Abstract:
In one aspect, an antenna pedestal includes a body having an inner cavity. The antenna pedestal includes a portal structure to access the inner cavity of the antenna pedestal. The portal structure also includes a threaded structure disposed around a portal accessing the inner cavity and comprising threads and a cover comprising threads configured to engage the threads of the threaded structure to close the portal. 
     In another aspect, a portal structure to access an inner cavity of a body includes a threaded structure disposed around a portal accessing the inner cavity of the body and a cover that includes threads configured to engage the threads of the threaded structure and configured to be placed over the port to provide electromagnetic interference (EMI) shielding when the cover and the threaded structure are screwed together. 
     One or more of the aspects above may be used for EMI shielding in antenna pedestals.

Description:
RELATED APPLICATIONS 
       [0001]    This application claims priority to provisional application Ser. No. 61/074,883, entitled “AN ANTENNA PEDESTAL INCLUDING A PORTAL STRUCTURE PROVIDING ELECTROMAGNETIC INTERFERENCE SHIELDING FEATURES,” filed Jun. 23, 2008, which is incorporated herein in its entirety. 
     
    
     GOVERNMENT SPONSORED RESEARCH 
       [0002]    This invention was made with support of the United States Government under Contract: N00039-04-C-0012. The United States Government may have certain rights in the invention. 
     
    
     BACKGROUND 
       [0003]    Electromagnetic interference (EMI) can cause disruption to electrical systems. One way to prevent EMI from affecting electronic circuitry is to shield the electronic circuit, a technique generally known as EMI shielding. Typically, EMI is performed by encasing the electronic components in metal having no gaps in the metal that would allow EMI to penetrate, for example, a Faraday cage. In general, a continuous metal contact is provided to ensure EMI shielding. 
       SUMMARY 
       [0004]    In one aspect, a portal structure to access an inner cavity of a body includes a threaded structure disposed around a portal accessing the inner cavity of the body, a cover comprising threads configured to engage the threads of the threaded structure and a lid comprising a metal and configured to be placed over the port and held securely by the cover to provide electromagnetic interference (EMI) shielding when the cover and the threaded structure are screwed together. 
         [0005]    In another aspect, a portal structure to access an inner cavity of a body includes a threaded structure disposed around a portal accessing the inner cavity of the body; and a cover that includes threads configured to engage the threads of the threaded structure and configured to be placed over the port to provide electromagnetic interference (EMI) shielding when the cover and the threaded structure are screwed together. 
         [0006]    In a further aspect, an antenna pedestal includes a body having an inner cavity. The antenna pedestal includes a portal structure to access the inner cavity of the antenna pedestal. The portal structure also includes a threaded structure disposed around a portal accessing the inner cavity and comprising threads and a cover comprising threads configured to engage the threads of the threaded structure to close the portal. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0007]      FIG. 1  is a prior art diagram of an environment of a radar system. 
           [0008]      FIG. 2  is a side-view of an antenna pedestal. 
           [0009]      FIG. 3  is a diagram of an antenna pedestal of  FIG. 2  taken along the reference line A-A. 
           [0010]      FIG. 4  is a diagram of a portal structure. 
           [0011]      FIG. 5A  is a top view of the portal structure. 
           [0012]      FIG. 5B  is a cross-section view of the portal structure taken along the reference line B-B. 
           [0013]      FIG. 6  is a view of an internal cavity of the antenna pedestal. 
           [0014]      FIG. 7  is a cross-section view of the antenna pedestal of  FIG. 2  taken along the reference line C-C. 
           [0015]      FIG. 8  is a cross-section view of the antenna pedestal of  FIG. 2  taken along the reference line D-D. 
           [0016]      FIG. 9  is view of a rotary cable configuration. 
           [0017]      FIG. 10  is viewed of an example of a rotary connector. 
           [0018]      FIG. 11A  is a partial cross-sectional view of a first connector portion. 
           [0019]      FIG. 11B  is a partial cross-sectional view of a second connector portion. 
           [0020]      FIG. 11C  is partial cross-sectional view of the rotary connector with the first connector portion separated from the second connector portion by springs. 
           [0021]      FIGS. 12A ,  12 B are views of another example of the rotary connector as a Y-connector  FIG. 13  is a view of further example of the rotary connector as a T-connector. 
           [0022]      FIG. 14  is a view of a still further example of a rotary connector as an elbow connector. 
       
    
    
     DETAILED DESCRIPTION 
       [0023]    Referring to  FIG. 1 , in a signal environment  10 , a system  12  may be susceptible to electromagnetic interference (EMI)  18  emanating from an EMI source  16 . The system may be a radar system, a communications system and so forth. The EMI source may be a radar system, a communications system and so forth. In one particular environment, aboard a naval vessel, the EMI source may be a communications antenna in close proximity to the system  12 . In one example, the system  12  includes an antenna  24  attached to the antenna pedestal  22  and cables  26  providing and receiving electrical signals with the system  12 . The cables  26  may provide, for example, electrical signals to motors (not shown) that orientate the antenna  24  to point in various directions. In this configuration the cables  26  are exposed to EMI and the flow of the electrical signals may be disrupted. Therefore, the cables  26  providing the electrical signals to the system  12  are EMI shielded. One solution is to place the cables within the antenna pedestal  22 . However, placing cables within the antenna pedestal  22  poses significant problems in that access to the cables  26  is limited in order to affect repairs, for example. Also, by being within the antenna pedestal  22  the cables  26  need to be able to move in at least two axes of rotation. 
         [0024]    Referring to  FIGS. 2 and 3 , an antenna pedestal  50  includes a base section  52 , a trunk section  56 , an arm section  62  and an antenna attachment section  68  for connecting to an antenna (not shown). The antenna pedestal  50  may move in at least two axes of rotation to orientate the antenna. For example, the arm section  62  is configured to rotate about an axis, J. The rotation about the J-axis forms an angle θ, which is measured from an axis J′ that is perpendicular to the J-axis. In one example, θ ranges from −45° to 45° (90° total). The antenna attachment section  68  is configured to rotate about an axis K. The rotation about the K-axis forms an angle α, which is measured from an axis K′ that is perpendicular to the K axis. In one example, a ranges from −30° to 120° (150° total). 
         [0025]    The antenna pedestal  50  includes an inner cavity (an inner cavity  180  in  FIG. 6 ) that is EMI shielded. For example, the base section  52 , the trunk section  56 , the arm section  62  and the antenna attachment section  68  form a continuous metal barrier protecting components within the inner cavity of the antenna pedestal  50  from EMI. 
         [0026]    The antenna pedestal  50  includes a number of portal structures  72   a - 72   c  used to access components within the inner cavity  180  of the antenna pedestal  50  that contribute to EMI shielding. For example, the trunk section  56  includes the portal structures  72   a ,  72   b , the arm section  62  includes the portal structure  72   c  and the antenna attachment section  68  includes the portal structures  72   d ,  72   e.    
         [0027]    Referring to  FIG. 4 , the portal structure  72  includes a cover  82  having threads (not shown), a lid  86  including metal and a threaded structure  92  including threads  96  formed around a portal  100 . The portal structure  72  also includes a wire  98  connected to the cover  82  by an anchor  102  and connected to the threaded structure  92  by an anchor  104 . The lid  86  is shaped to completely cover the portal  100  to provide a continuous metal-to-metal contact for EMT shielding. In one example, the cover  82  and the threaded structure  92  are similar to ajar cover and jar arrangement (e.g., a BALL® Jar). For example, by screwing the cover  82  to the threaded structure  92 , the lid  86  is held fixed to completely cover the portal  100  thereby forming an EMI shield. In other examples, the threaded structure  92  includes threads within an interior of the portal  100  while the cover  82  includes the threads  92  on its exterior (not shown). In one example, the lid  86  is made of a metal including a metal alloy. The threaded structure  92  being attached to the antenna pedestal  50  is also made of metal including a metal alloy to contribute to EMI shielding. Since the lid  86  completely covers the portal  100  and is contact with the threaded structure  92 , there is not a requirement that the cover  82  be composed of metal. For example, the cover  82  including its threads (not shown) may be made of nylon. In other examples, the lid  86  is integrated with the cover  82  to form a single piece. 
         [0028]    Prior art techniques of portal structures, used covers that required ten to twenty screws that took minutes to remove and replace. Because the screws were small, over time they were easily lost by technicians. By using the portal structure  72 , technicians are able to access key components within the antenna pedestal  50  for maintenance or repair within seconds.  FIG. 5A  is a top view of the portal structure  72  and  FIG. 5B  is a cross-sectional view of the portal structure  72  taken along the reference line B-B. 
         [0029]    Referring to  FIGS. 6 to 8 , within a cavity  180  of the antenna pedestal  50 , rotary cables  190  run from the base  52  through the antenna attachment section  68  and contain wires (e.g., wires  200   a - 200   d  in  FIG. 9 ) to carry signals to and from various electrical components within the antenna pedestal  50 . For example, rotary cables  190  provide electrical signals to motor assemblies (e.g., a motor assembly  184   a  and a motor assembly  184   b ) that control rotation of the antenna about the J-axis and the K-axis. In one example, the motor assemblies  184   a ,  184   b  include an elevation motor along with a rotor and a stator. As will be shown, rotary connectors such as a rotary connector  192  ( FIGS. 6 ,  8  and  10 ) and  20  a rotary connector  292  ( FIGS. 8 ,  12 A and  12 B), for example, allow portions of the rotary cables  190  to rotate to accommodate movements by the antenna pedestal  50  about the J-axis and the K-axis. In other examples, rotary connectors  392 ,  492  ( FIGS. 13 and 14 ) may also be used. 
         [0030]    Referring to  FIGS. 9 and 10 , one example of a rotary cable  190  is a rotary cable  190 ′. The rotary cable  190 ′ includes the rotary connector  192  including a first connector portion  194 , a second connector portion  196  and springs (e.g., a spring  210   a  and a spring  210   b  ( FIG. 11C )). The rotary cable  190 ′ also includes cable hoses  198   a ,  198   b . The cable hose  198   a  is connected to the first connector portion  194  and the cable hose  198   b  is connected to the second connector portion  196 . The cable hoses  198   a ,  198   b , are similar to garden hoses except the cable hoses  198   a ,  198   b  are EMI shielded and carry wires instead of water. For example, cable hoses  198   a ,  198   b  are EMI shielded cable hoses that carry wires  200   a - 200   d . In one example, wires  200   a - 200   d  supply power to the motor assemblies (e.g., the motor assemblies  184   a ,  184   b ) that rotate the antenna pedestal  50 . Like garden hoses, cables hoses  198   a ,  198   b  individually cannot rotate more than a few degrees about their longitudinal axis M. However, as will be shown further below, the rotary connector  192  ( FIG. 10 ) allows for rotation of one cable hose  198   a  or  198   b  about the longitudinal axis M while the other cable hose  198   b  or  198   a  remains substantially fixed with respect to the longitudinal axis M while ensuring that wires  200   a - 200   d  are EMI shielded. 
         [0031]    Referring to  FIG. 11A , the first connector portion  194  includes threads  204   a  for connection with the cable hose  198   a . The first connector portion  194  is shaped to form a channel  206   a  to carry the wires  200   a - 200   d.    
         [0032]    Referring to  FIG. 11B , the second connector  196  includes threads  204   b  for connection with the cable hose  198   b . The second connector portion  196  is shaped to form a channel  206   b  to carry the wires  200   a - 200   d . The second connector portion  196  is also shaped to form grooves (e.g., a groove  208   a  and a groove  208   b ). Each groove  208   a ,  208   b  runs in a concentric circle about longitudinal axis M. 
         [0033]    Referring to  FIG. 11C , the first connector portion  194  and the second connector portion  196  are separated by springs (e.g., a spring  210   a  and a spring  210   b ). The springs  210   a ,  210   b  ensures that at any point in time there is a continuous metal-to-metal contact between the first connector portion  194  and the second connector portion  196 . In one example, the springs  210   a ,  210   b  include a metal. In one example, springs  210   a ,  210   b  include a metal alloy. In other examples, the springs  210   a ,  210   b  are made of beryllium copper. 
         [0034]    In one example, the first connector portion  194  rotates about the longitudinal axis M while the second connector portion  196  is substantially fixed relative to the longitudinal axis M. In another example, the second connector portion  196  rotates about the longitudinal axis M while the first connector portion  194  is substantially fixed relative to the longitudinal axis M. 
         [0035]      FIGS. 12A and 12B  are views of another example of a rotary connector, a rotary connector  292 . In this example, the rotary connector  292  is a Y-connector. The rotary connector  292  includes a first connector portion  294  and a second connector portion  296 . The first connector portion  294  includes two ports (a port  298   a  and a port  298   b ) for connection to two cable hoses (not shown). In one example, the first connector portion  294  rotates about a longitudinal axis P while the second connector portion  296  is substantially fixed relative to the longitudinal axis P. In another example, the second connector portion  296  rotates about the longitudinal axis P while the first connector portion  294  is substantially fixed relative to the longitudinal axis P. 
         [0036]      FIG. 13  is a view of further example of a rotary connector, a rotary connector  392 . In this example, the rotary connector  392  is a T-connector. The rotary connector  392  includes a first connector portion  394  and a second connector portion  396 . The first connector portion  394  includes two ports (a port  398   a  and a port  398   b ) for connection to two cable hoses (not shown). In one example, the first connector portion  394  rotates about a longitudinal axis Q while the second connector portion  396  is substantially fixed relative to the longitudinal axis P. In another example, the second connector portion  396  rotates about the longitudinal axis Q while the first connector portion  394  is substantially fixed relative to the longitudinal axis P. 
         [0037]      FIG. 14  is a view of a still further example of a rotary connector as a rotary connector  492 . In this example, the rotary connector  492  is an elbow connector. The rotary connector  492  includes a first connector portion  494  and a second connector portion  496 . In one example, the first connector portion  494  rotates about a longitudinal axis R while the second connector portion  496  is substantially fixed relative to the longitudinal axis R. In another example, the second connector portion  496  rotates about the longitudinal axis R while the first connector portion  494  is substantially fixed relative to the longitudinal axis R. 
         [0038]    Elements of different embodiments described herein may be combined to form other embodiments not specifically set forth above. Other embodiments not specifically described herein are also within the scope of the following claims.