Single-layer wide-angle impedance matching (WAIM)

Abstract

A single-layer wide-angle impedance matching (WAIM) structure and methods of using the same are described. In one embodiment, an antenna comprises an aperture having a plurality of antenna elements operable to radiate radio frequency (RF) energy, and a single-layer wide-angle impedance matching (WAIM) structure coupled to the aperture to provide an impedance match between the aperture and free space.

Description

[Technical Field]

[0001] (Priority) This application claims the benefit under 35 U.S.C. 119(e) of U.S. Provisional Patent Application No. 63 / 027,190, filed May 19, 2020, and U.S. Non-Provisional Application No. 17 / 322,602, filed May 17, 2021, which are incorporated by reference in their entireties.

[0002] (Technical field) FIELD OF THE INVENTION Embodiments of the present invention relate to the field of satellite communications, and more particularly, embodiments of the present invention relate to wide angle impedance matching (WAIM) structures used in satellite antennas. [Background technology]

[0003] Antenna gain is one of the most important parameters for satellite communication systems because it determines network coverage and speed. More specifically, higher gain means better coverage and faster speeds, which is crucial in the highly competitive satellite market. On the satellite side, antenna gain across the receive (Rx) band can be important because the received power at the antenna is very low. This becomes even more important at the scan angles of flat-panel electronically scanned antennas due to increased attenuation and reduced antenna gain at these angles compared to broadside, making a high gain value a necessary parameter for closing the link between the antenna and the satellite. Over the transmit (Tx) band, gain is also important because lower gain requires more power to be supplied to the antenna to achieve the desired signal strength, which means higher costs, temperature, thermal noise, etc.

[0004] One type of antenna used in satellite communications is the radial aperture slot array antenna. In recent years, several improvements have been made to the performance of such radial aperture slot array antennas. One of the parameters that limits the radiation efficiency of these antennas is the impedance mismatch between the antenna aperture and free space. When this mismatch increases with the scan angle, this additional loss of radiation efficiency results in scan loss. The WAIM structure alleviates this problem by providing proper impedance matching.

[0005] Dipole loading has been mentioned for use in radial aperture slot array antennas. This loading can improve radiation efficiency by providing impedance matching. It can also be used to shift the frequency response. The slot dipole concept has also been applied to radial aperture slot array antennas to improve the directivity of the antenna, including improving the overall return loss performance of the antenna, especially for antennas operating broadside. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] U.S. Patent Application Serial No. 14 / 550,178 [Patent Document 2] U.S. Patent Application Serial No. 14 / 610,502 [Patent Document 3] U.S. Patent Publication No. 2015 / 0236412 Summary of the Invention

[0007] A single-layer Wide Angle Impedance Matching (WAIM) structure and methods for using the same are described. In one embodiment, an antenna comprises an aperture having a plurality of antenna elements operable to radiate radio frequency (RF) energy, and a single-layer Wide Angle Impedance Matching (WAIM) structure coupled to the aperture to provide impedance matching between the antenna aperture and free space.

[0008] The described embodiments and their advantages can best be understood by referring to the following description taken in conjunction with the accompanying drawings, which are not intended to limit in any way the changes in form and detail that may be made to the described embodiments by those skilled in the art without departing from the spirit and scope of the described embodiments. [Brief explanation of the drawings]

[0009] [Figure 1A] FIG. 1 illustrates an embodiment of a single-layer wide-angle impedance matching (WAIM) structure. [Figure 1B] FIG. 1 illustrates an embodiment of a single-layer wide-angle impedance matching (WAIM) structure. [Figure 2A] 10A-10C illustrate alternative placements of WAIM structures on apertures with various alignments. [Figure 2B] 10A-10C illustrate alternative placements of WAIM structures on apertures with various alignments. [Figure 2C] 10A-10C illustrate alternative placements of WAIM structures on apertures with various alignments. [Figure 2D] FIG. 1 illustrates the flexibility of using different feature dimensions to achieve the same performance. [Figure 2E] FIG. 1 illustrates the flexibility of using different feature dimensions to achieve the same performance. [Figure 2F] FIG. 1 illustrates the flexibility of using different feature dimensions to achieve the same performance. [Figure 3] FIG. 10 illustrates the gain and scan loss improvement for one embodiment of a single layer WAIM structure. [Figure 4] FIG. 1 is a flow diagram of one embodiment of a process for designing a single-layer WAIM structure. [Figure 5A] 10A-10C illustrate alternative capacitive surfaces for use in WAIM structures. [Figure 5B] 10A-10C illustrate alternative capacitive surfaces for use in WAIM structures. [Figure 5C] 10A-10C illustrate alternative capacitive surfaces for use in WAIM structures. [Figure 6] FIG. 1 shows an aperture having one or more arrays of antenna elements arranged in concentric rings around the input feed of a cylindrical feed antenna. [Figure 7] FIG. 2 is a perspective view of one row of antenna elements including a ground plane and a reconfigurable resonator layer. [Figure 8A] FIG. 1 illustrates an embodiment of a tunable wavelength resonator / slot. [Figure 8B] FIG. 1 is a cross-sectional view of one embodiment of a physical antenna aperture. [Figure 9A] FIG. 10 shows a portion of the first iris substrate layer with locations corresponding to the slots. [Figure 9B] FIG. 10 shows a portion of the second iris substrate layer including a slot. [Figure 9C] FIG. 10 shows a patch on a portion of the second iris substrate layer. [Figure 9D] FIG. 1 is a top view of a portion of a slotted array. [Figure 10] FIG. 1 is a side view of one embodiment of a cylindrical feed antenna structure. [Figure 11] FIG. 10 illustrates another embodiment of an antenna system with outgoing waves. [Figure 12] FIG. 10 is a diagram showing an embodiment of the arrangement of matrix drive circuits relative to antenna elements. [Figure 13] FIG. 1 illustrates an embodiment of a TFT package. [Figure 14] FIG. 1 is a block diagram illustrating another embodiment of a communication system having simultaneous transmit and receive paths. DETAILED DESCRIPTION OF THE INVENTION

[0010] In the following description, numerous details are set forth in order to provide a more thorough explanation of the present invention. However, it will be apparent to those skilled in the art that the present invention may be practiced without these specific details. In other instances, well-known structures and devices are shown in block diagram form, rather than in detail, in order to avoid obscuring the present invention.

[0011] A new wide-angle impedance matching (WAIM) structure for aperture antennas and a method for using the same are described. The WAIM structure improves the radiation efficiency of aperture antennas by providing a proper impedance match between the antenna aperture and free space. Improved scan loss also results from providing a better match at the scan angle. In one embodiment, the impedance match is a function of frequency, scan angle, and polarization of the propagating wave, since the impedance of the antenna aperture and the impedance of free space vary with these parameters.

[0012] In one embodiment, the WAIM design characteristics depend on the type of antenna aperture. In one embodiment, the antenna aperture is part of a leaky wave antenna and has a subwavelength radiating slot. In one embodiment, the antenna aperture is a metasurface having multiple antenna elements that radiate radio frequency (RF) energy. Such antenna elements can be surface scattering metamaterial antenna elements. An example of a liquid crystal (LC)-based surface scattering metamaterial antenna element is described in more detail below. However, the antenna elements are not limited to being LC-based antenna elements. For example, in another embodiment, the antenna elements are varactor-based metamaterial antenna elements, in which varactor diodes are used to tune the radiating slot antenna element. The equivalent circuit model of a radiating surface with a subwavelength radiating slot is a parallel resonator with a small resistive section. Therefore, the impedance curve versus frequency on the Smith chart is a circle toward the short section. In one embodiment, an L-type matching network including a parallel capacitance and a series inductance provides suitable impedance matching for this configuration.

[0013] In one embodiment, the WAIM structure is a single-layer structure having a two-dimensional periodic array of subwavelength capacitive patches. In one embodiment, the structure is printed on a dielectric substrate and separated from its aperture by a dielectric spacer (e.g., foam, etc.). One key advantage of the single-layer WAIM structure described herein over the prior art is that it can be easily prototyped and assembled at very low cost.

[0014] Embodiments of the WAIM structure have other important advantages, including low-cost manufacturing and a simple assembly process. In one embodiment, because design embodiments include a single-layer structure, this results in lower fabrication costs compared to alternatives, eliminates tight tolerances on several physical dimensions, and reduces the complexity of the assembly process. Also, flexibility is provided in the selection of dimensions for the impedance matching element, allowing them to be selected to fit well within the tolerances of the manufacturing technology.

[0015] Furthermore, and importantly, the embodiments described herein do not require positional / rotational alignment between the impedance matching element and the antenna aperture element. This eliminates positional tolerances and simplifies the assembly process, resulting in lower costs. Also, by not relying on alignment between the impedance matching element and the antenna element, the design provides highly repeatable RF performance.

[0016] Furthermore, the same RF performance can be achieved with a variety of pixel sizes. This allows for the use of cost-effective manufacturing techniques that do not necessarily offer tight tolerances on feature sizes. For example, in one embodiment, the WAIM structure comprises a substrate with elements screen-printed onto the substrate. The use of screen-printing in this case is a significantly lower-cost alternative to printed circuit board (PCB) technology.

[0017] It should be noted that the single layer WAIM structure can be used with a number of different antenna apertures. Examples of aperture antennas are described in more detail below. However, it should be noted that the WAIM structures disclosed herein may also be used with antenna apertures other than those described below.

[0018] In one embodiment, the single-layer WAIM structure comprises an L-shaped impedance network realized by a capacitive surface separated from the aperture by a dielectric spacer. In some embodiments, the capacitive impedance surface uses a 2D array of sub-wavelength elements. The sub-wavelength elements can be one or more of many different types. Some examples are sub-wavelength patches, dipoles, split-ring resonators (SRRs), etc.

[0019] FIG. 1A illustrates one embodiment of a WAIM structure. In this embodiment, a single-layer WAIM structure 100 overlies an antenna aperture including a metasurface having multiple antenna elements 101. In one embodiment, the antenna elements 101 comprise slot resonators (e.g., surface-scattering metamaterial antenna elements, RF-radiating antenna elements, etc.). The WAIM structure 100 comprises a two-dimensional (2D) array of subwavelength square patches 102. In one embodiment, the patches 102 are subwavelength patches to ensure that the structure, which is a metasurface, functions as a capacitive layer. In one embodiment, the patches 102 are capacitive patches. In one embodiment, the patches 102 are printed on a substrate. In one embodiment, the WAIM structure 100 is separated from the aperture by a dielectric spacer or foam.

[0020] The WAIM structure can be modeled using the equivalent circuit model shown in Figure 1B. Referring to the model in Figure 1B, the capacitive patch 102 is modeled by a parallel capacitance, and the spacer between the aperture and the patch 102 is modeled by a short section of transmission line.

[0021] This type of single-layer WAIM structure is desirable for several reasons. First, it provides flexibility in choosing physical parameters to achieve the same performance. The intrinsic capacitance of this surface is a function of the physical dimensions of the patch and its surrounding medium. Equation (1) shows a first-order approximation for calculating this capacitance value for a normal incident wave.

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[0022] Second, the impedance of this plane is independent of the scanning plane (i.e., φ) of the antenna. This is due to the 90-degree rotational symmetry of the structure and the fact that the intrinsic capacitance is formed by the electric field between the parallel edges of adjacent patches. This feature is desirable in certain antennas with apertures that are rotationally symmetric.

[0023] Third, in one embodiment, the surface impedance of the WAIM structure is a function of the scan angle and the polarization of the propagating wave. When properly designed, the WAIM structure provides an impedance match between the antenna aperture and the free space impedance for both orthogonal polarizations (i.e., TE and TM) at various scan angles.

[0024] Fourth, in one embodiment, the WAIM structure is extremely broadband, and therefore can potentially provide impedance matching for apertures with broadband radiating elements or multiple radiating elements at different frequencies. This feature is important in certain antennas where the aperture is occupied by multiple radiating elements.

[0025] One embodiment of the design procedure for an embodiment of a WAIM structure is based on its equivalent circuit model shown in Figure 1B. In this model, all parameters are functions of scan angle and wave polarization. Equations (2) and (3) show how the transmission line impedance changes as a function of scan angle and polarization (η is the broadside free space impedance). These equations are also valid in free space.

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[0026] Equations (4) and (5) show how the capacitance varies as a function of scan angle for orthogonal polarizations, where C0 is the broadside capacitance.

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[0027] Given that the dielectric substrate properties are predetermined, the key design parameters are the foam thickness and capacitance value C0. These values ​​are defined so that the design provides the desired impedance match in full scan and both transverse electric (TE) and transverse magnetic (TM) polarizations. This is a general solution since any other polarization can be decomposed into these two orthogonal polarizations.

[0028] The selected parameters in the equivalent circuit model are then mapped to physical parameters. Note that h is simply the thickness of the dielectric spacer (e.g., foam, dielectric laminate, polyester, polycarbonate, glass, honeycomb spacer, etc.). The capacitance is mapped to the patch dimensions and periodicity using Equation (1).

[0029] Note that in one embodiment, the single layer WAIM structure is attached to the dielectric spacer using an adhesive. In one embodiment, the dielectric spacer is attached to the antenna aperture using an adhesive. In one embodiment, the height of the dielectric layer is 60 mil. Alternatively, the dielectric layer may be other sizes (e.g., 1.5 mm). In alternative embodiments, the single layer WAIM structure, dielectric layer, and antenna layer are not attached together but are in contact with each other. In such cases, other antenna components (e.g., a radome) hold these components in place.

[0030] In one embodiment, the single layer WAIM is fabricated on top of the dielectric layer. In one embodiment, the single layer WAIM is screen printed on top of the dielectric layer, thereby reducing two layers to one.

[0031] There are many advantages associated with the embodiments of the WAIM structure disclosed herein. For example, as discussed above, the proposed design does not require positional / rotational alignment. Figures 2A-2C show alternative placements of the WAIM in an aperture using various alignments. In this case, the WAIM structure in each of these embodiments includes a square capacitive patch that is the same size.

[0032] Referring to FIG. 2A, a single-layer WAIM structure 201 includes a 2D array of capacitive patches 203 over an aperture with antenna element 202. The patches 203 in the 2D array are squares patterned across the array aligned horizontally and vertically. Referring to FIG. 2B, a single-layer WAIM structure 211 includes a 2D array of capacitive patches 213 over an aperture with antenna element 212. The 2D array in FIG. 2B is the same as that in FIG. 2A, except that it is rotated by 22.5 degrees. Referring to FIG. 2C, a single-layer WAIM structure 221 includes a 2D array of capacitive patches 223 over an aperture with antenna element 222. The 2D array in FIG. 2C is the same as that in FIG. 2A, except that it is rotated by 45 degrees (22.5 degrees relative to the 2D array in FIG. 2B).

[0033] Also, as discussed, the same performance can be achieved using 2D arrays of capacitive patches with different patch widths and periodicities. Figures 2D-2F illustrate examples of single-layer WAIM structures that achieve the same performance using various feature dimensions. Referring to Figure 2D, single-layer WAIM structure 231 includes a 2D array of capacitive patches 233 over an aperture with antenna elements 232. The patches 233 in the 2D array are square and patterned across horizontally and vertically aligned arrays. Referring to Figure 2E, single-layer WAIM structure 241 includes a 2D array of capacitive patches 243 over an aperture with antenna elements 242. However, the size of the patches in the 2D array in Figure 2E is smaller than the patches in Figure 2A. Referring to Figure 2F, single-layer WAIM structure 251 includes a 2D array of capacitive patches 253 over an aperture with antenna elements 252. In this case, the size of the patches in the 2D array in Figure 2F is smaller than the patches in Figure 2E (and therefore smaller than the patches in Figure 2D).

[0034] In one embodiment, the capacitive patches are metal (e.g., copper, silver, etc.) on a substrate (e.g., a printed circuit board (PCB) (e.g., FR4, etc.), polycarbonate, glass, etc.). In one embodiment, if the patches are screen printed, the substrate comprises polyester. The patches can be of various thicknesses. In one embodiment, the patch thickness is 17 um, 35 um, etc. In one embodiment, each square patch is 200 mil x 200 mil. However, as noted above, other sizes can be used (e.g., 250 mil x 250 mil, etc.).

[0035] The WAIM embodiments disclosed herein improve radiation efficiency by providing a proper impedance match between the antenna aperture and free space. Improved radiation efficiency results in improved antenna gain. FIG. 3 shows 60 deg gain measurements at the broadside and TE plane (H-pol) for an exemplary antenna aperture. Referring to FIG. 3, test results are shown for three sub-bands. The dashed line shows the measurement without the WAIM structure, and the solid line shows the gain with the WAIM structure installed. Significant improvements were observed when the WAIM structure was installed in both broadside and scanning. Since the gain improvement is greater than broadside, the scanning loss is also significantly improved.

[0036] Figure 4 is a flow diagram illustrating one embodiment of a process for designing a single-layer WAIM structure. Referring to Figure 4, the process begins by determining the antenna aperture impedance for various scan angles and polarizations (processing block 401). In one embodiment, this is performed using analytical and full-wave Floquet model simulations, using inputs including all antenna elements (e.g., all receive and transmit radiating elements on the aperture), scan angles, and polarizations (410).

[0037] Once the antenna aperture impedances for various scan angles and polarizations have been determined, processing logic inputs the parameter values ​​into a WAIM equivalent circuit model (processing block 402). In one embodiment, the inputs to the model include the results of performing an analytical ABCD-matrix calculation (411). The outputs are circuit model electrical parameters. In one embodiment, these outputs include transmission line length and capacitance values ​​in the equivalent circuit model.

[0038] Next, processing logic maps the electrical parameters to physical parameters (processing block 403). In one embodiment, this is done using first order approximations or full wave simulations (412) in a manner known in the art. Once the mapping is complete, processing logic runs a full wave aperture simulation on the design (processing block 404).

[0039] There are several alternative embodiments. For example, the WAIM structures disclosed herein can be used with any antenna aperture having an array of sub-wavelength radiating elements. Furthermore, the same element geometries can be extended to WAIM structures with multiple layers as impedance matching networks.

[0040] As also discussed above, capacitive surfaces can be implemented using two-dimensional arrays of various subwavelength elements. Figures 5A-5C illustrate examples of WAIM structures with alternative configurations. Referring to Figure 5A, a single-layer WAIM structure 500 includes a 2D pattern of square capacitive patches 501. Referring to Figure 5B, a single-layer WAIM structure 510 includes a 2D pattern of hexagonal capacitive patches 511. Referring to Figure 5C, a single-layer WAIM structure 520 includes a 2D pattern of split-ring resonators (SSRs) 521. Capacitive elements of other shapes can also be used.

[0041] Antenna system implementation example In one embodiment, the planar antenna is part of a metamaterial antenna system. An embodiment of a metamaterial antenna system for a communications satellite ground station is described. In one embodiment, the antenna system is a component or subsystem of a satellite ground station (ES) operating on a mobile platform (e.g., airborne, maritime, land, etc.) that operates using either Ka-band or Ku-band frequencies for civil commercial satellite communications. It should be noted that embodiments of the antenna system can also be used in ground stations that are not on mobile platforms (e.g., fixed or portable ground stations).

[0042] In one embodiment, the antenna system uses surface scattering metamaterial technology to form and steer transmit and receive beams via separate antennas.

[0043] In one embodiment, the antenna system is composed of three functional subsystems: (1) a waveguiding structure composed of a cylindrical wave feed architecture; (2) an array of wave-scattering metamaterial single cells that are part of the antenna elements; and (3) a control structure that commands the formation of an adjustable radiation field (beam) from the metamaterial scattering elements using holographic principles.

[0044] Antenna element FIG. 6 is a schematic diagram of one embodiment of a cylindrically fed holographic radial aperture antenna. Referring to FIG. 6, the antenna aperture has one or more arrays 601 of antenna elements 603 arranged in concentric rings around the input feed 602 of the cylindrically fed antenna. In one embodiment, the antenna elements 603 are radio frequency (RF) resonators that radiate RF energy. In one embodiment, the antenna elements 603 include both Rx and Tx irises interleaved and distributed across the surface of the antenna aperture. Examples of such antenna elements are described in more detail below. It should be noted that the RF resonators described herein can also be used in antennas that do not include a cylindrical feed.

[0045] In one embodiment, the antenna includes a coaxial feed used to provide a cylindrical wave feed via input feed 602. In one embodiment, a cylindrical wave feed architecture feeds the antenna from a central point with excitation radiating cylindrically outward from the feed point. That is, a cylindrical feed antenna generates an outward-traveling concentric feed wave. Nevertheless, the shape of the cylindrical feed antenna around the cylindrical feed can be circular, square, or any shape. In another embodiment, the cylindrical feed antenna generates an inward-traveling feed wave. In such cases, the feed wave most naturally originates from a circular structure.

[0046] In one embodiment, the antenna element 603 includes an iris, and the aperture antenna of Figure 6 is used to generate a main beam formed by using excitation from a cylindrical feed that radiates through a tunable liquid crystal (LC) material into the iris. In one embodiment, the antenna can be excited to radiate a horizontally or vertically polarized electric field at a desired scan angle.

[0047] In one embodiment, the antenna elements include a group of patch antennas. The group of patch antennas includes an array of scattering metamaterial elements. In one embodiment, each scattering element in the antenna system is part of a single cell consisting of a bottom conductor, a dielectric substrate, and a top conductor, where the top conductor incorporates complementary electrically inductive capacitive resonators ("complementary electrical LC" or "CELC") etched or deposited into the top conductor. As will be appreciated by those skilled in the art, LC in the context of CELC refers to inductance-capacitance, as opposed to liquid crystal.

[0048] In one embodiment, liquid crystal (LC) is disposed in the gap around the scattering element. This LC is driven by the direct-drive embodiment described above. In one embodiment, liquid crystal is encapsulated in each sub-cell, separating the bottom conductor associated with the slot from the top conductor associated with the patch of slots. The liquid crystal has a dielectric constant that is a function of the orientation of the molecules that make up the liquid crystal, and the molecular orientation (and therefore the dielectric constant) can be controlled by adjusting the bias voltage across the liquid crystal. In one embodiment, the liquid crystal utilizes this property to incorporate an on / off switch for energy transfer from guided waves to the CELC. When switched on, the CELC radiates electromagnetic waves like an electrically small dipole antenna. The teachings herein are not limited to having liquid crystals that behave binary with respect to energy transfer.

[0049] In one embodiment, the feed geometry of this antenna system allows the antenna elements to be positioned at a forty-five degree (45°) angle relative to the wave vector in the feed wave. Note that other positions (e.g., 40°) can be used. This element position allows for control of the free-space waves received by or transmitted / radiated from the elements. In one embodiment, the antenna elements are arranged with an element spacing that is less than the free-space wavelength at the antenna's operating frequency. For example, if there are four scattering elements per wavelength, the elements in a 30 GHz transmit antenna are approximately 2.5 mm (i.e., 1 / 4 of a 10 mm free-space wavelength at 30 GHz).

[0050] In one embodiment, two sets of elements are perpendicular to each other and simultaneously have equal amplitude excitation when controlled to the same tuning state. Rotating these sets of elements by + / - 45 degrees relative to the feed excitation simultaneously achieves both desired characteristics. Rotating one set by 0 degrees and the other by 90 degrees achieves the goal of orthogonality but not equal amplitude excitation. Note that 0 degrees and 90 degrees can be used to achieve isolation when an array of antenna elements in a single structure is fed from two sides.

[0051] The amount of radiated power from each single cell is controlled by applying a voltage (potential across the LC channel) to the patch using a controller. Traces to each patch are used to supply a voltage to the patch antenna. This voltage is used to tune or detune the capacitance and therefore the resonant frequency of the individual elements to achieve beamforming. The voltage required depends on the liquid crystal mixture used. The voltage tuning characteristics of a liquid crystal mixture are primarily described by a threshold voltage, above which the liquid crystal begins to be sensitive to voltage, and a saturation voltage, above which increasing the voltage no longer results in significant tuning in the liquid crystal. These two characteristic parameters can vary for different liquid crystal mixtures.

[0052] In one embodiment, as discussed above, a matrix drive is used to apply voltages to the patches to drive each cell separately from all other cells without having a separate connection for each cell (direct drive). Because of the high density of elements, a matrix drive is an efficient way to address each cell individually.

[0053] In one embodiment, the control structure for the antenna system includes two main components: an antenna array controller (including drive electronics) for the antenna system that resides below the wave-scattering structure, and a matrix drive switching array that is interspersed throughout the radiating RF array so as not to interfere with radiation. In one embodiment, the drive electronics for the antenna system adjusts the bias voltage to each scattering element by adjusting the amplitude or duty cycle of the AC bias signal to that element, and includes a commercial off-the-shelf LCD controller used in commercial television equipment.

[0054] In one embodiment, the antenna array controller also contains a microprocessor that executes software. The control structure may also incorporate sensors (e.g., GPS receiver, 3-axis compass, 3-axis accelerometer, 3-axis gyro, 3-axis magnetometer, etc.) that provide position and orientation information to the processor. The position and orientation information may be provided to the processor by other systems within the ground station and / or may not be part of the antenna system.

[0055] More specifically, the antenna array controller controls which elements are turned off and on at which phase and amplitude levels at the operating frequency, and these elements are selectively detuned to the frequency of operation by application of voltages.

[0056] For transmission, a controller supplies an array of voltage signals to the RF patches to generate a modulation or control pattern. The control pattern causes the elements to change to different states. In one embodiment, multi-state control is used, in which different elements are turned on and off to different levels, more closely approximating a sinusoidal control pattern rather than a square wave (i.e., a sinusoidal gray-shade modulation pattern). In one embodiment, rather than some elements radiating and some not radiating, some elements radiate more strongly than others. Variable emission is achieved by applying specific voltage levels, which adjust the liquid crystal dielectric constant by different amounts and variably detune the elements, causing some elements to radiate more than others.

[0057] The generation of focused beams by an array of metamaterial elements can be explained by the phenomena of constructive and destructive interference. Individual electromagnetic waves add up (constructive interference) if they have the same phase when they cross in free space, and cancel each other out (destructive interference) if they have opposite phases when they cross in free space. If the slots in a slotted antenna are positioned so that each successive slot is a different distance from the excitation point of the guided wave, the scattered wave from the element will have a different phase than the scattered wave from the previous slot. If the slots are spaced a quarter of a guided wavelength apart, each slot will scatter the wave with a quarter phase delay from the previous slot.

[0058] The use of arrays increases the number of constructive and destructive interference patterns that can be generated, theoretically enabling the beam to be steered in any direction plus or minus ninety degrees (90°) from the boresight of the antenna array using the principles of holography. Thus, by controlling which metamaterial single cells are turned on or off (i.e., by changing the pattern of which cells are turned on and which are turned off), different constructive and destructive interference patterns can be generated, allowing the antenna to change the direction of the main beam. The time required to turn single cells on and off dictates the speed at which the beam can switch from one position to another.

[0059] In one embodiment, the antenna system generates one steerable beam for the uplink antenna and one steerable beam for the downlink antenna. In one embodiment, the antenna system uses metamaterial technology to receive the beams, decode the signal from the satellite, and form a transmit beam that is directed toward the satellite. In one embodiment, the antenna system is an analog system, as opposed to antenna systems that use digital signal processing to form and steer beams electronically (such as phased array antennas). In one embodiment, the antenna system is considered a "surface" antenna, which is flat and relatively thin, especially when compared to traditional dish-style satellite receivers.

[0060] 7 shows a perspective view of one row of antenna elements including a ground plane and a reconfigurable resonator layer 1230. The reconfigurable resonator layer 1230 contains an array of tunable slots 1210. The array of tunable slots 1210 can be configured to point the antenna in a desired direction. Each of the tunable slots can be tuned / adjusted by changing the voltage across the liquid crystal.

[0061] Control module 1280 is coupled to reconfigurable resonator layer 1230 and modulates the array of variable wavelength slots 1210 by varying the voltage across the liquid crystal in FIG. 8A . Control module 1280 can include a field programmable gate array (“FPGA”), a microprocessor, a controller, a system-on-chip (SoC), or other processing logic. In one embodiment, control module 1280 includes logic (e.g., a multiplexer) for driving the array of variable wavelength slots 1210. In one embodiment, control module 1280 receives data including specifications for a holographic diffraction pattern to be driven onto the array of variable wavelength slots 1210. The holographic diffraction pattern is generated in response to the spatial relationship between the antenna and the satellite, and the holographic diffraction pattern can steer the downlink beam (and uplink beam, if the antenna system transmits) in a direction suitable for communication. Although not shown in the figures, a control module similar to control module 1280 can drive each array of variable wavelength slots described in the figures of this disclosure.

[0062] Radio frequency ("RF") holography can also be implemented using similar techniques, where a desired RF beam can be generated when an RF reference beam encounters an RF holographic diffraction pattern. In the case of satellite communications, the reference beam is in the form of a feed wave, such as feed wave 1205 (in some embodiments, approximately 20 GHz). To convert the feed wave into a radiation beam (for either transmission or reception purposes), an interference pattern between the desired RF beam (target beam) and the feed wave (reference beam) is calculated. The interference pattern is driven as a diffraction pattern onto an array of tunable wavelength resonators / slots 1210 such that the feed wave is "steered" into the desired RF beam (having the desired shape and direction). In other words, the feed wave encountering the holographic diffraction pattern "reconstructs" the target beam, which is formed according to the design requirements of the communications system. The holographic diffraction pattern encompasses the excitation of each element and is calculated using the Win is the wave equation in the waveguide, W out is calculated as follows, using the wave equation for the outgoing wave:

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[0063] 8A shows one embodiment of a variable wavelength resonator / slot 1210. The variable wavelength resonator / slot 1210 includes an iris / slot 1212, a radiating patch 1211, and a liquid crystal 1213 disposed between the iris 1212 and the patch 1211. In one embodiment, the radiating patch 1211 is co-located with the iris 1212.

[0064] FIG. 8B shows a cross-sectional view of one embodiment of a physical antenna aperture. The antenna aperture includes a ground plane 1245 and a metal layer 1236 within an iris layer 1233 included in a reconfigurable resonator layer 1230. In one embodiment, the antenna aperture of FIG. 8B includes multiple tunable resonators / slots 1210 of FIG. 8A. The irises / slots 1212 are defined by openings in the metal layer 1236. A feed wave, such as feed wave 1205 of FIG. 7, can have a microwave frequency compatible with a satellite communication channel. The feed wave propagates between the ground plane 1245 and the resonator layer 1230.

[0065] Reconfigurable resonator layer 1230 also includes a gasket layer 1233 and a patch layer 1231. Gasket layer 1233 is disposed between patch layer 1231 and iris layer 1232. Note that in one embodiment, a spacer can be replaced with gasket layer 1233. In one embodiment, iris layer 1232 is a printed circuit board ("PCB") that includes a copper layer as metal layer 1236. In one embodiment, iris layer 1232 is glass. Iris layer 1232 can be other types of substrates.

[0066] An opening is etched in the copper layer to form the iris / slot 1212. In one embodiment, the iris layer 1232 is conductively coupled to another structure (e.g., a waveguide) in Figure 8B by a conductive bonding layer. Note that in one embodiment, the iris layer is not conductively coupled by a conductive bonding layer, but instead is interconnected with a non-conductive bonding layer.

[0067] Alternatively, patch layer 1231 can be a PCB including metal as radiating patch 1211. In one embodiment, gasket layer 1233 includes spacers 1239 that provide mechanical separation between metal layer 1236 and patch 1211. In one embodiment, the spacers are 75 microns, although other sizes (e.g., 3-200 mm) can be used. As noted above, in one embodiment, the antenna aperture of FIG. 8B includes multiple variable wavelength resonators / slots, such as variable wavelength resonator / slot 1210 including patch 1211, liquid crystal 1213, and iris 1212 in FIG. 8A. A chamber for liquid crystal 1213 is defined by spacers 1239, iris layer 1232, and metal layer 1236. When the chamber is filled with liquid crystal, patch layer 1231 can be laminated onto spacers 1239 to seal the liquid crystal within resonator layer 1230.

[0068] The voltage between the patch layer 1231 and the iris layer 1232 can be modulated to tune the liquid crystal in the gap between the patch and the slot (e.g., variable wavelength resonator / slot 1210). Adjusting the voltage across the liquid crystal 1213 changes the capacitance of the slot (e.g., variable wavelength resonator / slot 1210). Thus, the reactance of the slot (e.g., variable wavelength resonator / slot 1210) can be changed by changing the capacitance. Also, the resonant frequency of the variable wavelength resonator / slot 1210 can be calculated using the following equation:

number

[0069] In one embodiment, the variable wavelength slots in a row are spaced λ / 5 apart from one another. Other spacings can also be used. In one embodiment, each variable wavelength slot in a row is spaced λ / 2 apart from the nearest variable wavelength slot in an adjacent row, so commonly oriented variable wavelength slots in different rows are spaced λ / 4 apart, although other spacings (e.g., λ / 5, λ / 6.3) are possible. In another embodiment, each variable wavelength slot in a row is spaced λ / 3 apart from the nearest variable wavelength slot in an adjacent row.

[0070] Embodiments of the present invention use reconfigurable metamaterial technology as described in U.S. patent application Ser. No. 14 / 550,178, filed Nov. 21, 2014, entitled "Dynamic Polarization and Coupling Control from a Steerable Cylindrically Fed Holographic Antenna," and U.S. patent application Ser. No. 14 / 610,502, filed Jan. 30, 2015, entitled "Ridged Waveguide Feed Structures for Reconfigurable Antenna."

[0071] Figures 9A-D show one embodiment of the various layers forming the slotted array. The antenna array includes antenna elements positioned in a ring, such as the exemplary ring shown in Figure 6. Note that in this example, the antenna array has two different types of antenna elements used for two different types of frequency bands.

[0072] FIG. 9A shows a portion of the first iris substrate layer with locations corresponding to the slots. Referring to FIG. 9A, the circles are open areas / slots in the metallization on the bottom side of the iris substrate to control the coupling of the elements to the feed. Note that this layer is optional and may not be used in all designs. FIG. 9B shows a portion of the second iris substrate layer including slots. FIG. 9C shows a patch covering a portion of the second iris substrate layer. FIG. 9D shows a top view of a portion of the slotted array.

[0073] FIG. 10 shows a side view of one embodiment of a cylindrically fed antenna structure. The antenna uses a dual layer feed structure (i.e., a two layer feed structure) to generate an inwardly traveling wave. In one embodiment, the antenna includes a circular profile, although this is not required; that is, a non-circular inwardly traveling structure can be used. In one embodiment, the antenna structure of FIG. 10 includes a coaxial feed, such as that described in U.S. Publication No. 2015 / 0236412, filed November 21, 2014, and entitled "Dynamic Polarization and Coupling Control from a Steerable Cylindrically Fed Holographic Antenna."

[0074] 10, a coaxial pin 1601 is used to excite the field at the lower level of the antenna. In one embodiment, the coaxial pin 1601 is a readily available 50 Ω coaxial pin. The coaxial pin 1601 is coupled (e.g., bolted) to the bottom of the antenna structure, which is a conductive ground plane 1602.

[0075] An internal conductor, interstitial conductor 1603, is spaced apart from conductive ground plane 1602. In one embodiment, conductive ground plane 1602 and interstitial conductor 1603 are parallel to one another. In one embodiment, the distance between ground plane 1602 and interstitial conductor 1603 is between 0.1 inches and 0.15 inches. In another embodiment, this distance can be λ / 2, where λ is the wavelength of the traveling wave at the operating frequency.

[0076] Ground plane 1602 is separated from gap conductor 1603 via spacer 1604. In one embodiment, spacer 1604 is a foam or air spacer. In one embodiment, spacer 1604 comprises a plastic spacer.

[0077] On top of the gap conductor 1603 is a dielectric layer 1605. In one embodiment, the dielectric layer 1605 is plastic. The purpose of the dielectric layer 1605 is to slow down the traveling waves relative to free space velocity. In one embodiment, the dielectric layer 1605 slows down the traveling waves by 30% relative to free space. In one embodiment, the refractive index range suitable for beamforming is 1.2 to 1.8, with free space, by definition, having a refractive index equal to 1. Other dielectric spacer materials, such as plastic, can be used to achieve this effect. Note that materials other than plastic can be used as long as they achieve the desired wave-slowing effect. Alternatively, the dielectric layer 1605 can be a material with a distributed structure, such as a periodic subwavelength metallic structure that can be defined by machining or lithography.

[0078] The RF array 1606 is on top of the dielectric layer 1605. In one embodiment, the distance between the gap conductor 1603 and the RF array 1606 is 0.1 to 0.15 inches. In another embodiment, this distance can be λ / 2, where λ is the effective wavelength in the medium at the design frequency.

[0079] The antenna includes side surfaces 1607 and 1608. The side surfaces 1607 and 1608 are angled such that the traveling wave feed from the coaxial pin 1601 propagates from the region below the gap conductor 1603 (the spacer layer) to the region above the gap conductor 1603 (the dielectric layer) by reflection. In one embodiment, the angle of the side surfaces 1607 and 1608 is 45 degrees. In an alternative embodiment, the side surfaces 1607 and 1608 can be replaced with continuous radii to achieve reflection. While FIG. 10 shows angled sides with a 45-degree angle, other angles can be used to achieve signal propagation from the lower feed level to the upper feed level. That is, given that the effective wavelength of the lower feed is generally different from the effective wavelength of the upper feed, some deviation from the ideal 45-degree angle can be used to aid in transmission from the lower feed level to the upper feed level. For example, in another embodiment, the 45-degree angle is replaced with a single step. A step on one end of the antenna goes around the dielectric layer, the gap conductor, and the spacer layer, and two identical steps are present at the other end of these layers.

[0080] In operation, when a feed wave is applied from coaxial pin 1601, the feed wave travels concentrically outward from coaxial pin 1601 in the region between ground plane 1602 and gap conductor 1603. The concentric emitted wave is reflected by sides 1607 and 1608 and travels inward in the region between gap conductor 1603 and RF array 1606. Reflections from the edges of the circular perimeter cause the wave to remain in phase (i.e., the reflection is an in-phase reflection). The traveling wave is slowed down by dielectric layer 1605. At this point, the traveling wave begins to interact with and excite the elements of RF array 1606 to obtain the desired scattering.

[0081] A termination 1609 is included in the antenna at the geometric center of the antenna to terminate the traveling wave. In one embodiment, the termination 1609 includes a pin termination (e.g., a 50 Ω pin). In another embodiment, the termination 1609 includes an RF absorber that terminates unused energy and prevents it from reflecting back through the antenna's feed structure. These can be used on top of the RF array 1606.

[0082] FIG. 11 shows another embodiment of an antenna system with an emitted wave. Referring to FIG. 11, two ground planes 1610, 1611 are substantially parallel to each other with a dielectric layer 1612 (e.g., a plastic layer) between the ground planes. An RF absorber 1619 (e.g., a resistor) couples the two ground planes 1610 and 1611 together. A coaxial pin 1615 (e.g., 50 Ω) feeds the antenna. An RF array 1616 resides on top of the dielectric layer 1612 and the ground plane 1610.

[0083] In operation, a feed wave is fed through the coaxial pin 1615 and travels concentrically outward to interact with the elements of the RF array 1616.

[0084] The cylindrical feed in both the antennas of Figures 10 and 11 improves the service angle of the antenna. In one embodiment, the antenna system has a service angle of seventy-five degrees (75°) from the boresight in all directions, instead of a service angle of plus or minus forty-five degrees in azimuth (±45° Az) and plus or minus twenty-five degrees in elevation (±25° El). As with any beamforming antenna composed of many individual radiators, the overall antenna gain depends on the gain of the constituent elements, which are themselves angle-dependent. When common radiating elements are used, the overall antenna gain typically decreases as the beam is pointed away from the boresight. A significant gain drop of about 6 dB can be expected at 75 degrees off the boresight.

[0085] Antenna embodiments with cylindrical feeds solve one or more problems, including dramatically simplifying the feed structure compared to antennas fed using a common divider network, thus reducing the overall antenna and antenna feed required, reducing sensitivity to manufacturing and control errors by maintaining high beam performance with coarser control (extending all to simple binary control), providing a more favorable sidelobe pattern compared to linear feeds since cylindrically oriented feed waves result in spatially diverse sidelobes in the far field, and allowing for dynamic polarization, including allowing left-hand circular, right-hand circular, and linear polarization, without the need for a polarizer.

[0086] Array of Wave Scattering Elements The RF array 1606 of Figure 10 and the RF array 1616 of Figure 11 include a wave scattering subsystem that includes a group of patch antennas (i.e., scatterers) that act as radiators. This group of patch antennas includes an array of scattering metamaterial elements.

[0087] In one embodiment, each scattering element in the antenna system is part of a single cell consisting of a bottom conductor, a dielectric substrate, and a top conductor incorporating complementary electrically inductive capacitive resonators (“complementary electric LC” or “CELC”), which are etched or deposited into the top conductor.

[0088] In one embodiment, liquid crystal (LC) is injected into the gap around the scattering elements. The liquid crystal is encapsulated in each sub-cell and further separates the lower conductors associated with the slots from the upper conductors associated with the patches. The liquid crystal has a dielectric constant that is a function of the orientation of the molecules that comprise the liquid crystal, and the molecular orientation (and therefore the dielectric constant) can be controlled by adjusting the bias voltage across the liquid crystal. Using this property, the liquid crystal acts as an on / off switch for the transfer of energy from guided waves to the CELC. When switched on, the CELC generates electromagnetic waves like an electrically small dipole antenna.

[0089] Controlling the LC thickness increases the beam switching speed. Reducing the gap (liquid crystal thickness) between the bottom and top conductors by fifty percent (50%) increases the speed by a factor of four. In another embodiment, the liquid crystal thickness results in a beam switching speed of approximately fourteen milliseconds (14 ms). In one embodiment, the LC is doped in a manner known in the art to improve the responsivity so that the seven millisecond (7 ms) requirement can be met.

[0090] The CELC element responds to a magnetic field applied parallel to the plane of the CELC element and perpendicular to the CELC gap filler. When a voltage is applied across the liquid crystal of the metamaterial scattering single cell, the magnetic field component of the guided wave induces magnetic excitations in the CELC, resulting in the generation of an electromagnetic wave at the same frequency as the guided wave.

[0091] The phase of the electromagnetic wave generated by a single CELC can be selected by the position of the CELC relative to the guided wave vector. Each cell generates a wave that is in phase with the guided wave parallel to the CELC. Because the CELC is smaller than the wavelength, the output wave has the same phase as the guided wave would have if it were passing directly underneath the CELC.

[0092] In one embodiment, the cylindrical feed geometry of this antenna system allows the CELC elements to be positioned at a forty-five degree (45°) angle relative to the wave vector of the wave feed. This positioning of the elements allows for control of the polarization of the free-space waves generated from or received by the elements. In one embodiment, the CELC is arranged with an element spacing that is less than the free-space wavelength of the antenna's operating frequency. For example, with four scattering elements per wavelength, the elements of a 30 GHz transmit antenna would be approximately 2.5 mm (i.e., 1 / 4 of a 10 mm free-space wavelength at 30 GHz).

[0093] In one embodiment, the CELC is implemented with patch antennas that include patches juxtaposed above a slot with liquid crystal between them. In this respect, the metamaterial antenna acts like a slot (scattering) waveguide. As with a slot waveguide, the phase of the output wave depends on the position of the slot relative to the guided wave.

[0094] Cell Placement In one embodiment, the antenna elements are arranged over the aperture of a cylindrically fed antenna to enable a systematic matrix drive circuit. The cell arrangement includes an arrangement of transistors for matrix drive. FIG. 12 shows one embodiment of the arrangement of the matrix drive circuit for the antenna elements. Referring to FIG. 12, a row controller 1701 is coupled to transistors 1711 and 1712 via row select signals Row1 and Row2, respectively, and a column controller 1702 is coupled to transistors 1711 and 1712 via a column select signal Column1. Furthermore, transistor 1711 is coupled to antenna element 1721 via connection 1731 to a patch, and transistor 1712 is coupled to antenna element 1722 via connection 1732 to a patch.

[0095] The first approach to implementing a matrix drive circuit on a cylindrically fed antenna, where single cells are arranged in an irregular grid, involves two steps. In the first step, the cells are arranged in concentric rings, each connected to a transistor placed beside the cell, which acts as a switch to drive each cell separately. In the second step, the matrix drive circuit is constructed to connect every transistor with a unique address as required by the matrix drive technique. The matrix drive circuit is constructed with row and column traces (similar to an LCD), but because the cells are arranged in a ring, there is no systematic way to assign a unique address to each transistor. This mapping problem results in an extremely complex circuit to cover all the transistors and significantly increases the number of physical traces to route. Due to the high cell density, these traces hinder the antenna's RF performance due to coupling effects. Furthermore, due to the complexity and high packing density of the traces, routing the traces cannot be performed using commercially available layout tools.

[0096] In one embodiment, the matrix drive circuitry is predefined before the cells and transistors are placed. This ensures a minimum number of traces are required to drive all the cells, each with a unique address. This approach reduces the complexity of the drive circuitry and simplifies routing, thereby improving the RF performance of the antenna.

[0097] More specifically, in one approach, in a first step, cells are arranged on a square grid consisting of rows and columns that represent each cell's unique address. In a second step, the cells are grouped and transformed into concentric rings, while preserving the cell's address and connectivity to the rows and columns defined in the first step. The goal of this transformation is not only to arrange the cells on rings, but also to maintain a constant distance between cells and between rings across the aperture. There are several ways to group cells to achieve this goal.

[0098] In one embodiment, a TFT package is used to allow for placement and unique addressing in a matrix drive circuit. Figure 13 shows one embodiment of a TFT package. Referring to Figure 13, a TFT and holding capacitor 1803 are shown along with input and output ports. There are two input ports connected to traces 1801 and two output ports connected to traces 1802, with rows and columns used to connect the TFTs together. In one embodiment, the row traces and column traces cross at a 90° angle to reduce, and in some cases minimize, coupling between the row traces and column traces. In one embodiment, the row traces and column traces are on different layers.

[0099] An embodiment of a full-duplex communication system In another embodiment, the compound antenna aperture is used in a full-duplex communication system. Figure 14 is a block diagram of another embodiment of a communication system having simultaneous transmit and receive paths. Although only one transmit path and one receive path are shown, the communication system may include more than one transmit path and / or more than one receive path.

[0100] 14, antenna 1401 includes two spatially interleaved antenna arrays independently operable to simultaneously transmit and receive at different frequencies as described above. In one embodiment, antenna 1401 is coupled to a diplexer 1445. This coupling can be by one or more feed networks. In one embodiment, in the case of a radially fed antenna, diplexer 1445 combines the two signals, and the connection between antenna 1401 and diplexer 1445 is a single wideband feed network capable of carrying both frequencies.

[0101] The diplexer 1445 is coupled to a low noise block downconverter (LNB) 1427, which performs noise filtering, downconversion, and amplification functions in a manner well known in the art. In one embodiment, the LNB 1427 resides in an outdoor unit (ODU). In another embodiment, the LNB 1427 is incorporated into the antenna arrangement. The LNB 1427 is coupled to a modem 1460, which is coupled to a computing system 1440 (e.g., a computer system, modem, etc.).

[0102] Modem 1460 includes an analog-to-digital converter (ADC) 1422, coupled to LNB 1427, that converts the received signal output from diplexer 1445 to digital format. Once converted to digital format, the signal is demodulated by demodulator 1423 and decoded by decoder 1424 to obtain the data encoded on the received signal. The decoded data is then sent to controller 1425, which sends the data to computing system 1440.

[0103] Modem 1460 further includes an encoder 1430 that encodes data transmitted from computing system 1440. The encoded data is modulated by a modulator 1431 and then converted to analog by a digital-to-analog converter (DAC) 1432. The analog signal is then filtered by a BUC (upconverter and high-pass amplifier) ​​1433 and provided to one port of a diplexer 1445. In one embodiment, BUC 1433 resides in an outdoor unit (ODU).

[0104] Diplexer 1445, which operates in a manner well known in the art, provides the transmit signal to antenna 1401 for transmission.

[0105] A controller 1450 controls an antenna 1401 that includes two arrays of antenna elements over a single compound physical aperture.

[0106] The communication system would be modified to include the combiner / arbiter described above. In such a case, the combiner / arbiter would be after the modems and before the BUC and LNB.

[0107] It should be noted that the full-duplex communication system shown in FIG. 14 has several applications, including but not limited to internet communication, vehicle communication (including software updates), and the like.

[0108] There are several exemplary embodiments described herein.

[0109] Example 1 is an antenna comprising an aperture having a plurality of antenna elements operable to radiate radio frequency (RF) energy, and a single-layer wide-angle impedance matching (WAIM) structure coupled to the aperture to provide impedance matching between the antenna aperture and free space.

[0110] Example 2 is the antenna of example 1, optionally including the single layer WAIM structure including a capacitive impedance surface having a two-dimensional (2D) array of sub-wavelength elements.

[0111] Example 3 is the antenna of example 2, optionally including the sub-wavelength element comprising a 2D array of capacitive patches.

[0112] Example 4 is the antenna of example 3, which can optionally include the capacitive patches being square-shaped patches.

[0113] Example 5 is the antenna of example 3, which can optionally include the capacitive patches being hexagonal-shaped patches.

[0114] Example 6 is the antenna of example 2, which can optionally include the sub-wavelength elements being split-ring resonators or dipoles.

[0115] Example 7 is the antenna of Example 1, which can optionally include that the single layer WAIM structure includes a substrate and the sub-wavelength elements of the single layer WAIM structure are screen printed on the substrate.

[0116] Example 8 is the antenna of example 1, optionally including the single layer WAIM structure separated from the aperture by at least a dielectric spacer.

[0117] Example 9 is the antenna of example 8, optionally including wherein the impedance of the single layer WAIM structure is based on the characteristics and physical dimensions of the surrounding medium.

[0118] Example 10 is the antenna of example 1 that can optionally include that the impedance of the single layer WAIM structure is a function of the scan angle and the polarization of the propagating wave and is independent of the scan plane of the antenna.

[0119] Example 11 is the antenna of example 1, which can optionally include that the single layer WAIM structure has rotational symmetry.

[0120] Example 12 is the antenna of example 1, optionally including the aperture including a metasurface.

[0121] Example 13 is an antenna comprising: a metasurface having a plurality of antenna elements operable to radiate radio frequency (RF) energy; and a single-layer wide-angle impedance matching (WAIM) structure coupled to an aperture to provide impedance matching between the antenna aperture and free space, wherein the single-layer WAIM structure has a capacitive impedance surface having a two-dimensional (2D) array of subwavelength elements.

[0122] Example 14 is the antenna of example 13, optionally including the sub-wavelength element comprising a 2D array of capacitive patches.

[0123] Example 15 is the antenna of example 14, which can optionally include the capacitive patch being a square patch or a hexagonal patch.

[0124] Example 16 is the antenna of example 13, which can optionally include the sub-wavelength element being a split ring resonator or a dipole.

[0125] Example 17 is the antenna of Example 13, which can optionally include the single layer WAIM structure including a substrate, and the sub-wavelength element of the single layer WAIM structure being screen printed on the substrate.

[0126] Example 18 is the antenna of example 13, which can optionally include the single layer WAIM structure separated from the aperture by at least a dielectric spacer.

[0127] Example 19 is the antenna of example 13, optionally including the impedance of the single layer WAIM structure being based on the physical dimensions of the feature and surrounding medium.

[0128] Example 20 is the antenna of example 13, which can optionally include that the impedance of the single layer WAIM structure is a function of the scan angle and the polarization of the propagating wave and is independent of the scan plane of the antenna.

[0129] Example 21 is an antenna comprising: a metasurface having a plurality of antenna elements operable to radiate radio frequency (RF) energy; a dielectric layer coupled to the metasurface; and a single-layer wide-angle impedance matching (WAIM) structure coupled to the dielectric layer to provide impedance matching between the antenna aperture and free space, wherein the single-layer WAIM structure includes a substrate having a two-dimensional (2D) array of capacitive elements screen-printed thereon.

[0130] Some portions of the foregoing detailed descriptions are presented in terms of algorithms and symbolic representations of operations on data bits within a computer memory. These algorithmic descriptions and representations are the means used by those skilled in the data processing arts to most effectively convey the substance of their work to others skilled in the art. An algorithm is here, and generally, conceived to be a self-consistent sequence of steps leading to a desired result. These steps require physical manipulations of physical quantities. Usually, though not necessarily, these quantities take the form of electrical or magnetic signals capable of being stored, transferred, combined, compared, and otherwise manipulated. It has proven convenient at times, principally for reasons of common usage, to refer to these signals as bits, values, elements, symbols, characters, terms, numbers, or the like.

[0131] It should be noted, however, that these and similar terms are all to be associated with the appropriate physical quantities and are merely convenient labels applied to these quantities. As will become apparent from the following description, unless otherwise indicated, it will be recognized that throughout the description, descriptions utilizing terms such as "processing" or "computing" or "calculating" or "determining" or "displaying" refer to the actions and processing of a computer system or similar electronic computing device that manipulates and transforms data represented as physical (electronic) quantities in the registers and memory of the computer system into other data that is similarly represented as physical quantities in the memory or registers of that computer system or other such information storage, transmission, or display device.

[0132] The present invention also relates to apparatus for performing the operations herein. This apparatus may be specially constructed for the required purposes, or it may comprise a general-purpose computer selectively activated or reconfigured by a computer program stored in the computer. Such computer program may be stored on a computer-readable storage medium such as, but not limited to, any type of disk, including floppy disks, optical disks, CD-ROMs, and magneto-optical disks, read-only memory (ROM), random-access memory (RAM), EPROM, EEPROM, magnetic or optical cards, or any type of medium suitable for storing electronic instructions, each coupled to a computer system bus.

[0133] The algorithms and displays presented herein are not inherently related to any particular computer or other apparatus. Various general-purpose systems can be used with programs in accordance with the teachings herein, or it may prove advantageous to construct more specialized apparatus to perform the required method steps. The required structure for a variety of these systems will be apparent from the description below. In addition, the present invention is not described with reference to any particular programming language. It will be appreciated that a variety of programming languages ​​can be used to implement the teachings of the present invention as described herein.

[0134] A machine-readable medium includes any mechanism for storing or transmitting information in a form readable by a machine (e.g., a computer). For example, machine-readable media include read-only memory ("ROM"), random-access memory ("RAM"), magnetic disk storage media, optical storage media, flash memory devices, etc.

[0135] Although many variations and modifications of the present invention will no doubt become apparent to those skilled in the art after reading the foregoing description, it should be understood that any particular embodiments shown and described by way of illustration should not be taken as limiting. Accordingly, references to details of various embodiments are not intended to limit the scope of the claims, which recite only those features regarded as essential to the invention.

Claims

1. An antenna, an aperture having a plurality of antenna elements operable to radiate radio frequency (RF) energy; a single-layer wide-angle impedance matching (WAIM) structure coupled to and separated from the plurality of antenna elements of the aperture to provide impedance matching between the aperture and free space, the single-layer WAIM structure including a capacitive impedance surface having a two-dimensional (2D) array of sub-wavelength elements, each sub-wavelength element of the 2D array of sub-wavelength elements including a capacitive patch; An antenna comprising:

2. The antenna of claim 1 , wherein the capacitive patch is a square patch.

3. The antenna of claim 1 , wherein the capacitive patch is a hexagonal patch.

4. The antenna of claim 1 , wherein the single-layer WAIM structure includes a substrate, and the sub-wavelength elements of the single-layer WAIM structure are screen-printed onto the substrate.

5. The antenna of claim 1 , wherein the single layer WAIM structure is separated from the aperture by at least a dielectric spacer.

6. 10. The antenna of claim 1, wherein the impedance of the single layer WAIM structure is a function of scan angle and polarization of the propagating wave.

7. The antenna of claim 1 , wherein the single layer WAIM structure has rotational symmetry.

8. The antenna of claim 1 , wherein the aperture comprises a metasurface.

9. An antenna, a metasurface having a plurality of antenna elements operable to radiate radio frequency (RF) energy; a single-layer wide-angle impedance matching (WAIM) structure coupled to and separated from the plurality of antenna elements of the metasurface to provide impedance matching between the metasurface and free space, the single-layer WAIM structure having a capacitive impedance surface with a two-dimensional (2D) array of sub-wavelength elements, each sub-wavelength element of the 2D array of sub-wavelength elements including a capacitive patch, the impedance of the single-layer WAIM structure being a function of scan angle and polarization of a propagating wave; An antenna comprising:

10. The antenna of claim 9 , wherein the sub-wavelength element comprises a 2D array of the capacitive patches.

11. The antenna of claim 10, wherein the capacitive patch is a square patch or a hexagonal patch.

12. The antenna of claim 9 , wherein the single-layer WAIM structure includes a substrate, and the sub-wavelength elements of the single-layer WAIM structure are screen-printed onto the substrate.

13. 10. The antenna of claim 9, wherein the single layer WAIM structure is separated from the aperture by at least a dielectric spacer.

14. An antenna, a metasurface having a plurality of antenna elements operable to radiate radio frequency (RF) energy; a dielectric layer coupled to the metasurface; and a single-layer wide-angle impedance matching (WAIM) structure coupled to the dielectric layer and separated from the plurality of antenna elements of the metasurface to provide impedance matching between the metasurface and free space, the single-layer WAIM structure including a substrate having a capacitive impedance surface on which a two-dimensional (2D) array of capacitive elements is screen-printed; and An antenna comprising:

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