Communications: radio wave antennas – Antennas – Antenna components
Reexamination Certificate
1999-03-02
2001-06-05
Phan, Tho G (Department: 2821)
Communications: radio wave antennas
Antennas
Antenna components
C343S880000, C343S882000, C343S912000, C052S111000
Reexamination Certificate
active
06243053
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to deployable antenna reflector structures. More particularly, the present invention relates to an improved antenna reflector structure that provides a reduced number of components without compromising mechanical stability or deployment reliability.
2. Discussion of the Related Art
In the field of space exploration, large structures must often be foldable in order to fit into launch vehicles having limited cargo capacity. Once in space, these structures must deploy to a size sufficiently large to justify the cost of launching them. A typical such structure is a large aperture antenna reflector. Current deployable antenna reflector structures are quite complex with large numbers of truss elements having varying sizes and varying designs. For example, antenna reflector deployment typically requires the pivoting of truss elements around multiple axes that point in multiple directions. This complexity causes the manufacture of a single antenna reflector to be very costly due to time consuming assembly and high component costs. Current antenna reflector structures are also not very adaptable to multiple applications.
A substantial reason for such complicated antenna reflector designs has been the need to achieve a sufficient level of mechanical stability as well as deployment reliability. Mechanical stability has typically been achieved through box truss hoops or multiple triangular configurations—both requiring three-dimensional element designs with multiple components. Deployment reliability has been achieved through complex synchronization mechanisms or solenoid operated latch arrangements—both requiring additional weight and cost. Deployment reliability also depends on the method of mesh stowing and deployment.
The large number of components also causes current antenna reflector structures to be extremely heavy, which reduces the launch vehicle cargo capacity and reduces the stowed natural frequency. The stowed natural frequency is significant because launch vibrations matching the natural frequency or one of its harmonics may cause substantial damage to the antenna reflector. Thus, there is a need to combat the problem created by complex antenna reflector structure designs without compromising mechanical stability or deployment reliability.
SUMMARY OF THE INVENTION
The deployable antenna reflector structure of the present invention uses a truss hoop with identical elements and parallel pivot axes to transition from a stowed position to a deployed position. The use of identical elements provides reduced manufacturing costs due to the reduction in components and the added simplicity of the design. The truss hoop achieves mechanical stability by making use of a two-dimensional element design having vertical portions and horizontal portions located in the same plane. An example of such a design is a S-shape. With adjacent identical elements facing in opposite directions, the parallel pivot axes connect the identical elements to create a structurally sound truss hoop.
The parallel pivot axes also add to simplicity without compromising mechanical stability. Each parallel pivot axis is defined by two pivot points. The first pivot point connects the horizontal portions of the identical elements and the second pivot point connects the vertical portions of the identical elements. The use of pivot points along parallel axes allows the truss hoop to maintain stiffness in spite of the two-dimensional design of the identical elements. The square of angular frequency for a truss hoop equals stiffness divided by mass. The design therefore provides a high natural frequency for the truss hoop due to an increased stiffness and decreased mass. The first pivot point provides potential energy when the structure is in the stowed position, and the second pivot point is a unidirectional joint that prevents the structure from transitioning out of the deployed position once deployed. Therefore, each pivot point serves a distinct purpose while maintaining structural simplicity.
The deployable antenna reflector structure also includes a reflector and a deployment control mechanism. The reflector guides antenna signals either to or from an antenna feed when the structure is in the deployed position. Compartmentalizing the reflector between the identical elements when the structure is in the stowed position improves deployment reliability and provides minimal stowing volume. The deployment control mechanism determines when the parallel pivot axes transition the structure from the stowed position to the deployed position.
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patent: 5864324 (1999-01-01), Acker et al.
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patent: 6028570 (2000-02-01), Gelger et al.
Keller Robert W.
Phan Tho G
TRW Inc.
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