Antenna device employing foldable memory metal and deployment method

Abstract

An artificial magnetic conductor (AMC) antenna device includes a ground plane and a flexible antenna element layer positioned above the ground plane. The ground plane includes a conductive base surface, a plurality of memory metal wires, and a frequency selective surface (FSS) layer above the base surface, wherein the FSS layer includes a plurality of conductive patches spaced apart from one another. Each of the memory metal wires electrically connects one of the conductive patches to the base surface. Each of the memory metal wires is rigid in a memorized shape state such that the FSS layer is fixedly spaced apart from the base surface during operation of the AMC antenna device. The memory metal wires are each flexible in a non-memorized shape state such that the FSS layer is collapsible toward the base surface when the antenna device is stowed.

Description

[0001] Cross-reference to related applications

[0002] This application claims priority to U.S. Provisional Application No. 63 / 091,922, filed October 14, 2020, with the United States Patent and Trademark Office, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This disclosure generally relates to storage and deployment techniques for antennas with a ground plane; and to artificial magnetic conductor (AMC) antennas. Background Technology

[0004] In conventional antennas above a ground plane, the radiating element is spaced a quarter wavelength (λ / 4) from the ground plane to achieve constructive interference of the reflected signal, thereby improving directivity. However, at relatively low frequencies, the λ / 4 distance may be longer than expected, resulting in a thicker antenna profile (e.g., 25 cm at 300 MHz).

[0005] By utilizing an artificial magnetic conductor (AMC) ground plane, the spacing between the ground plane and the radiating element is significantly smaller, enabling comparable directivity performance for the antenna. The AMC ground plane can comprise a conductive substrate surface and a "frequency selective surface" (FSS) composed of multiple spaced-apart conductive patches. These conductive patches can be electrically connected to the substrate surface via corresponding wires typically embedded in a low-loss dielectric. The resulting structure is thinner than conventional ground plane-based antennas, but is rigid and difficult to transport, especially for large-aperture antennas configured for frequencies below 1 GHz. Summary of the Invention

[0006] In one aspect of this disclosure, an artificial magnetic conductor (AMC) antenna device includes a ground plane and a flexible antenna element layer, the flexible antenna element layer including at least one antenna element above the ground plane. The ground plane includes a conductive substrate surface, a plurality of shape memory metal wires, and a frequency selective surface (FSS) layer above the substrate surface, wherein the FSS layer includes a plurality of spaced-apart conductive patches. Each of the shape memory metal wires electrically connects one of the conductive patches to the substrate surface. Each of the shape memory metal wires is rigid in its shape-memory state, such that the FSS layer is fixedly spaced from the substrate surface during operation of the AMC antenna device. The shape memory metal wires are flexible in their non-shape-memory state, such that the FSS layer can retract toward the substrate surface when the antenna device is retracted.

[0007] The AMC antenna device may further include a retaining structure configured to retain the antenna element layer and ground plane when the antenna device is retracted, wherein the FSS layer retracts toward the substrate surface.

[0008] The structure can keep the antenna element layers and ground plane in a coiled state.

[0009] The AMC antenna device may further include at least one actuator configured to remove the antenna element layer and ground plane from the holding structure.

[0010] On the other hand, a method for deploying an AMC antenna on an unmanned vehicle is provided. The AMC antenna includes: (i) an antenna element layer; and (ii) a ground plane having a conductive substrate surface, an FSS layer, and multiple shape memory metal wires electrically and mechanically coupling the conductive substrate surface to the FSS layer. When the AMC antenna device is stored, the shape memory metal wires are in a contracted, non-memory shape state. The method includes storing the AMC antenna in a holding structure; and removing the AMC antenna from the holding structure using an actuator to deploy the AMC antenna. When the ambient temperature exceeds a threshold, the shape memory metal wires automatically transition from a flexible state to a rigid state, thereby causing the FSS to be fixedly spaced from the substrate surface after the AMC antenna is removed from the holding structure. Attached Figure Description

[0011] The above and other aspects and features of the disclosed art will become more apparent from the following detailed description taken in conjunction with the accompanying drawings, in which like reference numerals indicate like elements or features. Various elements of the same or similar type can be distinguished by attaching a reference label with an underlined / dashed line and a second label (e.g., _1, _2) to differentiate like / like elements, or by directly attaching a reference label with the second label. However, if a given description uses only the first reference label, it applies to any like / like element having the same first reference label, regardless of the second label. Elements and features may not be drawn to scale in the drawings.

[0012] Figure 1 This is a perspective view of an example AMC antenna in an operational configuration according to an embodiment.

[0013] Figure 2 It is along Figure 1 The cross-sectional view taken from line 2-2 depicts an example interlayer structure of the AMC antenna.

[0014] Figure 3 It shows the connection to Figure 1 A schematic diagram of an example antenna feed for an AMC antenna element.

[0015] Figure 4 yes Figure 1 A perspective view of the upper central portion of the AMC antenna, showing the feed portion of the example antenna.

[0016] Figure 5It is along Figure 4 The cross-sectional view taken from line 5-5 depicts an example integration of the antenna feed within the AMC antenna.

[0017] Figure 6 This is a perspective view of an example antenna device according to an embodiment, including a retaining structure that holds the antenna during retraction. Figure 1 The AMC antenna remains in a coiled configuration.

[0018] Figure 7 This is a perspective view showing the area after the AMC antenna was removed during deployment. Figure 6 Antenna device.

[0019] Figure 8 It is a section taken along line 8-8. Figure 7 The cross-sectional view of the antenna device shows the shape memory metal wire in a contracted state.

[0020] Figure 9 Showing Figure 1 The antenna device is folded for storage.

[0021] Figure 10 This is a perspective view depicting an AMC antenna in a partially deployed state according to another embodiment.

[0022] Figure 11 yes Figure 10 A cross-sectional view of a portion of the AMC antenna.

[0023] Figure 12 This is a flowchart depicting the operation of an example method for deploying an AMC antenna on an unmanned vehicle according to an embodiment. Detailed Implementation

[0024] The following description, with reference to the accompanying drawings, is provided to aid in a comprehensive understanding of certain exemplary embodiments of the technology disclosed herein for illustrative purposes. The description contains various specific details to aid those skilled in the art in understanding the technology, but these details are to be considered illustrative only. For the purposes of simplicity and clarity, this description may be omitted where descriptions containing well-known functions and constructions might obscure the understanding of those skilled in the art.

[0025] Figure 1 This is a perspective view of an example artificial magnetic conductor (AMC) antenna in an operational configuration according to an embodiment. The AMC antenna 100 (interchangeably referred to as "AMC antenna assembly 100") may include a ground plane 105, an antenna element layer 130 having at least one antenna element, and an antenna feed (e.g., Figure 3 The 300, for clarity, is from Figure 1(omitted). The ground plane 105 may include: a substrate layer 110 having a conductive substrate surface; a frequency selective surface (FSS) layer 120; and a plurality of shape memory metal wires 115 electrically connecting the FSS layer 120 to the conductive substrate surface. In some embodiments, the element 115 may be an elongated structure other than the wires, such as shape memory metal pillars. The ground plane 105 having this textured surface configuration can be understood as a “high-impedance surface” within a given frequency band, where the surface wave modes are significantly different from those on a smooth metal surface. (Note that the term “frequency selective surface (FSS)” emphasizes the frequency-sensitive characteristics of the high-impedance surface.) The ground plane 105 can also be understood as a “non-phase reflector” with suppressed surface waves. The textured structure of the ground plane 105 allows the AMC antenna 100 to be made much thinner than conventional ground plane antennas (i.e., non-AMC antennas with radiating elements spaced λ / 4 apart on the ground plane).

[0026] FSS layer 120 includes a plurality of conductive patches 121_1 to 121_n, which are spaced apart from each other by narrow isolation regions (“lanes”) 123. Note that Figure 1 Each conductive patch 121 may include a conductive surface printed on a thin dielectric sheet, such as a polyimide film (e.g., The isolation region 123 can be a region of a dielectric sheet without printed conductors. Therefore, the conductive patches 121_1 to 121_n, together with the dielectric sheets (and in some cases, additional dielectric sheets on the opposite side of the printed conductors), can collectively form a continuous sheet or sandwich structure. The width of the isolation region 123 is smaller than the area of ​​the conductive patch 121, thereby creating capacitance between adjacent conductive patches 121 that contributes to the formation of a high-impedance surface. Each memory metal wire 115 can be oriented in the z (vertical) direction and electrically connects one of the conductive patches 121 to the conductive substrate surface of the substrate layer 110, thus providing a "bed of nails" structure between the substrate layer 110 and the FSS layer 120. Each of the substrate layer 110, the FSS layer 120, and the antenna element layer 130 can be a flexible sheet structure with a main surface oriented in the xy plane.

[0027] The shape memory metal wire 115 is rigid, such as... Figure 1As shown, the shape memory wire 115 is in a shape memory state that may occur when the ambient temperature is above a threshold (“shape memory threshold”). The shape memory wire 115 may be composed of nickel-titanium (NiTi) (also known as nitinol) or another suitable shape memory alloy (such as copper-aluminum-nickel or an alloy including copper, iron, zinc, and gold). Due to its rigidity in the shape memory state, the shape memory wire 115 can mechanically support the FSS 120 relative to the substrate 110 in an operating configuration to achieve a fixed spacing between them (e.g., uniform spacing between all regions of the FSS 120 and the substrate 110). The shape memory wire 115 is flexible in a non-shape memory state during the non-operating collapsed state, as will be discussed and illustrated later, which can be initiated when the ambient temperature is below the shape memory threshold. For example, the shape memory wire 115 composed of nitinol changes its state from austenitic to martensitic when cooled below the shape memory threshold, allowing the shape memory wire 115 to enter a flexible state. When the shape memory metal conductor 115 is flexible, the FSS layer 120 and antenna element layer 130 can contract towards the substrate layer 110, allowing the AMC antenna 100 to be stowed away in a smaller volume than it occupies in the operational state. This facilitates the stowage and transport of the AMC antenna 100, and in some cases, facilitates unmanned deployment on vehicles such as orbital satellites. In some examples, the AMC antenna 100 stows away in a rolled-up or folded holding structure, as described and illustrated below. When the AMC antenna 100 is removed from the holding structure and the ambient temperature exceeds the shape memory threshold, the shape memory metal conductor 115 can automatically transform back to austenite, i.e., the shape memory state. For the AMC antenna 100, the shape memory state can be linearly configured.

[0028] The AMC phenomenon is achievable through appropriate design of the number, geometry, and layout of the conductive patches 121; at least one antenna element of the antenna layer 120; the length of the shape memory metal wire 115; and the spacing between the antenna element layer 130 and the FSS 120. As previously described, the AMC phenomenon allows the AMC antenna 100 to be much thinner than conventional antennas with radiating elements spaced λ / 4 apart on the ground plane. For example, the AMC phenomenon allows for efficient antenna performance where the spacing between the antenna element layer 130 and the substrate surface 119 is << λ / 4, for example, in the range of λ / 40 to λ / 10. This efficiency can be achieved due to in-phase reflection and suppression of surface waves. Therefore, despite the close spacing between the layers, constructive interference occurs between the signal radiated directly into free space by the antenna element layer 130 and the same signal that initially propagates to the ground plane 105 and is then reflected from it.

[0029] exist Figure 1In this embodiment, an example antenna element is shown as a crossed dipole 135, which includes a first dipole element 132 and a second dipole element 134, the second dipole element being orthogonal to the first dipole element 132. Other types of antenna elements may be used instead, such as a single dipole antenna, a loop antenna, a microstrip patch element array, etc. The crossed dipole 135 may be printed on a dielectric sheet and shown in a hexagonal shape, the hexagon being... Figure 1 Each of the FSS layer 120 and the substrate layer 110 occupies a smaller surface area. In other examples, the antenna element layer 130 extends in the xy plane along with each of the FSS layer 120 and the substrate layer 110. An example configuration of the ground plane 105 includes a plurality of dielectric or metal ribs 117, each longitudinally oriented in the y or x direction, for increasing structural support at the bottom end of the memory metal wire 115. The conductive patches 121_1 to 121_n may each be arranged in a grid and have the same geometry, for example, all rectangular or all square, or all hexagonal, all circular, or other suitable shapes as shown. In some embodiments, the conductive patches 121_1 to 121_n may also be configured with the same or substantially the same dimensions (e.g., within manufacturing tolerances). Each conductive patch 121 is electrically connected to the corresponding memory metal wire 115 via a connection 128 at its central location. Note that the input portion of the substrate layer 110 may include input flaps 112 and edge ribs 184 for mechanical connection to a retaining structure in some applications.

[0030] Figure 2 It is along Figure 1 The cross-sectional view taken from line 2-2 depicts an example interlayer structure of the AMC antenna 100 during operation (deployment). Figure 2 In other cross-sectional views herein, features located later in the diagrams may be omitted for clarity. The substrate layer 110 may include a conductive substrate surface 119 adhered to or printed on the bottom surface of the flexible dielectric sheet 144 for structural integrity and to facilitate electrical and mechanical connections to the memory metal conductor 115 (interchangeably, "memory metal conductor" 115). Dielectric ribs 117 may be adhered to the top surface of the dielectric sheet 144 and support the connection of the memory conductor 115 to the substrate surface 119. Plated vias 158 may have been formed through the ribs 117 and the substrate layer 110. The bottom ends of the memory conductor 115 may have been inserted into the vias 158 and electrically connected to the conductive substrate surface 119 via conductive adhesive 157 surrounding the memory conductor 115 (e.g., molten and cooled solder) within the vias 158.

[0031] FSS layer 120 may include conductive patches 121_1 to 121_n sandwiched between lower dielectric sheet 154 and upper dielectric sheet 164. Alternatively, FSS layer 120 may consist of a single dielectric sheet 154 or 164 on which conductive patches 121 are printed. The mechanical and electrical connection 128 between the upper portion of memory conductor 115 and FSS layer 120 may include plated via 168, the upper portion of memory conductor 115, and conductive adhesive 167 within via 168. Figure 2 A single connection 128 is depicted between the memory wire 115 and a given conductive patch 121_j, which is spaced apart from adjacent conductive patches 121_(j-1) and 121_(j+1) by corresponding isolation regions 123. A dielectric sheet 164 including the isolation regions 123 can be formed by depositing dielectric material layered onto the conductive patches 121 after depositing the conductive patches 121 on the upper surface of the dielectric sheet 154. However, if the dielectric sheet 164 is omitted, the isolation regions 123 can be air gaps or dielectric fillers. Each of the dielectric sheets 144, 154, 164, and 174 can be a polyimide film such as...

[0032] Electrical connections 128 through the AMC antenna 100 can each be formed at a distance d1 above the dielectric sheet 144 (where the memory conductors are in a rigid state). In this way, the FSS layer 120 can be supported by memory conductors 115, the lower surface of which is uniformly spaced from the substrate layer 110 at a distance d1. An air gap 191 can exist in the region around the memory conductors 115.

[0033] Antenna element layer 130 may include at least one antenna element 132 printed on top of dielectric layer 174. An example mechanical connection between antenna element layer 130 and FSS layer 120 may include an extension 176 of memory conductor 115 extending above the upper surface of dielectric sheet 164, an electroplated blind via 178 in the lower surface of dielectric sheet 174, and a conductive adhesive 177 such as solder. The upper end of extension 176 may be inserted into via 178 and adhered to dielectric sheet 174 by melting and cooling adhesive 177. All or most of the memory conductor 115 located below antenna element layer 130 may similarly include extensions 176 adhered to dielectric sheet 174 in this manner. As a result, antenna element layer 130 may be entirely supported by memory conductor 115 and uniformly spaced from the upper surface of FSS layer 120 by a distance d2 (where memory conductor 115 is in a rigid state). Note that if antenna layer 130 is only centered relative to FSS layer 120, such as Figure 1As shown, the memory conductors 115 located outside the region of antenna layer 130 may omit the extension 176. These peripheral memory conductors 115 may all be designed to have the same or substantially the same length (e.g., within manufacturing tolerances), and their tips may be flush with the upper surface of dielectric sheet 164. Similarly, each of the memory conductors 115 located below antenna layer 130 may be designed identically or substantially identically, with an extension 176 of the same or substantially the same length (e.g., within manufacturing tolerances).

[0034] An air gap 171 may exist between layers 120 and 130 via the aforementioned mechanical connection between the FSS layer 120 and the antenna element layer 130. When the memory wire 115 is in a non-memory metal shape (flexible state), the antenna element layer 130 may contract relative to the FSS layer 120, thus reducing the distance d2 in the retracted state. In an alternative configuration, the extension 176 on the memory wire 115 is omitted throughout the AMC antenna 100; dielectric sheets 164 and 174 are fused or formed as a single dielectric sheet; and there is no air gap 171 between the FSS layer 120 and the antenna element layer 130.

[0035] Figure 3 This is a schematic diagram illustrating an example antenna feed 300 that can be connected to an antenna element 135 of an AMC antenna 100. The antenna feed 300 may include a balun 350; a first flexible coaxial cable 310 having a first end connected to the balun 350 and having an outer conductor 313 and an inner conductor 311; a second flexible coaxial cable 320 having a first end connected to the balun 350 and having an outer conductor 323 and an inner conductor 321; and first, second, third, and fourth interconnects 317, 319, 327, and 329, respectively. In some embodiments, there may be multiple connected baluns (e.g., a pair of connected baluns). A first dipole element 132 includes dipole arms 132a and 132b; a second dipole element 134 includes dipole arms 134a and 134b. The second end of the first coaxial cable 310 is connected to the first dipole element 132, wherein interconnect 317 connects the outer conductor 313 to dipole arm 132a and interconnect 319 connects the inner conductor 311 to dipole arm 132b. The second end of the second coaxial cable 310 is connected to the second dipole element 134, wherein interconnect 327 connects the outer conductor 323 to dipole arm 134a and interconnect 329 connects the inner conductor 321 to dipole arm 134b.

[0036] Figure 4 It describes Figure 1The image shows a perspective view of the upper central portion of the AMC antenna 100, illustrating a portion of the example antenna feed 300. The central portion of the cross dipole antenna element 135 may cover the intersection area of ​​concentrated, adjacent conductive patches 121_i, 121_(i+1), 121_(i+2), and 121_(i+3). An opening 375 in the FSS layer 120 may be formed in the central region by removing corner pieces from each of the conductive patches 121_i to 121_(i+3). Another opening 385 may have been formed in the central region of the antenna element layer 130. During the deployment state of the AMC antenna 100, coaxial cables 310 and 320 may extend vertically (in the z-direction) between the antenna element layer 130 and the substrate layer 110. During the retracted state, the coaxial cables may be retracted between the antenna element layer 130 and the substrate layer 110.

[0037] The second ends of coaxial cables 310 and 320 may pass through opening 375 and at least partially through opening 385. Interconnects 317 and 327 may each be implemented as wire-jointed connections. Alternatively, interconnects 317 and 327 may take the form of funnel-shaped metal portions integrated with conductor extensions. The funnel-shaped metal portions are soldered or otherwise electrically connected to the respective outer conductors 313 or 323, and the conductor extensions are soldered or otherwise electrically connected to the input points of dipole arms 132a or 134a. Interconnects 319 and 329 may be direct soldered connections to the input points of dipole arms 132b and 134b, respectively.

[0038] Figure 5 It is along Figure 4 The cross-sectional view taken by line 5-5 depicts an example integration of the antenna feed 300 within the AMC antenna 100. This view shows that a balun 350 may be disposed adjacent to the lower surface of the AMC antenna 100, and the lower ends of coaxial cables 310 and 320 may pass through an opening 365 in the substrate layer 110 and connect to the balun 350. Coaxial cables 310 and 320 may extend vertically side-by-side, with their upper ends passing through an opening 375 in the FSS layer 120 and an opening 385 in the dielectric sheet 174 of the antenna layer 130 to facilitate electrical connection to the cross-dipole antenna element 135. In the retracted state, coaxial cables 310 and 320 may retract similarly to memory wire 115 (as shown below). Figure 8 (As shown).

[0039] Figure 6 This is a perspective view of an example antenna device according to an embodiment, which includes a holding structure that holds the AMC antenna during retraction. Figure 7 This is a perspective view showing the area after the AMC antenna was removed during deployment. Figure 6 Antenna device. Figure 7 The view also shows an example arrangement of the AMC antenna relative to the retaining structure before insertion. See also Figure 6 and Figure 7 The AMC antenna assembly 200 includes an AMC antenna 100 and a holding structure 210 that holds the AMC antenna 100 in a coiled state during retraction. In this embodiment, the holding structure 210 is a generally cylindrical structure having first and second opposing end walls 216 and 218, a mandrel 225 between the end walls 216 and 218, and a support rod 228 coupling the end walls 216 and 218 to each other. Each of the end walls 216, 218 may have a helical groove 214 on its inner surface 212 to guide and hold the AMC antenna 100 in a coiled configuration. During retraction, at least opposing edge portions of the ground plane 105 remain coiled within the pair of helical grooves 214. If the antenna layer 130 is configured to extend co-exist with the ground plane 105, opposing edge portions of the antenna layer 130 may also be retained within the helical grooves 214.

[0040] The spindle 225 may have a mechanical link 272 (schematically shown) to the end rib 184 of the AMC antenna 100. To initially hold the AMC antenna 100 within the retaining structure 210, the AMC antenna 100 can be forced into a retracted state, such as... Figure 7 As shown. In the contracted state, the memory metal wire 115 is flexible and the FSS layer 120 contracts toward the substrate layer 110, such that the thickness of at least the edge portion of the contracted structure is thinner than the width of the groove 214. Note that in the contracted state, the FSS layer 120 can contract toward the substrate layer 110 in the +x direction, causing the FSS layer 120 to be offset relative to the substrate layer 110. Because these two layers are offset in the contracted state, the peripheral portion 110a of the substrate layer 110 is no longer covered by the corresponding portion of the FSS layer 120. For example, from the operational configuration, see, for example, Figure 1 The transition to a contracted configuration (or vice versa) can be analogous to a "four-bar linkage" mechanical action. In other words, the shape memory metal wire 115 can be considered analogous to a first pair of bars transitioning between vertical and horizontal orientations. The plate-like geometry of the substrate layer 110 and the FSS layer 120 can be analogous to a second pair of bars coupled to the first pair of bars, which move between aligned and offset states as the first pair of bars moves between vertical and horizontal orientations.

[0041] The spindle 225 is rotatable (e.g., clockwise) to pull the AMC antenna 100 into the retaining structure 210. As an example, a hand crank (not shown) or an actuator 275 with a connecting rod 273 may be coupled to the end 219 of the spindle 225 to apply a rotational force to pull the AMC antenna 100 into the retaining structure 210. Once the AMC antenna 100 is held within the retaining structure 210, the AMC antenna assembly 200 can be transported to a vehicle such as an orbiting satellite prior to launch and secured to the surface 285 of the vehicle. Because the retaining structure 210 is more robust to environmental conditions and motion than the AMC antenna 100 itself (if otherwise mounted on the surface 285 without protection), securing the retaining structure 210 to the surface 285 before deploying the AMC antenna 100 to the surface 285 improves the chances of successful deployment. As another example, the surface 285 is a planetary surface or the surface of an artificial structure on a planet. In this configuration, the holding structure 210, in which the AMC antenna 100 is fixed, can be transported by a drone and dropped onto the surface 285 for subsequent unmanned deployment.

[0042] To deploy the AMC antenna 100 from the holding structure 210, the spindle 225 can be rotated (e.g., counterclockwise) by the actuator 275, thereby allowing the AMC antenna 100 to slide out in a plate-like configuration when in its retracted state in the +x direction. Alternatively or additionally, another actuator 260 arranged on surface 285 can automatically pull the AMC antenna 100 out of the holding structure 210. For this purpose, the AMC antenna 100 may have an opening 129 on the side opposite the fin 112, through which the link 262 of the actuator 260 can be attached to the AMC antenna 100. Note that the actuator 260 and / or actuator 275 may be a robotic arm fixed to surface 285. Once the AMC antenna 100 is removed from the holding structure 210 in its retracted state, if the ambient temperature is above the shape memory threshold, the shape memory metal wires 115 can automatically change from flexible to rigid and orient themselves in the z direction. This transitions the AMC antenna 100 from its retracted state to its operational state, as... Figure 1 As shown. In the example, if the ambient temperature is below the memory shape threshold, heat can be applied to the AMC antenna 100, thereby raising the local temperature around the AMC antenna 100 and causing the memory wire 115 to transition to a memory shape state. In one example, heat is applied by applying a current to the memory wire 115, whereby the resistance of the memory wire 115 generates sufficient heat to cause the transition when the current flows.

[0043] Figure 8 It is along Figure 7The cross-sectional view of the AMC antenna 100 taken by line 8-8 shows an example structure of the AMC antenna 100 in a retracted state. When the AMC antenna 100 is retracted for stowage, the memory wire 115 is flexible and can be retracted to a generally horizontal orientation (typically oriented along the x-direction), whereby the spacing d3 between the substrate layer 110 and the FSS layer 120 is significantly smaller than the spacing d1, as... Figure 2 As shown. Additionally, the spacing d4 between the FSS layer 120 and the antenna layer 130 can be reduced relative to the distance d2 ( Figure 2 Because of the similar contraction of extension 176, the total thickness of the AMC antenna 100 can be significantly less than the total thickness in the operating state, thereby enabling compact retention within a suitable retention structure.

[0044] Figure 9 The AMC antenna 100 is shown in a folded state for easy storage, thus facilitating its transport. To fold the AMC antenna 100, it is first set to a retractable configuration and then folded at least once. A retaining structure of the form 199 is then used to hold the AMC antenna 100 in the folded state. As an example, the folded AMC antenna 100 can be transported to the surface 285 of an unmanned vehicle (e.g., Figure 6 and 7 As shown), and secured thereto by suitable fasteners (not shown) coupled to the retaining band 199. For subsequent deployment of the AMC antenna 100, a robotic arm or the like can cut the retaining band 199 and unfold the AMC antenna 100. The AMC antenna 100 can then be automatically switched to an operational state as the memory wires 115 transition to their rigid state in a manner similar to that described above (e.g., by applying heat).

[0045] Figure 10 It depicts a perspective view of an AMC antenna 100' in a partially deployed state according to another embodiment.

[0046] The difference between AMC antenna 100' and the aforementioned AMC antenna 100 is that the support rib 117 is omitted and it is an FSS layer.

[0047] Each conductive patch 121 of 120 employs an individual support structure. Figure 11This is a cross-sectional view showing an example support structure in the central region of the AMC antenna 100', i.e., in the region of the antenna element layer 130. For the conductive patch 121 located below the region of the antenna layer 130, the support structure may include a support 192 attached to the substrate layer 110, a support 193 attached to the FSS layer 120, and a support 194 attached to the antenna element layer 130. Each of the supports 192, 193, and 194 may have a button-like profile, occupying a circular region at least an order of magnitude smaller than the surface area of ​​the corresponding conductive patch 121. Each of the supports 192-194 may be composed of a dielectric material adhered to a corresponding dielectric sheet in layers 110, 120, or 130. Each support 192, 193, and 194 may have a central opening through which the memory wire 115 passes and is adhered to the corresponding support. For example, it can be combined with the above. Figure 2 A plated via is formed through the support 192 and the base layer 110 in a similar or identical manner to that described for rib 117, and the lower end of the memory wire 115 can be soldered to the support 192 and the base layer 110 using solder within the plated via. Similar plated vias may have been formed in the FSS layer 120 and the support 193 to adhere the central portion of the memory wire 115 to the support 193. Furthermore, blind vias may have been formed through the support 194 and the dielectric sheet 174 of the antenna element layer 130 to adhere the extension 176 of the memory wire 115 to the support 194 and the antenna element layer 130. For conductive patches 121 located on the periphery, such as conductive patch 121_m, not below the antenna element layer 130, only the supports 192 and 193 may be used, and the extension 176 may be omitted. Therefore, the upper end of the memory wire 115 may be flush with the upper surface of the FSS layer 120.

[0048] Other aspects of the AMC antenna 100' are the same as those described above for the AMC antenna 100. The AMC antenna 100' can be held and removed from holding structures such as 210 or 199 in a similar manner to that described above for the AMC antenna 100.

[0049] Figure 12 This is a flowchart depicting the operation of an example method 1200 for deploying an AMC antenna on an unmanned vehicle according to an embodiment. Using method 1200, the AMC antenna, such as 100 or 100', is first stored in its retracted state in a holding structure such as 210 or 199 (S1210). The holding structure, along with the AMC antenna stored therein, can then be transported to the unmanned vehicle (S1220). As previously described, some examples of unmanned vehicles (e.g., vehicles including surface 285) include orbiting satellites, planetary surfaces, or man-made structures on planetary surfaces.

[0050] The AMC antenna can then be deployed (S1230) by removing it from the holding structure using the actuators described above (e.g., 275 and / or 260), and allowing the memory metal wire 115 of the AMC antenna to automatically transition from a flexible state to a rigid state when the ambient temperature exceeds the memory shape threshold. Once the transition to the rigid state is complete, the AMC antenna is set for operation (e.g., in...). Figure 1 (As shown in the above configuration). As described above, if the ambient temperature during deployment is below the memory shape threshold, heat can be applied to the AMC antenna to raise the local temperature around the AMC antenna and cause the memory wire 115 to transition to a memory shape state. Heat can be applied by applying current to the memory wire 115, whereby the resistance of the memory wire 115 generates sufficient heat to cause the transition when the current flows. When the AMC antenna is in the operational configuration, a robotic arm or the like can fix the AMC antenna to the surface 285 of the carrier and electrically connect the balun 350 of the AMC antenna to the RF front end of the communication system, thereby initiating active communication of the AMC antenna to the signal.

[0051] While the techniques described herein have been specifically shown and described with reference to exemplary embodiments thereof, those skilled in the art will understand that various changes in form and detail may be made therein without departing from the spirit and scope of the claimed subject matter as defined by the appended claims and their equivalents.

Claims

1. An artificial magnetic conductor (AMC) antenna device (100, 200, 100'), comprising: Ground plane (105), which includes: The surface of the conductive substrate (119); A frequency selective surface (FSS) layer (120) above the substrate surface, the FSS layer comprising a plurality of spaced-apart conductive patches (121_1 to 121_n); and Multiple shape-memory metal wires (115), each electrically connecting one of the conductive patches to the substrate surface and respectively being rigid in a shape-memory state such that the FSS layer is fixedly spaced from the substrate surface during operation of the AMC antenna device, and respectively being flexible in a non-shape-memory state such that the FSS layer can retract toward the substrate surface when the antenna device is retracted; and The flexible antenna element layer (130) above the FSS layer includes at least one antenna element (135).

2. The AMC antenna device (100, 200, 100') according to claim 1, wherein: The plurality of conductive patches are a plurality of printed conductive patches on the first dielectric sheet (154); and The at least one antenna element is at least one printed conductive element on the second dielectric sheet (174); Each of the first dielectric sheet and the second dielectric sheet is flexible.

3. The AMC antenna device (100, 200, 100') according to claim 2, wherein; Each of the shape memory metal wires has a substantially identical length, ensuring that the FSS layer is uniformly spaced from the substrate surface; and The first dielectric sheet is mechanically coupled to the second dielectric sheet, such that the antenna element layer and the FSS layer are uniformly spaced apart.

4. The AMC antenna device (100, 200, 100') according to claim 3, wherein the memory metal wire includes a corresponding extension (176) extending above the FSS layer, and the first dielectric sheet is mechanically coupled to the second dielectric sheet and the first dielectric sheet is uniformly spaced from the second dielectric sheet by the extension when the memory metal wire is rigid in the memory shape state.

5. The AMC antenna device (200) of claim 1, further comprising a retaining structure (210) configured to retain the antenna element layer and the ground plane when the antenna device is retracted, wherein the FSS layer retracts toward the substrate surface.

6. The AMC antenna device (200) according to claim 5, further comprising at least one actuator (275, 260) configured to remove the antenna element layer and the ground plane from the holding structure.

7. The AMC antenna device (200) according to claim 5, wherein the retaining structure (210) holds the antenna element layer and the ground plane in a coiled state.

8. The AMC antenna device (200) according to claim 7, wherein the retaining structure (210) is a cylindrical structure comprising a pair of helical grooves (214) at their respective opposite ends, wherein the opposite edge portions of the ground plane are held coiled within the pair of helical grooves.

9. The AMC antenna device (100, 200, 100') according to claim 1, wherein the memory metal wire (115) is composed of nitinol.

10. The AMC antenna device (100, 200, 100') according to claim 1, further comprising a flexible antenna feed (310, 320) having a first end electrically connected to the at least one antenna element, an opposite end below the substrate surface, and a central portion extending between the substrate surface and the at least one antenna element through at least one opening (375) in the FSS layer.

11. The AMC antenna device (100, 200, 100') according to claim 10, further comprising a balun (350) disposed below the surface of the substrate and connected to the opposite end of the antenna feed.

12. The AMC antenna device (100, 200, 100') according to claim 10, wherein the antenna feed includes at least one flexible coaxial cable, wherein the at least one flexible coaxial cable has a linear shape when the memory metal conductor is in the memory shape state and has a contracted nonlinear configuration when the memory metal conductor is in the non-memory shape state.

13. The AMC antenna device (100, 200, 100') according to claim 1, wherein the at least one antenna element (135) comprises at least one cross dipole antenna element.

14. The AMC antenna device (100, 100') according to claim 1, wherein when the antenna device is retracted, both the ground plane and the antenna element layer are folded.

15. The AMC antenna device (100, 200, 100') according to claim 1, wherein the substrate surface comprises a printed conductive material on a flexible substrate (144).

16. The AMC antenna device (100, 200, 100') according to claim 1, further comprising a plurality of support structures (117, 192), each supporting a mechanical connection between one of the memory metal wires and the substrate surface and / or one of the conductive patches.

17. A method (1200) for deploying an artificial magnetic conductor (AMC) antenna (100, 100') on an unmanned vehicle (285), the method comprising: The AMC antenna is stored (S1210) in a holding structure (210, 199), the AMC antenna comprising: (i) an antenna element layer; and (ii) a ground plane having a conductive substrate surface, a frequency selective surface (FSS) layer, and a plurality of memory metal wires electrically and mechanically coupling the conductive substrate surface to the FSS layer, wherein when the AMC antenna is stored, the plurality of memory metal wires are in a contracted, non-memory shape state; and The AMC antenna is removed (S1230) from the holding structure using actuators (260, 275) to deploy the AMC antenna. When the ambient temperature exceeds a threshold, the memory metal wire automatically changes from a flexible state to a rigid state, causing the FSS layer to be fixedly spaced from the substrate surface after the AMC antenna is removed from the holding structure.

18. The method (1200) according to claim 17, wherein the unmanned vehicle is an orbital satellite (285).

19. The method (1200) of claim 17, wherein the retaining structure holds the AMC antenna in a coiled state, and the actuator causes the AMC antenna to roll out of the retaining structure in a plate-like shape.

20. The method (1200) of claim 19, wherein the AMC antenna further comprises a flexible antenna feed, the flexible antenna feed being stored in a coiled shape within the holding structure and unfolding during removal of the AMC antenna.

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