun such that the RF signal that reaches the other microstrip balun is 180° out of phase with the signal on trace  510   a  where it couples with its corresponding microstrip balun. Further illustrated is −45° feedline  510   b , which includes a power divider  520   b  and two traces coupled to power divider  620   b , first −45° trace  540   b  and second −45° trace  530   b.    
       FIG.  6   a    illustrates the LB dipole stem  400  from a “top-down” perspective, along with the balun circuit and relevant feedlines for an exemplary +45° polarization LB dipole signal. This perspective is looking “down” on the dipole stem  400  with the LB dipole  210  removed, such that the dipole stem  400  would be coming out perpendicularly out of the page. As can be seen in  FIG.  6 C , the dipole stem  400  has a first dipole stem plate  400   a  oriented along the first axis and a second dipole stem plate  400   b  oriented along the second axis. Illustrated are +45° signal feedline  510   a , power divider  520   a , and first trace  540   a . First trace  540   a  couples directly to microstrip balun  620   a  at connection point  610   a , whereby microstrip balun  620   a  is electrically coupled to corresponding microstrip ground plate  630   a , which is disposed on the proximal surface of the stem plate orthogonal to the stem plate on which microstrip balun  620   a  is disposed as it traces from connection point  610   a . Second trace  530   a  proceeds from power divider  520   a  and meanders before electrically coupling to opposite microstrip balun  650   a  via connection point  640   a  such that the signal arriving at connection  640   a  has a 180° phase delay relating to the signal arriving at connection point  610   a . Microstrip balun  650   a  further couples to opposite microstrip ground plate  660   a , which is disposed on the dipole stem plate orthogonal to the dipole stem plate on which connection point  640   a  is disposed. 
       FIG.  6   b    illustrates the LB dipole stem  400  at the same orientation as in  FIG.  6   a   . However,  FIG.  6   b    illustrates the feedline and balun circuitry for the −45° polarization LB dipole signal, Illustrated are −45° signal feedline  510   b , power divider  520   b , and first trace  540   b . First trace  540   b  couples directly to microstrip balun  620   b  at connection point  610   b , whereby microstrip balun  620   b  electrically couples to corresponding microstrip ground plate  630   b , which is disposed on a stem plate orthogonal to the stem plate on which microstrip balun is disposed as it traces from connection point  610   b . Second trace  530   b  proceeds from power divider  520   b  and meanders before electrically coupling to opposite microstrip balun  650   b  via connection point  640   b  such that the signal arriving at connection  640   b  has a 180° phase delay relating to the signal arriving at connection point  610   b . Microstrip balun  650   b  further couples to opposite microstrip around plate  660   b , which is disposed on the dipole stem plate orthogonal to the dipole stem plate on which connection point  640   b  is disposed. 
     Referring back to  FIG.  5   , it will be apparent that the microstrip baluns  620   a ,  650   a ,  620   b , and  650   b  substantially span the distance from respective connection points  610   a ,  640   a ,  610   b  and  640   b  upward to near the base of dipole arms  310   a/b  and  320   a/b . Further, microstrip ground plates  630   a ,  660   a ,  630   b , and  660   b  are each electrically coupled to a ground plane (not shown) in the multilayer PCB board to which dipole stem  400  is affixed. 
       FIG.  6   c    illustrates the LB dipole stem, similarly to  FIGS.  6   a  and  6   b   , with the balun circuitry for both +45° and −45° polarizations illustrated on the dipole stem. But first, some background. 
     It is known that two dipoles arms, oriented horizontally and vertically, with each dipole arm having a single RF feed, can be configured to radiate at +/−45 degree polarization orientations, through the use of hybrid couplers. There are several considerable drawbacks to this approach. First, each hybrid coupler incurs a 3 dB loss on each signal. Second, the hybrid coupler has limited isolation, which degrades the performance of the dipole in radiation two distinct RF signals at different polarizations. The structure according to the disclosure does not suffer these disadvantages. 
     Referring to  FIG.  6   c   , illustrated are the four microstrip baluns, each corresponding to a polarization and a phase delay:  620   a  (+45°/0°);  650   a  (±45°/0°);  620   b  (−45°/0°); and  650   b  (−45°/180°); and the four microstrip ground plates:  630   a  (+45°/0°, directly coupled to microstrip balun  620   a );  660   a  (+45°/180° directly coupled to microstrip balun  650   a );  630   b  (−45°/0°, directly coupled to microstrip balm  620   b ); and  660   b  (−45°/180°, directly coupled to microstrip balun  650   b ). The microstrip baluns are respectively coupled to their corresponding microstrip ground plates by making a 90° bend from the stem plate surface on which the microstrip balun is disposed to the proximal surface of the dipole orthogonal stem plate. 
     Referring to  FIGS.  6   c  and  3   a , and  3   b   , microstrip ground plate  660   b  is coupled to dipole arm  310   a  as follows. Dipole stem  400  as four tabs (not shown) that pass through vias  570   b  ( FIG.  3   b   ). Microstrip ground plate  660   b , as it is disposed on dipole stem plate  400 , has a conductive tab that extends through its corresponding via  370   b  where it is electrically coupled (e.g., soldered) to its corresponding solder pad  305   a  on dipole arm  310   a . Similarly, microstrip ground plate  630   b  is coupled to dipole arm  310   b  through a similar arrangement. Further, microstrip ground plate  660   a  is coupled to dipole arm  320   a , and microstrip ground plate  630   b  is coupled to dipole arm  320   b  by corresponding arrangements. 
     Another way to visualize  FIG.  6   c    is to divide the configuration into quadrants, whereby the top left (first) quadrant includes microstrip balun  650   a  and microstrip ground plate  660   a ; the top right (second) quadrant includes microstrip balun  650   b  and microstrip ground plate  660   b ; the bottom left (third) quadrant includes microstrip balun  620   b  and microstrip ground plate  630   b ; and the bottom right (fourth) quadrant includes microstrip balun  620   a  and microstrip ground plate  630   a.    
     The configuration of microstrip baluns and microstrip ground plates is as follows. Each microstrip ground plate conducts two independent currents. One current is directly sourced from the microstrip balun to which it is directly coupled, and the other is capacitively coupled from the microstrip balun disposed on the opposite side of the stem plate on which the microstrip ground plate is disposed. 
     For example, referring to  FIG.  6   c   , for the +45° polarization and 0° phase signal, the signal couples from connection point  610   a  to microstrip balun  620   a . The current on microstrip balun  620   a  capacitively couples to microstrip ground plate  660   b , through which the resulting current couples to dipole arm  310   a . Additionally, the current in microstrip balun  620   a  flows directly to microstrip ground plate  630   a , through which it couples to dipole arm  320   b . Given the tuning of the balun circuity between microstrip balun  620   a , and microstrip ground plates  660   b  and  630   a , a substantially equal current is respectively induced in dipole arms  310   a  and  320   b . This results in a radiated waveform with as polarization vector oriented at +45°, with the rightward and downward signals respectively serving as vector components of the +45° polarization vector. 
     A similar process occurs for the −45° signal with 180° phase delay. In this case, the phase delayed signal couples from connection point  640   a  to microstrip balun  650   a . The current microstrip balun  650   a  capacitively couples to microstrip ground plate  630   b , through which the resulting current couples to dipole arm  310   b . Additionally, the current in microstrip balun  650   a  flows directly to microstrip ground plate  660   a , through which it couples to dipole arm  320   a . Given the tuning of the balun circuitry between microstrip balun  640   a , and microstrip ground plates  630   b  and  660   a , a substantially equal current is respectively induced in dipole arms  310   b  and  320   a . This results in a radiated waveform with its polarization vector oriented at +45°, with the leftward and upward signals respectively serving as vector components of the +45° polarization vector. 
     The two +45° polarization signals, being 180° out of phase from each other, given the configuration of the baluns and the dipoles, results in a constructive interference of the two emitted RF waveforms, doubling the amplitude e of the radiated energy of just one of the +45° signal components. 
     The mode of operation is similar for the −45° signals. Referring to  FIG.  6   c   , for the −45° polarization and 0° phase signal, the signal couples from connection point  610   b  to microstrip balun  620   b . The current on microstrip balun  620   b  capacitively couples to microstrip ground plate  630   a , through which the resulting current couples to dipole arm  320   b . Additionally, the current in microstrip balun  620   b  flows directly to microstrip ground plate  630   b , through which it couples to dipole arm  310   b . Given the tuning of the balun circuitry between microstrip balun  620   b , and microstrip ground plates  630   a  and  630   b , a substantially equal current is respectively induced in dipole arms  310   b  and  320   b . This results in a radiated waveform with its polarization vector oriented at −45°, with the leftward and downward signals respectively serving as vector components of the −45° polarization vector. 
     A similar process occurs for the −45° signal with 180° phase delay. In this case, the phase delayed signal couples from connection point  640   b  to microstrip balun  650   b . The current on microstrip balun  650   b  capacitively couples to microstrip ground plate  660   a , through which the resulting current couples to dipole arm  320   a . Additionally, the current in microstrip balun  650   b  flows directly to microstrip ground plate  660   b , through which it couples to dipole arm  310   a . Given the tuning of the balun circuitry between microstrip balun  640   b , and microstrip ground plates  660   a  and  660   b , a substantially equal current is respectively induced in dipole arms  310   a  and  320   a . This results in a radiated waveform with is polarization vector oriented at −45°, with the rightward and upward signals respectively serving as vector components of the −45° polarization vector. 
     The two −45° polarization signals, being 180° out of phase from each other, given the configuration of the baluns and the dipoles, results in a constructive interference of the two emitted RF waveforms, doubling the amplitude of the radiated energy of just one of the −45° signal components. 
     Accordingly, instead of relying on hybrid couplers for splitting and combining the two RF signals, the feed network and balun configuration of the present disclosure splits and recombines the appropriate signals by superimposing two signals into each microstrip capacitor plate and thus to each arm of the LB dipole, creating orthogonal vertical and horizontal polarization vector components for each of the RF signals, thereby generating +/−45° polarization signals using vertical and horizontal dipoles, in doing so, it eliminates the need for hybrid coupler hardware within the antenna housing, and further eliminates the 3 dB loss and signal isolation problems symptomatic of the use of hybrid couplers. 
       FIG.  7   a    illustrates a portion of the feedline  510   a , power divider  520   a , first and second traces  540   a  and  530   a , microstrip baluns  620   a  and  650   a , and microstrip ground plates  630   a  and  660   a  of the +45° polarization component of the system, with the stem plates removed from view. This drawing is provided to better illustrate the physical structure of the microstrip baluns  620   a / 650   a  and microstrip ground plates  630   a / 660   a.    
       FIG.  7   b    provides a similar view of feedline  510   b , power divider  520   b , first and second traces  540   b  and  530   b , microstrip baluns  620   b  and  630   b , and microstrip ground plates  630   b  and  660   b.    
       FIG.  8    provides a closer view of the combined drawings of  FIGS.  7   a  and  7   b   , illustrating the respective connections between and relative orientations of microstrip baluns  620   a / 650   a  and microstrip ground plates  630   a / 1660   a  (+45°) and the respective connections between and relative orientations of microstrip baluns  620   b / 650   b  and microstrip ground plates  630   b / 660   b  (−45°).  FIG.  9    provides a similar view to that of  FIG.  8   , but with the stem plates present. 
     LB dipole  210  as described above may be operated in a circular polarization mode without modification to the components. To do this, instead of two separate RF signals being respectively assigned to the +45° and −45° signal paths, one may apply a single RF signal whereby, for example, the RF signal may be applied to +45° signal feedline  510   a , and the same RF signal, offset by a +90° phase delay, may be applied to −45° signal feedline  510   b . In doing so, dipole arms  310   a ,  320   b ,  310   b ),  320   a  will radiate the same RF signal, each with a 90° phase rotation between them, resulting in a left hand circular polarization RF propagation from LB dipole  210 . Alternatively, applying an RF signal to the +45° signal path, and the same RF signal with a −90° phase delay, results in a right hand circular polarized propagation, in which dipole arms  310   a ,  320   a ,  310   b , and  320   b  radiate the same RF signal, each with a 90° phase rotation between them, generate a right hand circular RF propagation from LB dipole  210 . 
       FIG.  10   a    illustrates an additional exemplary LB dipole  1000  according to the disclosure. LB dipole  1000  has a top side  1010   a  and a bottom side  1010   b . Top side  1010   a  includes, at its center, four solder pads  1005   a , each having a via  1070   a  through which a balun stem with a microstrip ground plate (not shown) are disposed so that the microstrip plate can be soldered to its respective solder pad  1005   a . As illustrated, four dipole arms extend out from the center, on which are disposed a conductive element  1040   a , an outward facing inductor trace  1050   a  that is coupled to a rectangular capacitive element  1060   a . Further in the outward direction of each LB dipole arm is a distal conductive element  1030   a , which may be substantially similar to conductive element  1040   a.    
     Further illustrated in  FIG.  10   a    is LB bottom side  1010   b . Disposed in the center of LB bottom side  1010   b  are four arrowhead conductive elements  1005   b , within which is disposed via  1070   b  through which a respective balun stem and microstrip plate (not shown) are disposed. Each arrowhead conductive element  1005   b  is coupled to an inductor trace  1050   b , which is further coupled to a rectangular capacitive element  1060   b . Disposed further outward on each LB dipole arm is a conductive element  1040   b , each of which is coupled to an inductor trace  1050   b  and further coupled to a rectangular capacitive element  1060   b.    
       FIG.  10   b    illustrates LB dipole  1000  along with a depiction of the inductors and capacitors that are formed by the elements on its top side  1010   a  and bottom side  1010   b . As with the example illustrated in  FIG.  4   , the conductive elements  1040   a/b  and  1030   a  are each disposed opposite a rectangular conductive element  1060   a/b  whereby each LB dipole arm comprises a series of inductors and capacitors whereby the capacitors are formed by the LB dipole arm PCB substrate with the conductive elements and capacitive elements on opposite sides thereof. The series of inductors and capacitors are tuned such that the LB dipole  1000  radiate in the low band frequencies and are effectively short circuited at high band frequencies. 
       FIG.  11    illustrates another exemplary LB dipole  1100  according to the disclosure. An advantage of LB dipole  1100  is that its dipole arm span is shorter than LB dipole  1000 , which reduces the interference or shadowing of the HB radiation patterns of HB dipoles  110 . In order to preserve bandwidth, given the shorter arm span, each arm is wider than for LB dipole  1000 .  FIG.  11    provides exemplary dimensions of 177 mm for the length of a given dipole arm of LB dipole  1100 , and 48.5 in for the width. It will be understood that these dimensions are examples and that variations to these dimensions are possible and within the scope of the disclosure. 
     LB dipole  1100  has a top side  1110   a  and a bottom side  1110   b . Top side  1110   a  has, at its center, four solder pad  1105   a , each having a respective via  1170   a  through which a balun stem with a microstrip ground plate (not shown) are disposed so that the microstrip plate can be soldered to its respective solder pad  1105   a . As illustrated, four dipole arms extend out from the center, on which are disposed a conductive element  1140   a , an outward facing inductor trace  1150   a  that is coupled to a rectangular capacitive element  1160   a . Further in the outward direction of each LB dipole arm is a distal conductive element  1130   a , which may be substantially similar to conductive element  1140   a . Top side  1110   a  also has a gap  1175   a  disposed between conductive elements  1140   a . Gap  1175   a  may have a width of about 1 mm. 
     Further illustrated in  FIG.  11    is LB bottom side  1110   b . Disposed in the center of LB bottom side  1110   b  are four arrowhead conductive elements  1105   b , within which is disposed via  1170   b  through which a respective balun stem and microstrip plate (not shown) are disposed. Each arrowhead conductive element  1105   b  has a portion of a “diamond” shaped capacitive element  1160   b . Disposed further outward on each LB dipole arm is a conductive element  1140   b , each of which is coupled to an inductor trace  1150   b  and further coupled to a diamond shaped capacitive element  1160   b . The arrangement of a series of capacitors and inductors created by the structure of LB dipole  1100  is similar to that of LB dipole  1000  except for the partial diamond capacitive element  1160  on LB dipole  1100  and the gaps  1175   a  between adjacent conductive elements  1100   a.    
       FIG.  12    plots the S-parameter performance of the exemplar LB dipole  1100 . 
     It will be understood that either of LB dipole  1000  and LB dipole  1010  may be used with the balun and feed network described above, in place of LB dipole  210 . This includes the circular polarization function described above and the 45 degree polarization tilting function described above with respect to  FIG.  6     c.    
     Further variations to the invention are possible and within the scope of the disclosure. For example, the disclosed structure of LB dipoles  210 ,  1000 , and  1100  may be used independently of the disclosed phase rotating feed network and balun circuitry. In such an example, the disclosed LB dipole  210 / 1000 / 1100  could be used with the antenna array face  100 , in which case the feed network and balun circuitry may be of a conventional variety due to the fact that the radiated +/−45° polarized RF propagation is parallel to each of the dipole arms. Further, other LB dipole structures may be used with the disclosed phase rotating feed network and balun circuitry. In this case, the substantial similarity between any alternative LB dipole and the disclosed LB dipoles include a cross-shaped arrangement of individual radiators, each of which is independently fed. 
     While various embodiments of the present invention have been described above, it should be understood that they have been presented by way of example only, and not limitation. It will be apparent to persons skilled in the relevant art that various changes in form and detail can be made therein without departing from the spirit and scope of the present invention. Thus, the breadth and scope of the present invention should not be limited by any of the above-described exemplary embodiments but should be defined only in accordance with the following claims and their equivalents.