Patent Application
20190074587
If an Application Data Sheet (ADS) has been filed on the filing date of this application, it is incorporated by reference herein. Any applications claimed on the ADS for priority under 35 U.S.C. §§ 119, 120, 121, or 365(c), and any and all parent, grandparent, great-grandparent, etc. applications of such applications, are also incorporated by reference, including any priority claims made in those applications and any material incorporated by reference, to the extent such subject matter is not inconsistent herewith.
The present application claims the benefit of the earliest available effective filing date(s) from the following listed application(s) (the “Priority Applications”), if any, listed below (e.g., claims earliest available priority dates for other than provisional patent applications or claims benefits under 35 USC § 119(e) for provisional patent applications, for any and all parent, grandparent, great-grandparent, etc. applications of the Priority Application(s)).
None
If the listings of applications provided above are inconsistent with the listings provided via an ADS, it is the intent of the Applicant to claim priority to each application that appears in the Domestic Benefit/National Stage Information section of the ADS and to each application that appears in the Priority Applications section of this application.
All subject matter of the Priority Applications and of any and all applications related to the Priority Applications by priority claims (directly or indirectly), including any priority claims made and subject matter incorporated by reference therein as of the filing date of the instant application, is incorporated herein by reference to the extent such subject matter is not inconsistent herewith.
The principal function of any antenna is to couple an electromagnetic wave guided within the antenna's structure to an electromagnetic wave propagating in free space. Many approaches exist to implement this coupling and have been studied due to the vast practical applications of antennas.
A determined object wave at the radiating aperture surface of an antenna can be approximately formed by applying a modulation pattern to metamaterial elements receiving RF energy from a feed network. The object wave at the radiating surface of an antenna is selected so that when propagated into a far-field, the resulting radiation pattern is of a desired shape. A computing system can compute an approximation of the object wave by calculating a modulation pattern to apply to metamaterial elements receiving RF energy from a feed network. The approximation can be due to a grid size of the metamaterial elements (discrete sampling of a continuous quantity). Once the modulation pattern is determined, it can be applied to the metamaterial elements and the RF energy can be provided in the feed network, causing emission of the approximated object wave from the antenna.
In construction of a modulation pattern, the process can be further divided into five operations. In a first operation, the fields in a field network are calculated. The field network includes a reference wave, desired far field pattern and determined object wave. In a second operation, an ideal hologram modulation pattern is calculated from the object and reference wave components of the field network. In a third operation, phase information in the ideal hologram modulation pattern is discarded. In a fourth operation, an aperture taper function is summed with the real portion of the ideal hologram. In a fifth operation, the sum pattern is normalized to form an aperture modulation pattern.
The foregoing summary is illustrative only and is not intended to be in any way limiting. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features will become apparent by reference to the drawings and the following detailed description.
In the following detailed description, reference is made to the accompanying drawings, which form a part hereof. In the drawings, similar symbols typically identify similar components, unless context dictates otherwise. The illustrative embodiments described in the detailed description, drawings, and claims are not meant to be limiting. Other embodiments may be utilized, and other changes may be made, without departing from the spirit or scope of the subject matter presented here.
Techniques, apparatus and methods are disclosed that enable a determined object wave to be approximately formed by applying a modulation pattern to metamaterial elements receiving RF energy from a feed network (the reference wave). For example, a desired object wave at a surface of an antenna is desired to be produced by an antenna. A computing system can calculate a modulation pattern to apply to metamaterial elements receiving RF energy to a feed network that will result in an approximation of desired object wave.
In an additional example, determinations can include the antenna system. In one example, the fields in a field network are calculated. An ideal hologram modulation pattern is calculated. Phase information of the hologram modulation pattern is discarded. An aperture taper function is scaled and multiplied with the magnitude portion of the ideal hologram. The sum pattern is normalized to form an aperture modulation pattern. The modulation pattern is formed by a product of the aperture modulation pattern and the desired object wave.
In antennas based on Metamaterial Surface Antenna Technology (MSA-T), coupling between the guided wave and propagating wave is achieved by modulating the impedance of a surface in electromagnetic contact with the guided wave. This controlled surface impedance is called the “modulation pattern.” The guided wave in the antenna is referred to as the “reference wave” or “reference mode,” and the desired free space propagating wave pattern is referred to as the “radiated wave” or “radiative mode.” An “object wave” is simply the far field radiated wave back-propagated to the aperture where both the modulation pattern and reference wave are present.
The general method for selecting the modulation pattern in MSA-T is derived from holographic principles where the surface modulation function (ψholo) is simply the beat of the reference wave (Eref) and the object wave (Eobj). This relationship can be expressed compactly as:
This equation suggests that the optimal modulation function only depends on the accuracy to which the radiative wave and reference wave are known. In Equation 1, if both Eref and Eobi are normalized, the function ψholo can take on any value in the complex plane in a circle with a magnitude less than one. It is assumed that the reference wave is well conditioned to not possess any zeros in the region of interest. This is frequently true as the reference wave is usually a phasor quantity with non-zero magnitude.
In some embodiments, the modulating elements used in MSA-Ts can be incapable of completely covering this complex unit circle. However, the modulation function can be adjusted to reflect the achievable modulation values the antenna elements can provide. In addition, the surface can be discretely sampled at fixed locations, leading any choice of modulation pattern to be a sampled approximation of the ideal modulation pattern (also known as an idealized modulation pattern).
Frequently, it is desirable to shape a radiated far-field pattern to manipulate beam width, steer multiple beams, form beam “nulls” or produce exotic beam shapes such as cosecant squared patterns. It can be challenging to synthesize these patterns in a finite aperture.
Phased array antennas have used a number of methods to shape the radiated far-field. However, in phased arrays, the modulating element is capable of arbitrary phase and amplitude modulation. The reference wave is also rendered trivial (Eref=1) by use of a corporate feed network. Thus the techniques used to synthesize beams for phased arrays are not directly translatable to MSA-T without some modification.
A method can be applied to controlling beam shaping in MSA-Ts where the input is the desired far-field pattern and the output is the modulation function applied to the discrete MSA-T array elements. In an embodiment, the reference wave in a method is assumed to be a guided wave propagating through a parallel-plate waveguide, a rectangular waveguide or a microstrip line, i.e., an excitation of the form E0e−iβx. In the embodiment, the method can be broken down into two parts, construction of an object wave and construction of a modulation pattern.
In construction of an object wave, the process can be further divided into four operations. In a first operation, a beam profile projection can be defined in the far-field. In a second operation, the far-field pattern can be converted into the spatial-frequency domain. In a third operation, the far-field pattern is back-propagated to an antenna plane. In a fourth operation, the pattern at the antenna is converted to the spatial domain.
In a first operation, a computing resource, such as a controller, defines a desired beam profile projected onto a two-dimensional plane located in the far-field from the antenna. A grid can be defined to have sufficient sampling density to capture propagating spatial frequencies. The grid can also be defined to have sufficient padding around the pattern to minimize aliasing. In some embodiments, when a discrete Fourier transform (rather than continuous) is used, the grid can be defined such that the coordinates of the sample points in the far-field plane will also correspond to element locations at the aperture plane. However, while convenient, the definition of sample points in such a way is not required.
In a second operation, a computing resource uses a Fourier transform to convert the spatial domain far-field pattern into the spatial-frequency domain (sometimes referred to in literature as k-space).
In a third operation, a computing resource constructs a transfer function of free space and uses the transfer function to back-propagate the k-space field description in the far-field back to the antenna plane. The form of the transfer function of free space can vary depending on the choice of coordinate system used. In some embodiments, the k-space can be convenient to use because the action of the free space transfer function on the k-space fields is multiplication and Fourier transforms in the discrete domain computationally efficient.
In some embodiments, an impulse response and convolution can be used, which avoids the use of Fourier transforms. However, depending on the situation, convolution can be computationally taxing.
In a fourth operation, a computing resource can use an inverse Fourier transform to convert the k-space pattern into the spatial domain. The resulting spatial-domain pattern represents the fields needed at the aperture plane to produce the desired far-field pattern. This field is sometimes called the “object wave.” After the fourth operation, the computing resource can then move to construction of a modulation pattern at the antenna using the determined object wave.
In construction of a modulation pattern, the process can be further divided into five operations. In a first operation, the fields in a field network are calculated. In a second operation, an ideal hologram modulation pattern is calculated. In a third operation, an aperture taper function is multiplied with the magnitude portion of the ideal hologram. In a fourth operation, phase information is discarded. In a fifth operation, the pattern is shifted and scaled to form the aperture modulation pattern.
In the first operation, a computing resource calculates the fields in the feed network at each radiating element while stimulating the feed input port. These fields are sometimes referred to as a “reference wave.” The reference wave structure is antenna dependent and can take on many forms. For MSA-Ts, it frequently has the form of a travelling wave moving along the surface of the antenna.
In the second operation, a computing resource forms an ideal hologram modulation pattern (also known as an ideal modulation pattern) by multiplying a reference wave with an object wave.
In the third operation, the computing resource can form a tapered modulation function by multiplying an aperture taper function with the ideal hologram.
In the fourth operation, the computing resource can take the magnitude of the ideal hologram, discarding phase information between the array elements.
In the fifth operation, the computing resource can normalize the tapered modulation pattern by shifting and scaling the tapered modulation pattern to lie within the upper and lower bounds of the element modulation range to form the aperture modulation pattern.
After the fifth operation, RF inputs can be activated to provide RF energy into the backplane or feed network. The modulation pattern can be applied to a control grid that causes the metamaterial elements to form the object wave that is then propagated into free space.
In some embodiments, a metamaterial can be used as a layer in a beam-forming system. An array of sub-wavelength elements may be configured to transmit an electromagnetic emission according to a specific pattern, direction, beam-formed shape, location, phase, amplitude and/or other transmission characteristic.
For example, according to various embodiments for electromagnetic transmission according to a transmission pattern, each sub-wavelength element may be configured with an electromagnetic resonance at one of a plurality of electromagnetic frequencies. Each sub-wavelength element may also be configured to generate an electromagnetic emission in response to the electromagnetic resonance.
The sub-wavelength elements may be described as “sub-wavelength” because a wavelength of the electromagnetic emission of each respective sub-wavelength element may be larger than a physical diameter of the respective sub-wavelength element. For example, the physical diameter of one or more of the sub-wavelength elements may be less than one-half the wavelength of the electromagnetic transmission within a given transmission medium, such as a quarter wavelength or one-eighth wavelength.
A beam-forming controller may be configured to cause radio frequency energy to be transmitted by one or more radio frequency energy sources at select frequencies. The select frequencies resonate with a select subset of the sub-wavelength elements. This causes the resonating sub-wavelength elements to generate electromagnetic emissions according to a selectable electromagnetic transmission pattern. The radio frequency energy may be conveyed to the various sub-wavelength elements via a common port, such as a waveguide or free space.
In some embodiments, sub-wavelength elements can be created with different frequency sensitivities. For example, sub-wavelength elements can be created with a sensitivity to a distribution of frequencies (such as an intentional distribution created with scaling the size of the elements). Each of the sub-wavelength elements in the pattern is activated by a different frequency. In one example, a first pattern of energy results when a feed of 76.9 gigahertz energy is coupled to the sub-wavelength elements. At 77.1 gigahertz, a second pattern of energy is emitted by the sub-wavelength elements. At 77.3 gigahertz, a third pattern is emitted by the sub-wavelength elements.
In some embodiments, a control layer can be used in conjunction with a metamaterial layer in the form of a grid of control elements. In one embodiment, the control layer is a liquid crystal grid (LCG, sometimes referred to as a matrix) in which a liquid crystal element can alter behavior of a transmission layer element (such as a metamaterial element). In another embodiment, the transmission layer can selectively vary a transmission coefficient of each element of the grid.
In one embodiment, electromagnetic energy from the backplane structure or feed network is coupled to an array of antenna elements, which, if uniformly excited, would generate a particular electromagnetic beam pattern. By coupling a pattern of electromagnetic energy from the backplane structure modulated by the electromagnetic energy, multiplied by the pattern caused by the control elements, a far-field beam pattern is produced by the antenna array. The far-field beam pattern is a convolution of the pattern that the antenna elements generate (as modified by the control elements) with the pattern that the electromagnetic energy generates if radiated by a uniform array of antenna elements.
It should be recognized that while patterns of amplitudes of radio frequency energy are discussed for clarity, patterns of phases of radio frequency energy and/or patterns of amplitudes of radio frequency energy, phases of radio frequency energy, or spatial distributions of intensities can also be used in embodiments. In addition, while embodiments discussed below focus on radio frequency energy for clarity, it should be recognized that other wave types can also be used, including pressure waves, including those found in gases and fluids.
The backplane 106 (also known as a backplane cavity or backplane structure) can receive RF energy from radiating elements 110 that receive the RF energy from RF inputs. The backplane 106 can then couple the RF energy into the array elements layer. The array elements layer can include a metamaterial layer 114 and a control grid 120. The control grid 120 can include individual control elements 118 that correspond to metamaterial elements 116. The control grid elements 118 can be used to enable transmission of RF energy by a corresponding metamaterial element 116 or disable transmission of RF energy by a corresponding metamaterial element 116. In some embodiments, the control grid 120 is a liquid crystal grid that selectively enables or disables control elements 118. In some embodiments, each sub-wavelength metamaterial element 116 may also be configured to generate an electromagnetic emission in response to the electromagnetic resonance of RF energy coupled to the sub-wavelength metamaterial element 116 from the backplane 106.
By using the control grid 120 to apply a modulation pattern to the metamaterial layer 114, the object wave 108 can be created at the aperture plane 102 of the antenna 112.
The control system 111 can create the desired object wave 108, such as one that has a desired far-field beam pattern, by calculating and applying a modulation pattern to the metamaterial layer 114.
For example, construction of a modulation pattern can be determined and then applied to an antenna system. The control system 111 calculates the fields in the feed network of the backplane 106 at each radiating element while stimulating the feed input port. The control system 111 determines an ideal hologram modulation pattern by multiplying a reference wave with the desired object wave 108. The control system 111 discards a phase part and takes a magnitude part of the determined ideal hologram. The control system 111 fits an aperture taper function which is multiplied to the magnitude of the ideal hologram. The pattern is shifted and scaled such that all elements have values greater than or equal to a lower bound of the element modulation range (or depth) and less than the upper bound of the element modulation range (or depth) to form the aperture modulation pattern. The control system 111 applies the modulation pattern to the aperture plane 102. The reference wave interacts with the modulation pattern to form the object wave 108 at the aperture plane 102.
After determining the modulation pattern, the control system 111 can create the desired object wave 108. RF inputs can be activated to provide RF energy into the backplane 106 or feed network, such as through radiating elements 110. The modulation pattern can be applied to the control grid 120 that causes the metamaterial elements 116 to form the object wave 108 that is then propagated into free space.
In an alternate embodiment, the control system 111 discards an imaginary part and takes a real part of the determined ideal hologram. The control system 111 fits an aperture taper function which has been scaled so that when it is added to the real part of the ideal hologram elements of the sum have values greater than or equal to a lower bound of the element modulation range (or depth). The control system 111 normalizes the sum pattern by the upper bound of the element modulation range (or depth) to form the aperture modulation pattern. The control system 111 applies the modulation pattern to the aperture plane 102 by taking the product of the modulation pattern and reference wave to form the radiated field at the aperture plane 102.
Once the antenna system 202 determines how to approximate the object wave 208, the antenna system 202 can provide an RF input 212 into the antenna 210 to create a guided wave (also known as a reference wave or reference mode). The antenna 210 can then use the guided wave to produce the object wave 208 at an aperture of the antenna 210. The object wave 208 then radiates from the antenna 210 to form a radiated wave (also known as a propagating wave or radiative wave). The radiated wave forms a beam pattern 204 as it radiates. The beam pattern 204 then approximates the desired two-dimensional beam profile 206.
Embodiments and implementations of the systems and methods described herein may include various operations, which may be embodied in machine-executable instructions to be executed by a computer system. A computer system may include one or more general-purpose or special-purpose computers (or other electronic devices). The computer system may include hardware components that include specific logic for performing the operations or may include a combination of hardware, software, and/or firmware.
Computer systems and the computers in a computer system may be connected via a network. Suitable networks for configuration and/or use as described herein include one or more local area networks, wide area networks, metropolitan area networks, and/or Internet or IP networks, such as the World Wide Web, a private Internet, a secure Internet, a value-added network, a virtual private network, an extranet, an intranet, or even stand-alone machines which communicate with other machines by physical transport of media. In particular, a suitable network may be formed from parts or entireties of two or more other networks, including networks using disparate hardware and network communication technologies.
One suitable network includes a server and one or more clients; other suitable networks may contain other combinations of servers, clients, and/or peer-to-peer nodes, and a given computer system may function both as a client and as a server. Each network includes at least two computers or computer systems, such as the server and/or clients. A computer system may include a workstation, laptop computer, disconnectable mobile computer, server, mainframe, cluster, so-called “network computer” or “thin client,” tablet, smart phone, personal digital assistant or other hand-held computing device, “smart” consumer electronics device or appliance, medical device, or a combination thereof.
Suitable networks may include communications or networking software, such as the software available from Novell®, Microsoft®, and other vendors, and may operate using TCP/IP, SPX, IPX, and other protocols over twisted pair, coaxial, or optical fiber cables, telephone lines, radio waves, satellites, microwave relays, modulated AC power lines, physical media transfer, and/or other data transmission “wires” known to those of skill in the art. The network may encompass smaller networks and/or be connectable to other networks through a gateway or similar mechanism.
Various techniques, or certain aspects or portions thereof, may take the form of program code (i.e., instructions) embodied in tangible media, such as floppy diskettes, CD-ROMs, hard drives, magnetic or optical cards, solid-state memory devices, a nontransitory computer-readable storage medium, or any other machine-readable storage medium wherein, when the program code is loaded into and executed by a machine, such as a computer, the machine becomes an apparatus for practicing the various techniques. In the case of program code execution on programmable computers, the computing device may include a processor, a storage medium readable by the processor (including volatile and nonvolatile memory and/or storage elements), at least one input device, and at least one output device. The volatile and nonvolatile memory and/or storage elements may be a RAM, an EPROM, a flash drive, an optical drive, a magnetic hard drive, or other medium for storing electronic data. One or more programs that may implement or utilize the various techniques described herein may use an application programming interface (API), reusable controls, and the like. Such programs may be implemented in a high-level procedural or an object-oriented programming language to communicate with a computer system. However, the program(s) may be implemented in assembly or machine language, if desired. In any case, the language may be a compiled or interpreted language, and combined with hardware implementations.
Each computer system includes one or more processors and/or memory; computer systems may also include various input devices and/or output devices. The processor may include a general purpose device, such as an Intel®, AMD®, or other “off-the-shelf” microprocessor. The processor may include a special purpose processing device, such as ASIC, SoC, SiP, FPGA, PAL, PLA, FPLA, PLD, or other customized or programmable device. The memory may include static RAM, dynamic RAM, flash memory, one or more flip-flops, ROM, CD-ROM, DVD, disk, tape, or magnetic, optical, or other computer storage medium. The input device(s) may include a keyboard, mouse, touch screen, light pen, tablet, microphone, sensor, or other hardware with accompanying firmware and/or software. The output device(s) may include a monitor or other display, printer, speech or text synthesizer, switch, signal line, or other hardware with accompanying firmware and/or software.
It should be understood that many of the functional units described in this specification may be implemented as one or more components, which is a term used to more particularly emphasize their implementation independence. For example, a component may be implemented as a hardware circuit comprising custom very large scale integration (VLSI) circuits or gate arrays, or off-the-shelf semiconductors such as logic chips, transistors, or other discrete components. A component may also be implemented in programmable hardware devices such as field programmable gate arrays, programmable array logic, programmable logic devices, or the like.
Components may also be implemented in software for execution by various types of processors. An identified component of executable code may, for instance, comprise one or more physical or logical blocks of computer instructions, which may, for instance, be organized as an object, a procedure, or a function. Nevertheless, the executables of an identified component need not be physically located together, but may comprise disparate instructions stored in different locations that, when joined logically together, comprise the component and achieve the stated purpose for the component.
Indeed, a component of executable code may be a single instruction, or many instructions, and may even be distributed over several different code segments, among different programs, and across several memory devices. Similarly, operational data may be identified and illustrated herein within components, and may be embodied in any suitable form and organized within any suitable type of data structure. The operational data may be collected as a single data set, or may be distributed over different locations including over different storage devices, and may exist, at least partially, merely as electronic signals on a system or network. The components may be passive or active, including agents operable to perform desired functions.
Several aspects of the embodiments described will be illustrated as software modules or components. As used herein, a software module or component may include any type of computer instruction or computer-executable code located within a memory device. A software module may, for instance, include one or more physical or logical blocks of computer instructions, which may be organized as a routine, program, object, component, data structure, etc., that perform one or more tasks or implement particular data types. It is appreciated that a software module may be implemented in hardware and/or firmware instead of or in addition to software. One or more of the functional modules described herein may be separated into sub-modules and/or combined into a single or smaller number of modules.
In certain embodiments, a particular software module may include disparate instructions stored in different locations of a memory device, different memory devices, or different computers, which together implement the described functionality of the module. Indeed, a module may include a single instruction or many instructions, and may be distributed over several different code segments, among different programs, and across several memory devices. Some embodiments may be practiced in a distributed computing environment where tasks are performed by a remote processing device linked through a communications network. In a distributed computing environment, software modules may be located in local and/or remote memory storage devices. In addition, data being tied or rendered together in a database record may be resident in the same memory device, or across several memory devices, and may be linked together in fields of a record in a database across a network.
Reference throughout this specification to “an example” means that a particular feature, structure, or characteristic described in connection with the example is included in at least one embodiment of the present invention. Thus, appearances of the phrase “in an example” in various places throughout this specification are not necessarily all referring to the same embodiment.
As used herein, a plurality of items, structural elements, compositional elements, and/or materials may be presented in a common list for convenience. However, these lists should be construed as though each member of the list is individually identified as a separate and unique member. Thus, no individual member of such list should be construed as a de facto equivalent of any other member of the same list solely based on its presentation in a common group without indications to the contrary. In addition, various embodiments and examples of the present invention may be referred to herein along with alternatives for the various components thereof. It is understood that such embodiments, examples, and alternatives are not to be construed as de facto equivalents of one another, but are to be considered as separate and autonomous representations of the present invention.
Furthermore, the described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. In the above description, numerous specific details are provided, such as examples of materials, frequencies, sizes, lengths, widths, shapes, etc., to provide a thorough understanding of embodiments of the invention. One skilled in the relevant art will recognize, however, that the invention may be practiced without one or more of the specific details, or with other methods, components, materials, etc. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring aspects of the invention.
Although the foregoing has been described in some detail for purposes of clarity, it will be apparent that certain changes and modifications may be made without departing from the principles thereof. It should be noted that there are many alternative ways of implementing both the processes and apparatuses described herein. Accordingly, the present embodiments are to be considered illustrative and not restrictive, and the invention is not to be limited to the details given herein, but may be modified within the scope and equivalents of the appended claims.
While various aspects and embodiments have been disclosed herein, other aspects and embodiments will be apparent to those skilled in the art. The various aspects and embodiments disclosed herein are for purposes of illustration and are not intended to be limiting, with the true scope and spirit being indicated by the following claims.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 14954726 | Nov 2015 | US |
| Child | 16102182 | US | |
| Parent | 14954732 | Nov 2015 | US |
| Child | 14954726 | US |
