Patent Description:
The present disclosure relates generally to mesh articles (e.g., an antenna). More particularly, the present disclosure relates to articles comprising a mesh formed of a Carbon Nano-Tube ("CNT") yarn.

Satellites require Radio Frequency ("RF") energy concentrating antennas to provide high gain. These antennas comprise precision parabolic or similar shaped antenna reflectors that are carried into space using launch vehicles. The antenna reflectors may be formed of knitted mesh materials. One such knitted mesh material comprises a gold plated tungsten wire (e.g., such as that disclosed in <CIT>) or a gold plated molybdenum wire. These gold plated wire mesh materials have two inherent deficiencies for antenna applications. First, the gold plated wire has a high solar absorptivity to hemispherical emissivity ratio (e.g., αsolar/εH = <NUM>) which results in high mesh temperatures. Secondly, the gold plated wire has a relatively high Coefficient of Thermal Expansion ("CTE") (e.g., approximately <NUM> ppm/C° for the tungsten wire and approximately <NUM> ppm/C° for the molybdenum wire). The high αsolar/εH ratio in conjunction with the high CTE results in thermal distortion of the antenna reflector due to on-orbit temperatures. This thermal distortion degrades antenna performance, for example, by reducing gain and increasing sidelobe levels.

Further prior art can be found in <CIT> which generally relates to optical and microwave reflectors comprising tendrillar mat structure, in<NPL>, in <NPL>, in <CIT> which generally relates to a multi-layer highly reflective flexible mesh surface and reflector antenna and in <CIT> which generally relates to a reflector surface for deployable reflector.

The invention is set out in the independent claim.

The present disclosure concerns an antenna reflector. The antenna reflector comprises a mesh material formed of a Carbon Nano-Tube ("CNT") yarn that is reflective of radio waves and has a low αsolar/εH ratio and a low CTE. The mesh material has an areal density that is less than ten percent of an areal density of a mesh material formed using a gold plated tungsten or molybdenum wire with a diameter equal to the diameter of the CNT yarn.

The low αsolar/εH ratio is less than <NUM>% of the αsolar/εH ratio of a gold plated tungsten or molybdenum wire. The low CTE is more than an order of magnitude less than a CTE of gold plated tungsten or molybdenum wire. For example, the low CTE is equal to -<NUM> ppm/C°. In those or other scenarios, the mesh material is a knitted mesh material. The knitted mesh material may have a tricot configuration and/or have <NUM>-<NUM> openings per <NUM> (<NUM>-<NUM> openings per inch).

The present solution will be described with reference to the following drawing figures, in which like numerals represent like items throughout the figures.

The present solution may be embodied in other specific forms without departing from its essential characteristics. The described embodiments are to be considered in all respects only as illustrative and not restrictive. The scope of the present solution is, therefore, indicated by the appended claims rather than by this detailed description.

Furthermore, the described features, advantages and characteristics of the present solution may be combined in any suitable manner in one or more embodiments. One skilled in the relevant art will recognize, in light of the description herein, that the present solution can be practiced without one or more of the specific features or advantages of a particular embodiment. In other instances, additional features and advantages may be recognized in certain embodiments that may not be present in all embodiments of the present solution.

Reference throughout this specification to "one embodiment", "an embodiment", or similar language means that a particular feature, structure, or characteristic described in connection with the indicated embodiment is included in at least one embodiment of the present solution.

The present solution concerns articles comprising a mesh formed of a CNT yarn. The present solution is described herein in relation to antenna applications. The present solution is not limited in this regard. The CNT yarn disclosed herein can be used in other applications in which a mesh with a low αsolar/εH ratio and/or a low CTE is needed, but these applications do not form part of the claimed invention.

One type of wire used for mesh antennas is a gold plated molybdenum wire (as noted above in the Background section of this paper). The gold plated molybdenum wire has the following properties: a small diameter (e.g., <NUM> - <NUM> mil); a high solar absorptivity to hemispherical emissivity ratio (e.g., αsolar/εH = <NUM>); and a high CTE (e.g., <NUM> ppm/C°). The mesh produced with gold plated molybdenum wire has an acceptable stiffness and areal density. Areal density refers to the mass of the mesh per unit area. The areal density of the mesh material is a function of wire diameter, knit type configuration, and/or openings per inch.

Despite the benefits of mesh antennas incorporating gold plated tungsten or molybdenum wire, these mesh antennas suffer from certain drawbacks. First, the gold plated wire has a high solar absorptivity to hemispherical emissivity ratio (e.g., αsolar/εH = <NUM>) which results in high mesh temperatures. Secondly, the gold plated wire has a relatively high CTE (e.g., approximately <NUM> ppm/C° for the tungsten wire and approximately <NUM> ppm/C° for the molybdenum wire). The high αsolar/εH ratio in conjunction with the high CTE results in thermal distortion of the antenna reflector due to on-orbit temperatures.

Accordingly, the mesh antennas of the present solution are formed from a CNT yarn rather than from a gold plated tungsten or molybdenum wire. The CNT yarn has the following properties: a small diameter (e.g., <NUM>-<NUM> mil); a low solar absorptivity to hemispherical emissivity ratio (αsolar/εH = <NUM>); and a low CTE (e.g., -<NUM> ppm/C°). The αsolar/εH ratio and low CTE of the CNT yarn allows for antenna reflectors with enhanced performance and higher operational frequency capabilities. The low αsolar/εH ratio reduces the thermal distortion experienced by the mesh reflector surface compared to that experienced in conventional mesh reflectors formed of gold plated tungsten or molybdenum wire by reducing mesh temperatures. The low CTE also reduces the thermal distortion experienced by the mesh reflector surface compared to that experienced in conventional mesh reflectors formed of gold plated tungsten or molybdenum wire. The knittability of the CNT yarn allows for a relatively wide range of possible openings per mm/inch (e.g., <NUM>-<NUM> openings per <NUM> / <NUM>-<NUM> openings per inch) in a knitted material. Additionally, the CNT yarn provides mesh materials with areal densities that are less than ten percent of the areal density of a mesh material formed using the gold plated tungsten or molybdenum wire with a diameter equal to the diameter of the CNT yarn.

Notably, the ability to create a usable mesh from a CNT yarn for antenna applications has not been achievable in the past. However, with the creation of a new CNT yarn described herein, a mesh that is usable for antenna applications is now achievable. The new CNT yarn is applicable to any mesh antenna. This includes antennas with unfurlable mesh reflectors (i.e., a deployable reflector that transitions from a closed position to an open position) and fixed mesh reflectors (i.e., an antenna reflector that does not deploy).

Referring now to <FIG>, there is provided an illustration of an illustrative mesh antenna <NUM> for radiating a narrow beam of radio waves for point-to-point communications in satellite dishes. The mesh antenna <NUM> has a CNT yarn incorporated therein. The CNT yarn includes, but is not limited to, a Miralon® yarn available from Nanocomp Technologies, Inc. of Merrimack, New Hampshire. An image of the CNT yarn is provided in <FIG>. The CNT yarn is strong, lightweight, and flexible. The CNT yarn has a low solar absorptivity to hemispherical emissivity ratio (e.g., αsolar/εH = <NUM>). In some scenarios, the low αsolar/εH ratio is less than <NUM>% of the αsolar/εH ratio of a gold plated tungsten or molybdenum wire. The CNT yarn also has a low CTE that is more than an order of magnitude less than a CTE of a gold plated tungsten or molybdenum wire. For example, the CNT yarn has a CTE equal to -<NUM> ppm/C°. All of these features of the CNT yarn are desirable in antenna applications and/or space based applications.

As shown in <FIG>, the mesh antenna <NUM> comprises an antenna reflector <NUM> configured to reflect Electro-Magnetic ("EM") energy in the radio wave band of the EM spectrum. The antenna reflector <NUM> is shown as comprising a fixed mesh reflector (i.e., an antenna reflector that does not deploy). The present solution is not limited in this regard. The antenna reflector <NUM> can alternatively comprise an unfurlable mesh reflector (i.e., a deployable reflector that transitions from a closed position to an open position). In both cases, a mechanical support structure is provided for the mesh. Such mechanical support structures are well known in the art, and therefore will not be described herein. For example, in a fixed mesh reflector scenario, the mechanical support structure comprises a hoop or ring <NUM> formed of a rigid or semi-rigid material (e.g., graphite composite, metal or plastic). In contrast, in an unfurlable mesh reflector scenario, the mechanical support structure typically comprises either radial or perimeter structural elements. A cord network may also be provided to assist in shaping the reflector surface and keeping the mesh taut during operation of the antenna <NUM>.

The antenna reflector <NUM> is formed of a knitted mesh material, has a generally parabolic shape, and has a relatively high directivity. The knitted mesh material includes, but is not limited to, a single layer of mesh. The knitted mesh material comprises a series of interlocking loops <NUM> formed from the CNT yarn. The knitted mesh material has a number of openings per inch selected based on the frequency of the EM energy to be reflected by the mesh antenna <NUM> (e.g., <NUM>-<NUM> openings per <NUM> / <NUM>-<NUM> openings per inch). The parabolic shape focuses a beam signal into one point.

The present solution is not limited to knitted mesh materials. In other applications, the mesh material is a weave material rather than a knitted material. The weave material comprises a first set of filaments intertwined with a second set of filaments. Interstitial spaces or openings may be provided between the filaments.

In some scenarios, the knitted mesh material of the antenna reflector <NUM> comprises a tricot type knit configuration as shown in <FIG>. The present solution is not limited in this regard. Other types of knit configurations can be used herein instead of the tricot knit configuration. The tricot type knitted material <NUM> has an opening count of <NUM>-<NUM> per <NUM> (<NUM>-<NUM> openings per inch). Each opening <NUM> is defined by multiple loops of CNT yarn <NUM>. The tricot type knitted material <NUM> has an areal density that is less than ten percent of an areal density of a tricot type knitted mesh material formed using a gold plated tungsten or molybdenum wire with a diameter equal to the diameter of the CNT yarn.

Claim 1:
An antenna reflector (<NUM>), comprising:
a mesh material formed of a Carbon Nano-Tube, CNT, yarn that is reflective of radio waves and has a low solar absorptivity to hemispherical emissivity ratio, αsolar/εH ratio, wherein the low αsolar/εH ratio is less than <NUM>% of a αsolar/εH ratio of a gold plated tungsten or molybdenum wire with a diameter equal to the diameter of the CNT yarn;
and a low Coefficient of Thermal Expansion, CTE, wherein the low CTE is more than an order of magnitude less than a CTE of a gold plated tungsten or molybdenum wire with a diameter equal to the diameter of the CNT yarn.