Patent Publication Number: US-10326213-B2

Title: Multi-band antenna for communication with multiple co-located satellites

Description:
BACKGROUND 
     Satellite communication using earth terminal antennas for consumers and for enterprise applications typically are reflector type and typically are on the order of 0.6 m to 1.2 m in size. The typical consumer antenna size may be approximately 0.6 m to 0.75 m, and prime fed offset parabolic reflector configurations are often used because it offers a low cost solution. A feed antenna, typically a horn type, is located at the focal point of the parabolic reflector. When operating with multi-band communication satellite payloads or multiple co-located satellites, it may be desirable to have coincident or near coincident earth terminal beams that correspond to the communication bands. When the communication bands are Ku, K, and Ka, for example, it may be desirable that the beams are near coincident beams at all three bands, which for example, may span 10.7 to 30.0 GHz. In addition, the polarization requirements at K and Ka bands are generally dual circular polarization (CP). At the Ku band, the polarization may be dual CP or may be dual linear polarization (LP). 
     SUMMARY 
     The following detailed description and accompanying drawings provide a better understanding of the nature and advantages of the present disclosure. 
     In accordance with the present disclosure, a multi-band antenna may include a horn to communicate signals in a first frequency band and a lower second frequency band, an in-line feed, and a single pair of sidewall feeds consisting of a first side feed and a second side feed. The horn may include a flared section comprising a plurality of transition regions between a first end and a second end. The horn may further include an in-line opening at the first end of the flared section. The in-line feed may be coupled to the in-line opening to communicate signals in the first frequency band. The horn may further include first and second openings to communicate signals in the second frequency band. The first and second opening may be formed through the smooth interior surface of one of the transition regions and arranged asymmetrically about the central axis of the horn. The first and second side feeds of the single pair of sidewall feeds respectively coupled to the first and second openings. The horn may further include a dielectric member along the central axis of the horn and extending through each of the plurality of transition regions of the flared section. 
     In accordance with the present disclosure, a multi-band antenna may include means for propagating signals in a first frequency band and a second frequency band, means for coupling signals in the first frequency band to the means for propagating in order to propagate signals along a central axis of the means for propagating, means for coupling signals in the second frequency band to first and second openings formed through a sidewall of the means for propagating and arranged asymmetrically about the central axis of the means for propagating. The means for coupling may consist of means for feeding first signals in the second frequency band coupled to the first opening and means for feeding second signals in the second frequency band coupled to the second opening, the means for feeding first signals and the means for feeding second signals associated with respective orthogonal polarizations. The multi-band antenna may further include means for reducing off-axis cross-polarization in signals in the first frequency band. 
     In accordance with the present disclosure, a method of designing a multi-band antenna may include selecting dimensions for a first flared section of a horn, including a length dimension and a flare angle. Dimensions may be selected for a second flared section of the horn, including a length dimension and a flare angle. The method may include determining a location on either the first flared section or on the second flared section to form exactly two sidewall feeds and selecting dimensions for a dielectric member to be axially positioned within the horn. The method may include iteratively adjusting the dimensions of the first flared section and the second flared section until a beamwidth of a signal in a first frequency band is approximately equal to a first predetermined beamwidth and a beamwidth of a signal in a second frequency band is approximately equal to a second predetermined beamwidth and iteratively adjusting dimensions of the dielectric member until a cross-polarization of the signal in the first frequency band is less than or equal to a predetermined cross-polarization value. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       With respect to the discussion to follow and in particular to the drawings, it is stressed that the particulars shown represent examples for purposes of illustrative discussion, and are presented in the cause of providing a description of principles and conceptual aspects of the present disclosure. In this regard, no attempt is made to show implementation details beyond what is needed for a fundamental understanding of the present disclosure. The discussion to follow, in conjunction with the drawings, makes apparent to those of skill in the art how embodiments in accordance with the present disclosure may be practiced. In the accompanying drawings: 
         FIG. 1  is a block diagram of a satellite communication system that can be improved by various embodiments of the present disclosure. 
         FIGS. 2A and 2B  depict an illustrative embodiment of a multi-band antenna in accordance with the present disclosure. 
         FIGS. 3 and 3A  show a feed assembly in accordance with various embodiments of the present disclosure. 
         FIGS. 4 and 4A  illustrate details of a feed assembly in accordance with the present disclosure. 
         FIG. 5  shows a cross-sectional view of a feed assembly in accordance with various embodiments of the present disclosure. 
         FIGS. 6, 6A, and 6B  show details of a horn assembly in accordance with the present disclosure. 
         FIGS. 7A, 7B, and 7C  show details of a flared section in accordance with various embodiments of the present disclosure. 
         FIGS. 8A and 8B  show details of dielectric components in accordance with the present disclosure. 
         FIGS. 9A, 9B, and 9C  show details of a side wall waveguide in accordance with various embodiments of the present disclosure. 
         FIGS. 10, 11A, 11B, 11C, and 11D  show details of an in-line feed assembly in accordance with the present disclosure. 
         FIG. 12  shows a configuration of a horn assembly in accordance with the present disclosure coupled to LNBs. 
         FIG. 13  shows a configuration of a horn assembly in accordance with the present disclosure coupled to a quadrature hybrid coupler. 
         FIG. 14  shows a process flow for designing a multi-band antenna in accordance with the present disclosure. 
         FIG. 15  illustrates an example of design system in accordance with the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     In the following description, for purposes of explanation, numerous examples and specific details are set forth in order to provide a thorough understanding of the present disclosure. It will be evident, however, to one skilled in the art that the present disclosure as expressed in the claims may include some or all of the features in these examples, alone or in combination with other features described below, and may further include modifications and equivalents of the features and concepts described herein. 
       FIG. 1  is a diagram of an example satellite communications system  100  that may be improved by systems, methods, and devices of the present disclosure. Satellite communication system  100  includes a network  120  interfaced with one or more gateway terminals  115 . Gateway terminal  115  may be configured to communicate with one or more user terminals  130  via satellite  105 . As used herein the term “communicate” may refer to both transmitting and receiving (i.e., bidirectional communication) or may refer to either transmitting or receiving (i.e., unidirectional communication) over a particular pathway. 
     Gateway terminal  115  may be referred to herein as the hub or ground station. Gateway terminal  115  may service uplink  135  and downlink  140  to and from satellite  105 . Gateway terminal  115  may also schedule traffic to user terminals  130 . Alternatively, the scheduling may be performed in other parts of satellite communication system  100 . Communication links between gateway terminal  115  and satellite  105  may use the same, overlapping, or different frequencies as communication links between satellite  105  and user terminals  130 . Gateway terminal  115  may also be located remotely from user terminals  130  to enable frequency reuse. By separating the gateway terminal  115  and user terminals  130 , spot beams with common frequency bands can be geographically separated to avoid interference. 
     Network  120  may be any type of network and can include for example, the Internet, an IP network, an intranet, a wide area network (WAN), a local area network (LAN), a virtual private network (VPN), a virtual LAN (VLAN), a fiber optic network, a cable network, a public switched telephone network (PSTN), a public switched data network (PSDN), a public land mobile network, and/or any other type of network supporting communications between devices as described herein. Network  120  may include both wired and wireless connections as well as optical links. Network  120  may connect gateway terminal  115  with other gateway terminals that may be in communication with satellite  105  or with other satellites. 
     Gateway terminal  115  may be provided as an interface between network  120  and satellite  105 . Gateway terminal  115  may be configured to receive data and information directed to one or more user terminals  130 . Gateway terminal  115  may format the data and information for delivery to respective terminals  130 . Similarly gateway terminal  115  may be configured to receive signals from satellite  105  (e.g., from one or more user terminals  130 ) directed to a destination accessible via network  120 . In some embodiments, gateway terminal  115  may also format the received signals for transmission on network  120 . In some embodiments, gateway terminal  115  may use antenna  110  to transmit forward uplink signal  135  to satellite  105 . Antenna  110  may comprise a reflector with high directivity in the direction of satellite  105  and low directivity in other directions. Antenna  110  may comprise a variety of alternative configurations which include operating characteristics such as high isolation between orthogonal polarizations, high-efficiency in the operational frequency band, low noise, and the like. 
     Satellite  105  may be a geostationary satellite that is configured to receive forward uplink signals  135  from the location of antenna  110  using a reflector antenna. Satellite  105  may receive the signals  135  from gateway terminal  115  and forward corresponding downlink signals  150  to one or more of user terminals  130 . The signals may be passed through a transmit reflector antenna (e.g., reflector antenna) to form the transmission radiation pattern (e.g., a spot beam). Satellite  105  may operate in multiple spot beam mode, transmitting and receiving a number of narrow beams directed to different regions on the earth. This allows for segregation of user terminals  130  into various narrow beams. Alternatively, the satellite  105  may operate in wide area coverage beam mode, transmitting one or more wide area coverage beams to multiple receiving user terminals  130  simultaneously. 
     Satellite  105  may be configured as a “bent pipe” or relay satellite. In this configuration, satellite  105  may perform frequency and polarization conversion of the received carrier signals before retransmission of the signals to their destination. A spot beam may use a single carrier, i.e. one frequency, or a contiguous frequency range per beam. In various embodiments, the spot or area coverage beams may use wideband frequency spectra. A variety of physical layer transmission modulation encoding techniques may be used by satellite  105  (e.g., adaptive coding and modulation). Satellite  105  may use on-board beamforming techniques or rely on off-board (ground based) beamforming techniques. 
     Satellite communication system  100  may use a number of network architectures consisting of space and ground segments. The space segment may include one or more satellites  105  while the ground segment may include one or more user terminals  130 , gateway terminals  115 , network operation centers (NOCs) and satellite and gateway terminal command centers. The terminals may be connected by a mesh network, a star network, or the like as would be evident to those skilled in the art. 
     Forward downlink signals  150  may be transmitted from satellite  105  to one or more user terminals  130 . User terminals  130  may receive downlink signals  150  using antennas  127 . In one embodiment, for example, antenna  127  and user terminal  130  together comprise a very small aperture terminal (VSAT), with antenna  127  measuring approximately 0.6 m in diameter and having approximately 2 W of power. In other embodiments, a variety of other types of antenna  127 , including PAFR antennas, may be used as user terminals  130  to receive downlink signals  150  from satellite  105 . Each of the user terminals  130  may comprise a single user terminal or, alternatively, may comprise a hub or router, not shown, that is coupled to multiple user terminals. Each user terminal  130  may be connected to various consumer electronics comprising, for example, computers, local area networks, Internet appliances, wireless networks, and the like. 
     In some embodiments, a multi-frequency time division multiple access (MF-TDMA) scheme may be used for upstream links  140  and  145 , allowing efficient streaming of traffic while maintaining flexibility and allocating capacity among each of the user terminals  130 . In these embodiments, a number of frequency channels may be allocated statically or dynamically. A time division multiple access (TDMA) scheme may also be employed in each frequency channel. In this scheme, each frequency channel may be divided into several timeslots that can be assigned to a connection (i.e., a user terminal  130 ). In other embodiments, one or more of the upstream links  140 ,  145  may be configured using other schemes, such as frequency division multiple access (FDMA), orthogonal frequency division multiple access (OFDMA), code division multiple access (CDMA), or any number of hybrid or other schemes known in the art. 
     User terminal  130  may transmit data and information to a network  120  destination via satellite  105 . User terminal  130  may transmit the signals by upstream link  145  to satellite  105  using antenna  127 . User terminal  130  may transmit the signals according to various physical layer transmission modulation encoding techniques, including for example, those defined with the DVB-S2, WiMAX, LTE, and DOCSIS standards. In various embodiments, the physical layer techniques may be the same for each of the links  135 ,  140 ,  145 ,  150 , or they may be different. 
     Satellite  105  may support non-processed, bent pipe architectures with one or more reflector antennas as described herein to produce multiple small spot beam patterns. The satellite  105  can include J generic pathways, each of which can be allocated as a forward pathway or a return pathway at any instant of time. Large reflectors may be illuminated by a phased array of feeds to provide the ability to make arbitrary spot and area coverage beam patterns within the constraints set by the size of the reflector and the number and placement of the feeds. Reflector antennas may be employed for both receiving uplink signals  130 ,  140 , transmitting downlink signals  140 ,  150 , or both in a full duplex mode. The beam forming networks (BFN) associated with the receive (Rx) and transmit (Tx) reflector antennas may be dynamic, allowing for quick movement of the locations of both the Tx and Rx beams. The dynamic BFN may be used to quickly hop both Tx and Rx wideband beam positions. 
     In some embodiments, satellite communication system  100  may include co-located satellites  105 ,  105   a . As used herein, the term “co-located” may refer to a separation angle between satellites  105 ,  105   a  to be about 1° or less. Stated another way, satellites  105 ,  105   a  may be deemed co-located if the angle of separation is small enough that the beam width of the signal in an upstream link (e.g.,  145 - 1 ,  145 - 1   a ) from user terminal  130  can cover both satellites  105 ,  105   a.    
     Each satellite  105 ,  105   a  may communicate with the same or different gateway terminals  115 ,  115   a  using respective antennas  110 ,  110   a  via respective upstream links  135 ,  135   a  and respective downstream links  140 ,  140   a . For example, satellites  105 ,  105   a  may be operated by different communication providers, having their own infrastructure. Similarly, satellites  105 ,  105   a  may communicate with user terminal  130 , each on its own frequency or multiple frequencies. For example, satellite  105  may communicate with user terminal  130 - 1  via upstream link  145 - 1  and downstream link  150 - 1 , and satellite  105   a  may communicate with user terminal  130 - 1  via upstream link  145 - 1   a  and downstream link  150 - 1   a.    
     In accordance with the present disclosure, each user terminal  130  may transmit and receive signals using an antenna  132  having a multi-band feed design (a multi-band antenna). This aspect of the present disclosure will be discussed in more detail below. 
     Referring to  FIGS. 2A and 2B , a multi-band antenna  232  in accordance with the present disclosure may comprise a reflector  202  and a feed assembly  204 . The transceiver/feed assembly  204  may be held in position relative to the reflector  202  by a support boom  206 . The multi-band antenna  232  may further include a mounting bracket  208  to mount the antenna  232  to structure (e.g. a house) associated with a user terminal (e.g.,  130 ,  FIG. 1 ). In some embodiments, the multi-band antenna  232  may be configured as a primary offset fed antenna. For example, the transceiver/feed assembly  204  may directly illuminate the reflector  202  along a direction  214  that is off-axis relative to an axis  212  of the reflector  202 . 
     Referring to  FIGS. 3 and 3A , in some embodiments, the transceiver/feed assembly  204  component of the multi-band antenna  232  ( FIG. 2A ) may include a transceiver module  302 . The transceiver module  302  may provide signals for transmission, e.g., from a user terminal (e.g.,  130 ,  FIG. 1 ), to satellite  105  or co-located satellites  105 ,  105   a  ( FIG. 1 ). The transceiver module  302  may also receive signals from satellite  105  or co-located satellites  105 ,  105   a . The transceiver module  302  may amplify and downconvert the received signals to be processed by the user terminal. The transceiver/feed assembly  204  may further include means for propagating signals in a first frequency band and a second frequency band and means for coupling signals to the means for propagating. In some embodiments, for example, the transceiver/feed assembly  204  may include a horn assembly  304  and an in-line feed assembly  306 . The in-line feed assembly  306  may couple signals between the transceiver module  302  and the horn assembly  304 , including signals to be transmitted to, received from, or otherwise communicated with satellite  105  or co-located satellites  105 ,  105   a  ( FIG. 1 ). 
     In accordance with the present disclosure, the horn assembly  304  may include means for coupling signals in the second frequency band to first and second openings formed through a sidewall of the horn assembly  304 . In some embodiments, for example, the horn assembly  304  may include a first side opening (port)  422   a  (first means for feeding signals) and a second side opening  422   b  (second means for feeding signals), as illustrated in  FIG. 3A  for example. The first and second side openings  422   a ,  422   b  may be slotted openings formed through the horn assembly  304 . As will be explained in more detail below, waveguides (not shown) may be coupled to the first and second side openings  422   a ,  422   b  of the horn assembly  304  to facilitate reception and/or transmission of signals in different frequency band than the signals communicated via the in-line feed assembly  306 . 
     In some embodiments, the transceiver module  302  may be configured to communicate first signals in a first frequency band. In some embodiments, for example, the first signals may be in the K band, the Ka band, the K and Ka band, etc. Accordingly, in accordance with the present disclosure, the horn assembly  304  may be configured for simultaneous communication in multiple bands. In some embodiments, for example, the horn assembly  304  may propagate first signals in the K band, the Ka band, the K and Ka band. The signals may have dual circular polarization. In other embodiments, the horn assembly  304  may simultaneously propagate the first signals with second signals in a second frequency band lower than the first frequency band. In some embodiments, for example, the second signals may be in the Ku band. As will be explained, in some embodiments, the second signals may propagate through the first and second side openings  422   a ,  422   b  of the horn assembly  304 . In some embodiments, signals in the second frequency band may have dual linear polarization. In other embodiments, signals in the second frequency band may have dual circular polarization. 
       FIG. 4  shows a perspective side view of the horn assembly  304  and in-line feed assembly  306  with illustrative first and second sidewall waveguides (feeds)  42   a ,  42   b  attached to the horn assembly  304 . In accordance with the present disclosure, the first and second side openings  422   a ,  422   b  shown in  FIG. 3A  may be coupled to respective first and second sidewall waveguides  42   a ,  42   b . In some embodiments, the first and second sidewall waveguides  42   a ,  42   b  may correspond to pathways for vertically polarized and horizontally polarized Ku band signals, respectively. 
       FIG. 4  further shows a longitudinal central axis  40  defined along a long axis of the horn assembly  304 . The central axis  40  may define the direction  214  of illumination of the feed assembly  204  illustrated in  FIG. 2B . An XYZ coordinate system provides a spatial reference for the cross-sectional view taken along view lines  5 - 5 , which will be described below in connection with  FIG. 5 . 
       FIG. 4A  depicts an exploded view of the horn assembly  304 , showing various components of the horn assembly  304  in accordance with embodiments of the present disclosure. The horn assembly  304  may include a flared section  402 . The horn assembly  304  may include means for reducing off-axis cross-polarization; in some embodiments, for example, a dielectric member  404  may be incorporated within an interior volume (cavity, space, etc.) of the flared section  402  along the central axis  40 . A support member  406  may support the dielectric member  404  within the flared section  402 . A cover (radome)  408  may serve as a close-out to protect the interior volume of the flared section  402  from environmental contaminants such as dust, moisture, and the like. A bezel  410  may snap on, screw on, or otherwise attach to the flared section  402  to hold the cover  408  in place. In other embodiments, additional sealing material (not shown) may be included to further seal off the interior volume of the flared section  402  from environmental contaminants. 
     In some embodiments, the bezel  410  may be a plastic material or other suitably flexible material to allow a snap fit attachment to the flared section  402 . For example, the bezel  410  shown in the inset in  FIG. 4A  may include ridges  410   a  configured to clip onto a flange  402   a  of the flared section  402  for a secure fit. In other embodiments, the bezel  410  may be threaded (not shown) and screwed onto matching threads (not shown) formed on the flange  402   a  of the flared section  402 . In other embodiments, the bezel  410  may be glued in place, and so on. 
     The cover  408  may be any dielectric material (e.g., a polycarbonate plastic) that is transparent to electromagnetic (EM) radiation in the frequency bands (e.g., K, Ka, Ku bands) used to communicate with the satellite  105  or co-located satellites  105 ,  105   a  ( FIG. 1 ). In a particular embodiment, for example, the cover  408  may be a Lexan™ plastic disk having a thickness of about 9-10 mils. In other embodiments, the cover  408  may be formed from other materials. In some embodiments, the cover  408  may be adhesively bonded to the face of flange  402   a . The cover  408  may further be adhesively bonded to the front face (e.g.,  804 ,  FIG. 8A ) of the support member  406 , and to one end of the dielectric member  404 . 
     The dielectric member  404  may help to reduce off-axis cross-polarization in the signals. In some embodiments, the dielectric member  404  may help to confine propagation of signals in the K/Ka band along the central axis  40 . By confining the K/Ka band signals along the central axis  40 , such signals may be less perturbed by the first and second side openings  422   a ,  422   b.    
     Typically, the beam width of the K/Ka band signals that radiate from radiating aperture  402   c  can be influenced by factors such as the size of the radiating aperture  402   c  and the flare angle at the aperture. The dielectric member  404  may reduce the influence of such factors and provide more control of the beam width of the K/Ka band signals than without the dielectric member  404 . 
     The support member  406  may be disposed within a portion of the interior volume in the flared section  402 . As will be explained in more detail below, the support member  406  may be configured to support the dielectric member  404  along the central axis  40 . 
     In accordance with some embodiments, the first and second side openings  422   a ,  422   b  may be formed through the flared section  402 . The flared section  402  may include an in-line opening (throat of the horn)  424  for communication of signals between the horn assembly  304  and the in-line feed assembly  306 . Alignment pins  478  may be provided on a rear flange  402   b  of the flared section  402  to facilitate alignment of a horn-side opening  502  ( FIG. 5 ) on the in-line feed assembly  306  to the in-line opening  424  of the flared section  402 . 
       FIG. 5  illustrates a cross-sectional view of the horn assembly  304  and in-line feed assembly  306  taken along view line  5 - 5  shown in  FIG. 4 . The flared section  402  may include segments (sections)  452 ,  454 ,  456 . In accordance with the present disclosure, each segment  452 - 456  may have a different flare angle. This aspect of the present disclosure will be discussed below. 
     The figure shows that in some embodiments the support member  406  may be shaped for a snug fit within the interior volume defined by segment  456  of the flared section  402 . The support member  406  may extend to a radiating aperture  402   c  of the flared section  402 . The bezel  410  may press the cover  408  against the support member  406  and flange  402   a  to further seal off the external environment. 
     A portion of the dielectric member  404  may be disposed within, and thereby supported by, the support member  406 . The dielectric member  404  may extend the length of the flared section  402 , spanning between one end of the flared section  402  at the radiating aperture  402   c  and another end of the flared section  402  at the in-line opening  424 , along the central axis  40 . The remaining length of dielectric member  404  may be suspended in the interior volumes of segments  454 ,  452 , unsupported by any structure. 
     The cross-sectional view of the in-line feed assembly  306  shows a transceiver-side opening  504  that can interface with a transceiver (e.g., transceiver module  302 ,  FIG. 3 ). A horn-side opening  502  can interface with the horn assembly  304 . More particularly, the horn-side opening  502  may align with the in-line opening  424 ; for example, facilitated by alignment pins  478  shown in  FIG. 4A . In some embodiments, the in-line feed assembly  306  may be a polarizer that includes a septum polarizer  506  disposed along the central axis  40 . Additional detail of the in-line feed assembly  306  is disclosed below. 
     The cross-sectional view shows the sidewall waveguide  42   a  may include a filter section  52  and an H-bend  54  to connect the filter section  52  to a stepped transition region  56 . The filter section  52  may have an opening that matches the dimensions of the first side opening  422   a.    
     In some embodiments, the sidewall waveguides  42   a ,  42   b  may be configured to propagate signals in the Ku band. However, the horn assembly  304  may propagate signals in the K and/or Ka band simultaneously with signals in the Ku band. Accordingly, in some embodiments, filter section  52  in each of the sidewall waveguides  42   a ,  42   b  may be configured as a low-pass waveguide filter to reject signals in the higher first frequency band (e.g., K and/or Ka bands). In other embodiments, the filter section  52  may be a band-pass type or a low-pass type filter. 
     An H-bend  54  may provide a suitable pathway for the signals between the horn assembly  304  and a terminal (e.g.,  130 ,  FIG. 1 ) connected to the horn assembly  304 . In given embodiment, additional H-bends and/or E-bends (not shown) may be required to properly route the signal. The H-bend  54  may guide signals from the filter section  52  to the stepped transition region  56 . In some embodiments, for example, side openings  422   a ,  422   b  may be smaller than standard waveguide dimensions. Accordingly, the stepped transition region  56  may be used to gradually increases the waveguide dimensions to a standard sized waveguide coupled to opening  58 . 
       FIG. 6  shows a perspective view of the configuration shown in  FIG. 4 . The view is a front-facing perspective view looking into the flared section  402  with the bezel  410  and support member  408  omitted. The figure illustrates the relative orientation of dielectric member  404  within the interior volume of the flared section  402 . 
     In accordance with embodiments of the present disclosure, the first and second side openings  422   a ,  422   b  may be asymmetrically radially arranged about the central axis  40 . In other words, the first and second side openings  422   a ,  422   b  may be at an angle other than 180° relative to each other about the central axis  40 . The embodiment shown in  FIG. 6 , for example, shows that the first and second side openings  422   a ,  422   b  are 90° relative to each other about the central axis  40 .  FIGS. 6A and 6B  illustrate that the side openings  422   a ,  422   b  may be formed on the flared section  402  at different radial orientations about the central axis  40  relative to the in-line feed assembly  306 . 
       FIGS. 7A, 7B, and 7C  depict various views of the flared section  402 , showing additional details of the flared section  402  in accordance with the present disclosure. In some embodiments, the flared section  402  may be a single cast part of suitable material, such as aluminum, alloys of aluminum, zinc, alloys of zinc, etc. In accordance with the present disclosure, each segment  452 ,  454 ,  456  of the flared section  402  may have respective smooth interior surfaces (walls)  702 ,  704 ,  706 , as represented for example in  FIGS. 7A and 7C . A single cast part can enable high-volume low-cost manufacturing methods. 
       FIG. 7B  shows additional details of the first and second side openings  422   a ,  422   b . In some embodiments, for example, surfaces  472   a ,  472   b  may be cut, machined, or otherwise formed into the exterior surface of the flared section  402 . The first and second side openings  422   a ,  422   b  may be formed through respective surfaces  472   a ,  472   b  of the flared section  402  to the interior volume of the flared section  402 . In some embodiments, alignment holes  474   a ,  474   b  may be drilled into respective surfaces  472   a ,  472   b . The alignment holes  474   a ,  474   b  may facilitate the alignment of respective sidewall waveguides  42   a ,  42   b  (e.g.,  FIG. 4A ) to respective first and second side openings  422   a ,  422   b . In some embodiments, screw holes  476   a ,  476   b  may be provided to secure the respective sidewall waveguides  42   a ,  42   b  to the flared section  402 . In other embodiments, the sidewall waveguides  42   a ,  42   b  may be welded (e.g., braze welding) onto the flared section  402 . 
     The rear flange  402   b  may include alignment pins  478   a ,  478   b  to facilitate alignment of the horn-side opening  502  ( FIG. 5 ) of the in-line feed assembly  306  to the in-line opening  424  of the flared section  402 . In some embodiments, screw holes  480  may be drilled into the rear flange  402   b  to secure the in-line feed assembly  306  ( FIG. 5 ) to the flared section  402 . 
     The cutaway view shown in  FIG. 7C  is obtained by rotating the flared section  402  in the direction shown in  FIG. 7B  so that the first side opening  422   a  is shown in cross section. The cross-sectional view shows the segments  452 ,  454 ,  456  that comprise the flared section  402 . In accordance with the present disclosure, each segment  452 - 456  may be characterized as a truncated cone having a vertex angle, referred herein as the flare angle, that is different from the other segments. In some embodiments, the segment  452  may be cylindrical having a flare angle of 0°. The segment  454  may have a flare angle represented by θ 1 , and segment  456  may have a flare angle represented by θ 2  (≠θ 1 ). In other embodiments, the flared section  402  may include additional segments (not shown) with different flare angles. 
     In various embodiments, the number of segments (e.g.,  452 - 456 ) and the flare angles (e.g., θ 1 , θ 2 ) may be varied to achieve different degrees of compactness of the flared section  402 , and hence the horn assembly  304  (e.g.,  FIG. 5 ). For example, having two segments (e.g.,  454 ,  456 ) and wide flare angles (θ 1 , θ 2 ) allows for a compact design; e.g., a length L of the flared section  402  that is smaller than found in conventional designs. The flare angles θ 1 , θ 2  between segments  454  and  456  define a first transition region  712  between a first input diameter d 1  at the in-line opening  424  and a second intermediate diameter d 2 , and a second transition region  714  between the second intermediate diameter d 2  and a third output diameter d 3  at the radiating aperture  402   c  of the flared section  402 . In some embodiments, the length L of the flared section  402  (e.g., the sum of L 1  and L 2 ) may be less than twice the output diameter d 3  at the radiating aperture  402   c  of the horn. 
     In some embodiments, the first and second side openings  422   a ,  422   b  may be formed in first transition region  712 . The first and second side openings  422   a ,  422   b  may be axially aligned at the same axial position along the central axis  40 . The axial position of the first and second side openings  422   a ,  422   b , for example, may be defined as a position on the central axis  40  with respect to a line  72  passing through the respective centers of the first and second side openings  422   a ,  422   b . The axial position may depend on the frequency band of the signals that pass through the first and second side openings  422   a ,  422   b , the number of segments (e.g., 454, 456), and the flare angles (e.g., θ 1 , θ 2 ). 
       FIGS. 8A and 8B  show additional details of dielectric member  404  and support member  406  shown in  FIG. 4A . In some embodiments, for example, the dielectric member  404  may have a tapered rod-shaped structure. The particular embodiment depicted in  FIGS. 8A and 8B  show a single taper. However, it will be appreciated that in other embodiments, the dielectric member  404  may have two or more sections having tapers with different angles. 
     A core  802  may be provided through the support member  406  along the central axis  40 . The core  802  may have a tapered profile that corresponds to the taper of the dielectric member  404 . The dielectric member  404  may be inserted into the core  802  through the front face  804  of the support member  406 . 
     The tapers in the core  802  and in the dielectric member  404  may be dimensioned so that the front face  808  of the dielectric member  404  can self-align flush with the front face  804  of the support member  406 . The portion of the dielectric member  404  within the core  802  can securely align the axis of dielectric member  404  with the central axis  40 . The portion of the dielectric member  404  that extends beyond the rear face  806  of the support member  406  can therefore be supported along the central axis  40  within the interior volume of segments  454 ,  452  of the flared section  402 , without additional supporting structure as shown in  FIG. 5 . 
     In some embodiments, the tapers in the core  802  and in the dielectric member  404  may also provide a friction fit to secure the dielectric member  404  in the support member  406  without the use of adhesives or other bonding agents. In other embodiments, a suitable adhesive may be used to secure the dielectric member  404  in support member  406 . 
     The dielectric member  404  may be formed from any suitable dielectric material. In some embodiments, for example, a Rexolite® or Ultem® plastic may be used. In general, the dielectric member  404  may comprise any material or combination of materials having suitable dielectric properties, mechanical properties, and thermal properties. The support member  406  may be a low-loss, low-dielectric constant, closed-cell foam material. In various embodiments, the support member  406  may be produced in a shape that corresponds to one or more of the segments (e.g.,  452 - 456 ,  FIG. 5 ) that comprise the flared section  402  ( FIG. 5 ). 
       FIGS. 9A, 9B, and 9C  show additional details of the first and second sidewall waveguides  42   a ,  42   b , shown in  FIG. 4  for example. Each sidewall waveguide (feed)  900  may include a opening  902 . The sidewall waveguide  900  may include alignment pins  906  that may line up with alignment holes (e.g.,  474   a ,  FIG. 7B ) on the flared section  402  (e.g.,  FIG. 7B ), to facilitate aligning the opening  902  to the side opening (e.g.,  422   a ,  FIG. 7B ) of the flared section  402 . 
     The sidewall waveguide  900  may comprise two waveguide halves  904   a ,  904   b . The opening  902  may be defined by a notched  902   a  formed in each waveguide half  904   a ,  904   b . The opening  58  (e.g.,  FIG. 5 ) may similarly be defined by a notch  906  formed at a base of each waveguide half  904   a ,  904   b . The side view of waveguide half  904   a  shown in  FIG. 9C  illustrates an example of the filter section  52 , the H-bend  56 , and the stepped transition region  56  described above. 
       FIGS. 10, 11A, 11B, 11C, and 11D  show additional details of the in-line feed assembly  306 , shown in  FIG. 4  for example. As mentioned above and with reference to  FIG. 10 , the horn-side opening  502  on the in-line feed assembly  306  may interface with the in-line opening  424  on the horn assembly  304 . 
     With reference to  FIGS. 11A-11D , in some embodiments, the in-line feed assembly  306  may be a polarizer. In a some embodiments, for example, the in-line feed assembly  306  may include waveguide housing  512  defined by a first part  512   a  and a second part  512   b . The in-line feed assembly  306  may further include a dual-band K/Ka band septum polarizer  506  that is sandwiched between the first and second parts  512   a ,  512   b  of the waveguide housing  512 . The septum polarizer  506  may define a common waveguide  514  and divided waveguides  516   a ,  516   b  within the waveguide housing  512 . The common waveguide  514  may terminate at the horn-side opening  502  of the in-line feed assembly  306 . 
     The septum polarizer  506  may divide the common waveguide  514  into divided waveguides  516   a ,  516   b  that terminate at the transceiver-side opening  504  of the in-line feed assembly  306 . In some embodiments, for example, each divided waveguide  516   a ,  516   b  may carry a signal that corresponds to right hand circular polarization or left hand circular polarization in the common waveguide  514 . 
     The exploded views of the in-line feed assembly  306  depicted in  FIGS. 11C and 11D  show that the horn-side opening  502  and the transceiver-side opening  504  can be defined in each of the first and second parts  512   a ,  512   b  of the waveguide housing  512 . For example, the horn-side opening  502  may be defined by portions  502   a ,  502   b  notched out of the front faces respectively of the first and second parts  512   a ,  512   b  of the waveguide housing  512 . Likewise, the transceiver-side opening  504  may be defined by portions  504   a ,  504   b  notched out of the rear faces respectively of the first and second parts  512   a ,  512   b  of the waveguide housing  512 . 
     It will be appreciated that in accordance with the present disclosure, the in-line feed assembly  306  is not restricted to circular polarization. In some embodiments, for example, the in-line feed assembly  306  may omit the septum polarizer  506  for linearly polarized signals, namely horizontal linear polarization or vertical linear polarization. 
     Referring to  FIG. 12 , in accordance with embodiments of the present disclosure, the waveguide pathways in side openings (e.g.,  422   a ,  422   b ,  FIG. 3A ) of horn assembly  304  can support two orthogonal linear polarizations, for example, in the Ku band.  FIG. 12 , for example, shows low-noise block downconverters (LNBs)  1202 ,  1204  to propagate linear polarized signal. Each LNB  1202 ,  1204  may connect to side openings (e.g.,  422   a ,  422   b ,  FIG. 3A ) of the horn assembly  304  using respective waveguide sections  1212 ,  1214 . In other embodiments, any suitable amplifier and downconverter module may be connected the side openings (e.g.,  422   a ,  422   b ,  FIG. 3A ) to provide dual-linear polarized operation. 
     In some embodiments, the waveguide sections  1212 ,  1214  may be integral with their respective LNB feeds  1202 ,  1204 . In other embodiments, the waveguide sections  1212 ,  1214  may be separate components from LNBs  1202 ,  1204 . Each LNB  1202 ,  1204  may include a respective coaxial connector  1222 ,  1224  for connecting to a terminal device (not shown). LNB  1202  can provide a linear polarized signal to its respective side opening (e.g.,  422   a ,  FIG. 3A ) on the horn assembly  304 , and likewise, LNB  1204  can provide an orthogonal linear polarized signal to its respective side opening (e.g.,  422   b ,  FIG. 3A ) on the horn assembly  304 . 
     Referring to  FIG. 13 , in some embodiments, the horn assembly  304  may be coupled to a quadrature hybrid coupler  1302  to convert between dual-circular polarization and dual-linear polarization, for example, in the Ku band. The quadrature hybrid coupler  1302  may include two waveguide couplers  1312 ,  1324  to couple to respective side openings (e.g.,  422   a ,  422   b ,  FIG. 3A ) of the horn assembly  304 . The quadrature hybrid coupler  1302  may include coax connectors  1322 ,  1324  for connection to a terminal (not shown). 
     In some embodiments such as shown in  FIG. 13 , the horn assembly  304  may use a 4 dB (unequal amplitude) quadrature hybrid coupler  1302  rather than the more common 3 dB (equal amplitude) quadrature hybrid coupler. The 4 dB coupler  1302  (or other non-3 dB coupler) may optimize Ku band cross-polarization discrimination performance that may result from the two side opening arrangement (e.g.,  422   a ,  422   b ,  FIG. 3A ) of the horn assembly  304 . 
     Referring to  FIG. 14 , a process for designing a multi-band antenna (e.g.,  232 ,  FIG. 2A ) in accordance with the present disclosure will be discussed. The design process may include the design for a horn assembly (e.g.,  304 ,  FIG. 3A ). In some embodiments, the process may be performed using suitable simulation tools. The horn assembly may be designed using, for example, the High Frequency Structure Simulator (HFSS) software available from Ansys, Inc. It will be appreciated that other simulation software may be used. The process will be explained with respect to the horn assembly illustrated in  FIGS. 7C and 8A  as examples. 
     At block  1402 , a first flared section (e.g.,  454 ) of a flared member (e.g.,  402 ) of the horn assembly may be designed, for example, by selecting an initial length dimension L 1  and a flare angle θ 1  measured relative to a central axis  40 . The flare angle may be defined by selecting sizes for the openings (e.g., d 1 , d 2 ) of the first flared section. As noted above, in accordance with some embodiments, of the present disclosure, signals in a first frequency band (e.g., K band, Ka band) may propagate along the central axis of the horn, while signals in a second frequency band lower that the first frequency band (e.g., Ku band) may propagate through sidewalls in the horn. Accordingly, in some embodiments, the opening d 1  at the throat (e.g.,  424 ) of the horn may be small enough to cut off propagation of signals in the second frequency band so that they do not propagate all the way through the throat. 
     At block  1404 , the design for a second flared section (e.g.,  456 ) of the flared member may include selecting an initial length dimension L 2  and a flare angle θ 2  measured relative to the central axis  40 . In some embodiments, one opening of the second flared section may be fixed by the opening d 2  in first flared section. Accordingly, the flare angle in the second flared section may be defined by selecting a size for the other opening (e.g., d 3 ) of the second flared section. 
     At block  1406 , design parameters may be selected for the sidewall openings (e.g.,  422   a ,  422   b ). The sidewall openings may be formed in the first or second flared sections. In accordance with the present disclosure, the sidewall openings may be asymmetrically arranged about the central axis  40 . In some embodiments, for example, the sidewall openings may be 90° apart. Design parameters for the sidewall openings may include their axial position, the axial length of the opening and the width of the openings. These parameters may depend considerations such as the size of the feeds used with the horn assembly, and the like. 
     At block  1408 , initial dimensions for a dielectric member (e.g.,  404 ) may be selected. The length (e.g., L 3 ) of the dielectric member may be determined by the lengths of the first and second flared sections described above. The cross-sectional design of the dielectric member may be defined by selecting diameters (e.g., d 3 , d 4 ) at the ends of the dielectric member. 
     At block  1410 , simulations of the horn may be performed using the selected design parameters. In some embodiments, for example, simulations may be run for signals in a first frequency band and signals in a second frequency band. In particular, respective beamwidth metrics for the first and second signals to a simulated target (e.g., a satellite) may be determined from the simulations. For example, a first beamwidth metric may be computed or otherwise determined for a first beam across a first frequency band. Likewise, a second beamwidth metric for a second beam across a second frequency band may be computed or otherwise determined. In some embodiments, several beamwidth metrics for the first beam may be computed or otherwise determined at each of several beam angles, and likewise for the second beam. 
     At block  1412 , simulations may be performed to determine a cross-polarization metric of the first beam and the second beam along the central axis through the length of the horn, between the throat (e.g.,  424 ) of the horn and the aperture (e.g.,  402   c ) of the horn. In some embodiments, a cross-polarization metric may be computed or otherwise determined at each of several beam angles. 
     At block  1414 , the metrics obtained at blocks  1410  and  1412  may be assessed against various criteria, for example, to assess a performance of the horn design. In some embodiments, for example, the first and second beamwidth metrics (block  1410 ) may be compared against criteria such as predetermined targets. A passing criterion, for example, may be that the first beamwidth metric is equal to a first predetermined beamwidth target, or at least falls within a range (e.g., +/− percentage) of the first predetermined beamwidth target. Likewise, a passing criterion for the second beamwidth, may be that the second beamwidth metric is equal to a second predetermined beamwidth target or at least falls within a range (e.g., +/− percentage) of the second predetermined beamwidth target. 
     In some embodiments, where several first and second beamwidth metrics are determined at different beam angles, each of the first beamwidth metrics and the second beamwidth metrics may be assessed against the respective first predetermined beamwidth target and second predetermined beamwidth target. In other embodiments, a beamwidth targets may be defined for each beam angle. 
     Likewise, a particular target value of cross-polarization may be used to assess cross-polarization performance of the dielectric member design. In some embodiments, for example, the cross-polarization target value may be met if the cross-polarization metric determined at  1412  is less than or equal to the cross-polarization target value. 
     In some embodiments, where a cross-polarization is determined for different beam angles, a particular target value of cross-polarization may be defined for each beam angle. A passing criterion may be that the cross-polarization metric is less than or equal to the cross-polarization target value at each of the beam angles. 
     If the criteria at block  1414  are met, then the design process may be deemed completed. If the criteria are not met, then processing may proceed to blocks  1416  and  1418 . For example, at block  1416  the design parameters (e.g., length, flare angle) for the first and second flared sections may be adjusted. The design parameters may be adjusted in several ways with each iteration. In some embodiments, for example, the dimensions for both flared sections may be adjusted with each iteration. In other embodiments, the dimensions for one flared section may be adjusted in a series of iterations until the criteria for that flared section are met, and then adjusting the dimensions for the other flared section in a second series of iterations. In still other embodiments, the design parameters may be changed in other ways with each iteration. 
     Similarly at block  1418 , the design of the dielectric member may be adjusted and processing may proceed to block  1410  for another iteration of the design process. For example, the diameter at either or both ends of the dielectric member may be changed with each iteration in the design process. 
     Referring to  FIG. 15 , an illustrative implementation of a design system to facilitate the design of a multi-band antenna (e.g.,  232 ,  FIG. 2A ), and in particular the horn assembly (e.g.,  304 ,  FIG. 3A ) may include a computer system  1502  having a processing unit  1512 , a system memory  1514 , and a system bus  1511 . The system bus  1511  may connect various system components including, but not limited to, the processing unit  1512 , the system memory  1514 , an internal data storage device  1516 , and a communication interface  1513 . 
     The processing unit  1512  may comprise a single-processor configuration, or may be a multi-processor architecture. The system memory  1514  may include read-only memory (ROM) and random access memory (RAM). The internal data storage device  1516  may be an internal hard disk drive (HDD), a magnetic floppy disk drive (FDD, e.g., to read from or write to a removable diskette), an optical disk drive (e.g., for reading a CD-ROM disk, or to read from or write to other high capacity optical media such as the DVD, and so on). 
     The internal data storage device  1516  and its associated non-transitory computer-readable storage media provide nonvolatile storage of data, data structures, computer-executable instructions, and so forth. Although the description of computer-readable media above refers to a HDD, a removable magnetic diskette, and a removable optical media such as a CD or DVD, it is noted that other types of media which are readable by a computer, such as zip drives, magnetic cassettes, flash memory cards, cartridges, and the like, may also be used, and further, that any such media may contain computer-executable instructions for performing the methods disclosed herein. 
     The system memory  1514  and/or the internal data storage device  1516  may store a number of program modules, including an operating system  1532 , one or more application programs  1534 , program data  1536 , and other program/system modules  1538 . For example, the application programs  1534 , which when executed, may cause the computer system  1502  to perform method steps of  FIG. 14 . The application programs  1534  may also include simulation software (e.g., the HFSS software mentioned above). An external data storage device  1542  may be connected to the computer system  1502 , for example, to store the design data for a feed or feed array. 
     Access to the computer system  1502  may be provided by a suitable input device  1544  (e.g., keyboard, mouse, touch pad, etc.) and a suitable output device  1546 , (e.g., display screen). In a configuration where the computer system  1502  is a mobile device, input and output may be provided by a touch sensitive display. 
     The computer system  1502  may operate in a networked environment using logical connections via wired and/or wireless communications to one or more remote computers (not shown) over a communication network  1552 . The communication network  1552  may be a local area network (LAN) and/or larger networks, such as a wide area network (WAN). 
     The above description illustrates various embodiments of the present disclosure along with examples of how aspects of the particular embodiments may be implemented. The above examples should not be deemed to be the only embodiments, and are presented to illustrate the flexibility and advantages of the particular embodiments as defined by the following claims. Based on the above disclosure and the following claims, other arrangements, embodiments, implementations and equivalents may be employed without departing from the scope of the present disclosure as defined by the claims.