Patent Publication Number: US-11664592-B2

Title: Compact antenna phase shifter with simplified drive mechanism

Description:
CROSS REFERENCE TO RELATED DISCLOSURE 
     This application is a continuation of 371 U.S. National Stage application Ser. No. 17/045,379, COMPACT ANTENNA PHASE SHIFTER WITH SIMPLIFIED DRIVE MECHANISM filed on Oct. 5, 2020, which is based upon an International Application No.: PCT/US19/28702 filed Apr. 23, 2019 and claims priority to U.S. Provisional Patent Application No. 62/661,230, filed Apr. 23, 2018, the entire contents of which are hereby incorporated by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to wireless communications, and more particularly, to small cell antennas incorporating mechanical phase shifters. 
     Related Art 
     Urban deployments of cellular network require antennas that are compact and offer a variety of gain profile configurations. A solution to this challenge is a cylindrical antenna having several internal array faces, or sectors, each corresponding to a given azimuthal portion of a 360 degree area of angular coverage. Often, depending upon the coverage area desired, it may be necessary for an antenna to have the ability to tilt its gain downwardly or upwardly. Such gain pattern adjustment is conventionally achieved with phase shifters that may be integrated into each antenna array face. 
     Conventional phase shifters have wiper arms that are individually engaged at the wiper arm distal end (opposite from the pivot end). This configuration has two principal disadvantages: (1) it increases the materials and number of parts associated with the phase shifter; and (2) it restricts the ability to reduce the size of the array face. The latter complication arises inasmuch as the wiper arms require a drive mechanism that extends to the outer edges of the array face along the azimuth axis. In the case of a small cell antenna, having a cylindrical configuration with three array faces, or sectors, (each oriented at 120 degree intervals, for example), a conventional drive mechanism interferes with the other array face PCBs. This is due to the configuration of the drive mechanism which is disposed at the outer edges of its respective array face. As such, the drive mechanism interferes with the other PCBs, i.e., where they meet. 
     Accordingly, a need exists for a phase shifter having a minimal profile and part count, enabling mounting of multiple array faces within a cylindrical/sector antenna. 
     SUMMARY OF THE INVENTION 
     An aspect of the present invention involves a phase shifter arrangement for an antenna. The phase shifter arrangement has pair of phase shifters, each phase shifter having a first wiper arm and a second wiper arm, the first and second wiper arm each having a proximal end and a distal end and a pivot axis disposed between the proximal end and the distal end. The first and second wiper arm each have a wiper arm conductive trace disposed on its underside wherein the conductive trace is disposed between the pivot axis and the distal end, and a drive pin slot disposed between the pivot axis and the proximal end. The phase shifter arrangement has a drive shaft that has a longitudinal axis and two drive pins, wherein the drive pins are disposed on opposite sides of the drive shaft at a lateral distance from the longitudinal axis of the drive shaft and mechanically coupled to the drive shaft by a plurality of struts. Each of the drive pins mechanically couples to a corresponding first wiper arm and second wiper arm of each of the pair of phase shifters, wherein as the drive shaft translates along the longitudinal axis, each drive pin slides within the drive pin slots of the corresponding first wiper arm and second wiper arm, causing the first wiper arm and second wiper arm to rotate in unison about their corresponding pivot axes. 
     Another aspect of the present invention involves an antenna that comprises an RF signal input port, a plurality of radiators, and a phase shifter arrangement electrically coupled between the RF signal input port and the plurality of radiators. The phase shifter arrangement has a pair of phase shifters, each phase shifter having a first wiper arm and a second wiper arm. The first and second wiper arm each have a proximal end and a distal end and a pivot axis disposed between the proximal end and the distal end. The first and second wiper arm each have a wiper arm conductive trace disposed on an its underside wherein the conductive trace is disposed between the pivot axis and the distal end, and a drive pin slot disposed between the pivot axis and the proximal end. The phase shifter arrangement has a drive shaft having a longitudinal axis and two drive pins, wherein the drive pins are disposed on opposite sides of the drive shaft at a lateral distance from the longitudinal axis of the drive shaft and mechanically coupled to the drive shaft by a plurality of struts, wherein each of the drive pins mechanically couples to a corresponding first wiper arm and second wiper arm of each of the pair of phase shifters. As the drive shaft translates along the longitudinal axis, each drive pin slides within the drive pin slots of the corresponding first wiper arm and second wiper arm, causing the first wiper arm and second wiper arm to rotate in unison about their corresponding pivot axes. 
     Another aspect of the invention involves an antenna having a plurality of array faces, each of the plurality of array faces corresponding to a distinct azimuth angle of coverage. Each of the array faces comprises a PCB structure, a plurality of radiators disposed on the PCB structure, and a phase shifter arrangement disposed on the PCB structure. The phase shifter arrangement has a pair of phase shifters, each of the phase shifters electrically coupled between one or more RF signal inputs and the plurality of radiators. Each phase shifter has a first wiper arm and a second wiper arm, the first and second wiper arm each having a proximal end and a distal end and a pivot axis disposed between the proximal end and the distal end. The first and second wiper arm each have a wiper arm conductive trace disposed on an its underside wherein the conductive trace is disposed between the pivot axis and the distal end, and a drive pin slot disposed between the pivot axis and the proximal end. The phase shifter arrangement has a drive shaft having a longitudinal axis and two drive pins, wherein the drive pins are disposed on opposite sides of the drive shaft at a lateral distance from the longitudinal axis of the drive shaft and mechanically coupled to the drive shaft by a plurality of struts, wherein each of the drive pins mechanically couples to a corresponding first wiper arm and second wiper arm of each of the pair of phase shifters. As the drive shaft translates along the longitudinal axis, each drive pin slides within the drive pin slots of the corresponding first wiper arm and second wiper arm, causing the first wiper arm and second wiper arm to rotate in unison about their corresponding pivot axes. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       So that the manner in which the features of the invention can be understood, a detailed description of the invention may be had by reference to certain embodiments, some of which are illustrated in the accompanying drawings. It is to be noted, however, that the drawings illustrate only certain embodiments of this invention and are therefore not to be considered limiting of its scope, for the scope of the disclosed subject matter encompasses other embodiments as well. The drawings are not necessarily to scale, emphasis generally being placed upon illustrating the features of certain embodiments of the invention. In the drawings, like numerals are used to indicate like parts throughout the various views. 
         FIG.  1    illustrates an exemplary cylindrical/sector antenna according to the disclosure wherein tri-sector antennas, each spanning one-hundred and twenty degrees of coverage. 
         FIG.  2    illustrates an exemplary phase shifter assembly according to the disclosure, as seen from the outward-facing side of an antenna array face. 
         FIG.  3    illustrates an exemplary phase shifter assembly according to the disclosure, as seen from the inward-facing side of an antenna array face. 
         FIG.  4    illustrates an exemplary phase shifter wiper arm according to the disclosure. 
         FIG.  5    is an edge view of an array face Printed Circuit Board (PCB) with a single phase shifter pair according to the disclosure. 
         FIG.  6   a    illustrates an internal perspective view of a sector antenna and an independently-driven phase shifter assembly for a single sector thereof. 
         FIG.  6   b    illustrates an internal perspective view of an omni-directional sector antenna and a commonly-driven phase shifter assembly for driving all sectors of the omni-directional antenna. 
         FIG.  7   a    is a top view of the sector antenna shown in  FIG.  6   a    depicting tri-sector arrays and an independently-driven phase shifter assembly disposed along the internal face of each sector. 
         FIG.  7   b    is a top view of the omni-directional sector shown in  FIG.  7   b    depicting a vertical shaft/spoked-web for simultaneously driving the phase shifters along all sectors of the omni-directional antenna. 
     
    
    
     DETAILED DESCRIPTION 
     The invention is directed to a phase shifter assembly wherein each wiper arm has a pivot point disposed proximal the center of a wiper arm, and wherein the end opposite the distal end engages with a drive pin. Both wiper arms of the phase shifter engage with a single drive pin and thus are both driven by a single shaft that is coupled to a drive motor. 
     The phase shifter assembly according to the disclosure requires less material and fewer parts than a conventional phase shifter. Further, because the drive mechanism is located substantially at the center of the phase shifter (along the azimuth axis), there is more room at the outer edges of the array face PCB to enable the shrinking of the array face in the azimuth dimension, enabling a smaller small cell antenna. 
       FIG.  1    illustrates an exemplary small cell antenna  100 . Antenna  100  may have a plurality of array faces  110   a ,  110   b , and  110   c , each of which corresponding to an azimuth direction A, B, and C, whereby each array face  110   a ,  110   b ,  110   c  has a gain pattern that substantially covers its corresponding azimuthal portion of 360 degrees. Azimuth directions A, B, and C may each be orthogonal to the surface of their corresponding array faces  110   a ,  110   b ,  110   c , and each may be orthogonal to the tilt (or vertical) axis z. The exemplary antenna  100  has three array faces, each spaced at 120 degrees, however, it will be understood that variations to this design, including the number and angular orientations of the array faces, are possible and within the scope of the disclosure. For example, each array face may span ninety (90) degrees or sixty (60) degrees. 
     Each of the array faces  110   a ,  110   b ,  110   c  has a printed circuit board (PCB) structure  112 , a plurality of radiators  130 , and a phase shifter assembly  120 . Each phase shifter assembly  120  provides a differential phase delay to sets of radiators  130  as a function of their location along the tilt axis z. Generally, the radiators  130  located at the center of the array face  110   a/b/c  along the tilt axis (phase center) are not given any phase delay, and rows of radiators  130  are given an increasing differential phase delay as a function of distance from phase center along the tilt axis. The general principles of phase shifters and how they function are generally known in the art. 
     Among the possible variations to the antenna  100  of the disclosure are two configurations: tri-sector, and omni-directional. For the tri-sector variation, each array face  110   a ,  110   b ,  110   c  operates independently. In the context used herein, the independent operation means that each array face  110   a ,  110   b ,  110   c  has its own RF signals coupled to its corresponding radiators  130 , and each phase shifter  120  operates independently. As such, each 120 degree sector operates independently, i.e., is not influenced by the RF signals in the adjacent sectors. In an omni variation, the three array faces  110   a ,  110   b ,  110   c  are unified in that all of the radiators  130  on array faces  110   a ,  110   b ,  110   c  are coupled to the same RF signal sources, and the phase shifters  130  operate in unison. 
       FIG.  2    illustrates an exemplary phase shifter assembly  120  according to the disclosure, as seen from the outward-facing side of an antenna array face  110  (use of “array face  110 ” may simply be any or all of the array faces  110   a ,  110   b ,  110   c ). The phase shifter assembly  120  may include two pairs of wiper arms  205   a  and  205   b , each of which is configured to rotate around their respective axis  210 , and are mutually, rotatably, and mechanically coupled by a drive pin  215 , which translates within a PCB slot  220 . As illustrated, the wiper arms  205   a ,  205   b  are oriented such that drive pin  215  is located at or near the full extent of its motion within PCB slot  220 . Further illustrated (in dotted lines) are wiper arms  205   a ,  205   b  with drive pin  215  in its center position within PCB slot  220 . Phase shifter assembly  120  further includes PCB openings  225  and  230 . PCB openings  225  and  230  which define an arcuate boundary corresponding to the sweep of the wiper arms  205   a ,  205   b  as they rotate in response to translation of the drive pin  215  within the PCB slots  220 . Each wiper arm  205   a ,  205   b  has a distal hook portion that mechanically engages with the edge of one of PCB openings  225 ,  230  (described below). 
     The phase shifter assembly  120  includes a plurality of a first input/output RF signal trace  24 , each of which electrically couple one conductive trace to another conductive trace. For example, the wiper arm  205   a ,  205   b  may electrically couple a first input/output RF signal trace  24  to an second input/output RF signal trace  245 . 
     By placing the axis  210  proximal to the center of each of the wiper arms  205   a ,  205   b , and by causing the wiper arms  205   a ,  205   b  to engage the drive pin  215  as illustrated, it is possible to drive both wiper arms  205   a ,  205   b  with a single drive mechanism (described below). In contrast, conventional wiper arms  205   a ,  205   b  have their axes at a proximal end, and are driven at their distal end. 
       FIG.  3    illustrates an exemplary phase shifter assembly  120  according to the disclosure, as seen from an inwardly-facing side of an antenna array face  110 . Wiper arms  205   a ,  205   b  are illustrated with dotted lines inasmuch as they are disposed on the other side of the PCB. Illustrated is a wiper arm drive shaft  300  that is mechanically coupled to drive pins  215  by support struts  305 . Translation along the tilt (or longitudinal) axis, causes the drive shaft  300  to uniformly engage the drive pins  215  in parallel. Accordingly, the drive shaft  300  drives the wiper arms  205   a ,  205   b  in unison within the respective PCB slots  220 . As a consequence, the wiper arms  205   a ,  205   b  rotate about the respective pivot points  210 . 
       FIG.  4    depicts is an isolated perspective view of an exemplary wiper arm  205   a  or  205   b  according to the disclosure. More specifically, and referring to  FIGS.  3  and  4   , each of wiper arm arms  205   a ,  205   b  has: (i) an aperture  405  for rotating about the pivot axis  210 , (ii) a hook or recurved end portion  415  disposed at one end, and (iii) a slot  410  for accepting the drive pin  215  which engages the wiper arms  205   a ,  205   b  as the drive shaft  300  translates with the PCB slot  220 . As mentioned hereinabove, the hook or recurved end portion  415  engages an edge of the PCB opening  225 ,  230  to assure electrical coupling between the wiper arms  205   a ,  205   b  and: (i) a conductive trace, (ii) a first input/output RF signal trace  240 , and/or (iii) a second input/output RF signal input trace  245 . Each of the wiper arms  205   a ,  205   b  also have a step feature  420 , the height of which may vary from one of the wiper arms  205   a ,  205   b  to the other of the wiper arms  205   a ,  205   b . Such features will become apparent in view of the following detailed discussion in  FIG.  5   . 
       FIG.  5    is an edge view of an antenna array face and printed circuit board PCB  112  with a wiper arm pair  205   a ,  205   b  according to the disclosure. The illustrated wiper arm pair  205   a ,  205   b  may be either one of the two pairs within wiper arm assembly  120 . Illustrated therein are PCB openings  225 ,  230 , shown as gaps in the PCB  112 ; wiper arms  205   a ,  205   b  (i.e., rotatably coupled to the PCB  112  via axis  210 ) and translatably coupled to the PCB  112  at an edge of the PCB openings  225 ,  230  via a distal hook  415 . The drive pin  215  is coupled to both wiper arms  205   a ,  205   b  and is translatably disposed within the PCB slot  220 . 
     It will be apparent that the first wiper arm  205   a  and the second wiper arm  205   b  define variable height dimensions with respect to each of their respective step features  420 . Firstly, it will be apparent that for both wiper arms  205   a ,  205   b  to engage the drive pin  215 , they must necessarily be staggered such that one is superimposed over the other. Secondly, even though the second wiper arm  205   b  is the “lower” of the two wiper arms  205   a ,  205   b  that its portion with drive pin slot  410  is closer to PCB  112  that is the respective portion of wiper arm  205   a , it continues to, or still, has a step feature. This is due to the fact that it remains desirable to provide distance between the lower of the two wiper arms  205   a ,  205   b  with any of the input/output RF signal traces  515  so as to prevent electrical signal interference with the input/output RF signal traces  515 . 
     Further illustrated in  FIG.  5    are wiper arm conductive traces  505  disposed on the underside of wiper arms  205   a ,  205   b . Wiper arm conductive traces  505  electrically couple with RF signal traces  240 , and imparts a phase delay on the RF signal traces, depending on the location of the RF signal trace (distal vs. proximal) and the angular orientation of the wiper arm  205   a/b  around the axis defined by pivot axis  210 . 
     In  FIGS.  6   a  and  7   a   , an internal perspective view of a sector antenna  110   a  is depicted. More specifically, an independently-driven phase shifter assembly  120  is provided for a single sector antenna  110   a . Therein, a wiper arm (obscured by the PCB structure) is displaced and slid along the input/output RF traces by the input drive shaft  300 . That is, the wiper arms  205   a ,  205   b  are pivotally coupled to the input drive shaft  300  by the drive pins  215  disposed at the distal ends of a support strut  305 . A rotary actuator  610  turns a sector drive shaft  605  which employs a worm gear transmission to covert the rotational motion of the actuator  610  into linear motion along the input drive shaft  300 . 
     Translation along the tilt (or longitudinal) axis, causes the drive shaft  300  to uniformly engage the drive pins  215  in parallel and the wiper arms  205   a ,  205   b  to rotate about the respective pivot points  210 . The top view of the sector antenna shown in  FIG.  7   a    depicts at least three independently-driven phase shifter assemblies  120 , each phase shifter assembly being disposed along the internal face of each sector. 
     In  FIGS.  6   b  and  7   b   , an internal perspective view of an omni-directional antenna is depicted. More specifically, a plurality of commonly-driven phase shifter assemblies  120   a ,  120   b ,  120   c  are driven in unison by a drive shaft/strut arrangement. Each of the phase shifter assemblies  120   a ,  120   b ,  120   c  is displaced by a combination of a central shaft  650  and a spoked support strut  655 ,  660 . The central shaft  610  is slideably mounted to the back-side of the PCB by a shaft fitting  665  and translates up and down by a rotary actuator  670 . 
     More specifically, a rotary actuator  670  drives a worm gear transmission to covert the rotational motion of the actuator  670  into linear motion along the central input shaft  610 . Translation along the tilt (or longitudinal) axis, is effected by the drive shaft  650  which engages and pivots each of the wiper arms  205   a ,  205   b  about each of their respective pivot axes  210 . The top view of the omni-directional antenna shown in  FIG.  7   a    depicts a plurality of independently-driven phase shifter assemblies  120   a ,  120   b ,  120   c  being displaced by a commonly actuated central shaft  650 . 
     While the instant invention has been shown and described herein in what are conceived to be the most practical and preferred embodiments, it is recognized that departures, modifications, adaptations, variations, and alterations in the described methods and systems may be made and will be apparent to those skilled in the art of the foregoing description which does not depart from the spirit and scope of the invention which is therefore not to be limited to the details herein. For this reason, such changes are desired to be included within the scoped of the appended claims. The descriptive manner which is employed for setting forth the embodiments should be interpreted as illustrative but not limitative of the full scope of the claims which embrace any and all equivalents thereto.