Embodiments of the invention are related to wireless communication; more particularly, embodiments of the invention are related to wireless antennas that utilize devices manufactured with mass transfer technologies.
Metasurface antennas have recently emerged as a new technology for generating steered, directive beams from a lightweight, low-cost, and planar physical platform. Such metasurface antennas have been recently used in a number of applications, such as, for example, satellite communication.
Metasurface antennas may comprise metamaterial antenna elements that can selectively couple energy from a feed wave to produce beams that may be controlled for use in communication. These antennas are capable of achieving comparable performance to phased array antennas from an inexpensive and easy-to-manufacture hardware platform.
By using simpler elements as compared to phased arrays, the operation of a metasurface is easier and faster. These elements, however, do not exhibit the same level of control as is achievable with phase shifters and amplifiers, common to phased array architectures. Some implementations of metasurface-based antennas do not provide independent control of both the magnitude and phase of each individual element in the array. Such control is desired at times.
Various embodiments of unit cells, rotations of cells, arrays, tunable capacitance devices, apertures, segmentation of apertures, templates, assembly and self-assembly methods for manufacture, mass transfer techniques, drive circuitry, metasurface antennas, metamaterial antennas, beamforming antennas, assemblies and components are described herein.
One embodiment is a unit cell for a metasurface, metamaterial or beamforming antenna. The unit cell has a substrate and a metal layer attached to the substrate. The metal layer defines an iris opening. One or more tunable capacitance devices are positioned within or across the iris opening. Each tunable capacitance device is for tuning for resonant frequency of the unit cell.
One embodiment is an antenna. The antenna has one or more substrates defining an antenna aperture. The antenna aperture has a plurality of unit cells. Each unit cell has a metal layer attached to a portion of the one or more substrates. The metal layer defines an iris opening. One or more tunable capacitance devices are positioned within or across the iris opening. Each tunable capacitance device is tunable for resonance frequency of the unit cell. The one or more tunable capacitance devices of the unit cells have uniform orientation across at least a portion of the antenna aperture.
One embodiment is a method of making an antenna, component of an antenna, or electronically scanned array. The method includes placing unit cells on a substrate. Each unit cell has a metal layer attached to the substrate and defines an iris opening. One or more tunable capacitance devices are positioned within or across the iris opening. Each tunable capacitance device is to tune resonance frequency of the unit cell. The method includes attaching the one or more tunable capacitance devices as part of completing each of the plurality of unit cells.
One embodiment is a method of fabricating an electronically scanned array using mass transfer technologies. The method includes providing a substrate having a metal layer. The metal layer is attached to the substrate, and defines iris openings. A self-assembly process is used to align one or more tunable capacitance devices with respect to each of the iris openings. The one or more capacitance devices are coupled to the substrate while aligned with respect to the iris openings.
Other aspects and advantages of the embodiments will become apparent from the following detailed description taken in conjunction with the accompanying drawings which illustrate, by way of example, the principles of the described embodiments.
The described embodiments and the advantages thereof may best be understood by reference to the following description taken in conjunction with the accompanying drawings. These drawings in no way limit any changes in form and detail that may be made to the described embodiments by one skilled in the art without departing from the spirit and scope of the described embodiments.
An improved design for metasurface elements, and more specifically tunable components, of metasurface or metamaterial antennas is described herein in various embodiments. A method for making metasurface elements, and more specifically tunable components, of metasurface or metamaterial antennas is described herein in various embodiments. The various designs are for arrays of iris openings and unit cells on substrates, and use diodes as varactors to tune resonant frequency of the iris openings. Design and placement of metasurface elements in a metasurface or metamaterial antenna govern the functionality and performance of the antenna.
Generally described, aspects of the present application correspond to systems, methods and apparatus related to tunable metasurface antennas, such as for use in holographic beam forming. The metasurface antennas may be manufactured with mass transfer technologies. Illustratively, mass transfer can include a number of different methodologies and techniques to manufacture high-resolution, direct-view displays with discrete components. Mass transfer techniques will allow the transfer of thousands or millions of components or packages, such as tunable components, onto a substrate in a single placement activity for application to radio frequency (“RF”) applications. Such an approach facilitates massive scalability with discrete components. Without limitation, the tunable components can include, but are not limited to, micro-electro-mechanical systems (“MEMS”), Varactor diodes, PIN diodes, MOSFET/BJT/HEMT, dual diode (varactor), and Ferroelectric diodes.
Aspects of the present application relate to application of mass transfer technologies and techniques to antenna manufacturing. In one aspect, the application of mass transfer technologies corresponds to antenna design. To implement discrete varactor diode or other tunable components, the antenna array or the antenna elements are designed in a way that allows the implementation of discrete components. At the same time, the performance parameters of the antenna such as, for example, but not limited to, the radiation efficiency are taken into consideration. Several antenna element designs will be described in detail below.
In another aspect, the application of mass transfer technologies and techniques are applied to bias circuitry. A tunable metasurface antenna incorporates a bias network that can control antenna elements on the array, such as individual control of the antenna elements. The components of a metasurface antenna, and their associated locations, are designed to not interfere with the radio-frequency (RF) signal of the antenna. Several bias circuitry components will be described in detail below.
In a further aspect, the application of mass transfer technologies and techniques can correspond to integration and topology methodologies. Integration and topology methodologies correspond generally to facilitating the interoperability of components of the mass manufacture antenna. Several integration and topology methodologies will be described below with regard to single layer substrates, multi-layer boards as well as multi-layer thin films on a single substrate.
In yet another aspect, the application of mass transfer technologies and techniques can impact scalability, and several scalability aspects will be described in detail below.
In one embodiment, a metamaterial antenna has discrete tunable antenna elements that are assembled with micrometer or millimeter scale parts coming from different processes. For example, in one embodiment, diodes produced on GaAs substrates need to be assembled onto a glass substrate with a TFT (thin film transistor) matrix. Such an assembly can be accomplished with a traditional pick-and-place method where individual discrete components are placed on a substrate. For example, individual components may be picked up with a robotic arm and placed onto an assembly site on the glass substrate. However, traditional pick-and-place methods correspond to a serial assembly process that requires a long assembly time and high cost. Pick-and-place methods become inefficient especially for small and thin parts where undesirable adhesion can occur due to electrostatic forces, van der Waals interaction or surface tension. Additionally, a serial pick-and-place method becomes much slower when features being assembled are not placed with respect to rectangular grid. This is a serious concern for a metasurface or metamaterial antenna since antenna features are repeated in a radial grid.
In other embodiments, discrete elements can be assembled in a parallel process which is often referred to as “self-assembly.” Self-assembly is a stochastic process where energy, for example agitation, is applied to the system to create free parts, for example unassembled parts moving on a glass substrate, which will interact with their surroundings to find a low energy state, for example parts assembling to trenches matching to their shape on a glass substrate. Self-assembly processes also don't depend on a rectangular grid to operate efficiently.
Antenna Design
In one aspect, multiple antenna unit cell designs include an iris opening (or slot) and patch as the core antenna components. A metasurface or metamaterial antenna has many such iris openings and unit cells, for example an array (or multiple arrays) of iris openings and unit cells. With reference to
In operation, the effective electromagnetic properties of each unit cell of
Alternative embodiments of a unit cell designs are illustrated in
One of the challenges with using a mass transfer technique for various metasurface antennas is that the antenna has an array of unit cells, where each unit cell has an arbitrary rotation, in some embodiments. In the diode manufacturing, however, creating wafers with thousands of diodes with arbitrary rotation can be challenging and expensive. An alternative way is to use diodes with uniform orientation on the wafer and let the pick and place or mass transfer technique to rotate the diodes as they get transferred. However, also this technique can be very challenging, slow and expensive.
More specifically, the unit cell design of
In another embodiment, circular discrete parts (e.g., diodes) shown in
In alternative embodiments, the circular diode has a junction diode or a metal-insulator-semiconductor (MIS) diode structure. This could be accomplished by tailoring the doping profiles and/or insulator/electrode locations.
Other types of diode structures can also be tailored to build a circular diode without a package.
In another method, a circular diode part can be built using a circular package and a conventional diode die. Conventional die can be attached to the circular package with a solder paste aligned to the central bonding pad (bonding pad-1) and wire bonding from the other electrode to the outer bonding pad.
In one embodiment, the metasurface has unit cells that do not have uniform diode orientation. For example, the orientation of the unit cells varies with their location on the metasurface. This has a huge impact on the cost of diodes and their transfer. To implement this concept, in one embodiment the placement of the unit cells has to be on a rectangular grid while the rotation can be arbitrary. With the proposed rotation agnostic unit cell design and uniform diode orientation, an entire antenna surface (aperture) may be constructed via mass transfer techniques using dies as reticles to populate a large surface. In this case, the antenna aperture is fabricated from small wafers that are all the same reprints.
In most mass transfer technologies the size of the tooling head (or stamp) that transfers the diodes from the wafer to the target substrate is relatively small compared to the size of the target substrate, e.g., the antenna aperture.
Furthermore, the segmentation of an illustrated antenna aperture can be used to simplify the rotation of diodes and reduce issues with their placement. In one embodiment, instead of covering a range of 0 to 180 degrees of rotation, the unit cells only have to cover a range 0 to 90 degrees of rotation and the segmentation does the rest through the rotation of segments. That can simplify the proposed rotation agnostic unit cell design.
The rotation of the diodes can be discretized further to simplify the design process.
Bias Circuitry
In order to tune the varactor diode, a tuning voltage needs to be applied between the two sides of the diode. The embodiments shown in
One of the ways to decouple the bias line from the patch electrode while maintaining a DC connection is to use resistive bias lines and/or discrete resistors.
Integration and Topology
The embodiments shown in
Referring to
Next, in an action 1004, thru vias are generated. In one embodiment, various well-known semiconductor processing steps and materials are used to form openings for the vias, and metal is deposited in the openings to form the connections. That is, to avoid ambiguity, the term “via” may be used to set forth opening or the metallic connection through the opening.
In an action 1006, the iris layer is deposited. In one embodiment, various well-known semiconductor processing steps and materials are used, and the iris layer is formed by depositing a metal layer, and etching the metal layer to define iris openings and further geometries in various embodiments. For example, electrodes may be formed in the iris layer.
In an action 1008, discrete elements are assembled. For example, diodes are assembled to the substrate, with each diode positioned in a unit cell that has an iris opening.
In another method, all the patterning and the assembly can be performed on one side of the substrate. In this method, discrete tunable elements are assembled on the same side of the substrate where TFT matrix is patterned or the iris features of the RF element are fabricated on the same side of the substrate where TFT matrix resides. This method enables fabrication of the RF antenna on a single substrate without double-sided processing of the substrate and/or thru via connection. The method uses the metal layer needed for the iris metal patterning as an electrical connection between the discrete tunable elements and the TFT matrix. It will be called an “iris interconnect” in this disclosure. A top view of the connection and a cross-sectional view is shown in
Referring to
In one embodiment, an iris metal 1204 layer is a few micrometers thick and it is deposited on a glass substrate 1210 using sputtering, electroplating or e-beam evaporation for example, or other process that may be devised. This metal layer is later etched to create iris openings 112, 402 (see, for example,
Still further, openings are created in the iris passivation layer for connecting the discrete tunable elements 1206 through respective element bond pads 1208 to the iris metal 1204 and the iris interconnect. This connection to the bonding or bond pads 1208 of the discrete tunable element(s) 1206 can be made using a solder 1214. Alternatively, such connections between bonding pads of the tunable elements and iris metal in this and other disclosed embodiments may be made with conductive paste, conductive polymer, conductive epoxy, silver epoxy, etc. in place of solder. Discrete parts can be assembled to this substrate using various methods, such as, but not limited to, pick-and-place, self-assembly, etc.
Discrete tunable elements 1108, 1110, and 1206 are shown in a rectangular shape in
Scalability
Discrete tunable capacitors are used as parts to be assembled in a metamaterial antenna. These could be varactor diodes, various semiconductor diodes (PIN diodes, MOSFET, BJT, HEMT, etc.) or MEMS structures. In one embodiment, the assembly site, or the final location of parts, is a glass substrate 1210 (e.g., as shown in
In accordance with aspects of the present application, in one embodiment a self-assembly process is directed to assembly of components to a designed location at a pre-determined orientation. Self-assembly processes can include but are not limited to using an assembly template (stencil) with designed gaps matching to the shape of the part, designing hydrophobic and hydrophilic areas on the part and the assembly site in addition to using steam or air-water interface to control the assembly location and orientation with surface tension, and designing parts to be magnetizable and controlling the assembly location and orientation with a magnetic field. Methods mentioned above can be used by themselves or in combination to assemble discrete tunable elements onto designed locations on a glass substrate in a unique orientation, for various embodiments. In some embodiments of an assembly method, the discrete tunable elements are in a liquid, gas or vacuum environment, and agitation is applied before or during application of magnetic field in a self-assembly process.
Note in one embodiment, the assembly template 1302 remains after assembly and does not impact the RF operation of the antenna (see
Instead of or in addition to magnetic force, one can also use shape matching in a self-assembly process. In shape-matching, parts are designed with non-symmetric shapes and assembly templates are designed with non-symmetric openings such that parts can fit into the assembly site in a unique orientation. In another embodiment, the assembly process uses hydrophilic and/or hydrophobic surfaces to determine assembly locations. Generally, a combination of those methods can be used in various embodiments. For example, hydrophilic and/or hydrophobic surfaces are used for determining the assembly location and magnetic force to determine the part orientation. Agitation could be applied in various versions of a self-assembly process. Agitation serves as a disassembly force which will remove parts which are at an assembly site but in a wrong orientation.
The assembly template 1302 is placed on top of the glass substrate 1210 before the assembly starts. The assembly template 1302 is aligned with alignment marks such that each gap in the template aligns to an assembly site 1304 (see
After the parts are transported to the assembly sites with the correct orientation, magnets 1606 are removed. The glass substrate 1210 and the assembly template 1302 are heated to reflow the solder 1214 and make electrical connections between the discrete tunable elements 1608 and the appropriate metal on the glass substrate 1210. In this example solder 1214 is pre-patterned on the glass substrate before the assembly. In another method, the solder 1214 can be pre-patterned on the parts before the assembly. Other conductive materials such as (thermo-responsive or UV-responsive solder pastes, nanoparticles, ACF bonds etc.) can also be used instead of the solder for electrical connection. Once the electrical connection is made, the assembly template 1302 can be removed, and the substrate is ready for the next step in the manufacturing process.
In a different method, openings in the iris metal can be used as a part of the assembly template. Thickness of the parts in this method are limited by iris metal thickness. Diode dies without a package should be used because of this limitation. Illustrations of assembled diode dies are shown in
Examples of Antenna Embodiments
The techniques described above may be used with flat panel satellite antennas. Embodiments of such flat panel antennas are disclosed. The flat panel antennas include one or more arrays of antenna elements on an antenna aperture. In one embodiment, the antenna aperture is a metasurface antenna aperture, such as, for example, the antenna apertures described below. In one embodiment, the antenna elements comprise diodes and varactors such as described above. In one embodiment, the flat panel antenna is a cylindrically fed antenna that includes matrix drive circuitry to uniquely address and drive each of the antenna elements that are not placed in rows and columns. In one embodiment, the elements are placed in rings.
In one embodiment, the antenna aperture having the one or more arrays of antenna elements is comprised of multiple segments coupled together. When coupled together, the combination of the segments form closed concentric rings of antenna elements. In one embodiment, the concentric rings are concentric with respect to the antenna feed.
Examples of Antenna Systems
In one embodiment, the flat panel antenna is part of a metamaterial antenna system, or an antenna having a metasurface as described herein. Embodiments of a metamaterial antenna system for communications satellite earth stations are described. In one embodiment, the antenna system is a component or subsystem of a satellite earth station (ES) operating on a mobile platform (e.g., aeronautical, maritime, land, etc.) that operates using either Ka-band frequencies or Ku-band frequencies for civil commercial satellite communications. Note that embodiments of the antenna system also can be used in earth stations that are not on mobile platforms (e.g., fixed or transportable earth stations).
In one embodiment, the antenna system uses surface scattering metamaterial technology (e.g., antenna elements) to form and steer transmit and receive beams through separate antennas. In one embodiment, the antenna systems are analog systems, in contrast to antenna systems that employ digital signal processing to electrically form and steer beams (such as phased array antennas).
In one embodiment, the antenna system is comprised of three functional subsystems: (1) a wave guiding structure consisting of a cylindrical wave feed architecture; (2) an array of wave scattering metamaterial unit cells that are part of antenna elements; and (3) a control structure to command formation of an adjustable radiation field (beam) from the metamaterial scattering elements using holographic principles.
Antenna Elements
Referring to
In one embodiment, an iris metal layer (i.e., a metal layer in which the iris opening 1904 is formed) is a few micrometers thick and it is deposited on a glass substrate 1910 using sputtering, electroplating or e-beam evaporation. This metal layer is later etched to create iris openings 112, 402, 1904 (see, for example,
Still further, openings are created in the iris passivation layer for connecting the pad on patch metal layer (e.g., pad 1909) to the iris metal. Additional openings including via 1916 are created in the passivation layer covering the patch metal layer (1931) to connect the patch 1906 and the pad 1909 to discrete tunable element 1908 through respective element bond pads 1912. This connection to the bonding or bond pads 1912 of the discrete tunable element 1908 can be made using a solder 1934. Alternative, such connections between bonding pads of the tunable elements and iris metal in this and other disclosed embodiments may be made with conductive paste, polymer, conductive epoxy, silver epoxy, etc. in place of solder. Discrete parts can be assembled to this substrate using various methods, such as, but not limited to, pick-and-place, self-assembly, etc.
Discrete tunable element 1908 is shown in a rectangular shape in
In one embodiment, the antenna includes a coaxial feed that is used to provide a cylindrical wave feed via input feed 2102. In one embodiment, the cylindrical wave feed architecture feeds the antenna from a central point with an excitation that spreads outward in a cylindrical manner from the feed point. That is, a cylindrically fed antenna creates an outward travelling concentric feed wave. Even so, the shape of the cylindrical feed antenna around the cylindrical feed can be circular, square or any shape. In another embodiment, a cylindrically fed antenna creates an inward travelling feed wave. In such a case, the feed wave most naturally comes from a circular structure.
In one embodiment, antenna elements 2103 comprise irises (iris openings) and the aperture antenna of
In one embodiment, each scattering element in the antenna system is part of a unit cell as described above. In one embodiment, the unit cell is driven by the direct drive embodiments described above. In one embodiment, the diode/varactor in each unit cell has a lower conductor associated with a slot from an upper conductor associated with its patch electrode (e.g., iris metal). The diode/varactor can be controlled to adjust the bias voltage between the iris opening and the patch electrode. Using this property, in one embodiment, the diode/varactor integrates an on/off switch for the transmission of energy from the guided wave to the unit cell. When switched on, the unit emits an electromagnetic wave like an electrically small dipole antenna. Note that the teachings herein are not limited to having unit cell that operates in a binary fashion with respect to energy transmission.
In one embodiment, the feed geometry of this antenna system allows the antenna elements to be positioned at forty-five-degree (45°) angles to the vector of the wave in the wave feed. Note that other positions may be used (e.g., at 40° angles). This position of the elements enables control of the free space wave received by or transmitted/radiated from the elements. In one embodiment, the antenna elements are arranged with an inter-element spacing that is less than a free-space wavelength of the operating frequency of the antenna. For example, if there are four scattering elements per wavelength, the elements in the 30 GHz transmit antenna will be approximately 2.5 mm (i.e., ¼th the 10 mm free-space wavelength of 30 GHz).
In one embodiment, the two sets of elements are perpendicular to each other and simultaneously have equal amplitude excitation if controlled to the same tuning state. Rotating them +/−45 degrees relative to the feed wave excitation achieves both desired features at once. Rotating one set 0 degrees and the other 90 degrees would achieve the perpendicular goal, but not the equal amplitude excitation goal. Note that 0 and 90 degrees may be used to achieve isolation when feeding the array of antenna elements in a single structure from two sides.
The amount of radiated power from each unit cell is controlled by applying a voltage to the patch electrode using a controller. Traces to each patch electrode are used to provide the voltage to the patch electrode. The voltage is used to tune or detune the capacitance and thus the resonance frequency of individual elements to effectuate beam forming. The voltage required is dependent on the diode/varactor being used.
In one embodiment, as discussed above, a matrix drive is used to apply voltage to the patch electrodes in order to drive each cell separately from all the other cells without having a separate connection for each cell (direct drive). Because of the high density of elements, the matrix drive is an efficient way to address each cell individually.
In one embodiment, the control structure for the antenna system has two main components: the antenna array controller, which includes drive electronics for the antenna system, is below the wave scattering structure of surface scattering antenna elements such as described herein, while the matrix drive switching array is interspersed throughout the radiating RF array in such a way as to not interfere with the radiation. In one embodiment, the drive electronics for the antenna system comprise commercial off-the shelf LCD controls used in commercial television appliances that adjust the bias voltage for each scattering element by adjusting the amplitude or duty cycle of an AC bias signal to that element.
In one embodiment, the antenna array controller also contains a microprocessor executing the software. The control structure may also incorporate sensors (e.g., a GPS receiver, a three-axis compass, a 3-axis accelerometer, 3-axis gyro, 3-axis magnetometer, etc.) to provide location and orientation information to the processor. The location and orientation information may be provided to the processor by other systems in the earth station and/or may not be part of the antenna system.
More specifically, the antenna array controller controls which elements are turned off and those elements turned on and at which phase and amplitude level at the frequency of operation. The elements are selectively detuned for frequency operation by voltage application.
For transmission, a controller supplies an array of voltage signals to the RF patches to create a modulation, or control pattern. The control pattern causes the elements to be turned to different states. In one embodiment, multistate control is used in which various elements are turned on and off to varying levels, further approximating a sinusoidal control pattern, as opposed to a square wave (i.e., a sinusoid gray shade modulation pattern). In one embodiment, some elements radiate more strongly than others, rather than some elements radiate and some do not. Variable radiation is achieved by applying specific voltage levels, which adjusts the liquid crystal permittivity to varying amounts, thereby detuning elements variably and causing some elements to radiate more than others.
The generation of a focused beam by the metamaterial array of elements can be explained by the phenomenon of constructive and destructive interference. Individual electromagnetic waves sum up (constructive interference) if they have the same phase when they meet in free space, and waves cancel each other (destructive interference) if they are in opposite phase when they meet in free space. If the slots in a slotted antenna are positioned so that each successive slot is positioned at a different distance from the excitation point of the guided wave, the scattered wave from that element will have a different phase than the scattered wave of the previous slot. If the slots are spaced one quarter of a guided wavelength apart, each slot will scatter a wave with a one fourth phase delay from the previous slot.
Using the array, the number of patterns of constructive and destructive interference that can be produced can be increased so that beams can be pointed theoretically in any direction plus or minus ninety degrees (90°) from the bore sight of the antenna array, using the principles of holography. Thus, by controlling which metamaterial unit cells are turned on or off (i.e., by changing the pattern of which cells are turned on and which cells are turned off), a different pattern of constructive and destructive interference can be produced, and the antenna can change the direction of the main beam. The time required to turn the unit cells on and off dictates the speed at which the beam can be switched from one location to another location.
In one embodiment, the antenna system produces 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 beams and to decode signals from the satellite and to form transmit beams that are directed toward the satellite. In one embodiment, the antenna systems are analog systems, in contrast to antenna systems that employ digital signal processing to electrically form and steer beams (such as phased array antennas). In one embodiment, the antenna system is considered a “surface” antenna that is planar and relatively low profile, especially when compared to conventional satellite dish receivers.
Control module 2280, or a controller, is coupled to reconfigurable resonator layer 2230 to modulate the array 2212 of tunable slots 2210 by varying the voltage to the diodes/varactors. Control module 2280 may include a Field Programmable Gate Array (“FPGA”), a microprocessor, a controller, System-on-a-Chip (SoC), or other processing logic. In one embodiment, control module 2280 includes logic circuitry (e.g., multiplexer) to drive the array 2212 of tunable slots 2210. In one embodiment, control module 2280 receives data that includes specifications for a holographic diffraction pattern to be driven onto the array 2212 of tunable slots 2210. The holographic diffraction patterns may be generated in response to a spatial relationship between the antenna and a satellite so that the holographic diffraction pattern steers the downlink beams (and uplink beam if the antenna system performs transmit) in the appropriate direction for communication. Although not drawn in each figure, a control module similar to control module 2280 may drive each array of tunable slots described in various embodiments in the disclosure.
Radio Frequency (“RF”) holography is also possible using analogous 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 2205 (approximately 20 GHz in some embodiments). To transform a feed wave into a radiated beam (either for transmitting or receiving purposes), an interference pattern is calculated between the desired RF beam (the object beam) and the feed wave (the reference beam). The interference pattern is driven onto the array of tunable slots 2210 as a diffraction pattern so 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 object beam, which is formed according to design requirements of the communication system. The holographic diffraction pattern contains the excitation of each element and is calculated by whologram=win*wout, with win as the wave equation in the waveguide and wout the wave equation on the outgoing wave.
A voltage between the patch electrode and the iris opening can be modulated to tune the antenna element (e.g., the tunable resonator/slot). Adjusting the voltage varies the capacitance of a slot (e.g., the tunable resonator/slot). Accordingly, the reactance of a slot (e.g., the tunable resonator/slot) can be varied by changing the capacitance. Resonant frequency of the slot also changes according to the equation f=1/2π√{square root over (LC)} where f is the resonant frequency of the slot and L and C are the inductance and capacitance of the slot, respectively. The resonant frequency of the slot affects the energy radiated from feed wave 2205 propagating through the waveguide. As an example, if feed wave 2205 is 20 GHz, the resonant frequency of a slot 2210 may be adjusted (by varying the capacitance) to 17 GHz so that the slot 2210 couples substantially no energy from feed wave 2205. Or, the resonant frequency of a slot 2210 may be adjusted to 20 GHz so that the slot 2210 couples energy from feed wave 2205 and radiates that energy into free space. Although the examples given are binary (fully radiating or not radiating at all), full gray scale control of the reactance, and therefore the resonant frequency of slot 2210 is possible with voltage variance over a multi-valued range. Hence, the energy radiated from each slot 2210 can be finely controlled so that detailed holographic diffraction patterns can be formed by the array of tunable slots.
In one embodiment, tunable slots in a row are spaced from each other by λ/5. Other spacings may be used. In one embodiment, each tunable slot in a row is spaced from the closest tunable slot in an adjacent row by λ/2, and, thus, commonly oriented tunable slots in different rows are spaced by λ/4, though other spacings are possible (e.g., λ/5, λ/6.3). In another embodiment, each tunable slot in a row is spaced from the closest tunable slot in an adjacent row by λ/3.
Referring to
Separate from conducting ground plane 2302 is interstitial conductor 2303, which is an internal conductor. In one embodiment, conducting ground plane 2302 and interstitial conductor 2303 are parallel to each other. In one embodiment, the distance between ground plane 2302 and interstitial conductor 2303 is 0.1-0.15″. In another embodiment, this distance may be λ/2, where λ is the wavelength of the travelling wave at the frequency of operation.
Ground plane 2302 is separated from interstitial conductor 2303 via a spacer 2304. In one embodiment, spacer 2304 is a foam or air-like spacer. In one embodiment, spacer 2304 comprises a plastic spacer.
On top of interstitial conductor 2303 is dielectric layer 2305. In one embodiment, dielectric layer 2305 is plastic. The purpose of dielectric layer 2305 is to slow the travelling wave relative to free space velocity. In one embodiment, dielectric layer 2305 slows the travelling wave by 30% relative to free space. In one embodiment, the range of indices of refraction that are suitable for beam forming are 1.2-1.8, where free space has by definition an index of refraction equal to 1. Other dielectric spacer materials, such as, for example, plastic, may be used to achieve this effect. Note that materials other than plastic may be used as long as they achieve the desired wave slowing effect. Alternatively, a material with distributed structures may be used as dielectric layer 2305, such as periodic sub-wavelength metallic structures that can be machined or lithographically defined, for example.
An RF array 2306 is on top of dielectric layer 2305. In one embodiment, the distance between interstitial conductor 2303 and RF array 2306 is 0.1-0.15″. In another embodiment, this distance may be λeff/2, where λeff is the effective wavelength in the medium at the design frequency.
The antenna includes sides 2307 and 2308. Sides 2307 and 2308 are angled to cause a travelling wave feed from coax pin 2301 to be propagated from the area below interstitial conductor 2303 (the spacer layer) to the area above interstitial conductor 2303 (the dielectric layer) via reflection. In one embodiment, the angle of sides 2307 and 2308 are at 45° angles. In an alternative embodiment, sides 2307 and 2308 could be replaced with a continuous radius to achieve the reflection. While
In operation, when a feed wave is fed in from coaxial pin 2301, the wave travels outward concentrically oriented from coaxial pin 2301 in the area between ground plane 2302 and interstitial conductor 2303. The concentrically outgoing waves are reflected by sides 2307 and 2308 and travel inwardly in the area between interstitial conductor 2303 and RF array 2306. The reflection from the edge of the circular perimeter causes the wave to remain in phase (i.e., it is an in-phase reflection). The travelling wave is slowed by dielectric layer 2305. At this point, the travelling wave starts interacting and exciting with elements in RF array 2306 to obtain the desired scattering.
To terminate the travelling wave, a termination 2309 is included in the antenna at the geometric center of the antenna. In one embodiment, termination 2309 comprises a pin termination (e.g., a 50Ω pin). In another embodiment, termination 2309 comprises an RF absorber that terminates unused energy to prevent reflections of that unused energy back through the feed structure of the antenna. These could be used at the top of RF array 2306.
In operation, a feed wave is fed through coaxial pin 2415 and travels concentrically outward and interacts with the elements of RF array 2416.
The cylindrical feed in both the antennas of
Embodiments of the antenna having a cylindrical feed solve one or more problems. These include dramatically simplifying the feed structure compared to antennas fed with a corporate divider network and therefore reducing total required antenna and antenna feed volume; decreasing sensitivity to manufacturing and control errors by maintaining high beam performance with coarser controls (extending all the way to simple binary control); giving a more advantageous side lobe pattern compared to rectilinear feeds because the cylindrically oriented feed waves result in spatially diverse side lobes in the far field; and allowing polarization to be dynamic, including allowing left-hand circular, right-hand circular, and linear polarizations, while not requiring a polarizer.
Array of Wave Scattering Elements
RF array 2306 of
In one embodiment, the cylindrical feed geometry of this antenna system allows the unit cells elements to be positioned at forty-five-degree (45°) angles to the vector of the wave in the wave feed. This position of the elements enables control of the polarization of the free space wave generated from or received by the elements. In one embodiment, the unit cells are arranged with an inter-element spacing that is less than a free-space wavelength of the operating frequency of the antenna. For example, if there are four scattering elements per wavelength, the elements in the 30 GHz transmit antenna will be approximately 2.5 mm (i.e., ¼th the 10 mm free-space wavelength of 30 GHz).
Cell Placement
In one embodiment, the antenna elements are placed on the cylindrical feed antenna aperture in a way that allows for a systematic matrix drive circuit. The placement of the cells includes placement of the transistors for the matrix drive.
In an initial approach to realize matrix drive circuitry on the cylindrical feed antenna with unit cells placed in a non-regular grid, two steps are performed. In the first step, the cells are placed on concentric rings and each of the cells is connected to a transistor that is placed beside the cell and acts as a switch to drive each cell separately. In the second step, the matrix drive circuitry is built in order to connect every transistor with a unique address as the matrix drive approach requires. Because the matrix drive circuit is built by row and column traces (similar to LCDs) but the cells are placed on rings, there is no systematic way to assign a unique address to each transistor. This mapping problem results in very complex circuitry to cover all the transistors and leads to a significant increase in the number of physical traces to accomplish the routing. Because of the high density of cells, those traces disturb the RF performance of the antenna due to coupling effect. Also, due to the complexity of traces and high packing density, the routing of the traces cannot be accomplished by commercially available layout tools.
In one embodiment, the matrix drive circuitry is predefined before the cells and transistors are placed. This ensures a minimum number of traces that are necessary to drive all the cells, each with a unique address. This strategy reduces the complexity of the drive circuitry and simplifies the routing, which subsequently improves the RF performance of the antenna.
More specifically, in one approach, in the first step, the cells are placed on a regular rectangular grid composed of rows and columns that describe the unique address of each cell. In the second step, the cells are grouped and transformed to concentric circles while maintaining their address and connection to the rows and columns as defined in the first step. A goal of this transformation is not only to put the cells on rings but also to keep the distance between cells and the distance between rings constant over the entire aperture. In order to accomplish this goal, there are several ways to group the cells.
In one embodiment, a TFT package is used to enable placement and unique addressing in the matrix drive.
An Example of a Full Duplex Communication System
In another embodiment, the combined antenna apertures are used in a full duplex communication system.
Referring to
Diplexer 2745 is coupled to a low noise block down converter (LNBs) 2727, which performs a noise filtering function and a down conversion and amplification function in a manner well-known in the art. In one embodiment, LNB 2727 is in an out-door unit (ODU). In another embodiment, LNB 2727 is integrated into the antenna apparatus. LNB 2727 is coupled to a modem 2760, which is coupled to computing system 2740 (e.g., a computer system, modem, etc.).
Modem 2760 includes an analog-to-digital converter (ADC) 2722, which is coupled to LNB 2727, to convert the received signal output from diplexer 2745 into digital format. Once converted to digital format, the signal is demodulated by demodulator 2723 and decoded by decoder 2724 to obtain the encoded data on the received wave. The decoded data is then sent to controller 2725, which sends it to computing system 2740.
Modem 2760 also includes an encoder 2730 that encodes data to be transmitted from computing system 2740. The encoded data is modulated by modulator 2731 and then converted to analog by digital-to-analog converter (DAC) 2732. The analog signal is then filtered by a BUC (up-convert and high pass amplifier) 2733 and provided to one port of diplexer 2745. In one embodiment, BUC 2733 is in an out-door unit (ODU).
Diplexer 2745 operating in a manner well-known in the art provides the transmit signal to antenna 2701 for transmission.
Controller 2750 controls antenna 2701, including the two arrays of antenna elements on the single combined physical aperture.
The communication system would be modified to include the combiner/arbiter described above. In such a case, the combiner/arbiter after the modem but before the BUC and LNB.
Note that the full duplex communication system shown in
With reference to
All of the methods and tasks described herein may be performed and fully automated by a computer system. The computer system may, in some cases, include multiple distinct computers or computing devices (e.g., physical servers, workstations, storage arrays, cloud computing resources, etc.) that communicate and interoperate over a network to perform the described functions. Each such computing device typically includes a processor (or multiple processors) that executes program instructions or modules stored in a memory or other non-transitory computer-readable storage medium or device (e.g., solid state storage devices, disk drives, etc.). The various functions disclosed herein may be embodied in such program instructions, or may be implemented in application-specific circuitry (e.g., ASICs or FPGAs) of the computer system. Where the computer system includes multiple computing devices, these devices may, but need not, be co-located. The results of the disclosed methods and tasks may be persistently stored by transforming physical storage devices, such as solid state memory chips or magnetic disks, into a different state. In some embodiments, the computer system may be a cloud-based computing system whose processing resources are shared by multiple distinct business entities or other users.
Depending on the embodiment, certain acts, events, or functions of any of the processes or algorithms described herein can be performed in a different sequence, can be added, merged, or left out altogether (e.g., not all described operations or events are necessary for the practice of the algorithm). Moreover, in certain embodiments, operations or events can be performed concurrently, e.g., through multi-threaded processing, interrupt processing, or multiple processors or processor cores or on other parallel architectures, rather than sequentially.
The various illustrative logical blocks, modules, routines, and algorithm steps described in connection with the embodiments disclosed herein can be implemented as electronic hardware (e.g., ASICs or FPGA devices), computer software that runs on computer hardware, or combinations of both. Moreover, the various illustrative logical blocks and modules described in connection with the embodiments disclosed herein can be implemented or performed by a machine, such as a processor device, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A processor device can be a microprocessor, but in the alternative, the processor device can be a controller, microcontroller, or state machine, combinations of the same, or the like. A processor device can include electrical circuitry configured to process computer-executable instructions. In another embodiment, a processor device includes an FPGA or other programmable device that performs logic operations without processing computer-executable instructions. A processor device can also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration. Although described herein primarily with respect to digital technology, a processor device may also include primarily analog components. For example, some or all of the rendering techniques described herein may be implemented in analog circuitry or mixed analog and digital circuitry. A computing environment can include any type of computer system, including, but not limited to, a computer system based on a microprocessor, a mainframe computer, a digital signal processor, a portable computing device, a device controller, or a computational engine within an appliance, to name a few.
The elements of a method, process, routine, or algorithm described in connection with the embodiments disclosed herein can be embodied directly in hardware, in a software module executed by a processor device, or in a combination of the two. A software module can reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disk, a removable disk, a CD-ROM, or any other form of a non-transitory computer-readable storage medium. An exemplary storage medium can be coupled to the processor device such that the processor device can read information from, and write information to, the storage medium. In the alternative, the storage medium can be integral to the processor device. The processor device and the storage medium can reside in an ASIC. The ASIC can reside in a user terminal. In the alternative, the processor device and the storage medium can reside as discrete components in a user terminal.
Conditional language used herein, such as, among others, “can,” “could,” “might,” “may,” “e.g.,” and the like, unless specifically stated otherwise, or otherwise understood within the context as used, is generally intended to convey that certain embodiments include, while other embodiments do not include, certain features, elements or steps. Thus, such conditional language is not generally intended to imply that features, elements or steps are in any way required for one or more embodiments or that one or more embodiments necessarily include logic for deciding, with or without other input or prompting, whether these features, elements or steps are included or are to be performed in any particular embodiment. The terms “comprising,” “including,” “having,” and the like are synonymous and are used inclusively, in an open-ended fashion, and do not exclude additional elements, features, acts, operations, and so forth. Also, the term “or” is used in its inclusive sense (and not in its exclusive sense) so that when used, for example, to connect a list of elements, the term “or” means one, some, or all of the elements in the list.
Disjunctive language such as the phrase “at least one of X, Y, or Z,” unless specifically stated otherwise, is otherwise understood with the context as used in general to present that an item, term, etc., may be either X, Y, or Z, or any combination thereof (e.g., X, Y, or Z). Thus, such disjunctive language is not generally intended to, and should not, imply that certain embodiments require at least one of X, at least one of Y, and at least one of Z to each be present.
While the above detailed description has shown, described, and pointed out novel features as applied to various embodiments, it can be understood that various omissions, substitutions, and changes in the form and details of the devices or algorithms illustrated can be made without departing from the spirit of the disclosure. As can be recognized, certain embodiments described herein can be embodied within a form that does not provide all of the features and benefits set forth herein, as some features can be used or practiced separately from others. The scope of certain embodiments disclosed herein is indicated by the appended claims rather than by the foregoing description. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope.
The present application is a non-provisional application of and claims the benefit of U.S. Provisional Patent Application No. 62/887,239 filed Aug. 15, 2019 and entitled “Metasurface Antennas Manufactured with Mass Transfer Technologies”, which is incorporated by reference in its entirety.
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