Patent Description:
This disclosure relates generally to storage and deployment techniques for antennas with ground planes; and to artificial magnetic conductor (AMC) antennas.

In a traditional antenna over a ground plane, the radiating element is spaced one quarter wavelength (λ/<NUM>) from the ground plane to achieve constructive interference with the reflected signal and thereby increase directivity. At relatively low frequencies, however, the λ/<NUM> distance may be longer than desired, resulting in a thick antenna profile (e.g., <NUM> at <NUM>).

With an artificial magnetic conductor (AMC) ground plane, the spacing between the ground plane and the radiating element is significantly smaller, and comparable directivity performance may be realized for the antenna. An AMC ground plane may include a conductive base surface and a "frequency selective surface" (FSS) composed of a plurality of conductive patches separated from one another. The conductive patches may be electrically connected to the base surface through respective wires which are typically embedded within a low loss dielectric. The resulting structure, although thinner than traditional ground plane based antennas, is stiff and burdensome to transport, particularly for large aperture antennas configured for frequencies below <NUM>.

<CIT> describes a light weight stowable phased array lens antenna assembly. <CIT> describes a mechanically reconfigurable artificial magnetic conductor. Reference is made to <NPL>.

An invention is set out in the independent claims.

In an aspect of the present disclosure, an artificial magnetic conductor (AMC) antenna apparatus according to claim <NUM> is provided.

The AMC antenna apparatus may further include a retaining structure configured to retain, when the AMC antenna apparatus is stowed: (i) the antenna element layer; (ii) the ground plane with the FSS layer collapsed towards the base surface; and (iii) the inflatable bladder system. The retaining structure may retain the antenna element layer, the ground plane, and the inflatable bladder system in a coiled state.

The AMC antenna apparatus may further include at least one actuator configured to remove the antenna element layer, the ground plane, and the inflatable bladder system from the retaining structure.

In another aspect, a method of stowing and deploying an AMC antenna on an unmanned carrier according to claim <NUM> is provided.

The above and other aspects and features of the disclosed technology will become more apparent from the following detailed description, taken in conjunction with the accompanying drawings in which like reference characters indicate like elements or features. Various elements of the same or similar type may be distinguished by annexing the reference label with an underscore / dash and second label that distinguishes among the same / similar elements (e.g., _1, _2), or directly annexing the reference label with a second label. However, if a given description uses only the first reference label, it is applicable to any one of the same / similar elements having the same first reference label irrespective of the second label. Elements and features may not be drawn to scale in the drawings.

The following description, with reference to the accompanying drawings, is provided to assist in a comprehensive understanding of certain exemplary embodiments of the technology disclosed herein for illustrative purposes. The description includes various specific details to assist a person of ordinary skill the art with understanding the technology, but these details are to be regarded as merely illustrative. For the purposes of simplicity and clarity, descriptions of well-known functions and constructions may be omitted when their inclusion may obscure appreciation of the technology by a person of ordinary skill in the art.

<FIG> is a perspective view of an example artificial magnetic conductor (AMC) antenna apparatus, <NUM>, in an operational configuration, according to an embodiment. AMC antenna apparatus <NUM> may include an AMC antenna <NUM> and a retaining structure <NUM> for retaining AMC antenna <NUM> during stowage. (Note that AMC antenna <NUM> may also be referred to herein sometimes as an AMC antenna apparatus, interchangeably. ) <FIG> depicts AMC antenna <NUM> in a configuration following its removal from retaining structure <NUM> and subsequent to operations that transform its structure from a collapsed configuration to an expanded, operational configuration, described hereafter.

<FIG> is a cut-away perspective view showing an example structure of a portion of the AMC antenna apparatus of <FIG>. Referring collectively to <FIG> and <FIG>, AMC antenna <NUM> may include a ground plane <NUM>, an antenna element layer <NUM> with at least one antenna element <NUM>, and an antenna feed (e.g., <NUM> of <FIG>, omitted from <FIG> and <FIG> for clarity). Ground plane <NUM> may include: a base layer <NUM> having a conductive base surface; a frequency selective surface (FSS) layer <NUM>; and a plurality of flexible conductors <NUM> electrically connecting FSS layer <NUM> to the conductive base surface. A conductor <NUM> can comprise an electrically conductive material such as a metal. A conductor <NUM> can be in any of a variety of possible forms. For example, a conductor <NUM> can be a wire, a column, a spring, a trace, or the like.

Ground plane <NUM> with such a textured surface configuration of conductive features may be understood as a "high impedance surface" within a given frequency band, in which surface wave modes differ significantly from those on a smooth metallic surface. (Note that the term "frequency selective surface (FSS)" emphasizes the frequency sensitive nature of the high impedance surface. ) Ground plane <NUM> may also be understood as an "in-phase reflector" with suppressed surface waves. The textured structure of ground plane <NUM> enables AMC antenna <NUM> to be made substantially thinner than traditional ground plane antennas, i.e., non-AMC antennas with a radiating element spaced λ/<NUM> over a ground plane.

AMC antenna <NUM> further includes a latch mechanism L (e.g., comprising individual latches L<NUM> to LN) between base layer <NUM> and FSS layer <NUM>. Latch mechanism L is configured to transition from an unlatched state to a latched state when AMC antenna <NUM> is deployed from a stowed configuration. In the latched state, illustrated in <FIG> and <FIG>, base layer <NUM> is fixedly separated from FSS layer <NUM> by a predetermined distance. AMC antenna <NUM> further includes an inflatable bladder system, e.g., with a first bladder 103a ("first bladder portion") and a second bladder 103b ("second bladder portion") between base layer <NUM> and FSS layer <NUM>. As described further below, when the inflatable bladder system is deflated and latch mechanism L is unlatched, FSS layer <NUM> may collapse against base layer <NUM>, rendering the resulting AMC antenna <NUM> structure very thin. This enables AMC antenna <NUM> to be stowed in a coiled configuration within retaining structure <NUM>. When AMC antenna <NUM> is removed from retaining structure <NUM> on a surface <NUM> of a carrier such as an orbital satellite, the bladder system receives a gas input to set up AMC antenna <NUM> in its operational configuration. To this end, the bladder system inflates to produce force sufficient to cause latch mechanism L to transition from the unlatched state to the latched state, whereby FSS layer <NUM> is appropriately separated from base layer <NUM> by the desired predetermined distance.

A plurality of flexible printed circuit boards (PCBs) <NUM> may each be disposed between base layer <NUM> and FSS layer <NUM>, where each PCB <NUM> includes a group of the flexible conductors <NUM>. As illustrated in <FIG>, each PCB <NUM> may be oriented substantially orthogonal to base layer <NUM> and FSS layer <NUM> when the latch mechanism is in the latched state. As illustrated in <FIG> discussed below, each PCB <NUM> may at least partially collapse with respect to base layer <NUM> and FSS layer <NUM> when latch mechanism L is unlatched. In this state, a major surface of each PCB <NUM> may tilt towards base layer <NUM>, closing the air gap between base layer <NUM> and FSS layer <NUM> to provide a compact configuration for stowing. It is noted here that in other embodiments, the flexible conductors <NUM> are provided between FSS layer <NUM> and base layer <NUM> as stand-alone conductors without embedding within PCBs <NUM> (PCBs <NUM> are omitted).

FSS layer <NUM> includes a plurality of conductive patches 121_1 to 121_n separated from one another by narrow isolation regions ("streets") <NUM>. Each conductive patch <NUM> may include a conductive surface printed on a thin dielectric sheet such as a polyimide film (e.g., Kapton®), and the isolation regions <NUM> may be regions of the dielectric sheet without a printed conductor. Thus, conductive patches 121_1 to 121_n along with the dielectric sheet (and in some cases, an additional dielectric sheet on the opposite side of the printed conductor) may collectively form a continuous sheet-like or sandwich-type structure. The width of an isolation region <NUM> is small relative to the area of a conductive patch <NUM>, generating a capacitance between adjacent conductive patches <NUM> that contributes to forming the high impedance surface. Each conductor <NUM> may be oriented in the z (vertical) direction and electrically connect one of the conductive patches <NUM> to the conductive base surface of base layer <NUM>, such that a "bed of nails" structure (reinforced with the dielectric of PCBs <NUM>) is provided between base layer <NUM> and FSS layer <NUM>. Each of base layer <NUM>, FSS layer <NUM> and antenna element layer <NUM> may be flexible sheet-like structures having major surfaces oriented in the x-y plane.

Through suitable design of the number, geometry and layout of conductive patches <NUM>; the at least one antenna element of antenna layer <NUM>; the lengths of conductors <NUM>; and the spacing between antenna element layer <NUM> and FSS <NUM>, an AMC phenomenon is realizable. As noted, the AMC phenomenon enables AMC antenna <NUM> to be significantly thinner than the traditional antenna having a radiating element spaced λ/<NUM> over a ground plane. For instance, the AMC phenomenon allows for efficient antenna performance with spacing between the antenna element layer <NUM> and base surface <NUM> << λ/<NUM>, e.g., in the λ/<NUM> to λ/<NUM> range. Such efficiency may be realized due to in-phase reflection and suppression of surface waves. Thus, despite the close spacing between the layers, constructive interference occurs between a signal radiated directly into free space by antenna element layer <NUM> and the same signal initially propagated towards, and then reflected from, ground plane <NUM>.

In the embodiment of <FIG>, an example antenna element <NUM> is illustrated as a crossed-dipole including a first dipole element <NUM> and a second dipole element <NUM> orthogonal to first dipole element <NUM>. Other types of antenna elements may be substituted, such as a single dipole, a loop antenna, an array of microstrip patch elements, and so forth. The crossed-dipole <NUM> may be printed on a dielectric sheet, illustrated with a hexagonal shape occupying a smaller surface area than each of FSS layer <NUM> and base layer <NUM> in <FIG>. In other examples, antenna element layer <NUM> is coextensive in the x-y plane with each of FSS layer <NUM> and base layer <NUM>. An example construction of ground plane <NUM> may include a plurality of dielectric or metallic ribs <NUM>, each oriented longitudinally in the y or x directions, for added structural support of bottom ends of conductors <NUM>. For example, ribs <NUM> may be arranged in a lattice pattern comprising rows (e.g., oriented along or substantially parallel to the x axis in <FIG>) of multiple ribs and columns (e.g., oriented along or substantially parallel to the y axis in <FIG>) of multiple ribs. As another example, as illustrated in <FIG>, each rib <NUM> may extend substantially the length (e.g., oriented along or substantially parallel to the y axis of <FIG>) of the base layer <NUM>. As yet another example, the base layer <NUM> may comprise one or more continuous ribs <NUM>. As still another example, the base layer <NUM> may not include ribs <NUM>. Conductive patches 121_1 to 121_n may each be arranged in a lattice and have identical geometries, e.g., all rectangular or all square as depicted, or alternatively all hexagonal, all circular or other suitable shape. Conductive patches 121_1 to 121_n may also be configured with identical or substantially identical dimensions (e.g., within manufacturing tolerances) in some embodiments. Each conductive patch <NUM> may electrically connect to a respective conductor <NUM> through a connection <NUM> in a central location thereof.

<FIG> is a perspective view showing retaining structure <NUM> of AMC antenna apparatus <NUM> retaining AMC antenna <NUM> in a coiled configuration during stowage. All of the elements of AMC antenna <NUM> illustrated in <FIG> and <FIG> may be retained coiled within retaining structure <NUM>. In addition, other elements of AMC antenna <NUM> described hereafter, e.g., an antenna feed and balun(s), may be stored coiled within retaining structure <NUM>. The balun(s) may be hardwired to an RF front end located externally of retaining structure <NUM> through a flexible cable(s) having a section wound within retaining structure <NUM> and unwound when AMC antenna <NUM> is removed from retaining structure <NUM>.

<FIG> is a perspective view depicting AMC antenna <NUM> immediately after removal thereof from retaining structure <NUM> during deployment. The view of <FIG> also illustrates an example arrangement of AMC antenna <NUM> with respect to retaining structure <NUM> prior to insertion therein. In these conditions, bladders 103a and 103b are deflated, such that FSS layer <NUM> may be collapsed against base layer <NUM> (latching mechanism L is unlatched and may be lying flat between FSS layer <NUM> and base layer <NUM> during the deflated state of the bladder system). The resulting structure of AMC antenna <NUM> is flattened such that it may be readily inserted and coiled within retaining structure <NUM> during initial stowage, and subsequently uncoiled for removal during deployment. Bladder 103a may include a gas insertion port 102a coupled to a gas line 104a. Bladder 103b may include a gas insertion port 102b coupled to a gas line 104b. Following removal from retaining structure <NUM>, gas may be inserted into each of gas lines 104a and 104b to inflate bladders 103a and 103b to inflated states such as that illustrated in <FIG>. It is noted here that at least one additional bladder portion of the bladder system may be provided within AMC antenna <NUM>, e.g., an oblong bladder arranged longitudinally between peripheral portions 110a and 120a. The additional bladder may have its own insertion port and gas line or may be coupled to each of bladders 103a and 103b to provide a continuous bladder system arranged along three sides of AMC antenna <NUM>. In the latter case, only one port and gas line, e.g., 102a and 104a, may be included in the bladder system. The illustrated bladder system is an example. The bladder system can have different configurations and arrangements of bladders.

With continuing reference to <FIG>, latching mechanism L is exemplified as comprising a plurality of latches L<NUM> to LN (e.g., N=<NUM> as depicted) distributed along opposite peripheral portions of AMC antenna <NUM>. For instance, FSS layer <NUM> may include first through fourth oblong peripheral portions (strips) 120a, 120b, 120c and 120d, which may overlay corresponding peripheral portions 110a, 110b, 110c and <NUM>10d, respectively, when the bladder system is inflated. A first group of latches, L<NUM>, L<NUM> and LN may be distributed between peripheral portions 110b and 120b, and a second group of latches, L<NUM>, L<NUM> and L<NUM>, may be distributed between peripheral portions 110a and 120a. Bladder 103a is disposed between peripheral portions 110c and 120c; bladder 103b is disposed between peripheral portions 120d and 110d. In other embodiments, one or more additional latches may be distributed adjacent to bladder 103a between peripheral portions 110c and 120c, and one or more further latches may be disposed adjacent to bladder 103b between peripheral portions 110d and 120d.

Retaining structure <NUM> in this embodiment is a generally cylindrical structure with first and second opposite end walls <NUM> and <NUM>, a spindle <NUM> between end walls <NUM> and <NUM>, and support rods <NUM> that couple end walls <NUM> and <NUM> to one another. Each of end walls <NUM>, <NUM> may have a spiraling groove <NUM> on an inner surface <NUM> thereof to facilitate guiding and retaining AMC antenna <NUM> in a coiled configuration. Opposite edge portions of at least ground plane <NUM> are retained coiled within the pair of spiraling grooves <NUM> during stowage. If antenna layer <NUM> is configured coextensive with ground plane <NUM>, opposite edge portions of antenna layer <NUM> may also be retained within spiraling grooves <NUM>.

Spindle <NUM> may have a mechanical link <NUM> (shown schematically) to peripheral portion 110a of base layer <NUM>. To initially retain AMC antenna <NUM> within retaining structure <NUM>, AMC antenna <NUM> may be placed in a collapsed state as shown in <FIG>. In the collapsed state, conductors <NUM> are bent and FSS layer <NUM> is collapsed towards base layer <NUM> such that the thickness of at least the edge portions of the collapsed structure is thinner than the width of grooves <NUM>. Note that in the collapsed state, FSS layer <NUM> may be collapsed towards base layer <NUM> in the +x direction such that FSS layer <NUM> is offset with respect to base layer <NUM>. Because the two layers are offset in the collapsed condition, peripheral portion 110a of base layer <NUM> is no longer overlaid by the corresponding peripheral portion 120a of FSS layer <NUM>.

Spindle <NUM> may be rotated (e.g., clockwise) to draw AMC antenna <NUM> within retaining structure <NUM>. As an example, a hand crank (not shown) or an actuator <NUM> with link <NUM> may be coupled to an end <NUM> of spindle <NUM> to impart a rotational force to draw AMC antenna <NUM> within retaining structure <NUM>. Once AMC antenna <NUM> is so retained, AMC antenna apparatus <NUM> may be transported to a carrier, such as an orbital satellite prior to launch, and secured to surface <NUM> of the carrier. Since retaining structure <NUM> is more robust to environmental conditions and motion than AMC antenna <NUM> itself (if otherwise mounted on surface <NUM> without protection), securing retaining structure <NUM> to surface <NUM> prior to deployment of AMC antenna <NUM> on surface <NUM> may improve the odds of successful deployment. As another example, surface <NUM> is a planetary surface or a surface of a man-made structure on a planet. In this case, retaining structure <NUM> with AMC antenna <NUM> secured therein may be transported by a drone and dropped onto surface <NUM> for subsequent unmanned deployment.

To deploy AMC antenna <NUM> from retaining structure <NUM>, spindle <NUM> may be rotated (e.g., counter-clockwise) by actuator <NUM>, whereby AMC antenna <NUM> may slide out in a plate-like configuration while in its collapsed state in the +x direction. Alternatively, or additionally, another actuator <NUM> arranged on surface <NUM> may automatically pull out AMC antenna <NUM> from retaining structure <NUM>. To this end, AMC antenna <NUM> may have an opening <NUM> on peripheral portion 120b, through which a link <NUM> of actuator <NUM> may attach to AMC antenna <NUM>. Note that actuator <NUM> and/or actuator <NUM> may be a robotic arm secured to surface <NUM>.

<FIG> is a cross-sectional view of a portion of AMC antenna <NUM>, illustrating various structures thereof in a collapsed state during stowage. It is seen that in the collapsed state, PCBs <NUM> are each tilted with respect to FSS layer <NUM> and base layer <NUM>, such that in the cross-sectional view, each PCB <NUM> forms an acute angle with base layer <NUM>. Each conductor <NUM> may include a lower end 116b and an upper end 116a, discussed below.

<FIG> is a plan view of an example flexible PCB <NUM>. <FIG> is a cross-sectional view taken along the lines <NUM>-<NUM> of <FIG>, illustrating an example layered structure of a flexible PCB <NUM>. PCB <NUM> may have a generally rectangular profile. Each PCB <NUM> may have a group of conductors <NUM> embedded therein and extending widthwise from edge to edge. Each conductor <NUM> may include an upper end 116a and a lower end 116b, each in the form of a rectangular or square tab. Conductors <NUM> may be sandwiched between a first dielectric film <NUM> and a second dielectric film <NUM>, e.g., Kapton® or FR4.

<FIG> is a cross-sectional view taken along the lines <NUM>-<NUM> of <FIG>, depicting an example inter-layer structure of AMC antenna <NUM> during an operational (deployed) state. <FIG> depicts an example connection structure with respect to a single conductor <NUM> of a PCB <NUM> underlaying antenna element layer <NUM>; the same connection structure may be applied with respect to all conductors <NUM> of AMC antenna <NUM> underlaying antenna element layer <NUM>. For those conductors <NUM> outside the region of antenna element layer <NUM>, the upper structure may differ (discussed below). (Note also that in <FIG> and other cross-sectional views herein, features located behind those illustrated may be omitted for clarity. ) Base layer <NUM> may include a conductive base surface <NUM> adhered to or printed at a bottom surface of a flexible dielectric sheet <NUM> for structural integrity and to facilitate electrical and mechanical connections to conductors <NUM>. A dielectric rib <NUM> may be adhered to a top surface of dielectric sheet <NUM> and support a connection of a conductor <NUM> to base surface <NUM>. A plated through hole <NUM> may have been formed through rib <NUM> and base layer <NUM>. A bottom end 116b of conductor <NUM> may have been inserted within through hole <NUM> and electrically connected to conductive base surface <NUM> with a conductive adherent <NUM> surrounding end 116b within through hole <NUM>, e.g., solder that was melted and cooled.

FSS layer <NUM> may include conductive patches 121_1 to 121_n sandwiched between a lower dielectric sheet <NUM> and an upper dielectric sheet <NUM>. Alternatively, FSS layer <NUM> is constructed with a single dielectric sheet <NUM> or <NUM> with conductive patches <NUM> printed thereon. A mechanical and electrical connection <NUM> between upper portion of conductor <NUM> and FSS layer <NUM> may comprise a plated through hole <NUM>, upper end 116a, and a conductive adherent <NUM> within through hole <NUM>. <FIG> depicts a single connection <NUM> between a conductor <NUM> and a given conductive patch 121_j, which is separated by respective isolation regions <NUM> from adjacent conductive patches 121_(j-<NUM>) and 121_(j+<NUM>). Dielectric sheet <NUM> including isolation regions <NUM> may have been formed by layered deposition of dielectric material atop conductive patches <NUM>, subsequent to deposition of conductive patches <NUM> on the upper surface of dielectric sheet <NUM>. However, if dielectric sheet <NUM> is omitted, isolation regions <NUM> may be air gaps or a dielectric filler. Each of dielectric sheets <NUM>, <NUM>, <NUM> and <NUM> may be a polyimide film such as Kapton®.

Electrical connections <NUM> throughout AMC antenna <NUM> may each be provided at a fixed distance above dielectric sheet <NUM> (with latch mechanism L in the latched state). In this manner, FSS layer <NUM> is supported with its lower surface uniformly spaced throughout by a fixed distance from base layer <NUM>. An air gap <NUM> may be present in the regions surrounding conductors <NUM>.

Antenna element layer <NUM> may include the at least one antenna element <NUM> printed atop dielectric layer <NUM>. An example mechanical connection between antenna element layer <NUM> and FSS layer <NUM> may include a rigid extension portion <NUM> of upper end 116a of conductor <NUM> extending above the upper surface of dielectric sheet <NUM>, a plated blind via <NUM> in the lower surface of dielectric sheet <NUM>, and an electrically conductive adherent <NUM> such as solder. The upper end of extension <NUM> may have been inserted within via <NUM> and adhered to dielectric sheet <NUM> by melting and cooling adherent <NUM>. All or most of conductors <NUM> underlaying antenna element layer <NUM> may likewise include an extension <NUM> adhered to dielectric sheet <NUM> in this manner. As a result, antenna element layer <NUM> may be entirely supported by conductors <NUM> and uniformly spaced a close distance away from the upper surface of FSS layer <NUM>. It is noted that if antenna layer <NUM> is only centrally located with respect to FSS layer <NUM>, as in the example of <FIG>, then the conductors <NUM> located outside the region of antenna layer <NUM> may omit extensions <NUM>. These peripheral conductors <NUM> may all be designed with the same or substantially the same length (e.g., within manufacturing tolerances), and the top ends may be flush with the upper surface of dielectric sheet <NUM>. In a similar vein, each of the conductors <NUM> underlaying antenna layer <NUM> may be identically or substantially identically designed, with extensions <NUM> of the same or substantially the same length (e.g., within manufacturing tolerances). With the above-described mechanical connection between FSS layer <NUM> and antenna element layer <NUM>, a narrow air gap <NUM> may exist between layers <NUM> and <NUM>. In an alternative configuration, extensions <NUM> on conductors <NUM> are omitted throughout AMC antenna <NUM>; dielectric sheets <NUM> and <NUM> are fused or formed as a single dielectric sheet; and no air gap <NUM> exists between FSS layer <NUM> and antenna element layer <NUM>.

<FIG> is a schematic diagram illustrating an example antenna feed, <NUM>, that may connect to antenna element <NUM> of AMC antenna <NUM>. Antenna feed <NUM> may include a pair of baluns <NUM>; a first flexible coaxial cable <NUM> having a first end connected to baluns <NUM> and having an outer conductor <NUM> and an inner conductor <NUM>; a second flexible coaxial cable <NUM> having a first end connected to baluns <NUM> and having an outer conductor <NUM> and an inner conductor <NUM>; and first, second, third and fourth interconnects <NUM>, <NUM>, <NUM> and <NUM>, respectively. First dipole element <NUM> includes dipoles arms 132a and 132b; second dipole element <NUM> includes dipole arms 134a and 134b. A second end of first coaxial cable <NUM> connects to first dipole element <NUM>, with interconnect <NUM> connecting outer conductor <NUM> to dipole arm 132a and interconnect <NUM> connecting inner conductor <NUM> to dipole arm 132b. A second end of second coaxial cable <NUM> connects to second dipole element <NUM>, with interconnect <NUM> connecting outer conductor <NUM> to dipole arm 134a and interconnect <NUM> connecting inner conductor <NUM> to dipole arm 134b.

<FIG> is a perspective view depicting an example central portion of an upper part of AMC antenna <NUM>, illustrating a portion of the example antenna feed <NUM>. A central portion of crossed-dipole antenna element <NUM> may overlay an intersection region of centralized, adjacent conductive patches 121_i, 121_(i+<NUM>), 121_(i+<NUM>) and 121_(i+<NUM>). An opening <NUM> in FSS layer <NUM> may be formed in the centralized region, by removing a corner piece of each of conductive patches 121_i to <NUM>(i+<NUM>). Another opening <NUM> may have been formed in a centralized region of antenna element layer <NUM>. Coaxial cables <NUM> and <NUM> may extend vertically (z direction) between antenna element layer <NUM> and base layer <NUM> during the deployed state of AMC antenna <NUM>. During the stowage state, coaxial cables may be caused to collapse between antenna element layer <NUM> and base layer <NUM>.

The second ends of coaxial cables <NUM> and <NUM> may penetrate opening <NUM> and at least partially penetrate opening <NUM>. Interconnects <NUM> and <NUM> may each be embodied as wire bonds. Alternatively, interconnects <NUM> and <NUM> are in the form of a funnel shaped metal section integrated with a conductive extension. The funnel shaped metal section is soldered or otherwise electrically connected to the respective outer conductors <NUM> or <NUM>, and the conductive extension is soldered or otherwise electrically connected to an input point of dipole arm 132a or 134a. Interconnects <NUM> and <NUM> may be direct solder connections to input points of dipole arms 132b and 134b, respectively.

<FIG> is a cross-sectional view taken along the lines <NUM>-<NUM> of <FIG>, depicting an example integration of antenna feed <NUM> within AMC antenna <NUM>. This view shows that baluns <NUM> may be disposed adjacent to the lower surface of AMC antenna <NUM>, and the lower ends of coaxial cables <NUM> and <NUM> may penetrate an opening <NUM> in base layer <NUM> and connect to baluns <NUM>. Coaxial cables <NUM> and <NUM> may run vertically side by side, with upper ends thereof penetrating opening <NUM> in FSS layer <NUM> and opening <NUM> in dielectric sheet <NUM> of antenna layer <NUM> to facilitate the electrical connection to crossed-dipole antenna element <NUM>. In the stowed state, coaxial cables <NUM> and <NUM> may be collapsed similar to conductors <NUM> (collapsed state illustrated in <FIG>).

<FIG> is a partial end view of AMC antenna <NUM>, illustrating an example latch, Li, in a collapsed, unlatched state of AMC antenna <NUM>. <FIG> is the same partial end view of AMC antenna <NUM> in a latched, operational state following deployment. Any of latches L<NUM>-LN of AMC antenna <NUM> may have the structure of latch Li, which may include an upper rod <NUM>, a lower rod <NUM>, and a central latching coupler <NUM> that couples upper and lower rods <NUM> and <NUM>. An upper end support <NUM> may be attached to FSS layer <NUM> and form a movable joint with an upper portion of upper rod <NUM>. A lower end support <NUM> may be attached to base layer <NUM> and form a movable joint with lower rod <NUM>. Thus, in the unlatched state, upper rod <NUM> forms an acute angle with FSS layer <NUM> and lower rod <NUM> forms an acute angle with base layer <NUM>, such that FSS layer <NUM> and base layer <NUM> are closely spaced for optimal stowage of AMC antenna <NUM>. In the latched state, upper rod <NUM> and lower rod <NUM> are aligned vertically, thereby providing a fixed, predetermined spacing between base layer <NUM> and FSS layer <NUM>.

<FIG> is a flow chart depicting operations of an example method, <NUM>, of deploying AMC antenna <NUM> on an unmanned carrier according to an embodiment. With method <NUM>, AMC antenna <NUM> is first stored in its collapsed state in a retaining structure, e.g., retaining structure <NUM> described above (S1310). The retaining structure may then be transported with AMC antenna <NUM> stored therein to an unmanned carrier (S1320). As mentioned earlier, some examples of the unmanned carrier (e.g., a carrier including surface <NUM>) include an orbital satellite, a planetary surface or a man-made structure on a planetary surface.

The AMC antenna may then be deployed (S1330) by removing the same from the retaining structure using an actuator (e.g., <NUM> and/or <NUM>) as described above, and inflating the bladder system (e.g., bladders 103a and 103b) sufficiently to cause the latch mechanism (e.g., "L") to transition from the unlatched state to the latched state. As a result of the latching, FSS layer <NUM> becomes properly spaced from base layer <NUM> and AMC antenna <NUM> is set up for operation, e.g., in the above-described configuration shown in <FIG>.

With the AMC antenna in an operational configuration, a robotic arm or the like (e.g., actuator <NUM> with link <NUM>) may secure the AMC antenna to the surface <NUM> of the carrier. In an embodiment, balun <NUM> is already hardwired to an RF front end of a communication system, e.g., through a flexible cable (not shown) having a section coiled within retaining structure <NUM> during stowage and uncoiled when AMC antenna <NUM> is removed. If balun <NUM> is not so hardwired, a robotic arm or the like may electrically connect balun <NUM> to the RF front end. In either case, active communication of signals by the AMC antenna may be initiated once the RF front end connection to balun <NUM> is secured.

Claim 1:
An artificial magnetic conductor, AMC, antenna apparatus (<NUM>) comprising:
a ground plane (<NUM>) comprising:
a base layer (<NUM>) comprising a conductive base surface (<NUM>);
a frequency selective surface, FSS, layer (<NUM>) above the base layer, the FSS layer comprising a plurality of conductive patches (<NUM>) separated from one another; and
a plurality of flexible conductors (<NUM>), each electrically connecting one of the conductive patches to the conductive base surface;
a flexible antenna element layer (<NUM>) above the FSS layer, comprising at least one antenna element (<NUM>);
a latch mechanism (L) between the base layer and the FSS layer, configured to transition from an unlatched state to a latched state, wherein in the latched state, the conductive base surface is fixedly separated from the FSS layer by a predetermined distance; and
an inflatable bladder system (103a, 103b) between the base layer and the FSS layer, configured to receive a gas input during deployment of the AMC antenna apparatus and inflate to produce force sufficient to cause the latch mechanism to transition from the unlatched state to the latched state.