Abstract:
The present invention provides an improved single antenna system that allows reception of RF energy at multiple frequencies. In one embodiment, the antenna is implemented as a multi-beam, multi-feed antenna having a primary reflector fitted with a dual mode feed tube and a switchable LNB that supports both Ka band and Ku band reception. In another embodiment, the antenna is implemented as a multi-beam, multi-feed antenna having a primary reflector fitted with a feed horn and a LNB that is capable of providing movement such that the feed horn with the LNB is at a focal point with the primary reflector for both Ka and Ku band reception. In another embodiment, the antennae is implemented as a multi-beam, multi-feed antenna having a primary reflected fitted with a feed horn assembly and a switchable LNB that supports both Ka band and Ku band reception.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention is generally related to the field of satellite communications and antenna systems, and is more specifically directed to multi-feed antenna systems that allow for reception of RF energy from multiple satellites positioned in several orbital slots broadcasting at multiple frequencies. 
       BACKGROUND OF THE INVENTION 
       [0002]    An increasing number of applications require systems that employ a single antenna designed to receive from and/or transmit RF energy to multiple satellites positioned in several orbital slots broadcasting at multiple frequencies. 
         [0003]    On a given single reflector system, a feed (horn or radiating element) is needed for each satellite to be received from (or transmitted to). In cases where the satellites are transmitting different frequency range signals, the antenna dish must change in size and/or shape to reflect enough incident radiated power to a low noise block feed (LNBF) converter such that the signals in different frequency range can be detected and processed by the LNBF. Another option is to provide additional reflector systems to receive and transmit signals of different frequency range. However, both changing the size/and or shape of a single reflector system and/or adding multiple reflector systems at a give location can be difficult and costly. 
         [0004]    Currently, there are few solutions in the art that provide for a single antenna system capable of receiving signals from multiple satellites at different frequencies. One such solution is provided in U.S. Patent Publication No. 2008/0271092 to KVH Industries, Inc., in which an apparatus is provided for controlling a satellite antenna to locate a satellite with a desired frequency signal. 
         [0005]    Thus, there is a need to provide an improved single antenna system that allows for reception of at least three or more RF signals on a moving platform. 
       OBJECTS AND SUMMARY OF THE INVENTION 
       [0006]    One of the objectives of the present invention is to design an antenna that is capable of receiving or transmitting at least three separate RF signals with orthogonal, linear or circular polarization on a moving platform. This is accomplished by moving an antenna to allow Ku and Ka band frequencies to pass to an LNB converter. The systems described herein allow for a near home experience for a mobile DirecTV user. 
         [0007]    In certain embodiments, the present invention is directed to a rear feed antenna system having a dual band Ka/Ku feed with a LNBF assembly having means to switch/move the LNBF between the Ku and Ka LNB ports in the assembly to asynchronously receive Ka, Ku and Ka band signals. An antenna system of this embodiment would comprise, e.g., a primary reflector configured to receive band signals from at least two different satellites; a sub-reflector configured to receive the band signals from the primary reflector; a feed horn assembly configured to receive the band signals from the sub-reflector; a sub-assembly configured to receive and convert the at least two different band signals from the feed horn assembly; and a mechanical actuator configured to align the sub-assembly with the feed horn assembly. 
         [0008]    In other embodiments, the present invention is directed to a prime focus Ka/Ku dual band TV receive only antenna system. An antenna system of this embodiment would comprise, e.g., a primary reflector configured to receive band signals from at least two different satellites; a feed horn assembly comprising a first feed horn and a second feed horn, wherein the first and second feed horns are configured to receive the band signals from the primary reflector; and a sub-assembly configured to receive and convert the at least two different band signals from the feed horn assembly. 
         [0009]    In certain preferred embodiments of the prime focus system, the Ka-band feed horn is maintained directly on the reflector focus and the Ku-band feed horn is displaced from the focus. Thus, the relative position of the Ka/Ku feed horn assembly (LNBF) is fixed with respect to the main reflector. In other preferred embodiments, the feed horn position is moved with respect to the main reflector. 
     
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         [0010]      FIG. 1A  depicts an embodiment of the present invention wherein the antenna system is a rear-focus system. 
           [0011]      FIG. 1B  depicts a side view of the dual-band feed horn and LNB assembly. 
           [0012]      FIG. 1C  depicts the waveguide interface at the dual-band feed horn. 
           [0013]      FIG. 1D  depicts a side view of the dual-band feed horn containing a dielectric rod. 
           [0014]      FIG. 2A  depicts an embodiment of the present invention wherein the antenna system is a prime focus system. 
           [0015]      FIG. 2B  depicts a front view of the antenna shown in  FIG. 2A . 
           [0016]      FIG. 2C  depicts a feed horn assembly containing three feed horns. 
           [0017]      FIG. 3  depicts a flow chart of a mobile satellite communication system implemented to control the movement of the antennas of the present invention. 
           [0018]      FIG. 4A  depicts an alternate embodiment of the present invention wherein the antenna system is a prime focus system. 
           [0019]      FIG. 4B  depicts a rear view of the antenna of  FIG. 4A . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0020]    Rear-Focus Systems 
         [0021]    Certain embodiments of the present invention provide for a rear feed antenna system having a dual band Ka/Ku feed with a LNBF assembly having means to switch/move the LNBF between the Ku and Ka LNB ports in the assembly to asynchronously receive Ka, Ku and Ka band signals, as shown in  FIG. 1A .  FIG. 1A  illustrates schematic view of a rear focus mobile satellite-antenna system  10  installed on a moving platform (not shown) according to one embodiment of the present invention. The antenna system  10  is preferably an axially symmetrical reflector system. The system  10  includes a primary reflector  12  capable of receiving signals directly from the satellites (not shown). The reflector shown in the present embodiment is a near parabola-shaped reflector and is made of metals such as aluminum or steel, or composite materials, such as carbon loaded fiber. The primary reflector  12  includes an opening  12   a  at its front to accommodate a dual-band feed horn  14  extending from the front to the rear of the reflector  12  as shown in  FIG. 1A . The dual-band feed horn  14  is made of aluminum and low loss dielectric material such as, e.g., Rexolite, which is a cross-linked polystyrene, and is connected to the primary reflector  12  preferably via injection molding. As illustrated in  FIG. 1A , the primary reflector  12  is coaxially disposed about the dual-band frequency feed horn  14 . A sub-assembly  16  preferably a low-noise block (LNB) converter assembly is affixed to one end of the feed horn  14  at the rear of the primary reflector  12  as shown. 
         [0022]    The system  10  further includes at least a sub-reflector  18  disposed to face towards the front of the primary reflector  12 . Specifically, the front surface of the sub-reflector  18  includes a reflecting surface facing the front surface of the primary reflector  12 . In this embodiment, the sub-reflector  18  is an axially displaced ellipse, and relatively small compared to the primary reflector  12 . The sub-reflector  18  shares the same axis as the primary reflector  12  and the feed tube  14 . As a result, the sub-reflector  18  is positioned to receive and transmit communication signals between the feed tube  14  and the primary reflector  12 . The primary reflector  12  is secured to the sub-reflector  18  preferably via support brackets  19  extending between the primary reflector  12  and the sub-reflector  18  as shown. 
         [0023]    It is noted that the above described embodiments of the present invention can be used in conjunction with the mounting arrangement of the antenna assembly on a moving platform as disclosed in commonly owned issued U.S. Pat. No. 7,443,355, which is hereby incorporated by reference. It is further noted that optimal efficiency can be achieved by adjusting the geometries of the primary and sub-reflectors, as can be seen in, e.g., Granet C, “A Simple Procedure for the Design of Classical Displaced-Axis Dual-Reflector Antennas Using a Set of Geometric Parameters”,  Antennas and Propagation Magazine, IEEE , Vol.  41  ( 6 ), December 1999, pp. 64-72, also incorporated herein by reference. 
         [0024]      FIG. 1B  illustrates a side view of the dual-band feed horn  14  connected to the LNB assembly  16  as configured in accordance with a preferred embodiment. The LNB assembly  16  illustrated at  FIGS. 1A and 1B  preferably comprise three LNBs  16   a ,  16   b  and  16   c , which are located within the LNB assembly  16  to receive Ka, Ku and Ka band signals respectively. Although three LNBs are shown in  FIG. 1 , a greater or lesser number of LNBs can be utilized for a given antenna without departing from the scope of the invention. 
         [0025]    In general, the system  10  uses different frequency range signals transmitted asynchronously from satellites (not shown) at different orbital locations to be received by the reflector  12  for transmission to the dual-band feed horn  14 , which are then forwarded to the appropriate LNB  16  depending on the frequency range of the signal. Each of the LNBs  16  are configured to receive the signals sent by the feed horn  14  and further function to amplify and down convert to a lower frequency band recognized and processed by a Integrator Receiver Decoder (IRD), as will be described in greater detail below. 
         [0026]    The dual-band feed horn  14  operates simultaneously at Ku-band (10.7 to 12.75 GHz) and Ka-band (18.3-18.8 and 19.7-20.2 GHz). The dual band feed horn  14  collects the received signals from the primary reflector  12  and sub-reflector  18 , as will be described in further detail below. The received signals from both bands are available at a circular waveguide interface  17 , as shown in  FIG. 1C . This waveguide interface  17  consists of interface  17   a ,  17   b  and  17   c  which are part of LNBs  16   a ,  16   b  and  16   c  respectively. This common waveguide interface  17  supports both Ku and Ka bands. 
         [0027]    In alternate embodiments, as shown in  FIG. 1D , the cross section of the waveguide at the common interface of the dual-band feed horn  14  includes a co-axially located dielectric rod  15  which is configured to route the band signals to the subassembly  16 . The dielectric rod  15  is inserted preferably into the Ku-band feed (not shown) within the feed horn  14  and supports the dominant HE 11  mode. The rod  15  is appropriately sized for dominate mode operation at Ka-band, and is preferably made from a low loss dielectric material such as, e.g., Rexolite, which is across-linked polystyrene. 
         [0028]    The frequency band of operation is selectable based on the band signal received from the satellites. A mechanical motor or actuator  19  as shown in  FIG. 1A  is preferably-placed in the sub-assembly  16  to provide movement to the sub-assembly  16  such that the appropriate LNB  16   a ,  16   b  and  16   c  is aligned with the feed horn  14  depending upon the frequency band signal received from the satellites. Specifically, each of the waveguide interfaces  17   a ,  17   b  and  17   c  of the LNB  16   a ,  16   b  and  16   c  are aligned with the feed horn  14  to receive their respective band signals. Referring back to  FIG. 1A , when Ku-band reception is selected, the waveguide interface  17   b  of the LNB  16   b  is aligned with the feedhorn  14 . Likewise when Ka-band reception is selected, the waveguide interface  17   a  or  17   c  of the corresponding Ka-band LNB  16   a  or  16   c  are aligned with the feed horn  14 . 
         [0029]    More particularly, a first satellite (not shown) located preferably at 101 degrees west longitude delivers a beam  30  in a Ku frequency band of 11 GHz to 12 GHz to the primary reflector  12 . 
         [0030]    The active surface of the primary reflector  12  reflects this beam signal  30  to the sub-reflector  18 , The reflecting surface of sub-reflector  18  in turn reflects the beam signal  30  directly into the feed horn  14 . The mechanical actuator  19  causes movement in the LNB  16  such that the LNB  16   b  with its respective waveguide interface  17   b  is aligned with the feed horn  14 . A circular waveguide transition (not shown) routes the beam signal  30  between the dual band feed horn  14  and the Ku-band LNB  16   b  via the circular waveguide interface  17   b . The circular waveguide transition is designed to provide a low reflection path between the partially dielectric loaded circular waveguide and the standard circular waveguide (without partial dielectric loading). The Ku band LNB  16   b  amplifies and down converts the beam signal  30  to a lower frequency band. 
         [0031]    A second satellite (not shown) positioned preferably at 99 degrees west longitude delivers a beam  32  in a Ka frequency band of 18 GHz to 20 GHz. The active surface of the primary reflector  12  reflects this beam signal  32  to the sub-reflector  18 . The reflecting surface of the sub-reflector  18  in turn reflects the beam  32  to the feed tube  14 . The Ka band LNB  16   a  amplifies and down converts the beam signal  32  to a lower frequency band. In one embodiment the Ka beam signal  32  is routed between the dual band feed horn  14  and the Ka-band LNB  16   a  via the circular waveguide interface  17   a  by the mechanical actuator  19  causing a movement to the LNB  16  such that the LNB  16   a  with its respective waveguide interface  17   a  is aligned with the feed horn  14 . So, in this embodiment, at the output to the Ka-band transition, a circular waveguide without dielectric loading is provided which matches the circular waveguide diameter of the Ka-band LNB  16   a . In the alternate embodiments containing a dielectric rod  15  as shown in  FIG. 1D , a circular waveguide tapered transition with tapered coaxially supported dielectric rod routes the beam signal  32  into the Ka band LNB  16   a.    
         [0032]    A third satellite (not shown) located preferably at 103 degrees west delivers a beam  34  similar to the beam  32  such that it also contains Ka frequency of 18 GHz to 20 GHz. The active surface of the primary reflector  12  reflects this beam signal  34  to the sub-reflector  18 . The reflecting surface of the sub-reflector  18  in turn reflects the beam  32  to the feed tube  14 . The feed tube  14  guides this beam signal  34  to directly into the Ka band LNB  16   c , as described above, which amplifies and down converts the beam signal  34  to a lower frequency band. Similarly as discussed above, in one embodiment the Ka beam signal  34  is routed between the dual band feed horn  14  and the Ka-band LNB  16   c  via the circular waveguide interface  17   c  by the mechanical actuator  19  causing a movement to the LNB  16  such that the LNB  16   c  with its respective waveguide interlace  17   c  is aligned with the feed horn  14 . in the alternate embodiments containing a dielectric rod  15  as shown in  FIG. 1D , a circular waveguide tapered transition with tapered coaxially supported dielectric rod routes the signal into the Ka band LNB  16   c.    
         [0033]    Prime-Focus Systems 
         [0034]    Certain embodiments of the present invention provide for a prime focus Ka/Ku dual band TV receive only antenna system. In such configurations the relative position between the main reflector and the feed horns can be shifted in a variety of ways to seamlessly reconfigure to the new frequency band. For example, in certain embodiments, the feed horn can be transversely displaced. In alternate embodiments, the reflector can be transversely displaced. In yet other embodiments, the tilt angle of the reflector may be altered so that the focus of the reflector is at a particular feed horn. Alternate embodiments provide for the feed horns to be mounted on a mechanical boom in front of the primary reflector, and the angle between the primary reflector Boresite and the boom (i.e., the “boom angle” or “boom tilt”) can be adjusted to effectively displace the feed horn position. The feed horns are then aligned with the reflector focus in their respective boom angles. 
         [0035]      FIG. 2A  illustrates schematic view of a prime focus mobile satellite-antenna system  20  installed on a moving platform (not shown) according to another embodiment of the present invention.  FIG. 2B  illustrate a front view of the antenna  20  as configured in accordance with a preferred embodiment. The antenna system  20  is preferably an offset reflector system. The system  20  includes a primary reflector  12  capable of receiving signals directly from the satellites (not shown). The reflector shown in the present embodiment is a parabola-shaped reflector and is made of metals such as aluminum or steel, or metalized plastic. 
         [0036]    The system  20  also includes a feed horn assembly  22  containing at least two feed horns  23   a  and  23   b  operating at the first and second frequency bands. Ku-band and Ka-band respectively, the feed horns having at least two adjacent openings  22   a  at one end and the other end connected to a Low Noise Block (LNB) converter  24 . Specifically, the opening ends  22   a  of the feed horns are disposed to face the front surface of the primary reflector  12  as shown. In this embodiment, the feed horn assembly  22  shares the same axis as the primary reflector  12 . As a result, the feed horn is positioned to receive and transmit communication signals between the primary reflector  12  and the LNB converter  24 . The primary reflector  12  is secured to the combined feed horn and the LNB converter preferably via support brackets  13  for stable mounting. 
         [0037]    The system  20  is positioned to focus on the bands on either the Ku satellites or the Ka satellites, in a more preferred embodiment, the system  20  includes three feed horns  23   a ,  23   b , and  23   c , as depicted in  FIG. 2C . In such an embodiment, the feed horns operate at Ka, Ku and Ka bands. The position openings of the feed horns are such that the opening of the higher frequency (Ka-band) feed horn  23   b  or  23   c  is exactly at the focus point of the reflector antenna (not shown). This insures that the highest gain is achieved at Ka-Band. The Ka-band pattern is centered with respect to the reflector (not shown). As a result, the Ku-band feed horn  23   a  is transversely displaced in the focal plane from the optimum focus point of the reflector. This feed offset displaces the Ku-band antenna pattern peak and slightly reduces the available gain. The Ku-band main beam offset is determined by the reflector geometry, including the focal length and reflector focal length to depth ratio, and the feed displacement. The other Ka-band feed not centered at the focal point is not used. 
         [0038]    Referring back to  FIG. 2A , in a preferred embodiment of the present invention, the system  20  further comprises a standard sized motor  26 , e.g., a stepper motor as manufactured by Shinano Kensi Corporation, preferably installed on the LNB converter  24  as shown in  FIG. 2A  or alternatively separately connected to the LNB  24 . The motor  26  functions to provide movement of the LNB feed horn  23 , which in turns moves the primary reflector  12  so the feed horn  23  is positioned at the focal point of the primary reflector  12 . This way maximum gain is achieved in the antenna  20  as will be described in greater detail below. 
         [0039]      FIG. 3  depicts one example of a mobile satellite communication system  30  implemented to control the movement of the antenna  20  in accordance with embodiments of the present invention. This system  30  is also installed on the same moving platform (not shown) as the antenna  20 . The system  30  includes a control module  32 , which receives information from a Ka band receiver  34   a  and Ku band receiver  34   b . Control module  32  processes information provided by the receivers  34   a  and  34   b  and issues commands to the antenna  30 . Receivers  34   a  and  34   b  are preferably an Integrated Receiver Decoders (IRD), which function to decode the Ka and the Ku band signal respectively received from the antenna  20  and produce an output signal that is delivered to the TV  36  via a link such as cable. Note that the signal received by the antenna  20  is an amplified low frequency band signal converted by the LNB converter  24  in the antenna  20 . The system  30  as disclosed in the present invention can be used in conjunction with the mobile satellite communication system on a moving vehicle as disclosed in commonly owned issued U.S. Pat. No. 5,835,057 which is hereby incorporated by reference. 
         [0040]    The control module  32  preferably includes a processor (not shown) to execute programmed instructions to process information provided by the receiver  32 . The processor also functions to execute programmed instructions to issue the command(s) to the antenna  20  to cause the antenna  20  to be directed towards a particular satellite. The movement of the antenna  20  is caused by the commands sent by the control module  32 . The commands activate the motor  26  to move the feed horn  23  and the LNB  24  such that the feed horn  23  associated with the desired beam is centered. This embodiment is advantageous, as it does not require the tilt of the antennae to be adjusted. The process as to how the system  30  functions is provided in greater detail below. 
         [0041]    If the user wishes to watch something on a Ku band, the user may press a channel on a remote of the TV  36 , the signal of which is received by the Ku band receiver  34   b . This signal includes information on the Ku band based on the channel selected by the user. The receiver  34   b  identifies the satellite that provides the Ku frequency band and sends this information to the control module  32 . Alternatively, the control module  32  identifies the satellite that matches with Ku frequency band based on some data stored in a memory (not shown) in the module  32 . The control module  32  in turn executes programmed instructions to process this information and issues a command to the antenna  20  to provide the movement of the antenna  20 . Specifically, the commands issued by the control module  32  cause the motor  26  to move or slide the feed horn  23  so the reflector  12  points to a satellite (not shown) transmitting the Ku band signal. As a result, the Ku feed horn  23  is centered in order to receive the maximum gain. The maximum gain condition is determined when the feed horn aperture of the requested frequency band is located at the focal point of the reflector. When the satellite transmits Ku band signals  30  to the reflector  12 , the active surface of the primary reflector  12  reflects these band signals  30  directly into LNB feed tube  23 . The feed horn  23  guides these beam signals  30  directly into the LNB  24 , which amplifies and down converts to a lower frequency band. These lower frequency band signals are then sent to the receiver  34   b , which in turn decodes this signal and produces an output signal that is delivered to the TV  36 . 
         [0042]    Alternatively, if the user wants to watch something in high definition TV, the user can press another channel on a remote of the TV  36 , the signal of which is received by the receiver  34   a . This signal includes information on a Ka band based on the channel selected by the user. The receiver  34   a  recognizes that a change in the frequency is needed for a transmission for the selected HD channel and further identifies the satellite that provides the Ka frequency band and sends this information to the control module  32 . Alternatively, the control module  32  identifies the satellite that matches with Ka frequency band based on some data stored in a memory (not shown) in the module  32 . The control module  32  in turn executes programmed instructions to process this information and issues a command to the antenna  20  to provide the movement of the antenna  20 . Specifically, the commands issued by the control module  32  cause the motor  26  to move or slide the feed horn  22  so the reflector  12  points to a satellite (not shown) transmitting the Ka band signal. As a result, the feed horn  22  is at the focal point of the primary reflector  12  in order to receive the maximum gain. When the satellite transmits Ka band signals  32  to the reflector  12 . the active surface of the primary reflector  12  reflects these band signals  32  directly into LNB feed tube  23 . The feed horn  23  guides these beam signals  32  directly into the LNB  24 , which amplifies and down converts to a lower frequency band. These lower frequency band signals are then sent to the receiver  34   a , which in turn decodes this signal and produces an output signal which is delivered to the TV  36 . 
         [0043]      FIG. 4A  illustrates schematic view of a prime mobile satellite-antenna system  40  installed on a moving platform (not shown) according to an alternate embodiment of the present invention.  FIG. 4B  illustrate a rear view of the antenna  40  as configured in accordance with a preferred embodiment. As illustrated in  FIGS. 4A and 4B , the antenna system  40  is similar to the system  20  except that the LNB converter  24  is replaced by a Low Noise Block (LNB) assembly  16  of  FIGS. 1A and 1B . As discussed above, the LNB assembly  16  preferably comprises three LNBs  16   a ,  16   b  and  16   c , which are located within the LNB assembly  16  to receive Ka, Ku and Ka band signals respectively. 
         [0044]    In this embodiment, the feed horn  23  is centered when the user selects programming using the Ku-band signal. When Ka-band signal is selected, the feed is translated in the appropriate direction to maximize the signal, and tracking is converted to Ka-band. When the user selects the Ka-band at the higher/lower frequency than previously selected, the feed is then translated in the opposite direction in order to maximize the Ka-band signal at the selected frequency. 
         [0045]    These embodiment provides advantages over the methods of operation described in U.S. Publication No. 2008/0271092, in that if it is determined that the antenna should receive a signal from a second satellite, and that satellite is operating at another frequency band (i.e., Ka-band), the embodiment described above allows for the antenna to reconfigure to the new frequency band in a seamless operation sense for the user. The feed horns, boom tilt or reflector positions can all be translated for selected operation at the Ka/Ku/Ka band positions. 
         [0046]    It is noted that the above described embodiments of the present invention can be used in conjunction with the satellite tracking system on a moving vehicle as disclosed in commonly owned issued U.S. Pat. No. 5,835,057 which is hereby incorporated by reference. 
         [0047]    While the present invention has been described with respect to what are some embodiments of the invention, it is to be understood that the invention is not limited to the disclosed embodiments. To the contrary, the invention is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.