Abstract:
A collapsible antenna assembly for portable, outdoor satellite communication systems is provided. When connected to complementary electronics, the apparatus enables the transmission and reception of communications signals from any selected terrestrial location by means of a satellite link. The apparatus is implemented in a physical form that minimizes the overall physical dimensions such that portability is improved. The apparatus consists of an antenna reflector, transmit assembly, feed horn assembly, a boom, a tripod, and a mounting platform, which permits the antenna reflector to be oriented to operate with any selected satellite. The entire apparatus can be folded and disassembled to fit inside of a suitcase.

Description:
FIELD  
         [0001]    The present invention relates generally to portable wireless communications systems used for transmitting and receiving signals to and from satellites.  
         BACKGROUND OF THE INVENTION  
         [0002]    Satellite communications are used in an increasing variety of applications. The applications include television broadcasting, wherein a satellite transmitter is used to broadcast a signal to receiving earth terminals located within the area illuminated by the satellite transmitting antenna. Such systems commonly employ a receive terminal fixed in location, for home-based television reception, for example. Another application is for bidirectional transmission of information between two or more fixed terrestrial locations via satellite. Such systems generally employ large antennae, mounted on rotatable platforms, capable of accessing one or more satellites.  
           [0003]    Advancements in microwave technology have significantly reduced the size and cost of the electronic components used for transmission and reception of satellite signals. These advancements enable construction of small, lightweight portable earth terminals, which can be moved from location to location, and can be rapidly deployed. Such portable earth terminals have application in the areas of satellite newsgathering, transmission of data and video from remote sites (e.g. surveying and exploration applications), and in military communications systems.  
           [0004]    Prior art terrestrial stations have been developed by essentially miniaturizing known system components, without maximizing portability and without taking advantage of alternative configurations made possible by new microwave technologies. Prior art stations often comprise multiple independent units or components, which must be interconnected to form a terrestrial station. Such stations are more costly to ship, require additional set up time, and involve a risk of loss of one or more of the components and/or of incompatibility of components. In addition, the need for multiple containers to carry all of the independent components often dictates that more than one person is needed to move and assemble the station. Where greater compactness has been achieved, it has been at the expense of smaller antenna sizes, which reduce the overall system gain achievable, thus lowering the communications potential of such systems. Also, such systems are not designed for rapid stowage and deployment by relatively mechanically unskilled personnel who did not possess specialized tools.  
           [0005]    In one example of the prior art, U.S. Pat. No. 5,660,366, issued to Palmer, discloses a portable earth terminal which is capable of receiving signals from a satellite, but not of transmitting signals to a satellite. The apparatus disclosed by Palmer is intended to be transported in a vehicle, such as a recreational vehicle, and requires a separate antenna.  
           [0006]    U.S. Pat. No. 5,019,833, issued to Nonaka, discloses a portable parabolic antenna capable of receiving satellite signals only. The antenna cannot be compacted for stowage or transport.  
           [0007]    U.S. Pat. No. 5,999,839, issued to Schefte et al., discloses an antenna system consisting of two approximately equal antenna sections, which can be either folded or telescoped. In it&#39;s stowed or collapsed state, the size of the antenna is reduced only by a factor of two.  
           [0008]    In U.S. Pat. No. 4,816,838, issued to Mizuno et al., a flat plate receive-only antenna is disclosed. The antenna is hinged to a mounting plate and cannot be folded or reduced in size for stowage or transport.  
           [0009]    Another example of the prior art, U.S. Pat. No. 6,031,878, issued to Tomasz et al., discloses an apparatus for the reception of signals from a satellite by a fixed earth terminal. No means for transmitting a signal to a satellite is disclosed. Furthermore, the antenna is not an integral part of the disclosed apparatus, nor is it foldable or collapsible.  
           [0010]    U.S. Pat. No. 5,915,020, issued to Tilford et al., discloses means for the reception of video signals from a satellite by a portable earth terminal. No means of transmitting a signal to a satellite is disclosed, neither are means for reducing the size of the antenna for stowage or transport.  
           [0011]    U.S. Pat. No. 5,061,945, issued to Hull et al., discloses a portable satellite antenna consisting of fan-like segments, which collapse, with fan segments stacked one behind the other, such that the dimensions are approximately equal to that of a single fan segment. However, the antenna of Hull is mechanically complex, making it fragile and susceptible to damage or malfunction in harsh or dirty environments.  
           [0012]    Accordingly, it is an object of the current invention to provide a rugged, compact and portable antenna assembly for a satellite terminal capable of transmitting and receiving voice, video, and data signals from remote locations.  
           [0013]    It is a further object to provide an antenna assembly which can be reduced to a compact configuration that can be contained in a single suitcase-sized container and that can be carried by a single person without undue effort.  
           [0014]    It is a further object to provide a portable antenna assembly capable of rapid deployment without the need for specialized tools.  
         SUMMARY OF THE INVENTION  
         [0015]    These and other objects have been realized in a portable antenna assembly capable of transmitting and receiving voice, video and data signals through a satellite link, when used with additional electronics, such as downconverters, upconverters, etc. The portable antenna assembly comprises an antenna, mounting platform, tripod, boom, transmit assembly, and feed horn assembly.  
           [0016]    The antenna is in the form of a parabola, however, unlike conventional parabolic antennae, it is closer to a rectangle in shape than an ellipse. The rectangular shape results in antenna segments that fit conveniently and efficiently into a rectangular case. The antenna is fabricated from separable segments that can be fastened together, when the antenna is deployed, and taken apart, when the antenna is stowed. The fastenings for the segments are such that accurate and rapid assembly can be achieved by unskilled personnel without the need for specialized tools.  
           [0017]    The antenna is connected to the mounting platform, which consists of two flat plates in close contact that swivel relative to one another about a central point. The mounting platform enables the antenna to be pointed in any direction in a horizontal plane. The antenna is connected to the mounting platform by a hinge point that allows the elevation angle of the antenna to be varied anywhere from horizontal to vertical. The mounting platform also includes a compass, an inclinometer, and a level indicator, all of which are useful in establishing a correct operating position for the antenna with respect to the ground and the satellite.  
           [0018]    The feed horn assembly is supported at the focal point of the antenna by a boom arm attached to one of the segments of the antenna.  
           [0019]    The portable antenna assembly is supported on three legs, which mount to the underside of the bottom plate of the mounting platform.  
           [0020]    The portable antenna assembly is capable of being collapsed and contained within a single suitcase-sized unit that can be carried and handled by one person. The portable antenna assembly may be rapidly, easily and simply assembled and positioned to transmit and receive signals to and from a satellite, when used in conjunction with additional electronics, such as downconverters, upconverters, etc.  
           [0021]    Other objects, features, aspects and advantages of the present invention will become apparent to those of ordinary skill from the following detailed description of the invention taken in conjunction with the accompanying drawings 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0022]    The invention itself both as to organization and method of operation, as well as additional objects and advantages thereof, will become readily apparent from the following detailed description when read in connection with the accompanying drawings, wherein:  
         [0023]    [0023]FIG. 1 is a perspective view of the portable antenna assembly ;  
         [0024]    [0024]FIG. 2 is a cut away view of the Boom Arm;  
         [0025]    [0025]FIG. 3 is a side view of the Feed Horn Assembly;  
         [0026]    [0026]FIG. 4 is a rear perspective view of the portable antenna assembly; and  
         [0027]    [0027]FIG. 5 is a side view of the portable antenna assembly in its fully collapsed or folded form.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0028]    [0028]FIG. 1 depicts the preferred embodiment illustrating how the components of the invention are interconnected and assembled to form a complete portable antenna assembly  100 . Portable antenna assembly  100  is seen to be composed of the following major components: antenna reflector  101 , backing plate  102 , mounting platform  114 , tripod legs  104 , boom arm  103 , and feed horn assembly  105 .  
         [0029]    Antenna reflector  101  is seen to be composed of four separable parabolic segments  110 ,  112  each comprising approximately one quarter of the full antenna reflector  101 . Parabolic segment  112  is attached to the backing plate  102 . Whilst the shape of conventional antennas is normally elliptical, the antenna reflector  101  of the present invention is approximately square or rectangular. This shape achieves an optimum illuminated area, whilst providing the optimum shape for compact packaging and transport. The rectangular shape results in antenna segments that fit conveniently and efficiently into a rectangular case. However, as is obvious to those skilled in the art, other shapes, both of the antenna reflector  101  and of the antenna segments  110 ,  112 , may be used in order to fit into carrying cases of different shapes and/or sizes.  
         [0030]    The four segments  110 ,  112  of antenna reflector  101  are mechanically connected to one another along their edges by means of a multiplicity of built-in quarter turn, quick release cam nuts  106 , (only one of which is shown for purposes of illustration).  
         [0031]    A receive cable  109  is used to connect the feed horn assembly  105  to a connector on backing plate  102 .  
         [0032]    The feed horn assembly  105 , supported by the boom arm  103 , is located at the focal point of the antenna reflector  101 . The boom arm  103  is attached to the lower part of that parabolic segment  112  of the antenna reflector  101 , which is attached to the backing plate  102 , and extends to the focal point of the antenna reflector  101 . Since the length of the boom arm  103  is likely greater than the maximum desired dimension of the portable antenna assembly  100  when it is collapsed and stowed for transport, (i.e. the boom arm  103  is longer than segments  110 ,  112 ) the boom arm  103  consists of two sections of approximately equal length, which can are reversibly connected to form the complete boom  103 .  
         [0033]    The boom arm  103  is shown in greater detail in FIG. 2. In the preferred embodiment, the boom arm  103  is in the form of a hollow-tube of circular cross-section, comprising two separable sections, inner section  201  and outer section  202 . The boom arm  103  is shown to enclose two waveguide sections  203  and  204 . The waveguide sections  203 ,  204  are of approximately equal length. The lengths of the waveguide sections  203 ,  204  and of the inner and outer sections  201 ,  202 , are equal to or less than the longest dimension of the parabolic segments  110 ,  112  of the antenna reflector  101 .  
         [0034]    The boom arm  103  is also used as a means for connecting the output of a transmit assembly (not shown) to the feed horn assembly  105 . This is accomplished by locating the two waveguide sections  203 ,  204  within the boom arm  103 . These two sections of waveguide  203 ,  204  are disconnected from one another for transport when the boom arm sections  201 ,  202  are disconnected.  
         [0035]    [0035]FIG. 3 depicts the feed horn assembly  105 , which consists of the antenna feed horn  301 , the ortho mode transducer  302 , the low noise block receiver  303 , and the circular rotation joint  304 . The circular rotation joint  304  permits the ortho mode transducer to be rotated in order to align the polarization of the antenna feed horn  301  with that of the satellite with which communication is to be established, whilst maintaining the feed horn assembly  105  itself fixed with respect to, the antenna reflector  101 . Flexible waveguide  305  is used to connect the waveguide section  204  contained within boom arm  103  to the transmit port on the ortho mode transducer  302 .  
         [0036]    [0036]FIG. 4 illustrates how one parabolic segment  112  of the antenna reflector  101  is attached to a backing plate  102 . In the preferred embodiment a transmit assembly (not shown) is mounted to the backing plate (referring again to FIG. 1, receive cable  109  connects the feed horn assembly  105  to the transmit assembly via a connector on backing plate  102 ). The transmit assembly typically consists of a DC power distribution unit, an RF monitor, a transmitter, and a high power microwave amplifier, however, other transmit assembly configurations may be used without departing from the scope of the present invention.  
         [0037]    With reference to FIG. 4, the backing plate  102  contains two hinge points  402  located at attachment points to top plate  411 . The purpose of the hinge points  402  is to permit the inclination of the antenna reflector  101  to the desired elevation angle in order to point at a satellite. Backing plate  102  also includes an inclinometer (not shown), which permits measurement of the angle of inclination of the antenna reflector  101 . An adjustable elevation rod  404 , connected at one end to the backing plate  102  and at the other end to the top plate  411 , is operative to adjust the angle of inclination of the antenna reflector  101 . The elevation rod  404  is removable, thus permitting backing plate  102  to be folded down parallel to top plate  411  for compact stowage. There is also a level detector (not shown) incorporated into the top plate, to facilitate leveling of the overall apparatus when deployed.  
         [0038]    The distance by which hinge points  402  are offset from top plate  411  is selected such that the transmit assembly (not shown) mounted on the backing plate  102  fits into the space between the backing plate  102  and top plate  411  when the antenna reflector  101  is folded down against the top plate  411  for stowage and/or transport.  
         [0039]    Backing plate  102  also provides an interface of low thermal resistance to enable efficient heat transfer from the transmit assembly through the backing plate  102 , to the top plate  411 . The mounting platform  114  is thereby used as a heat sink.  
         [0040]    Referring again to FIG. 4, the mounting platform  114  comprises two nearly circular plates, the top plate  411  and the bottom plate  415 , which swivel about a central point. The mounting platform  114  enables the antenna to be pointed in any direction in a horizontal plane. Fixing the position of top plate  411  with respect to bottom plate  415  is achieved by means of clamps  414 . When the clamps  414  are tightened, movement of the top plate  411  with respect to the bottom plate  415  is restricted. A compass  413  is attached to the top plate  411  to enable measurement of the azimuth.  
         [0041]    Bottom plate  415  has attachment points (not shown) for reversible attachment of tripod legs  104 . Referring to FIGS. 1 and 4, each tripod leg  104  is telescopically extendable, comprising two square aluminum tubes of approximately equal length. Between the two surfaces of the tubes is a layer of Ultra-High-Molecular-Weight Polyethylene, which acts as a bearing, sealing and sliding surface. Each leg  104  has two spring-loaded pins  107 ; one to retain the respective leg  104  in the retracted position and another to retain leg in the extended position. The spring-loaded pins  107  are located on the top surface of each leg  104  and are covered with a flexible neoprene membrane to seal against dust and dirt, whilst still permitting movement of the spring-loaded pins  107 .  
         [0042]    Referring again to FIG. 1, the end of each tripod leg  104  that is in contact with the ground has a threaded level adjustment foot  108 . Each threaded level adjustment foot  108  consists of a length of threaded rod that is positioned in a threaded hole in the end of the respective tripod leg  104 . The threaded level adjustment feet  108  can be used to fine tune the overall length of the respective tripod legs  108  and to level the portable antenna assembly  100  on uneven surfaces.  
         [0043]    In FIG. 5, the portable antenna assembly  100  is shown in the collapsed or folded state so that it may be conveniently transported in a case by one person. The antenna reflector  101  is disassembled and three of the antenna segments  110  are stacked one on top of the fourth segment  112 , (attached to the backing plate  102 ) such that the segments  110 ,  112  occupy a minimum volume. The antenna segment  112  is folded down about hinge point  402  such that it is parallel with top plate  411 . The tripod legs  104  are detached and placed against the mounting platform  114 . Only one Tripod Leg  104  is shown, telescopically retracted.  
         [0044]    Although the various components of the present invention have only been referred to generically in the description of the present invention, the implementation of the various components of the present invention will be easily and readily accessible to those skilled in the art of communications systems. It will be readily apparent to those skilled in the art that many modifications and variations could be effected without departing from the spirit or scope of the novel concepts of the present invention.  
         [0045]    Accordingly, while this invention has been described with reference to illustrative embodiments, this description is not intended to be construed in a limiting sense. It is therefore contemplated that the appended claims will cover any modifications or embodiments as fall within the true scope of the invention.