EXPANDABLE APERTURE COUPLED STACKED PATCH ANTENNA

Abstract

A stacked patch antenna is expandable from a thinner stowed configuration in which the gaps between the conductor layers are reduced, to a thicker deployed configuration in which the gaps are expanded to their required dimensions. The expansion mechanism can include rotation of threaded rods, pneumatic expansion of telescoping rods, and/or injection of a gas, a chemical sublimate, and/or an expandable foam into the gaps. In embodiments, the stowed thickness of the antenna can be approximately equal to the sum of the thicknesses of the conductor panels. In some of these embodiments high dielectric layers are not included. In other of these embodiments high dielectric layers are formed by filling gaps with a high dielectric foam. Embodiments implement aperture coupling to the stacked patch antenna. An array of the stacked patch antennae can be folded about a satellite until deployment, and can be planar when unfolded and deployed.

Claims

1. An expandable stacked patch antenna that can be implemented on a communication platform for RF communication, the stacked patch antenna comprising: a ground plane applied to a ground plane panel; a plurality of conducting patches substantially aligned with each other above the ground plane, each of the conducting patches being applied to a patch supporting panel; an RF feed suitable for communication with the stacked patch antenna; and to an expansion mechanism configured to transition the plurality of conducting patches from: a stowed configuration in which gaps between the ground plane and patch supporting panels are minimized; to a deployed configuration in which the gaps between the ground plane and patch supporting panels are enlarged as needed such that the antenna is optimized for communication over a specified range of RF frequencies.

2. The stacked patch antenna of claim 1, wherein the RF feed is an aperture coupled to the stacked patch antenna.

3. The stacked patch antenna of claim 1, wherein the expansion mechanism includes at least one rotatable threaded rod configured to adjust at least one of the gaps between the ground plane and patch supporting panels.

4. The stacked patch antenna of claim 1, wherein the expansion mechanism includes at least one telescoping, pneumatically extendable rod configured to adjust at least one of the gaps between the ground plane and patch supporting panels when the telescoping rod is extended.

5. The stacked patch antenna of claim 4, wherein the telescoping rod includes at least one locking pin or nub configured to fix and secure a length of the telescoping rod when the telescoping rod is extended.

6. The stacked patch antenna of claim 1, wherein the expansion mechanism includes a fluid reservoir containing a fill material, the fluid reservoir being in fluid communication with a thin-walled inflatable container that is inserted within one of the gaps between the ground plane and patch supporting panels, the fluid reservoir and thin-walled inflatable container being configured to expand the gap in which the thin-walled container is inserted when the thin-walled inflatable container is inflated with the fill material.

7. The stacked patch antenna of claim 6, wherein the fill material is one of: a gas; a chemical sublimate; an expandable foam; a low dielectric fill material having a dielectric constant of less than 1.2; and a high dielectric fill material having a dielectric constant of greater than 2.

8. The stacked patch antenna of claim 1, wherein at least one of the gaps between the ground plane and patch supporting panels is determined by at least one limiting cable extending between the layers that bound the gap.

9. The stacked patch antenna of claim 1, wherein the stacked patch antenna is an antenna array comprising a plurality of stacked patch sub-antennae.

10. The stacked patch antenna of claim 9, wherein when the stacked patch antenna is in its deployed configuration, the stacked patch sub-antennae are arranged in a planar cross pattern comprising four stacked patch sub-antennae extending in four perpendicular directions from a common center area.

11. The stacked patch antenna of claim 10, further comprising a fifth stacked patch sub-antenna located in the common center area.

12. The stacked patch antenna of claim 9, wherein when the stacked patch antenna is in its deployed configuration, the stacked patch sub-antennae are arranged as a single, linear row of stacked patch sub-antennae.

13. The stacked patch antenna of claim 9, wherein when the stacked patch antenna is in its deployed configuration, the stacked patch sub-antennae are arranged as a grid of stacked patch sub-antennae.

14. The stacked patch antenna of claim 9, wherein when the stacked patch antenna is in its stowed configuration, the antenna array is folded about the communication platform.

15. A method of implementing a high gain broadband antenna on a communication platform, the method comprising: providing a stacked patch antenna according to claim 1, the stacked patch antenna being in its stowed configuration; incorporating the stacked patch antenna onto and/or into the communication platform; and activating the expansion mechanism of the stacked patch antenna, thereby causing the stacked patch antenna to transition to its deployed configuration.

16. The method of claim 15, wherein the communication platform is a satellite, and wherein the expansion mechanism is activated after launch of the satellite into space.

17. The method of claim 15, wherein the expansion mechanism includes a fluid reservoir containing a fill material, the fluid reservoir being in fluid communication with an inflatable thin-walled container that is inserted within one of the gaps between the ground plane and patch supporting panels, the fluid reservoir and thin-walled inflatable container being configured to expand the gap in which the thin-walled container is inserted when the thin-walled inflatable container is inflated with the fill material.

18. The method of claim 17, wherein the thin-walled container is shaped as a cuboid when inflated with the fill material.

19. The method of claim 15, wherein the expansion mechanism includes at least one of: a threaded rod configured to adjust at least one of the gaps between the ground plane and patch supporting panels; and a telescoping, pneumatically extendable rod configured to adjust at least one of the gaps between the ground plane and patch supporting panels when the telescoping rod is extended.

20. The method of claim 19, wherein the stacked patch antenna is an antenna array comprising a plurality of stacked patch sub-antennae, and wherein when the stacked patch antenna is in its stowed configuration, the antenna array is folded about the communication platform.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0039] FIG. 1A is an exploded view of a microstrip antenna of the prior art;

[0040] FIG. 1B is an exploded view of a stacked patch antenna of the prior art;

[0041] FIG. 1C is an exploded view of a four element, cross-shaped stacked patch antenna array of the prior art, shown in a planar, deployed configuration;

[0042] FIG. 1D is a perspective view of the antenna array of FIG. 1C folded about the surfaces of a satellite;

[0043] FIG. 1E is an exploded view of a stacked patch antenna of the prior art where the patches are arranged in a single column above a cubical Small Sat;

[0044] FIG. 1F is a perspective view that illustrates how the two outer patch sub-antennae of the stacked array of FIG. 1E can be folded down toward the cube-sat 114 during stowage.

[0045] FIG. 2 is an exploded view of a stacked patch antenna of the prior art having gaps between the conducting layers that are filled with dielectric spacer layers;

[0046] FIG. 3A is a cross-sectional side view of an embodiment of the present invention in which the expansion mechanism includes threaded rods, where the embodiment is shown in a collapsed configuration;

[0047] FIG. 3B is a cross-sectional side view of the embodiment of FIG. 3A shown in an expanded, deployed configuration;

[0048] FIG. 4A is a cross-sectional side view of an embodiment of the present invention in which the expansion mechanism includes pneumatically expandable telescoping rods, where the embodiment is shown in a collapsed configuration;

[0049] FIG. 4B is a cross-sectional side view of the embodiment of FIG. 4A shown in an expanded, deployed configuration;

[0050] FIG. 4C is a cross-sectional side view of an embodiment similar to FIG. 4B shown in an expanded, deployed configuration, wherein each of the expanded layers is fixed to one of a plurality of nested inner sections of the telescoping rods;

[0051] FIG. 5 is a cross-sectional side view of an embodiment of the present invention in which the expansion mechanism includes thin-walled inflatable containers inserted between the conductive panels, as well as a fill-containing reservoir provided within the satellite that is in fluid communication with the containers; and

[0052] FIG. 6 is a cross-sectional side view of an embodiment similar to FIG. 5, but including both a reservoir containing low dielectric material and a separate reservoir containing high dielectric material.

DETAILED DESCRIPTION

[0053] The present disclosure is a high gain, broadband antenna design that can be implemented on a communication platform. Embodiments are, suitable for space constrained platforms, including Small-Sats. The disclosed antenna is an expandable stacked patch antenna having a significantly reduced weight and stowed thickness in which the gaps between the conductor layers are reduced or eliminated, while being expanded upon deployment by an expansion mechanism so as to provide the required gaps between the conductor layers.

[0054] In some embodiments, spacer layers 200a, 200b, 202 are not included in the design, such that the total thickness of the antenna in its stowed configuration is approximately equal to the sum of the thicknesses of the panels 102a, 102b, 106 upon which the conductors are deposited. In the embodiment of FIG. 3A, a high dielectric foam spacer layer 202 is included in the design, and is not compressed in the stowed configuration. Accordingly, the total thickness of the antenna when stowed is the sum of the thicknesses of the panels 102a, 102b, 106 and the high dielectric spacer layer 202.

[0055] In the embodiment of FIG. 3A, the expansion mechanism includes threaded rods 300. FIG. 3A illustrates the embodiment in the stowed configuration, occupying minimal space and without the added weight of dielectric spacers. In the illustrated embodiment, there are two patches 100a, 100b located on respective high dielectric layer 102a, 102b. There is a high dielectric spacer layer 202 orientated above the ground plane 106 and the entire unit is located inside a cube sat 114. It should be apparent that similar embodiments can include additional patches following the same design. A separate feed substrate panel 108 has an upper surface and a bottom surface with a ground plane 106 on the upper surface with and RF feed 112 (see FIG. 2) applied to the bottom surface of the panel 108. The RF feed is coupled to the receiver or transceiver of the satellite.

[0056] During deployment of the antenna of FIG. 3A, the threaded rods 300 are raised and lowered by an electric motor 302 according to instructions received from a controller 304. In the illustrated example, the motor 302 rotates a shaft 306 which is terminated by worm gears that transfer rotation to bushings 308 that are in threaded engagement with the rods 300. The uppermost layer 102a of the patch antenna is fixed to and lifted by the rods 300, while the middle layers 102b, 202 include enlarged holes that allow the threaded rods 300 to pass through. In one example the layers 102a, 102b, 202, 108 are square or rectangular, and there are four threaded rods 300 located in holes in the corners of the layers.

[0057] FIG. 3B is a cross sectional side view of the embodiment of FIG. 3A shown after deployment of the antenna. It can be seen in the figure that as the upper layer 102a is lifted by the threaded rods 300, the middle layers 102B, 202 are lifted by limiting cables 310 that extend from the upper layer 102a to the middle layers 102b, 202. Additional limiting cables 310 extend from the middle layers 102b, 202 to the feed substrate panel 108. The gaps between the layers 102a, 102b, 202 are thereby fixed according to the lengths of the limiting cables 310.

[0058] In some embodiments, extension of the rods 300 continues until the limiting cables 310 are fully extended or until the rods 300 are fully extended or a stop pin is reached when the optimal spacing is achieved.

[0059] In similar embodiments, a separate set of threaded rods is associated with and fixed to each of the layers 102a, 102b, 202, while clearance holes are provided in the other layers as needed, such that all of the layers 102a, 102b, 202 are lifted by their associated threaded rods 300. This approach not only provides for deployment of the antenna, but also enables the gaps to be adjusted after deployment so as to optimize the antenna for different transmit frequencies and bandwidths.

[0060] In various embodiments, low dielectric gaps can be filled with are air, a gas such as nitrogen, or a vacuum, since vacuum and virtually all gases and have very similar low dielectric constants.

[0061] The optimal spacings between the patches 102a, 102b, 202 and the ground plane 108 are selected so as to provide optimal performance for the desired frequency range. For example, the spacing can be selected such that the radio waves generated by all of the patches add together coherently in the desired transmit direction at the center frequency of the antenna bandwidth or at the highest frequency of the antenna bandwidth. Another approach is to adjust the spacing between patches such that each pair is optimized for a slightly different frequency, thereby “stagger tuning” the antenna and further increasing its bandwidth. Known approaches to determining the panel and dielectric materials and the gaps between patches can be used when designing embodiments of the present disclosure, such as the approaches and formulae that appear in IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION, VOL. 46, NO. 9, SEPTEMBER 1998, which is incorporated herein in its entirety for all purposes.

[0062] In other embodiments, the expansion mechanism employs pneumatically expandable telescoping rods. In the example of FIG. 4A, each of the telescoping rods includes two concentric sections 400, 402, with the inner section 402 being sealed such that gas from a pressurized gas cylinder 404 in fluid communication with the outer sections 400 via connecting pipes 406 can push the inner section 402 upwards to a pre-defined height. FIG. 4A illustrates the embodiment in its stowed, minimum thickness configuration, while FIG. 4B illustrates the same embodiment after deployment of the antenna. There can be locking pins or nubs on the rods 400, 402 such that the rods 400, 402 are secured in place once deployed to the desired heights. In a manner similar to the example of FIGS. 3A and 3B, the inner telescoping rods 402 are fixed to the uppermost layer 102a, while clearance holes are provided in the middle layers 102b, 202, which are lifted and fixed in position by limiting cables 310.

[0063] With reference to FIG. 4C, in similar embodiments separate, nested inner sections 402a, 402b are provided, with each of the nested inner sections 402a, 402b being fixed to one of the expanded layers 102a, 102b, 202. Upon expansion, locking pins or nubs on the rods 400, 402a, 402b ensure that they are deployed to their desired lengths. The lengths of the nested sections 402a, 402b thereby determine the gap spacings.

[0064] With reference to FIG. 5, in other embodiments the expansion mechanism comprises thin-walled inflatable containers 500a, 500b that are inserted between the panels 102a, 102b, 108 on which the conductors are deposited, as well as at least one reservoir 502 provided within the satellite 114 that is in fluid communication with the containers 500a, 500b and contains a fill material. Deployment of the antenna is accomplished in these embodiments by causing a controller 304 to open a valve 504 so as to inject the fill material from the reservoir 502 into the thin-walled containers 500a, 500b, thereby inflating the thin-walled containers 500a, 500b and separating the panels 102a, 102b, 106 from each other to create the required gaps.

[0065] In various embodiments, the fill material is a gas, such as air, carbon dioxide, or nitrogen gas, a low dielectric constant chemical sublimate having a dielectric constant less than 1.2 (e.g. benzoic acid), and/or a low dielectric expandable foam having a dielectric constant that is less than 1.2. Limiting cables (not shown) can also be included between the panels 102a, 102b, 106 to precisely define the maximum size of each of the gaps upon inflation of the thin-walled containers 500a, 500b.

[0066] In the embodiment of FIG. 5, the thin-walled containers 500a, 500b are cuboids that fill the gaps in a precisely controlled manner. This approach can be preferred, for example, when the thin-walled containers are to be filled with a high dielectric foam. In other embodiments where the fill material has a low dielectric constant, the thin-walled containers 500a, 500b can take on any shape, in that their function is entirely to separate the layers 102a, 102b, 108, while limiting cables can be used to fix the gap sizes.

[0067] It will be noted that the embodiment of FIG. 5 does not include a high dielectric spacer layer 202. With reference to FIG. 6, in some embodiments where it is desirable to include one or more high dielectric constant spacer layers 600, the expansion mechanism includes a plurality of reservoirs 502, 602 wherein at least one of the reservoirs 600 is filled with a high dielectric fill material, such as a high dielectric foam, having a dielectric constant of greater than 2. Deployment of the antenna in these embodiments includes causing the controller 304 to open both of the valves 604, thereby inflating each of a plurality of thin-walled containers 500a, 500b, 600 with material from the plurality of reservoirs 502, 602. In the illustrated embodiment, two cuboid thin-walled containers 500a, 500b are filled with a low dielectric foam, while a third cuboid thin-walled container 600 is filled with a high dielectric foam. This approach has the advantage of providing a high dielectric spacer layer without significantly increasing the stowed thickness of the antenna.

[0068] Depending on the embodiment, the satellite 114 can communicate with the antenna by any mechanism known in the art, such as by extending a microstrip feed line to the primary, bottom-most patch element 108. While not visible in the drawings, the antennae of FIGS. 3-6 include aperture coupled feeds in communication with the satellite 114 in a manner similar to FIG. 2. This approach can simplify the design, in that only a single feed line to each aperture is required, which require no reconfiguration when the antenna is deployed.

[0069] In various embodiments, the disclosed antenna is an antenna assembly that includes a plurality of expandable stacked patch antennae, for example in a manner similar to FIGS. 1C-1F. In the stowed configuration, some of these embodiments include folding of stacked patch antennae toward surfaces of the satellite 114, for example in a manner similar to FIG. 1D or FIG. 1F.

[0070] The foregoing description of the embodiments of the disclosure has been presented for the purposes of illustration and description. Each and every page of this submission, and all contents thereon, however characterized, identified, or numbered, is considered a substantive part of this application for all purposes, irrespective of form or placement within the application. This specification is not intended to be exhaustive or to limit the disclosure to the precise form disclosed. Many modifications and variations are possible in light of this disclosure.

[0071] Although the present application is shown in a limited number of forms, the scope of the disclosure is not limited to just these forms, but is amenable to various changes and modifications. The disclosure presented herein does not explicitly disclose all possible combinations of features that fall within the scope of the disclosure. The features disclosed herein for the various embodiments can generally be interchanged and combined into any combinations that are not self-contradictory without departing from the scope of the disclosure. In particular, the limitations presented in dependent claims below can be combined with their corresponding independent claims in any number and in any order without departing from the scope of this disclosure, unless the dependent claims are logically incompatible with each other.