The present invention relates generally to grounding systems. More specifically, the invention relates to a grounding system that provides for a continuous ground plane between components that move relative to one another.
A good ground plane is essential to proper operation of a number of antenna systems. Active array antennas in particular have a need for a continuous ground plane. Without such a ground plane, undesirable effects can disrupt received signals and impair antenna performance. The importance of ground planes for antennas is described in U.S. Pat. No. 6,100,855 to Vinson, et al., the entire content of which is expressly incorporated herein by reference.
Antenna systems can include a number of radiating elements. Examples of antenna systems can be found in U.S. Pat. No. 6,366,259 to Pruett et al. and U.S. Pat. No. 7,391,382 to Mason et al., the entire content of each is expressly incorporated herein by reference. The radiating elements can send and receive signals provided by way of a main feed network. Often, the radiating elements are mounted such that a small space, such as a gap, exists between the elements. In some applications, the antenna systems are mounted to moving devices, such as aircraft or other vehicles. In such case, the radiating elements can be exposed to significant vibration. Both the gaps in antenna structure and the vibration create challenges to implementing and maintaining a continuous ground plane for an antenna system.
Systems to account for vibration and/or gaps in a ground plane have been proposed. These systems include, for example, copper fingers, spiral gaskets, and metallized tape. Among other limitations, such systems are unable to provide a continuous ground plane for antennas having relative movement between radiating elements.
Aspects of the invention relate to a compact continuous ground plane system. In one embodiment, the invention relates to an assembly for forming a continuous ground plane for an antenna having at least two elements configured to move relative to one another, the ground assembly including a first element having a housing, a plunger disposed within the housing, a second element, a wear plate coupled to the second element, and a spring disposed between the plunger and the housing, the spring configured to urge the plunger toward the wear plate, where the plunger is configured to be moved within the housing and to make electrical contact with the wear plate.
Referring now to the drawings, embodiments of assemblies for forming continuous ground planes are illustrated. In many embodiments, the grounding assemblies include a plunger, a spring, a retaining housing and a wear plate for electrically coupling adjacent radiating elements to one another despite relative movement. The plunger can have a T-shaped “dove tail” end and a tapered end with a rounded contact point to minimize wear on the wear plate. The “dove tail” end can be retained within the retaining housing.
The spring can be a wavy spring mounted between the plunger and the retaining housing such that the spring provides a force to the plunger directed away from the radiating element. The retaining housing is mounted to a radiating element. The wear plate is mounted to an adjacent radiating element and configured to make contact with the plunger. The assembly can sustain electrical contact between the radiating elements despite a predetermined amount of relative motion between the radiating elements. In some cases, the relative motion can be caused by vibration. In several embodiments, the relative motion is caused when the radiating elements are part of an antenna that is mounted to a moving vehicle, such as an aircraft. In a number of embodiments, the relative motion can occur in different directions. In many embodiments, the ground plane assemblies are configured to sustain electrical contact despite the relative motion in different directions.
A first housing 216 is coupled to a side of the first radiating element 202. Similarly, a second housing 218 is coupled to a side of the second radiating element 204. The first radiating element 202 is mounted to a first antenna support structure 220, and the second radiating element 204 is mounted to a second antenna support structure 222. In most embodiments, the second antenna support structure has a chamfer disposed along a lower edge of the structure (not visible) and the gap 206.
When compressed, the spring 210 is configured to provide a force on the plunger 208 directed away from the first radiating element 202 and toward the adjacent second radiating element 204. In effect, the spring 210 can urge the plunger toward the wear plate 212. The plunger 208 can move laterally within the retaining housing 214 for a distance limited by the width of the cavity within the housing 214 and the width of the spring 210 in a compressed state. The spring 210 resists movement of the plunger 208 toward the first radiating element 202. In one embodiment, such movement can be caused by a vibrational force applied to the grounding assembly.
In some embodiments, the spring 210 is a wavy spring having a number of wave-like bends in a thin flat metallic material. In one embodiment, the spring 210 is made of tin plated steel. In other embodiments, the spring is made of other suitably conductive and compression resistant materials. In one embodiment, the spring is made of a non-conductive material. In such case, an alternate means of making an electrical connection between the plunger and the first radiating element can be used. In one embodiment, the alternate means includes one or more wires coupling the retaining housing and the plunger.
In some embodiments, the spring is a leaf spring. In several embodiments, the spring has an elongated body that extends approximately the length of the first radiating element. In other embodiments, the spring may be replaced by a number of discrete springs having a similar structure in a shorter form factor. In one embodiment, the spring can be replaced with a number of coil springs.
In the exploded side view of
In some embodiments, the plunger is made of aluminum. In several embodiments, the plunger is plated with a material including both nickel and chrome. In such case, the material is conducive to establishing good electrical continuity between the plunger and those objects that come in contact with the plunger. In other embodiments, the plunger is made of other conductive materials and/or coated with other conductive materials. In some embodiments, the plunger is hollow. In many embodiments, the plunger has an elongated body that extends approximately the length of the first radiating element. In some embodiments, a number of discrete plungers can be used that are shorter in length than the first radiating element. In other embodiments, the plunger can take other shapes providing for constant electrical contact with the wear plate.
In the embodiment illustrated in
In several embodiments, the materials for the wear plate, the plunger and their respective coating materials are selected to prevent galling. Galling can be thought of as a condition where excessive friction between high spots results in localized welding with subsequent splitting and a further roughening of rubbing surfaces of one or both of two mating parts. In practice, galling can be caused when the same materials come in contact with one another on the adjacent mating parts. To prevent galling, embodiments of the grounding assembly can avoid using common metals for mating parts (e.g., plunger and wear plate). In the embodiment illustrated in
Returning to
In some embodiments, the radiating elements and coupled housings are made of hollow aluminum. In several embodiments, the antenna support structures are made of hollow aluminum. In other embodiments, other suitable materials can be used for the radiating elements, the plunger, the spring, and the wear plate.
In a number of embodiments, the components of the grounding assembly effectively provide self-contained connection systems and thus the final antenna system can be assembled and unassembled easily as opposed to antenna systems using prior art technologies (e.g., conductive tapes or gaskets). In one embodiment, for example, the components of the grounding assembly include the plunger in its retaining housing fully installed on the first radiating element and the wear plate fully installed on the second radiating element. In such case, after components of the grounding assembly have been fully assembled on the first radiating element and second radiating elements, the radiating elements can be installed on the antenna system by placing the first radiating element into a first slot and by sliding the second radiating element into an adjacent slot on the antenna system while allowing the plunger to retract whereby an elongated point of contact between the plunger and wear plate is achieved. In one embodiment, the first radiating element and second radiating elements are components of a first antenna assembly and a second antenna assembly, respectively, where each assembly includes components in addition to the radiating elements.
In a number of embodiments, the final assembly step for the antenna system therefore requires no tools and the system can be uninstalled just as easily without tools. Prior art systems, on the other hand, such as those using conductive tapes, gaskets, and the like are generally not capable of being easily uninstalled and reinstalled. For example, prior art technologies such as copper finger gaskets, conductive plates or the like can require one or more fasteners for installation of the grounding assembly. In such case, additional time and tools are required for installation, disassembly and any subsequent reassembly of the grounding system or antenna.
Proper grounding can also be important in dealing with electromagnetic interference (EMI) problems. Electromagnetic interference, or radio frequency interference (or RFI), is generally defined as an unwanted disturbance that affects an electrical circuit due to electromagnetic radiation emitted from an external source. The disturbance can interrupt, obstruct, or otherwise limit the effective performance of the electrical circuit. The source can be any object that carries rapidly changing electrical currents, such as an electrical circuit. In certain circumstances, an antenna transmitting and receiving signals at a relatively fast rate is such an electrical circuit and can be a troublesome source of EMI.
Improper grounding can be a primary means of noise coupling and other interference. The embodiments of grounding assemblies described herein are useful for preventing the unintended radiation of signals that would effectively become EMI. In systems demonstrating EMI problems, the grounding assemblies described herein can be used to minimize such EMI, especially in circumstances where the specific components responsible for EMI generation move relative to one another.
While the above description contains many specific embodiments of the invention, these should not be construed as limitations on the scope of the invention, but rather as examples of specific embodiments thereof. Accordingly, the scope of the invention should be determined not by the embodiments illustrated, but by the appended claims and their equivalents.
This work was sponsored under Department of Defense Contract No. F19628-00-C -0100-MP-RTIP, and subcontract A140000084-MP-RTIP. The government has certain rights in this invention.
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