Patent Description:
An antenna that is configured to be mounted to a space vehicle, such as a satellite, usually includes a number of antenna ribs that support a flexible antenna reflector layer, such as a conductive mesh. The antenna is initially stowed, and when in orbit, the antenna is deployed from its stowed position. To ensure that the antenna is deployed in orbit without snagging and binding, great care is taken when initially stowing the antenna. These antennas usually include cords and ties that interconnect the flexible antenna reflector layer to the rigid antenna ribs and ensure that when the antenna is deployed, the proper antenna curvature, such as a parabolic configuration, is maintained. The antenna cords and ties are configured to ensure there is no snagging or binding when the antenna is deployed and ensure sufficient tension is imparted to the flexible antenna reflector layer to maintain not only the desired antenna configuration, but also maintain adequate antenna performance.

Many of these antenna unfortunately are not configured for stowing in orbit. Even a partial, in-orbit stow increases the chances that the antenna ties, cords, or reflector layer may entangle during redeployment. For example, if the antenna is partially stowed in orbit, and then redeployed, often one or more of the cords, ties or flexible antenna reflector layer may bind or "snag," making redeployment challenging. Even after redeployment, if only a small segment of the flexible antenna reflector layer is folded or snagged, that segment can create undesirable antenna performance, and may sometimes even render the antenna inoperable. There are therefore advantages in configuring an antenna that may be fully deployed, and later partially or fully stowed in orbit, and then successfully deployed again without bunching, entangling or snagging the ties, cords or flexible antenna reflector layer. Examples for antennas that are configured to be mounted to a space vehicle, such as a satellite, are disclosed by the documents <CIT>, <CIT>, <CIT> and <CIT>.

In general, an antenna may comprise a plurality of rigid antenna ribs, adjacent antenna ribs being relatively moveable between first and second positions, and a flexible antenna reflector layer. A flexible support member may extend behind the flexible antenna reflector layer between adjacent antenna ribs, the flexible support strip having first and second sets of openings therein. A drawstring may extend through the first set of openings in the flexible support member between adjacent ribs. A rear support cord may be behind the flexible support member between adjacent ribs. A plurality of tie cords may end between the flexible antenna reflector layer and the rear support cord and may pass through respective ones of the second set of openings in the flexible support member. A biasing member may maintain tension in the drawstring as adjacent antenna ribs move between the first and second positions so that the flexible support member defines a pleated support body for the flexible antenna reflector layer.

The adjacent antenna ribs may be movable to a fully stowed position. The first position may comprise a deployed position and the second position may comprise a partially stowed position. The first and second sets of openings may be arranged in an alternating pattern along the flexible support member. The flexible support member may comprise a flexible strip. The biasing member may comprise a constant force spring, for example.

The flexible antenna reflector layer may comprise a conductive mesh. The plurality of antenna ribs and flexible antenna reflector surface layer may define a parabolic antenna reflector surface. An antenna hub may pivotally mount the plurality of antenna ribs. An antenna feed may be associated with the flexible antenna reflector layer. The plurality of antenna ribs may be configured to be mounted to a space vehicle.

Another aspect is directed to a method for making an antenna. The method includes coupling a flexible support member extending behind a flexible antenna reflector layer between adjacent antenna ribs, the flexible support strip having first and second sets of openings therein and adjacent antenna ribs being relatively moveable between first and second positions. The method also includes coupling a drawstring extending through the first set of openings in the flexible support member between adjacent ribs and coupling a plurality of tie cords ending between the flexible antenna reflector layer and a rear support cord and passing through respective ones of the second set of openings in the flexible support member.

The method also includes coupling a biasing member for maintaining tension in the drawstring as adjacent antenna ribs move between the first and second positions so that the flexible support member defines a pleated support body for the flexible antenna reflector layer.

Other objects, features and advantages of the present embodiments will become apparent from the detailed description which follows, when considered in light of the accompanying drawings in which:.

The present description is made with reference to the accompanying drawings, in which exemplary embodiments are shown. However, many different embodiments may be used, and thus, the description should not be construed as limited to the particular embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.

Referring now to <FIG> and <FIG>, an antenna is illustrated generally at <NUM> and includes a plurality of rigid antenna ribs <NUM> configured to be mounted to a rigid structure, bus, and/or space vehicle <NUM>, and in this example, a satellite as illustrated by the dashed configuration in <FIG>. Adjacent antenna ribs <NUM> are movable to a fully stowed position, such as when the space vehicle <NUM> as a satellite is launched into orbit. Adjacent antenna ribs <NUM> are also relatively movable between first and second positions, such as the first position corresponding to a deployed position <NUM> (<FIG>, <FIG> and <FIG>), and a second position as a partially stowed position <NUM> (<FIG>). In this example, an antenna hub <NUM> pivotally mounts the plurality of rigid antenna ribs <NUM> and may be an integral part of or mounted to the space vehicle, such as the illustrated satellite <NUM>.

A flexible antenna reflector layer <NUM>, such as formed from a conductive mesh, is carried by the rigid antenna ribs <NUM>, and in this example shown in <FIG> and <FIG>, defines a parabolic antenna reflector surface as shown by the parabolic curvature in those sectional views. In <FIG>, the dashed line referenced at <NUM> defines a cut section of the flexible antenna reflector layer, which normally covers the entire surface area defined between the rigid antenna ribs <NUM>. An antenna feed <NUM> as shown in <FIG> may be associated with the flexible antenna reflector layer <NUM> and include associated cabling or other interconnects that may interface to a transmitter or receiver carried by the space vehicle <NUM>.

A flexible support member <NUM> formed as a flexible strip may extend behind the flexible antenna reflector layer <NUM> between adjacent antenna ribs <NUM> as best shown in <FIG> and the side elevation image of <FIG>, and include first and second sets of openings <NUM>,<NUM> therein (<FIG>). A drawstring <NUM> extends through the first set of openings <NUM> in the flexible support member <NUM> between adjacent antenna ribs <NUM> and a rear support cord <NUM> is behind the flexible support member <NUM> between adjacent antenna ribs. In the example shown in <FIG>, nine (<NUM>) parallel drawstrings <NUM> extend between the illustrated antenna ribs <NUM>, and each drawstring includes an associated flexible strip <NUM>. It should be understood that this number is dependent on many factors and may change based on additional development. A much larger number of rear support cords <NUM> extend between the antenna ribs <NUM> as shown in <FIG>.

A plurality of tie cords <NUM> extend and end between the flexible antenna reflector layer <NUM> and the rear support cord <NUM> and pass through respective ones of the second set of openings <NUM> in the flexible support member <NUM> (<FIG>). A biasing member <NUM>, such as a constant force spring, maintains tension in the drawstring <NUM> as adjacent antenna ribs <NUM> move between the first and second positions <NUM>,<NUM> so that the flexible support member <NUM> defines a pleated support body for the flexible antenna reflector layer <NUM>. In an example, the first and second sets of openings <NUM>,<NUM> are arranged in an alternating pattern along the flexible support member <NUM>, which in this example is formed as a flexible strip. These openings <NUM>,<NUM> may be different in length (separation) from each other depending on the amplitudes of the flexible support member <NUM> and geometries of the rear support cords <NUM>.

The flexible antenna reflector layer <NUM> (the conductive mesh) is pleated by the flexible strip <NUM> as the adjacent antenna ribs <NUM> are moved into the second position <NUM> corresponding to the partially stowed position as shown in <FIG>. The flexible strips <NUM> create a series of parabolic curve sections that are constrained by the existing rear support cords <NUM> and plurality of tie cords <NUM> that extend and end between the flexible antenna reflector layer <NUM> and the rear support cords to assist in managing the rear support cords, tie cords, and flexible antenna reflector layer during stow and deploy operations.

The kinematic movement of the rigid antenna ribs <NUM> while stowing in orbit may disrupt the curvature and tension of the flexible antenna reflector layer <NUM>. The flexible strip <NUM> may introduce a new parabolic shape. The flexible strip <NUM> may be formed of a material to impart the parabolic shape and have some material memory. The flexible strip <NUM> also may have different amplitudes between the crest and trough and may be dependent upon the distance between the flexible antenna reflector layer as the conductive mesh <NUM> and the rear support cords <NUM>. The flexible support member <NUM> in the example of <FIG> is shown in one configuration based upon one rear support cord <NUM> geometry. However, the amplitudes of the flexible support member <NUM> may increase or decrease depending on the curvature of the rear support cords <NUM>. Each drawstring <NUM> is held constantly taut by its biasing member <NUM> that maintains tension in the drawstring as adjacent antenna ribs <NUM> move between the first and second positions <NUM>,<NUM> so that the flexible support member <NUM> defines a pleated support body for the flexible antenna reflector layer <NUM>.

The drawstring <NUM> extends through the first set of openings <NUM> in the flexible support member <NUM> between adjacent antenna ribs <NUM>. The drawstring <NUM> cooperates with the plurality of tie cords <NUM> that extend and end between the flexible antenna reflector layer <NUM> and rear support cord <NUM> and passes through respective ones of the second set of openings <NUM> in the flexible support member <NUM>. As the drawstring <NUM> is held constantly taut by the biasing member <NUM>, the distance between where the drawstring <NUM> enters and exits the flexible strip <NUM> develops a unique "pleating" result that occurs naturally to match the excess length of the rear support cord <NUM> and flexible antenna reflector layer <NUM> as a conductive mesh that is managed during partial stowing of the antenna <NUM> in orbit.

In the example of the antenna <NUM> shown in <FIG>, rear support cords <NUM> are spaced along the adjacent antenna ribs <NUM>. The drawstrings <NUM> and flexible support members <NUM> as the flexible strips are placed in this example between about every fourth to sixth rear support cord <NUM> depending on the configuration of the antenna <NUM> and how much control the rear support cords <NUM> and flexible antenna reflector layer <NUM> require in management during the stowing and deployment operation.

The length of the flexible strip <NUM>, the number of periods, amplitudes, and tie cord <NUM> spacing (<FIG>) is dependent upon the distance between the adjacent antenna ribs <NUM> and the number of rear support cords <NUM> and the shape of the antenna <NUM>. The drawstring <NUM> constrains the flexible strip <NUM> along a single axis to prevent buckling, twisting and/or snagging during stowing and deployment operations of the antenna <NUM>.

As noted before, the biasing member <NUM> may be formed as a constant force spring and maintains the tension in the drawstring <NUM> as adjacent antenna ribs <NUM> move between the first and second positions <NUM>,<NUM> so that the flexible support member as the flexible strip <NUM> defines a pleated support body for the flexible antenna reflector layer <NUM>. In the example of the schematic diagram of the biasing member <NUM> of <FIG>, a biasing member housing <NUM> supports a spool <NUM> with the drawstring <NUM> wrapped around the spool and contained within the biasing member housing. The spool <NUM> is carried by a support shaft <NUM> and a constant force spring <NUM> has one end attached to the support shaft <NUM>, and the other end attached to the spool <NUM> to maintain constant tension on the drawstring <NUM>. In this example, the biasing member <NUM> formed with the constant force spring <NUM> may be configured as a <NUM>:<NUM> system where the length of the constant force spring is equal to the length of the drawstring <NUM> to be stored.

Each drawstring <NUM> includes an associated biasing member <NUM> connected to the drawstring <NUM> (<FIG>). In the example of <FIG>, nine biasing members <NUM> are connected to the nine drawstrings <NUM>. Although not illustrated, it is also possible to use a geared spring real that incorporates a shaft and a constant force spring <NUM> that is attached to a gear contained within a housing and a spool carried by another shaft. The drawstring <NUM> is wrapped around the spool carried by the second shaft. This second type of system could be a <NUM>:<NUM> system where the length of a constant force spring <NUM> is one-third of the length of the drawstring <NUM> to be stored. This differentiator is important because due to weight constraints or physical properties of the constant force spring <NUM>, the overall length may be limited in size and may not be able to extend all the way across the panel defined by the flexible antenna reflector layer <NUM> to the other adjacent antenna rib <NUM> towards the outboard portions of the flexible antenna reflector layer.

The antenna <NUM> achieves a "hands-off," in orbit stow and deploy process. The flexible antenna reflector layer as a conductive mesh <NUM> in an example may be pleated successfully without tangling, and the rear support cords <NUM> and tie cords <NUM> successfully managed not only during stowing of as much as <NUM>%-<NUM>% of the antenna <NUM>, but also during a redeployment cycle. This configuration allows the antenna <NUM> to be more resilient in operation during specific mission scenarios and overcomes the technical drawbacks with current deployable conductive mesh and reflector antenna technologies.

The antenna <NUM> also minimizes and alleviates the requirement for adaptation of numerous types of stowage devices to organize and stow the various components of the antenna, including the flexible antenna reflector layer as the example conductive mesh <NUM>. Different manufacturing techniques may be used and an example is shown in the high-level flowchart of <FIG>. A method for making the antenna <NUM> is illustrated generally at <NUM>.

Claim 1:
An antenna (<NUM>) comprising:
a plurality of rigid antenna ribs (<NUM>), adjacent antenna ribs being relatively moveable between first and second positions (<NUM>, <NUM>); and
a flexible antenna reflector layer (<NUM>);
wherein the antenna is characterized by
a flexible support member (<NUM>) extending behind the flexible antenna reflector layer (<NUM>) between adjacent antenna ribs, the flexible support member having first and second sets of openings (<NUM>, <NUM>) therein;
a drawstring (<NUM>) extending through the first set of openings (<NUM>) in the flexible support member between adjacent ribs;
a rear support cord (<NUM>) behind the flexible support member between adjacent ribs;
a plurality of tie cords (<NUM>) ending between the flexible antenna reflector layer and the rear support cord and passing through respective ones of the second set of openings (<NUM>) in the flexible support member; and
a biasing member (<NUM>) for maintaining tension in the drawstring as adjacent antenna ribs move between the first and second positions so that the flexible support member defines a pleated support body for the flexible antenna reflector layer.