# Patent

## Title
Portal structure providing electromagnetic interference shielding features

## 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.

## Background
RELATED APPLICATIONS
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
This invention was made with Government support under Contract Number N00039-04-C-0012 awarded by the Department of the Navy. The United States Government has certain rights in the invention.


BACKGROUND
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
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.
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.
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
FIG. 1 is a prior art diagram of an environment of a radar system.
FIG. 2 is a side-view of an antenna pedestal.
FIG. 3 is a diagram of an antenna pedestal of FIG. 2 taken along the reference line A-A.
FIG. 4 is a diagram of a portal structure.
FIG. 5A is a top view of the portal structure.
FIG. 5B is a cross-section view of the portal structure taken along the reference line B-B.
FIG. 6 is a view of an internal cavity of the antenna pedestal.
FIG. 7 is a cross-section view of the antenna pedestal of FIG. 2 taken along the reference line C-C.
FIG. 8 is a cross-section view of the antenna pedestal of FIG. 2 taken along the reference line D-D.
FIG. 9 is view of a rotary cable configuration.
FIG. 10 is viewed of an example of a rotary connector.
FIG. 11A is a partial cross-sectional view of a first connector portion.
FIG. 11B is a partial cross-sectional view of a second connector portion.
FIG. 11C is partial cross-sectional view of the rotary connector with the first connector portion separated from the second connector portion by springs.
FIGS. 12A, 12B 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.
FIG. 14 is a view of a still further example of a rotary connector as an elbow connector.



DETAILED DESCRIPTION
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.
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).
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.
The antenna pedestal 50 includes a number of portal structures 72a-72c 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 72a, 72b, the arm section 62 includes the portal structure 72c and the antenna attachment section 68 includes the portal structures 72d, 72e. 
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.
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.
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 200a-200d 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 184a and a motor assembly 184b) that control rotation of the antenna about the J-axis and the K-axis. In one example, the motor assemblies 184a, 184b 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 a rotary connector 292 (FIGS. 8, 12A and 12B), 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.
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 210a and a spring 210b (FIG. 11C)). The rotary cable 190′ also includes cable hoses 198a, 198b. The cable hose 198a is connected to the first connector portion 194 and the cable hose 198b is connected to the second connector portion 196. The cable hoses 198a, 198b, are similar to garden hoses except the cable hoses 198a, 198b are EMI shielded and carry wires instead of water. For example, cable hoses 198a, 198b are EMI shielded cable hoses that carry wires 200a-200d. In one example, wires 200a-200d supply power to the motor assemblies (e.g., the motor assemblies 184a, 184b) that rotate the antenna pedestal 50. Like garden hoses, cables hoses 198a, 198b 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 198a or 198b about the longitudinal axis M while the other cable hose 198b or 198a remains substantially fixed with respect to the longitudinal axis M while ensuring that wires 200a-200d are EMI shielded.
Referring to FIG. 11A, the first connector portion 194 includes threads 204a for connection with the cable hose 198a. The first connector portion 194 is shaped to form a channel 206a to carry the wires 200a-200d. 
Referring to FIG. 11B, the second connector 196 includes threads 204b for connection with the cable hose 198b. The second connector portion 196 is shaped to form a channel 206b to carry the wires 200a-200d. The second connector portion 196 is also shaped to form grooves (e.g., a groove 208a and a groove 208b). Each groove 208a, 208b runs in a concentric circle about longitudinal axis M.
Referring to FIG. 11C, the first connector portion 194 and the second connector portion 196 are separated by springs (e.g., a spring 210a and a spring 210b). The springs 210a, 210b 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 210a, 210b include a metal. In one example, springs 210a, 210b include a metal alloy. In other examples, the springs 210a, 210b are made of beryllium copper.
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.
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 298a and a port 298b) 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.
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 398a and a port 398b) 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.
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.
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.

## Claims

1. An antenna pedestal comprising a body having an inner cavity, comprising:
a portal structure comprising:
a single threaded structure disposed around a portal providing access to one or more components housed in the inner cavity of the body of the antenna pedestal, the single threaded structure comprising threads; and
a cover comprising threads configured to engage the threads of the single threaded structure to close the portal.

2. The antenna pedestal of claim 1 wherein the portal structure further comprises a lid comprising metal and configured to be placed over the portal and held securely by the cover to provide electromagnetic interference (EMI) shielding when the cover and the single threaded structure are screwed together.

3. The antenna pedestal of claim 2 wherein the lid comprises nylon threads.

4. The antenna pedestal of claim 1 wherein the cover comprises a metal and is configured to provide electromagnetic interference (EMI) shielding when the cover and the single threaded structure are screwed together.

5. The antenna pedestal of claim 1 wherein the single threaded structure is metal.

6. The antenna pedestal of claim 1 wherein the single threaded structure comprises threads formed around an exterior of the portal structure.

7. The antenna pedestal of claim 1 wherein the single threaded structure comprises threads formed around an interior of the portal.

8. The antenna pedestal of claim 1, further comprising a wire comprising:
a first portion attached to the cover; and
a second portion attached to the single threaded structure.

9. The antenna pedestal of claim 1 wherein the one or more components comprise a cable comprising wires supplying power to motors configured to rotate the antenna pedestal.

10. The antenna pedestal of claim 1 wherein the body comprises:
a trunk section;
an arm section; and
an antenna attachment section,
wherein the portal structure is positioned in one of the trunk section, the arm section and the antenna attachment section.