Abstract:
An apparatus, e.g. a hybrid antenna, includes a plurality of antenna arrays. Each array includes antenna elements, and each array is located on a polygonal antenna body such that each array faces a different direction. An RF network includes first and second duplexers and a divider. The first duplexer is configured to split a received multifrequency drive signal into a first component having a first frequency and a second component having a second frequency. The divider is configured to split the first component into attenuated portions, and to direct one of the attenuated portions to a first of the plurality of antenna arrays. The second duplexer is configured to combine another of the attenuated portions with the second drive signal component to form a combined drive signal component, and to direct the combined drive signal component to a second of the antenna arrays.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates generally to the field of wireless communications, and, more particularly, but not exclusively, to methods and apparatus useful for transmitting and receiving radio-frequency signals. 
       BACKGROUND 
       [0002]    This section introduces aspects that may be helpful to facilitate a better understanding of the inventions. Accordingly, the statements of this section are to be read in this light and are not to be understood as admissions about what is in the prior art or what is not in the prior art. Any techniques or schemes described herein as existing or possible are presented as background for the present invention, but no admission is made thereby that these techniques and schemes were heretofore commercialized, or known to others besides the inventors. 
         [0003]    An antenna is typically directional or omni-directional. A directional antenna directs radio frequency (RF) signal power in a specific direction, while an omni-directional antenna distributes the power approximately equally in all directions. The structure of a directional antenna is typically very different from that of an omni-directional antenna. A directional antenna typically radiating elements mounted to a groundplane, focusing RF power in a single direction. An omni-directional antenna typically either has no groundplane, so the RF radiates about equally in all directions, or has multiple sets of radiating elements and groundplanes that each radiate equally to provide 360 degrees of coverage. Some antennas combine directional and omni-directional antennas in a single assembly, vertically stacking the antennas, e.g. with the omni-directional antenna on the bottom of the overall structure and the directional antenna stacked on top, or vice versa. Such structures may be physically too large for various reasons to be suitable. 
       SUMMARY 
       [0004]    The inventors disclose various apparatus and methods that may be beneficially applied to, e.g., radio frequency transmission and/or reception. While such embodiments may be expected to provide improvements in performance and/or reduction of cost or size relative to existing antennas, no particular result is a requirement of the present invention unless explicitly recited in a particular claim. 
         [0005]    One embodiment provides an apparatus, e.g. a hybrid antenna, including a plurality of antenna arrays. Each array includes antenna elements, and each array is located on a polygonal antenna body such that each array faces a different direction. An RF network includes first and second duplexers and a divider. The first duplexer is configured to split a received multifrequency drive signal into a first component having a first frequency and a second component having a second frequency. The divider is configured to split the first component into attenuated portions, and to direct one of the attenuated portions to a first of the plurality of antenna arrays. The second duplexer is configured to combine another of the attenuated portions with the second drive signal component to form a combined drive signal component, and to direct the combined drive signal component to a second of the antenna arrays. 
         [0006]    In some embodiments the polygonal antenna body has a triangular cross-section, and the plurality of antenna arrays includes three antenna arrays. Each array has a neighboring antenna array on each of two neighboring sides of the antenna body, and each of the antenna arrays is arranged to direct radio-frequency energy at an angle of about 120° with respect to each of its neighboring antenna arrays. In some embodiments the antenna arrays are arranged around an axis that is oriented vertically with respect to the ground. In some embodiments each of the antenna elements comprises a dipole antenna. In some embodiments the network is configured to operate bidirectionally. 
         [0007]    Another embodiment provides an apparatus, e.g. a hybrid antenna, including first and second duplexers and a power divider. Each of the duplexers has a common port, a high-pass filter port and a low-pass filter port. The power divider includes a common port and a plurality of attenuated ports. A first filter port type of the first duplexer is connected to a same filter port type of the second duplexer. A second filter port type of the first duplexer is connected to a common port of the power divider. A same second filter port type of the second duplexer is connected to a first attenuated port of the power divider. 
         [0008]    Some embodiments also include a first antenna array connected to a common port of the second duplexer, and a second antenna array connected to a second attenuated port of the divider. In some such embodiments each of the antenna elements comprises a dipole antenna. Some embodiments further include a first antenna array connected to a common port of the second duplexer, a second antenna array connected to a second attenuated port of the power divider, and a third antenna array connected to a third attenuated port of the power divider, wherein the first, second and third antenna arrays are each located on a different side of a polygonal antenna body such that each array faces a different direction. In some embodiments the polygonal antenna body has a triangular cross-section, and the plurality of antenna arrays consists of three antenna arrays, each having a neighboring antenna array on each of two neighboring faces, and each of the antenna arrays being arranged to direct radio-frequency energy at an angle of about 120° with respect to each of its neighboring antenna arrays. 
         [0009]    Other embodiments include methods, e.g. of manufacturing an apparatus, configured as described for any of the preceding embodiments. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    A more complete understanding of the present invention may be obtained by reference to the following detailed description when taken in conjunction with the accompanying drawings wherein: 
           [0011]      FIG. 1A /B respectively illustrate a perspective view and an axial view of a conventional omni-directional antenna having three faces oriented 120° from each other; 
           [0012]      FIG. 2A / 2 B illustrate a stylized view of the conventional antenna of  FIGS. 1A / 1 B, wherein the antenna is “unfolded” to provide a view of all faces of the antenna in the plane of the drawing; 
           [0013]      FIG. 3  illustrates the conventional antenna of  FIGS. 1A / 1 B, in which a power divider distributes a transmitted RF signal about equally among the three faces; and 
           [0014]      FIG. 4  illustrates, in a stylized fashion, three faces of a hybrid antenna according to one or more embodiments, in which two duplexers cooperate with a power divider to selectively distribute two RF signal frequencies among three faces to provide omni-directional transmission of one frequency and unidirectional transmission of the other frequency. 
       
    
    
     DETAILED DESCRIPTION 
       [0015]    Various embodiments are now described with reference to the drawings, wherein like reference numerals are used to refer to like elements throughout. While such embodiments may be expected to provide improvements in performance and/or reduction of cost of relative to conventional approaches, no particular result is a requirement of the present invention unless explicitly recited in a particular claim. In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of one or more embodiments. It may be evident, however, that such embodiment(s) may be practiced without these specific details. In other instances, well-known structures and devices are shown in block diagram form in order to facilitate describing one or more embodiments. 
         [0016]    There exists a need for an antenna design that distributes the power of the antenna directionally for some frequencies and omni-directionally for other frequencies. One known solution is to vertically stack the antennas. The omni directional antenna may be combined with a directional antenna stacked on top or vice a versa. This solution is unsuitable in some applications, e.g. because a size constraint for aesthetic reasons may undesirably constrain the placement of the antennas, detrimentally affecting performance of the combined antenna. 
         [0017]    Embodiments disclosed herein address one or more deficiencies of conventional implementation, e.g. by providing a more size-efficient technique of using an omni antenna with multiple sets of radiating elements and groundplanes, but use internal duplexers so that the frequency for which directional patterns are desired only goes to one set of radiating elements, while the frequencies for which omni-directional coverage is required continue to go to all of the multiple sets of radiating elements. 
         [0018]      FIGS. 1A / 1 B illustrate aspects of a conventional omni-directional antenna  100  to guide the reader in the following discussion of various embodiments.  FIG. 1A  illustrates a perspective view of the antenna  100 , while  FIG. 1B  illustrates a top-down plan view of the antenna  100  of  FIG. 1A . Referring concurrently to  FIGS. 1A and 1B , the antenna  100  includes a plurality of antenna elements  110 . The antenna elements  110  may be, e.g. dope antennas. The antenna elements  110 , which may radiate or receive RF signals, are arranged in linear arrays, e.g. three arrays  120   a ,  120   b ,  120   c , that each include four antenna elements  110  in the illustrated example. Ground planes  130   a ,  130   b  and  130   c  may be nominally rectangular, with additional ground reference provided by grounded wings  140 . The arrays  120   a / 120   b / 120   c  and ground planes  130   a / 130   b / 130   c  are nominally arranged symmetrically around an axis or rotation  150 . 
         [0019]      FIG. 2A  illustrates a side view of the antenna  100  as facing the dipole array  120   b . For convenience of visualization, the triangular arrangement of the antenna  100  may be projected, or “unfolded” onto a rectangular plane as illustrated in  FIG. 2B , wherein the ground planes  130   a ,  130   b ,  130   c  are shown as lying in the plane only for the purpose of illustration. In other words, the arrangement shown in  FIG. 2B  is schematic and does not correspond to a physical arrangement of the antennas arrays  120   a / 120   b / 120   c  and the ground planes  130   a / 130   b / 130   c.    
         [0020]      FIG. 3  illustrates a conventional scheme of delivering power to the antenna elements  110 . In this scheme, RF power driving the antenna  100  typically enters a connector at the bottom of the antenna  100  and is the split via an unreferenced three-way power divider such that each of the three arrays  130   a / 130   b / 130   c  receive a same amount of power. An omni-directional pattern may thereby be formed with three beam peaks of equal intensity. Of course this method of delivering power may be applied to other conventional antennas with more than three antenna arrays. Notably, this conventional scheme does not provide an ability to use the antenna  100  in a directional manner. 
         [0021]      FIG. 4  illustrates an apparatus, e.g. an antenna  400 , according to an embodiment of the disclosure. The antenna  400  is illustrated schematically similar to  FIG. 2B  to show to connections to several antenna arrays. The schematic presentation may correspond to an antenna structure similar to the conventional antenna  100 , but is not limited to such a conventional arrangement. Moreover, where such an antenna has an axis of rotation similar to the axis  150  ( FIG. 1 ), such an axis may be perpendicular to a ground surface, but is not limited to such a configuration. Unlike the conventional antenna  100 , the antenna  400  may provide omni-direction operation for some frequencies, and unidirectional operation for other frequencies. Thus a separate directional antenna array is not needed, and space may be saved in an antenna installation, e.g. a cellular tower. The illustrated embodiment presents without limitation a configuration suitable for operating omnidirectionally with respect to a first frequency f 1  and uni-directionally a second frequency f 2 . The antenna  400  may be considered and referred to as “hybrid” antenna to reflect its ability to transmit and or receive signals in an omnidirectional and/or unidirectional manner. 
         [0022]    Before describing the operation of the antenna  400 , some nomenclature is set forth to assist interpretation of the described embodiment and the claims. 
         [0023]    A duplexer is a device that may be used to separate an RF signal carrying two frequency components, e.g. f 1  and f 2 , received at a common port, and output each frequency at one of two filter ports. The term “filter port” refers to the operation of the duplexer to exclude one of the two received frequencies from each filter port output, but this term does not imply any particular internal configuration of the duplexer, and is not to be construed to limit the duplexer to any particular internal configuration. As used herein, the duplexer has two type of filter ports, a high-pass filter port to which a higher-frequency component of an input signal may be directed, and a low-pass filter port to which a higher-frequency component of an input signal may be directed. In the following discussion either type of port may be referred to as a “first type” or a “second type”. Where a filter port of a first duplexer is described or claimed to be coupled to a same port type of a second duplexer, either the high-pass filter ports of the two duplexers are directly coupled (e.g. no intervening RF components other than an RF cable), or the low-pass filter ports are directly coupled. Unless stated otherwise, any duplexer described or claimed may operate bidirectionally, e.g. to separate two frequency components received at the common port, or to combine two frequencies received at the filter ports into a single signal. 
         [0024]    A power divider, or simply “divider”, is a device that may split an RF signal received at a common port among two or more “attenuated ports” without regard to frequency. Unless otherwise stated, the division is about equal among the attenuation ports; thus a divider having N attenuation ports may split a signal having unity power into N signals having a power of 1/N. Unless stated otherwise, any divider described or claimed may operate bidirectionally, e.g. to split a signal received at the common port among the attenuation ports, or to combine signals received at the attenuation ports. 
         [0025]    Referring now to  FIG. 4 , the operation of the antenna  400  is described for the case that a signal is transmitted by the antenna  400 . It will be immediately apparent to those skilled in the pertinent art that the operation may be reversed for the case of a signal received by the antenna  400 . Furthermore, the embodiment is described without limitation for the case of a signal including two frequency components, f 1  and f 2 , either of which may be the higher frequency. 
         [0026]    An RF network  401  receives an RF signal that includes f 1  and f 2  signal components. A first duplexer  410  receives the RF signal at a common port  420 , and provides separated f 1  and f 2  signal components at corresponding unreferenced filter ports. A three-way divider  430  receives the f 1  signal component from the duplexer  410 , and divides the f 1  signal into three portions such that about one third of the signal appears at each of three unreferenced attenuated ports. First and second attenuated ports provide signals  440  and  450  respectively to the antenna array  110   a  and the antenna array  110   b  to be transmitted. 
         [0027]    A second duplexer  460  receives the f 2  signal component of the received RF signal from the same filter port type of the duplexer  410 , and a portion of the f 1  signal from the third attenuated port of the divider  430 , combines the f 1  and f 2  signals components, and directs the combined f 1  and f 2  signal  470  to the antenna array  110   c . Thus, while the antenna arrays  110   a  and  110   b  only receive the f 1  signal, the antenna array  110   c  may receive both the f 1  and f 2  signals. This configuration provides the antenna  400  the capability of transmitting an omni-directional pattern for f 1 , and a uni-directional pattern for f 2 . 
         [0028]    It is noted that either of f 1  and f 2  may be present or absent. Moreover, as previously noted, the network  401  may operate bidirectionally to receive a signal with frequency f 1  from the antenna arrays  110   a ,  110   b ,  110   c  and/or a signal with frequency f 2  from the antenna array  110   c , combine the f 1  and f 2  (if both are present), and provide the received signal component(s) at the common port of the duplexer  410  for further processing. Moreover, the described principle may be applied to as few as two antenna arrays, or to more than three antenna arrays. The described principle may also be applied to an antenna configuration in which all of N antenna arrays are configured to transmit and/or receive at a first frequency, e.g. f 1 , and any number fewer than N of the antenna arrays are configured to transmit and/or receive at a second frequency, e.g. f 2 . 
         [0029]    Unless explicitly stated otherwise, each numerical value and range should be interpreted as being approximate as if the word “about” or “approximately” preceded the value of the value or range. 
         [0030]    It will be further understood that various changes in the details, materials, and arrangements of the parts which have been described and illustrated in order to explain the nature of this invention may be made by those skilled in the art without departing from the scope of the invention as expressed in the following claims. 
         [0031]    The use of figure numbers and/or figure reference labels in the claims is intended to identify one or more possible embodiments of the claimed subject matter in order to facilitate the interpretation of the claims. Such use is not to be construed as necessarily limiting the scope of those claims to the embodiments shown in the corresponding figures. 
         [0032]    Although the elements in the following method claims, if any, are recited in a particular sequence with corresponding labeling, unless the claim recitations otherwise imply a particular sequence for implementing some or all of those elements, those elements are not necessarily intended to be limited to being implemented in that particular sequence. 
         [0033]    Reference herein to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the invention. The appearances of the phrase “in one embodiment” in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments necessarily mutually exclusive of other embodiments. The same applies to the term “implementation.” 
         [0034]    Also for purposes of this description, the terms “couple,” “coupling,” “coupled,” “connect,” “connecting,” or “connected” refer to any manner known in the art or later developed in which energy is allowed to be transferred between two or more elements, and the interposition of one or more additional elements is contemplated, although not required. Conversely, the terms “directly coupled,” “directly connected,” etc., imply the absence of such additional elements. 
         [0035]    The embodiments covered by the claims in this application are limited to embodiments that (1) are enabled by this specification and (2) correspond to statutory subject matter. Non-enabled embodiments and embodiments that correspond to non-statutory subject matter are explicitly disclaimed even if they formally fall within the scope of the claims. 
         [0036]    The description and drawings merely illustrate the principles of the invention. It will thus be appreciated that those of ordinary skill in the art will be able to devise various arrangements that, although not explicitly described or shown herein, embody the principles of the invention and are included within its spirit and scope. Furthermore, all examples recited herein are principally intended expressly to be only for pedagogical purposes to aid the reader in understanding the principles of the invention and the concepts contributed by the inventor(s) to furthering the art, and are to be construed as being without limitation to such specifically recited examples and conditions. Moreover, all statements herein reciting principles, aspects, and embodiments of the invention, as well as specific examples thereof, are intended to encompass equivalents thereof. 
         [0037]    Although multiple embodiments of the present invention have been illustrated in the accompanying Drawings and described in the foregoing Detailed Description, it should be understood that the present invention is not limited to the disclosed embodiments, but is capable of numerous rearrangements, modifications and substitutions without departing from the invention as set forth and defined by the following claims.