The present invention relates to the field of antennas, and is more particularly concerned with a lightweight deployable aperture reflectarray antenna reflector for use in spacecrafts and the like.
It is well known in the art of spacecraft antennas to use reflectors with large apertures to increase the RF (Radio-Frequency) performance of the antenna. When the size of such large aperture reflectors is larger than the launch vehicle shroud, they are usually in a stowed aperture configuration for spacecraft launch (in addition of the reflector boom support structure being also stowed against the spacecraft), and need to be unfurled in a deployed aperture configuration once on orbit (and in a previously deployed configuration of the reflector boom support structure). Deployable aperture reflectors are very complex in nature, with many movable parts required to achieve a desired precise as-deployed reflecting surface shapes. Common deployable reflector designs used in L-, C- and Ku-band applications generally employ a combination of rigid deploying members, hinges and a compliant RF reflective mesh which is tensioned to confer a parabolic shape. The shaping of such a design is typically limited to a global concave geometry with the possibility of coarse localized convex shapes. A reflector surface requires better surface accuracy for use at higher frequency bands (such as at Ka-band, V-band, etc.).
Such deployable apertures are time consuming and expensive to design and manufacture, especially for higher frequency band application, thus driving the need for more parts in order to achieve a finer surface definition when the aperture is in its final deployed aperture configuration, on orbit.
Reflectarrays have been proposed as a mean to make a planar mechanical surface yield the performance of an ideally shaped reflector (parabolic or other). The use of a planar reflector however results in significant bandwidth limitation due to the difference between the frequency sensitive resonant element (reflectarray) correction and that which would be achieved with the desired true time delay reflector optics.
Accordingly, there is a need for an improved deployable aperture reflectarray reflector for use in spacecrafts and the like.
It is therefore a general object of the present invention to provide an improved deployable aperture reflectarray reflector to obviate the above-mentioned problems.
An advantage of the present invention is that the deployable aperture reflector, using the reflectarray technology, achieves the desired virtual theoretical electrical reflecting (or conducting) surface shape.
Another advantage of the present invention is that the deployable aperture reflectarray reflector allows for reduced overall weight, design and analysis times and costs, and manufacturing time and cost, including less moving parts for the aperture deployment than a conventional fine shaping of a reflecting surface, for a same electrical RF performance.
A further advantage of the present invention is that the deployable aperture reflectarray reflector allows for the use of simpler/coarser initial shapes of the different facetted cells that are electrically (RF-wise) refined with metallic (or electrically reflecting/conducting) patches.
Still another advantage of the present invention is that the deployable aperture reflectarray reflector typically includes a plurality of flexible cell surfaces composed of at least one generally RF transparent layer having electrically conductive patch elements thereon (reflectarray technology).
Yet another advantage of the present invention is that the deployable reflectarray reflector can be optimized to provide different performance characteristics for different frequency bands.
Yet a further advantage of the present invention is that the deployable reflectarray reflector can reproduce an equivalent refined optical shaping of multiple localized convex and concave geometries from a surface constituted of coarse flat surfaces (at least in one direction).
Still a further advantage of the present invention is that the reflective assembly is only tensioned into shape in its deployed configuration. It is flexible and compliant such that a minimum stowed volume can be achieved.
According to an aspect of the present invention there is provided a deployable aperture reflector for use in antennas to reflect an RF electromagnetic signal of a predetermined signal frequency band, said reflector comprising:
In one embodiment, the at least one layer includes one layer carrying the RF resonant elements thereon.
In one embodiment, the at least one layer includes one layer carrying the RF resonant elements on at least one of a front side and a rear side thereof.
In one embodiment, the at least one layer includes a plurality of layers, at least one of the plurality of layers carrying the RF resonant elements thereon.
In one embodiment, the at least one layer includes a front layer and a rear layer spaced from one another, said rear layer being flexible and generally reflective to the RF electromagnetic signal, said front layer being flexible and generally transparent to the RF electromagnetic signal, said front layer carrying the RF resonant elements thereon.
In one embodiment, each said faceted cell is substantially rectilinear in at least one direction, conveniently in a generally circumferential direction.
In one embodiment, each said faceted cell is substantially rectilinear in both a generally circumferential direction and a generally radial direction.
In one embodiment, each said faceted cell is substantially curved in at least one direction, conveniently in a generally radial direction.
Other objects and advantages of the present invention will become apparent from a careful reading of the detailed description provided herein, with appropriate reference to the accompanying drawings.
Further aspects and advantages of the present invention will become better understood with reference to the description in association with the following Figures, in which similar references used in different Figures denote similar components, wherein:
With reference to the annexed drawings the preferred embodiment of the present invention will be herein described for indicative purpose and by no means as of limitation.
Referring to
The embodiment of
Since the optimal desired electrical surface shape 36 is usually curved in all directions, while the surfaces of each of the faceted cells 32 are generally rectilinear into at least one direction (such as the circumferential direction in the embodiment of
Now referring more specifically to
In
When a plurality of layers 38 are used to form the faceted cells 32 of the RF reflective assembly 30, it could be considered to use some, preferably RF transparent, spacers 42 between adjacent layers 38 to control the distance there between.
As shown in
As illustrated in
In one embodiment, the at least one layer includes a plurality of layers, with at least one of the plurality of layers carrying the RF resonant elements thereon.
In one embodiment, the at least one layer includes a front layer 38f and a rear layer 38r spaced from one another. The rear layer 38r could be flexible and generally reflective to the RF electromagnetic signal, while the front layer 38f would be flexible and generally transparent to the RF electromagnetic signal, with the front layer 38f having or carrying the RF resonant elements 40 thereon.
Although not illustrated, one skilled in the art would readily realize that, without departing from the scope of the present invention, when a plurality of layers 38 are considered for each faceted cell 32, at least one of the plurality of layers 38 carries the RF resonant elements 40 thereon. Also, a same layer 38 could have patches 40 on at least one of a front side and a rear side thereof.
Although the present invention has been described with a certain degree of particularity, it is to be understood that the disclosure has been made by way of example only and that the present invention is not limited to the features of the embodiments described and illustrated herein, but includes all variations and modifications within the scope of the invention as hereinabove described and hereinafter claimed.
This application claims priority of U.S. Provisional Application for Patent No. 62/668,304 filed May 8, 2018, the content of which is incorporated herein by reference in its entirety.
Number | Date | Country | |
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62668304 | May 2018 | US |