# Patent

## Title
Surface scattering antenna array

## Abstract

An array of scattering and/or reflector antennas are configured to produce a series of beam patterns, where in some embodiments the scattering antenna and/or the reflector antenna includes complementary metamaterial elements. In some embodiments control circuitry is operably connected to the array to produce an image of an object in the beam pattern.

## Background
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.
CROSS-REFERENCE TO RELATED APPLICATIONS
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)).
PRIORITY APPLICATIONS
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.
SUMMARY
In one embodiment, an apparatus comprises: a scattering antenna having a first plurality of scattering elements, each of the scattering elements in the first plurality of scattering elements having an individual electromagnetic response to an incident electromagnetic wave, and wherein the scattering antenna is configured to produce a first radiation field responsive to the incident electromagnetic wave; a reflector antenna arranged to receive at least a portion of the first radiation field, the reflector antenna having a second plurality of scattering elements, wherein the reflector antenna is responsive to reflect a portion of the first radiation field to produce a second radiation field different from the first radiation field; and a detector configured to receive at least a portion of the second radiation field.
In another embodiment, an apparatus comprises: a source configured to produce an incident electromagnetic wave; a reflector antenna arranged to receive the incident electromagnetic wave, the reflector antenna having a first plurality of scattering elements, wherein the reflector antenna is responsive to reflect a portion of the incident electromagnetic wave to produce a first radiation field; and a scattering antenna configured to receive at least a portion of the first radiation field, the scattering antenna having a second plurality of scattering elements, each of the scattering elements in the second plurality of scattering elements having an individual electromagnetic response to an incident electromagnetic wave.
In another embodiment, a system comprises: a source configured to produce electromagnetic energy and operably connected to a scattering antenna to radiate the electromagnetic energy in a field of view; a reflector antenna arranged relative to the scattering antenna to receive the electromagnetic energy and to produce a set of beam patterns in the field of view, the set of beam patterns being at least partially determined by at least one of a set of scattering antenna patterns, a set of reflector antenna patterns, and a set of frequencies of the electromagnetic energy produced by the source; a detector configured to receive electromagnetic energy from the set of beam patterns; and circuitry coupled to the detector and configured to reconstruct an image of a scene within the field of view using a compressive imaging algorithm based on the set of beam patterns.
In another embodiment, a method comprises: producing a first series of radiation fields; reflecting at least a portion of the first series of radiation fields to produce a second series of radiation fields different from the first series of radiation fields; reflecting at least a portion of the first series of radiation fields to produce a second series of radiation fields different from the first series of radiation fields; detecting at least a portion of each radiation field in the second series of radiation fields; and reconstructing an image of a scene that is illuminated by the first and second series of radiation fields using a compressive imaging algorithm.
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.



BRIEF DESCRIPTION OF THE FIGURES
FIG. 1 is a schematic of a surface scattering antenna array.
FIG. 2 is a schematic of a surface scattering antenna array.
FIG. 3 is a schematic of a surface scattering antenna array.
FIG. 4 is a schematic of a surface scattering reflector antenna.
FIG. 5 is a schematic of a cross-section of a unit cell of a surface scattering reflector antenna.
FIG. 6 is a schematic of a side view of a unit cell of a surface scattering reflector antenna.
FIG. 7 is a schematic of a system including a surface scattering reflector antenna.



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.
FIG. 1 shows one embodiment of a system 100 that includes a scattering antenna 102, a reflector antenna 104, and circuitry 106 arranged to image an object 108. Scattering antennas (also called surface scattering antennas) were described in Bily et al., “Surface Scattering Antennas”, U.S. Patent Application Publication No. 2012/0194399 (hereinafter, Bily1), which is incorporated herein by reference, and in Bily et al., “Surface Scattering Antenna Improvements”, U.S. patent application Ser. No. 13/838,934, filed Mar. 15, 2013, (hereinafter, Bily2). Reflector antennas (also called surface scattering reflector antennas) were described in Bowers et al, “Surface Scattering Reflector Antenna”, U.S. patent application Ser. No. 14/102,253, filed Dec. 10, 2013, (hereinafter, Bowers), which is incorporated herein by reference. Reflector antennas are further described in detail later in this specification. Compressive imaging systems that incorporate surface scattering antennas were described in Smith et al., “Metamaterial Devices and Methods of Using the Same”, U.S. Patent Application Publication No. 2013/0335256 (hereinafter, Smith1), which is incorporated herein by reference, and in Smith et al., “Metamaterial Devices and Methods of Using the Same”, P.C.T. Application Publication No. WO/2014/025425 (hereinafter, Smith2).
In the embodiment in FIG. 1, the scattering antenna 102 includes a waveguide 110 with scattering elements 112, where the scattering elements may include complementary metamaterial elements as described in Bily1 and in Bily2. The waveguide 110 of the scattering antenna 102 is configured to receive electromagnetic energy from a source 114, wherein the electromagnetic energy propagates through the waveguide and is radiated by the scattering elements 112 to produce the first radiation field 118.
A portion of the first radiation field 118 is then received by the reflector antenna 104 having scattering elements 116, which re-radiates a portion of the energy to produce the second radiation field 119. The first and second radiation fields 118, 119 combine to form a beam pattern 120 in the location of an object 108 to be imaged. The beam pattern 120 depends on many factors, including but not limited to: the frequency of the electromagnetic energy, the pattern of the scattering elements 112 in the scattering antenna 102, the pattern of the scattering elements 116 in the reflector antenna 104, and the physical locations of each of the scattering elements 112, 116 in the scattering antenna 102 and the reflector antenna 104, which may be determined by the relative positions and orientations of the scattering antenna 102 and the reflector antenna 104. As is described in Bily1, Bily2, and Bowers, the scattering elements 112, 116 may in some embodiments be adjustable such that the first and second radiation fields 118, 119 are adjustable, and therefore the beam pattern 120 is adjustable responsive to the adjustment(s) to the scattering elements 112, 116.
The system further comprises a detector 122 that is configured to receive electromagnetic energy, where in FIG. 1 the detector is operably connected to the scattering antenna 102 to receive energy from the beam pattern 120 via the scattering antenna 102. Although FIG. 1 shows the detector 122 as being integral to the scattering antenna 102, in other embodiments the detector 122 may be separate. For example, the detector 122 may include a dipole antenna, a horn antenna, or another type of detector placed in the location of the beam pattern 120.
As described above, the beam pattern 120 is variable according to a number of factors. The circuitry 106 is configured with a compressive imaging algorithm (compressive imaging systems that incorporate surface scattering antennas were described in Smith1) to produce an image of an object 108 by determining a signal from the detector 122 for a known set of beam patterns 120.
In some embodiments the waveguide 110 is configured to allow a discrete set of modes to propagate, wherein each mode in the discrete set of modes corresponds to a frequency. Each mode may then correspond to first and second radiation fields 118, 119.
In some embodiments the circuitry 106 may be operably connected to one or more elements of the system in order to change the beam pattern 120. For example, the beam pattern 120 may be varied by varying the frequency of the electromagnetic energy, and the source 114 may be operably connected to the circuitry 106 to receive a signal to vary the frequency of the electromagnetic energy produced by the source 114. Further, the beam pattern 120 may be varied according to the configuration of the scattering elements 112 in the scattering antenna 102. This is explained in detail in Bily1. In such an embodiment, the circuitry 106 may be operably connected to the scattering antenna 102 to change the configuration of the scattering elements 102. Further, the beam pattern 120 may be varied according to the configuration of the scattering elements 116 in the reflector antenna 104. This is explained in detail in Bowers. In such an embodiment, the circuitry 106 may be operably connected to the reflector antenna 104 to change the configuration of the scattering elements 116. The scattering antenna 102 and the reflector antenna 104 each has a position and an orientation, and the relative position and orientation of each of these antennas with respect to the other can also change the beam pattern. In some embodiments the scattering antenna 102 and/or the reflector antenna 104 may be mounted on a moveable device such that the relative position and/or orientation of the antennas may be varied, and in such an embodiment the circuitry may be operably connected to control the position(s) and/or the orientation(s) of one or more of the antennas. Further, the beam pattern can be changed by changing more than one of the above described parameters. For example, the frequency of the electromagnetic energy and the configuration of the scattering elements in the scattering antenna 102 may be changed.
The frequency range of the electromagnetic energy may depend on the particular application, and may, for example, include RF frequencies and/or millimeter wave frequencies.
In one embodiment, the scattering antenna 102 may be replaced by another reflector antenna 104, as shown in FIG. 2. In this embodiment, the source 114 is configured to produce electromagnetic energy that impinges on the reflector antenna 104 to produce the first radiation field and the detector 122 is any device that is configured to detect electromagnetic energy in the frequency range(s) produced by the source 114, and is placed in such a way that it can receive energy from the beam pattern 120.
FIG. 3 shows another embodiment of a system 300 that includes a scattering antenna 102, a reflector antenna 104, and circuitry 106 arranged to image an object 108. In the embodiment in FIG. 3, the source 114 is configured to produce electromagnetic energy 115 that impinges on the reflector antenna 104. The source 114 is shown as a horn antenna, however it may be a different type of source, such as a dipole antenna or other source. The reflector antenna 104 is responsive to reflect a portion of the incident electromagnetic energy to produce a first radiation field 118. The scattering antenna 102 is configured to receive at least a portion of the first radiation field 118, specifically, the portion that overlaps the measurement field pattern 302 of the scattering antenna 102. The detector 122 receives a signal that is a function of the first radiation field 118 produced by the reflector antenna 104, the distribution of the scattering elements 112 on the scattering antenna 102, and, where the scattering antenna 102 has a variable configuration, the signal received by the detector will also be a function of the state of the scattering elements 112.
Similar to what was described for FIG. 1, the apparatuses shown in FIGS. 2 and 3 may be configured with circuitry and may be controlled by the circuitry and have variability in ways similar to that of FIG. 1.
Although the embodiments in FIGS. 1-3 are shown with two antennas (i.e., scattering and/or reflector antennas 102, 104), some embodiments may include more than two antennas 102 and 104. For example, one embodiment may include a scattering antenna 102 and two or more reflector antennas 104, where the reflector antennas may be positioned to produce a selected beam pattern 120. Such an embodiment may be used, for example, in a room where the reflector antennas 104 are used to selectively illuminate different portions of the room. Further, although FIGS. 1-3 show the two antennas as facing one another, in other embodiments the antennas may have a different configuration, and further, where one or more antennas are mounted on a moveable device, the relative angle and/or positions of the antennas may be varied in time, thus varying the beam patterns created by the array.
There are many different permutations of the embodiments shown in FIGS. 1-3. For example, FIG. 1 shows a scattering antenna 102 producing the first radiation field 118, acting effectively as the source for the array. However, FIGS. 2 and 3 show a reflector antenna 104 producing the first radiation field 118. Thus, either a scattering antenna 102 or a reflector antenna 104 can be configured to produce the first radiation field 118. Further, any number of scattering antennas 102 and/or reflector antennas 104 may be configured together in an array. The scattering elements 112, 116 in these antennas may be configured to be adjustable or static. Further still, the position and/or orientation of the antennas in the array may be configured to be adjustable as a function of time. Thus, an antenna array can be configured in a multitude of different ways according to a particular configuration.
A schematic illustration of a surface scattering reflector antenna 400 is depicted in FIG. 4. The surface scattering reflector antenna 400 includes a plurality of scattering elements 402a, 402b that are distributed along a substrate 404. The substrate 404 may be a printed circuit board (such as FR4 or another dielectric with a surface layer of metal such as copper or another conductor), or a different type of structure, which may be a single layer or a multi-layer structure. The broken line 408 is a symbolic depiction of an electromagnetic wave incident on the surface scattering reflector antenna 400, and this symbolic depiction is not intended to indicate a collimated beam or any other limitation of the electromagnetic wave. The scattering elements 402a, 402b may include metamaterial elements and/or other sub-wavelength elements that are embedded within or positioned on a surface of the substrate 404.
The surface scattering reflector antenna 400 may also include a component 406 configured to produce the incident electromagnetic wave 408. The component 406 may be an antenna such as a dipole and/or monopole antenna.
When illuminated with the component 406, the surface scattering reflector antenna 400 produces beam patterns dependent on the pattern formed by the scattering elements 402a, 402b and the frequency and/or wave vector of the radiation. The scattering elements 402a, 402b each have an adjustable individual electromagnetic response that is dynamically adjustable such that the reflected beam pattern is adjustable responsive to changes in the electromagnetic response of the elements 402a, 402b. In some embodiments the scattering elements 402a, 402b include metamaterial elements that are analogous to the adjustable complementary metamaterial elements described in Bily1, previously cited.
The scattering elements 402a, 402b are adjustable scattering elements having electromagnetic properties that are adjustable in response to one or more external inputs. Various embodiments of adjustable scattering elements are described, for example, in D. R. Smith et al., “Metamaterials for surfaces and waveguides”, U.S. Patent Application Publication No. 2010/0156573, which is incorporated herein by reference, and in Bily1, and further in this disclosure. Adjustable scattering elements can include elements that are adjustable in response to voltage inputs (e.g. bias voltages for active elements (such as varactors, transistors, diodes) or for elements that incorporate tunable dielectric materials (such as ferroelectrics)), current inputs (e.g. direct injection of charge carriers into active elements), optical inputs (e.g. illumination of a photoactive material), field inputs (e.g. magnetic fields for elements that include nonlinear magnetic materials), mechanical inputs (e.g. MEMS, actuators, hydraulics), etc. In the schematic example of FIG. 4, scattering elements 402a, 402b that have been adjusted to a first state having first electromagnetic properties are depicted as the first elements 402a, while scattering elements that have been adjusted to a second state having second electromagnetic properties are depicted as the second elements 402b. The depiction of scattering elements having first and second states corresponding to first and second electromagnetic properties is not intended to be limiting: embodiments may provide scattering elements that are discretely adjustable to select from a discrete plurality of states corresponding to a discrete plurality of different electromagnetic properties, or continuously adjustable to select from a continuum of states corresponding to a continuum of different electromagnetic properties. Moreover, the particular pattern of adjustment that is depicted in FIG. 4 (i.e. the alternating arrangement of elements 402a and 402b) is only an exemplary configuration and is not intended to be limiting.
In the example of FIG. 4, the scattering elements 402a, 402b have first and second couplings to the incident electromagnetic wave 408 that are functions of the first and second properties, respectively. For example, the first and second couplings may be first and second polarizabilities of the scattering elements at the frequency or frequency band of the incoming wave 408. In one approach the first coupling is a substantially non-zero coupling whereas the second coupling is a substantially zero coupling. In another approach both couplings are substantially non-zero but the first coupling is substantially greater than (or less than) the second coupling. On account of the first and second couplings, the first and second scattering elements 402a, 402b are responsive to the incoming electromagnetic wave 408 to produce a plurality of scattered electromagnetic waves having amplitudes that are functions of (e.g. are proportional to) the respective first and second couplings. A superposition of the scattered electromagnetic waves, along with the portion of the incoming electromagnetic wave 408 that is reflected by the substrate 404, comprises an electromagnetic wave that is depicted, in this example, as a plane wave 410 that radiates from the surface scattering reflector antenna 400.
The emergence of the plane wave 410 may be understood by regarding the particular pattern of adjustment of the scattering elements (e.g. an alternating arrangement of the first and second scattering elements in FIG. 4) as a pattern that scatters the incoming electromagnetic wave 408 to produce the plane wave 410. Because this pattern is adjustable, some embodiments of the surface scattering elements may be selected according to principles of holography. Suppose, for example, that the incoming wave 408 may be represented by a complex scalar input wave Ψin, and it is desired that the surface scattering reflector antenna produce an output wave that may be represented by another complex scalar wave Ψout. Then a pattern of adjustment of the scattering elements may be selected that corresponds to an interference pattern of the input and output waves along the antenna. For example, the scattering elements may be adjusted to provide couplings to the guided wave or surface wave that are functions of (e.g. are proportional to, or step-functions of) an interference term given by Re[ΨoutΨin]. In this way, embodiments of the surface scattering reflector antenna 400 may be adjusted to provide arbitrary antenna radiation patterns by identifying an output wave Ψout corresponding to a selected beam pattern, and then adjusting the scattering elements accordingly as above. Embodiments of the surface scattering antenna may therefore be adjusted to provide, for example, a selected beam direction (e.g. beam steering), a selected beam width or shape (e.g. a fan or pencil beam having a broad or narrow beamwidth), a selected arrangement of nulls (e.g. null steering), a selected arrangement of multiple beams, a selected polarization state (e.g. linear, circular, or elliptical polarization), a selected overall phase or distribution of phases, or any combination thereof. Alternatively or additionally, embodiments of the surface scattering reflector antenna 400 may be adjusted to provide a selected near-field radiation profile, e.g. to provide near-field focusing and/or near-field nulls.
Because the spatial resolution of the interference pattern is limited by the spatial resolution of the scattering elements, the scattering elements may be arranged along the substrate 404 with inter-element spacings that are much less than a free-space wavelength corresponding to an operating frequency of the device (for example, less than one-third or one-fourth of this free-space wavelength). In some approaches, the operating frequency is a microwave frequency, selected from frequency bands such as Ka, Ku, and Q, corresponding to centimeter-scale free-space wavelengths. This length scale admits the fabrication of scattering elements using conventional printed circuit board technologies, as described below.
In some approaches, the surface scattering reflector antenna 400 includes a substantially one-dimensional arrangement of scattering elements, and the pattern of adjustment of this one-dimensional arrangement may provide, for example, a selected antenna radiation profile as a function of zenith angle (i.e. relative to a zenith direction that is parallel to the one-dimensional wave-propagating structure). In other approaches, the surface scattering reflector antenna includes a substantially two-dimensional arrangement of scattering elements, and the pattern of adjustment of this two-dimensional arrangement may provide, for example, a selected antenna radiation profile as a function of both zenith and azimuth angles (i.e. relative to a zenith direction that is perpendicular to the substrate 404).
In some approaches, the substrate 404 is a modular substrate 404 and a plurality of modular substrates may be assembled to compose a modular surface scattering antenna. For example, a plurality of substrates 404 may be assembled to produce a larger aperture having a larger number of scattering elements; and/or the plurality of substrates may be assembled as a three-dimensional structure (e.g. forming an A-frame structure, a pyramidal structure, a wine crate structure, or other multi-faceted structure).
In some applications of the modular approach, the number of modules to be assembled may be selected to achieve an aperture size providing a desired telecommunications data capacity and/or quality of service, and or a three-dimensional arrangement of the modules may be selected to reduce potential scan loss. Thus, for example, the modular assembly could comprise several modules mounted at various locations/orientations flush to the surface of a vehicle such as an aircraft, spacecraft, watercraft, ground vehicle, etc. The modules need not be contiguous. In these and other approaches, the substrate may have a substantially non-linear or substantially non-planar shape whereby to conform to a particular geometry, therefore providing a conformal surface scattering reflector antenna (conforming, for example, to the curved surface of a vehicle).
More generally, a surface scattering reflector antenna is a reconfigurable antenna that may be reconfigured by selecting a pattern of adjustment of the scattering elements so that a corresponding scattering of the incident electromagnetic wave 408 produces a desired output wave. Thus, embodiments of the surface scattering reflector antenna may provide a reconfigurable antenna that is adjustable to produce a desired output wave by adjusting a plurality of couplings.
In some approaches, the reconfigurable antenna is adjustable to provide a desired polarization state of the output wave. Suppose, for example that first and second subsets of the scattering elements provide electric field patterns that are substantially linearly polarized and substantially orthogonal (for example, the first and second subjects may be scattering elements that are perpendicularly oriented on a surface of the substrate 404). Then the antenna output wave EOM may be expressed as a sum of two linearly polarized components.
Accordingly, the polarization of the output wave may be controlled by adjusting the plurality of couplings, e.g. to provide an output wave with any desired polarization (e.g. linear, circular, or elliptical).
FIGS. 5 and 6 show a top (FIG. 5) and cross sectional view (FIG. 6; cross section corresponds to dashed line 502 in FIG. 5) of one exemplary embodiment of a unit cell 500 of a scattering element (such as 402a and/or 402b) of the surface scattering reflector antenna 400. In this embodiment the substrate 404 includes a dielectric layer 602 and a conductor layer 604, where the scattering element (402a, 402b) is formed by removing a portion of the conductor layer to form a complementary metamaterial element 504, in this case a complementary electric LC (CELC) metamaterial element that is defined by a shaped aperture 506 that has been etched or patterned in the conductor layer 604 (e.g. by a PCB process).
A CELC element such as that depicted in FIGS. 2 and 3 is substantially responsive to a magnetic field that is applied parallel to the plane of the CELC element and perpendicular to the CELC gap complement, i.e., in the x direction for the orientation of FIG. 5 (cf. T. H. Hand et al., “Characterization of complementary electric field coupled resonant surfaces,” Applied Physics Letters, 93, 212504 (2008), herein incorporated by reference). Therefore, a magnetic field component of an incident electromagnetic wave can induce a magnetic excitation of the element 504 that may be substantially characterized as a magnetic dipole excitation oriented in the x direction, thus producing a scattered electromagnetic wave that is substantially a magnetic dipole radiation field.
Noting that the shaped aperture 506 also defines a conductor island 508 which is electrically disconnected from outer regions of the conductor layer 604, in some approaches the scattering element can be made adjustable by providing an adjustable material within and/or proximate to the shaped aperture 506 and subsequently applying a bias voltage between the conductor island 508 and the outer regions of the conductor layer 604. For example, as shown in FIG. 5, the unit cell may include liquid crystal 510 in the region between the conductor island 508 and the outer regions of the conductor layer 604. Liquid crystals have a permittivity that is a function of orientation of the molecules comprising the liquid crystal; and that orientation may be controlled by applying a bias voltage (equivalently, a bias electric field) across the liquid crystal; accordingly, liquid crystals can provide a voltage-tunable permittivity for adjustment of the electromagnetic properties of the scattering element. Methods and apparatus for containing the liquid crystal are described in Bily1.
For a nematic phase liquid crystal, wherein the molecular orientation may be characterized by a director field, the material may provide a larger permittivity ∈1 for an electric field component that is parallel to the director and a smaller permittivity ∈2 for an electric field component that is perpendicular to the director. Applying a bias voltage introduces bias electric field lines that span the shaped aperture and the director tends to align parallel to these electric field lines (with the degree of alignment increasing with bias voltage). Because these bias electric field lines are substantially parallel to the electric field lines that are produced during a scattering excitation of the scattering element, the permittivity that is seen by the biased scattering element correspondingly tend towards ∈1 (i.e. with increasing bias voltage). On the other hand, the permittivity that is seen by the unbiased scattering element may depend on the unbiased configuration of the liquid crystal. When the unbiased liquid crystal is maximally disordered (i.e. with randomly oriented micro-domains), the unbiased scattering element may see an averaged permittivity ∈ave ̃(∈1+∈2)/2. When the unbiased liquid crystal is maximally aligned perpendicular to the bias electric field lines (i.e. prior to the application of the bias electric field), the unbiased scattering element may see a permittivity as small as ∈2. Accordingly, for embodiments where it is desired to achieve a greater range of tuning of the permittivity that is seen by the scattering element, the unit cell 500 may include positionally-dependent alignment layer(s) disposed at the top and/or bottom surface of the liquid crystal layer 510, the positionally-dependent alignment layer(s) being configured to align the liquid crystal director in a direction substantially perpendicular to the bias electric field lines that correspond to an applied bias voltage. The alignment layer(s) may include, for example, polyimide layer(s) that are rubbed or otherwise patterned (e.g. by machining or photolithography) to introduce microscopic grooves that run parallel to the channels of the shaped aperture 506.
Alternatively or additionally, the unit cell may provide a first biasing that aligns the liquid crystal substantially perpendicular to the channels of the shaped aperture 506 (e.g. by introducing a bias voltage between the conductor island 508 and the outer regions of the conductor layer 604), and a second biasing that aligns the liquid crystal substantially parallel to the channels of the shaped aperture 506 (e.g. by introducing electrodes positioned above the outer regions of the conductor layer 604 at the four corners of the unit cell, and applying opposite voltages to the electrodes at adjacent corners); tuning of the scattering element may then be accomplished by, for example, alternating between the first biasing and the second biasing, or adjusting the relative strengths of the first and second biasings. Examples of types of liquid crystals that may be used are described in Bily1.
Turning now to approaches for providing a bias voltage between the conductor island 508 and the outer regions of the conductor layer 604, it is first noted that the outer regions of the conductor layer 604 extends contiguously from one unit cell to the next, so an electrical connection to the outer regions of the conductor layer 604 of every unit cell may be made by a single connection to this contiguous conductor. As for the conductor island 508, FIG. 5 shows an example of how a bias voltage line 512 may be attached to the conductor island. In this example, the bias voltage line 512 is attached at the center of the conductor island and extends away from the conductor island along a plane of symmetry of the scattering element; by virtue of this positioning along a plane of symmetry, electric field lines that are experienced by the bias voltage line during a scattering excitation of the scattering element are substantially perpendicular to the bias voltage line that could disrupt or alter the scattering properties of the scattering element. The bias voltage line 512 may be installed in the unit cell by, for example, depositing an insulating layer (e.g. polyamide), etching the insulating layer at the center of the conductor island, and then using a lift-off process to pattern a conducting film (e.g. a Cr/Au bilayer) that defines the bias voltage line 512.
The cross sectional shape of the complementary metamaterial element 504 shown in FIG. 5 is just one exemplary embodiment, and other shapes, orientations, and/or other characteristics may be selected according to a particular embodiment. For example, Bily1 describes a number of CELC's that may be incorporated in the device as described above, as well as ways in which arrays of CELC's may be addressed.
FIG. 7 shows a system incorporating the surface scattering reflector antenna of FIG. 4 with a separate detector 702 and control circuitry 704. In this embodiment the detector 702 and the component 406 that produces the incident wave are housed in separate units, however as mentioned previously in some embodiments they may be housed together in the same unit. The control circuitry 704 is operably connected to both the detector 702 and the component 406, and may transmit and/or receive signal(s) to/from these units. Although the detector 702 and the component 406 are shown as exemplary embodiments of elements that are operably connected to the control circuitry 704, in other embodiments the system may include other devices (for example, power supplies, additional detectors configured to detect the radiation pattern produced by the antenna, detectors configured to monitor conditions of the antenna, or a different device that may be added according to a particular embodiment) that may also be operably connected to the control circuitry 704. In some embodiments the control circuitry 704 is receptive to a signal 406, where the signal 406 may be a user input or other outside input. The control circuitry 704 may also be operably connected to control the surface scattering reflector antenna 400 to adjust the configuration of the antenna in ways as previously described herein.
In some approaches the control circuitry 704 includes circuitry configured to provide control inputs that correspond to a selected or desired radiation pattern. For example, the control circuitry 704 may store a set of configurations of the antenna, e.g. as a lookup table that maps a set of desired antenna radiation patterns (corresponding to various beam directions, beam widths, polarization states, etc. as described previously herein) to a corresponding set of values for the control input(s). This lookup table may be previously computed, e.g. by performing full-wave simulations of the antenna for a range of values of the control input(s) or by placing the antenna in a test environment and measuring the antenna radiation patterns corresponding to a range of values of the control input(s). In some approaches control circuitry may be configured to use this lookup table to calculate the control input(s) according to a regression analysis; for example, by interpolating values for the control input(s) between two antenna radiation patterns that are stored in the lookup table (e.g. to allow continuous beam steering when the lookup table only includes discrete increments of a beam steering angle). The control circuitry 704 may alternatively be configured to dynamically calculate the control input(s) corresponding to a selected or desired antenna radiation pattern, e.g. by, for example, computing a holographic pattern (as previously described herein). Further, the control circuitry 704 may be configured with one or more feedback loops configured to adjust parameters until a selected radiation pattern is achieved.
The foregoing detailed description has set forth various embodiments of the devices and/or processes via the use of block diagrams, flowcharts, and/or examples. Insofar as such block diagrams, flowcharts, and/or examples contain one or more functions and/or operations, it will be understood by those within the art that each function and/or operation within such block diagrams, flowcharts, or examples can be implemented, individually and/or collectively, by a wide range of hardware, software, firmware, or virtually any combination thereof. In one embodiment, several portions of the subject matter described herein may be implemented via Application Specific Integrated Circuits (ASICs), Field Programmable Gate Arrays (FPGAs), digital signal processors (DSPs), or other integrated formats. However, those skilled in the art will recognize that some aspects of the embodiments disclosed herein, in whole or in part, can be equivalently implemented in integrated circuits, as one or more computer programs running on one or more computers (e.g., as one or more programs running on one or more computer systems), as one or more programs running on one or more processors (e.g., as one or more programs running on one or more microprocessors), as firmware, or as virtually any combination thereof, and that designing the circuitry and/or writing the code for the software and or firmware would be well within the skill of one of skill in the art in light of this disclosure. In addition, those skilled in the art will appreciate that the mechanisms of the subject matter described herein are capable of being distributed as a program product in a variety of forms, and that an illustrative embodiment of the subject matter described herein applies regardless of the particular type of signal bearing medium used to actually carry out the distribution. Examples of a signal bearing medium include, but are not limited to, the following: a recordable type medium such as a floppy disk, a hard disk drive, a Compact Disc (CD), a Digital Video Disk (DVD), a digital tape, a computer memory, etc.; and a transmission type medium such as a digital and/or an analog communication medium (e.g., a fiber optic cable, a waveguide, a wired communications link, a wireless communication link (e.g., transmitter, receiver, transmission logic, reception logic, etc.), etc.).
In a general sense, those skilled in the art will recognize that the various embodiments described herein can be implemented, individually and/or collectively, by various types of electro-mechanical systems having a wide range of electrical components such as hardware, software, firmware, and/or virtually any combination thereof; and a wide range of components that may impart mechanical force or motion such as rigid bodies, spring or torsional bodies, hydraulics, electro-magnetically actuated devices, and/or virtually any combination thereof. Consequently, as used herein “electro-mechanical system” includes, but is not limited to, electrical circuitry operably coupled with a transducer (e.g., an actuator, a motor, a piezoelectric crystal, a Micro Electro Mechanical System (MEMS), etc.), electrical circuitry having at least one discrete electrical circuit, electrical circuitry having at least one integrated circuit, electrical circuitry having at least one application specific integrated circuit, electrical circuitry forming a general purpose computing device configured by a computer program (e.g., a general purpose computer configured by a computer program which at least partially carries out processes and/or devices described herein, or a microprocessor configured by a computer program which at least partially carries out processes and/or devices described herein), electrical circuitry forming a memory device (e.g., forms of memory (e.g., random access, flash, read only, etc.)), electrical circuitry forming a communications device (e.g., a modem, communications switch, optical-electrical equipment, etc.), and/or any non-electrical analog thereto, such as optical or other analogs. Those skilled in the art will also appreciate that examples of electro-mechanical systems include but are not limited to a variety of consumer electronics systems, medical devices, as well as other systems such as motorized transport systems, factory automation systems, security systems, and/or communication/computing systems. Those skilled in the art will recognize that electro-mechanical as used herein is not necessarily limited to a system that has both electrical and mechanical actuation except as context may dictate otherwise.
All of the above U.S. patents, U.S. patent application publications, U.S. patent applications, foreign patents, foreign patent applications and non-patent publications referred to in this specification and/or listed in any Application Data Sheet are incorporated herein by reference, to the extent not inconsistent herewith.
One skilled in the art will recognize that the herein described components (e.g., operations), devices, objects, and the discussion accompanying them are used as examples for the sake of conceptual clarity and that various configuration modifications are contemplated. Consequently, as used herein, the specific exemplars set forth and the accompanying discussion are intended to be representative of their more general classes. In general, use of any specific exemplar is intended to be representative of its class, and the non-inclusion of specific components (e.g., operations), devices, and objects should not be taken limiting.
With respect to the use of substantially any plural and/or singular terms herein, those having skill in the art can translate from the plural to the singular and/or from the singular to the plural as is appropriate to the context and/or application. The various singular/plural permutations are not expressly set forth herein for sake of clarity.
While particular aspects of the present subject matter described herein have been shown and described, it will be apparent to those skilled in the art that, based upon the teachings herein, changes and modifications may be made without departing from the subject matter described herein and its broader aspects and, therefore, the appended claims are to encompass within their scope all such changes and modifications as are within the true spirit and scope of the subject matter described herein. It will be understood by those within the art that, in general, terms used herein, and especially in the appended claims (e.g., bodies of the appended claims) are generally intended as “open” terms (e.g., the term “including” should be interpreted as “including but not limited to,” the term “having” should be interpreted as “having at least,” the term “includes” should be interpreted as “includes but is not limited to,” etc.). It will be further understood by those within the art that if a specific number of an introduced claim recitation is intended, such an intent will be explicitly recited in the claim, and in the absence of such recitation no such intent is present. For example, as an aid to understanding, the following appended claims may contain usage of the introductory phrases “at least one” and “one or more” to introduce claim recitations. However, the use of such phrases should not be construed to imply that the introduction of a claim recitation by the indefinite articles “a” or “an” limits any particular claim containing such introduced claim recitation to claims containing only one such recitation, even when the same claim includes the introductory phrases “one or more” or “at least one” and indefinite articles such as “a” or “an” (e.g., “a” and/or “an” should typically be interpreted to mean “at least one” or “one or more”); the same holds true for the use of definite articles used to introduce claim recitations. In addition, even if a specific number of an introduced claim recitation is explicitly recited, those skilled in the art will recognize that such recitation should typically be interpreted to mean at least the recited number (e.g., the bare recitation of “two recitations,” without other modifiers, typically means at least two recitations, or two or more recitations). Furthermore, in those instances where a convention analogous to “at least one of A, B, and C, etc.” is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., “a system having at least one of A, B, and C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). In those instances where a convention analogous to “at least one of A, B, or C, etc.” is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., “a system having at least one of A, B, or C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). It will be further understood by those within the art that typically a disjunctive word and/or phrase presenting two or more alternative terms, whether in the description, claims, or drawings, should be understood to contemplate the possibilities of including one of the terms, either of the terms, or both terms unless context dictates otherwise. For example, the phrase “A or B” will be typically understood to include the possibilities of “A” or “B” or “A and B.”
With respect to the appended claims, those skilled in the art will appreciate that recited operations therein may generally be performed in any order. Also, although various operational flows are presented in a sequence(s), it should be understood that the various operations may be performed in other orders than those which are illustrated, or may be performed concurrently. Examples of such alternate orderings may include overlapping, interleaved, interrupted, reordered, incremental, preparatory, supplemental, simultaneous, reverse, or other variant orderings, unless context dictates otherwise. Furthermore, terms like “responsive to,” “related to,” or other past-tense adjectives are generally not intended to exclude such variants, unless context dictates otherwise.
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.

## Claims

1. An apparatus comprising:
a scattering antenna having a first plurality of scattering elements, each of the scattering elements in the first plurality of scattering elements having an individual electromagnetic response to an incident electromagnetic wave, and wherein the scattering antenna is configured to produce a first radiation field responsive to the incident electromagnetic wave;
a reflector antenna arranged to receive at least a portion of the first radiation field, the reflector antenna having a second plurality of scattering elements, wherein the reflector antenna is responsive to reflect a portion of the first radiation field to produce a second radiation field different from the first radiation field;
a detector configured to receive at least a portion of the second radiation field; and
wherein the scattering antenna includes a waveguide supportive of a discrete set of modes, and wherein the scattering antenna is configured to produce a first set of radiation field patterns corresponding to the set of modes.

2. The apparatus of claim 1 wherein each scattering element in the first plurality of scattering elements has an adjustable individual electromagnetic response, and further comprising:
circuitry operably connected to the first plurality of scattering elements to provide a first set of adjustments.

3. The apparatus of claim 2 wherein the first set of adjustments is selected to produce a set of beam patterns corresponding to the first radiation field.

4. The apparatus of claim 2 wherein each scattering element in the second plurality of scattering elements has an adjustable individual electromagnetic response, and further comprising:
circuitry operably connected to the second plurality of scattering elements to provide a second set of adjustments.

5. The apparatus of claim 4 wherein the first and second set of adjustments are selected to produce a set of beam patterns corresponding to the second radiation field.

6. The apparatus of claim 4 further comprising:
a source configured to produce the incident electromagnetic wave, the incident electromagnetic wave having a frequency; and
circuitry is operably connected to the source to provide a third set of adjustments, wherein the third set of adjustments are configured to vary the frequency of the incident electromagnetic wave.

7. The apparatus of claim 6 wherein the first, second, and third set of adjustments are selected to produce a set of beam patterns corresponding to the second radiation field.

8. The apparatus of claim 1 wherein each scattering element in the second plurality of scattering elements has an adjustable individual electromagnetic response, and further comprising:
circuitry operably connected to the second plurality of scattering elements to provide a set of adjustments.

9. The apparatus of claim 8 wherein the set of adjustments is selected to produce a set of beam patterns corresponding to the second radiation field.

10. The apparatus of claim 1 further comprising:
a source configured to produce the incident electromagnetic wave, the incident electromagnetic wave having a frequency; and
circuitry operably connected to the source to provide a set of adjustments, wherein the set of adjustments are configured to vary the frequency of the incident electromagnetic wave to produce a set of beam patterns corresponding to the first and second radiation fields.

11. An apparatus comprising:
a scattering antenna having a first plurality of scattering elements, each of the scattering elements in the first plurality of scattering elements having an individual electromagnetic response to an incident electromagnetic wave, and wherein the scattering antenna is configured to produce a first radiation field responsive to the incident electromagnetic wave;
a reflector antenna arranged to receive at least a portion of the first radiation field, the reflector antenna having a second plurality of scattering elements, wherein the reflector antenna is responsive to reflect a portion of the first radiation field to produce a second radiation field different from the first radiation field;
a detector configured to receive at least a portion of the second radiation field; and
circuitry operably connected to the detector and configured to reconstruct an image of a scene that is substantially within at least one of the first and second radiation fields using a compressive imaging algorithm.

12. The apparatus of claim 11 wherein each scattering element in the first plurality of scattering elements has an adjustable individual electromagnetic response, and wherein the circuitry is operably connected to the first plurality of scattering elements to provide a set of adjustments selected according to the compressive imaging algorithm.

13. The apparatus of claim 11 wherein each scattering element in the second plurality of scattering elements has an adjustable individual electromagnetic response, and wherein the circuitry is operably connected to the second plurality of scattering elements to provide a set of adjustments selected according to the compressive imaging algorithm.

14. The apparatus of claim 11 further comprising a source configured to produce the incident electromagnetic wave, the incident electromagnetic wave having a frequency, and wherein the circuitry is operably connected to the source to vary the frequency of the incident electromagnetic wave according to the compressive imaging algorithm.

15. The apparatus of claim 11 wherein each scattering element in the first plurality of scattering elements has an adjustable individual electromagnetic response, and further comprising:
circuitry operably connected to the first plurality of scattering elements to provide a first set of adjustments.

16. The apparatus of claim 15 wherein the first set of adjustments is selected to produce a set of beam patterns corresponding to the first radiation field.

17. The apparatus of claim 15 wherein each scattering element in the second plurality of scattering elements has an adjustable individual electromagnetic response, and further comprising:
circuitry operably connected to the second plurality of scattering elements to provide a second set of adjustments.

18. The apparatus of claim 17 wherein the first and second set of adjustments are selected to produce a set of beam patterns corresponding to the second radiation field.

19. The apparatus of claim 17 further comprising:
a source configured to produce the incident electromagnetic wave, the incident electromagnetic wave having a frequency; and
circuitry is operably connected to the source to provide a third set of adjustments, wherein the third set of adjustments are configured to vary the frequency of the incident electromagnetic wave.

20. The apparatus of claim 19 wherein the first, second, and third set of adjustments are selected to produce a set of beam patterns corresponding to the second radiation field.

21. The apparatus of claim 11 wherein each scattering element in the second plurality of scattering elements has an adjustable individual electromagnetic response, and further comprising:
circuitry operably connected to the second plurality of scattering elements to provide a set of adjustments.

22. The apparatus of claim 21 wherein the set of adjustments is selected to produce a set of beam patterns corresponding to the second radiation field.

23. The apparatus of claim 11 further comprising:
a source configured to produce the incident electromagnetic wave, the incident electromagnetic wave having a frequency; and
circuitry operably connected to the source to provide a set of adjustments, wherein the set of adjustments are configured to vary the frequency of the incident electromagnetic wave to produce a set of beam patterns corresponding to the first and second radiation fields.

24. An apparatus comprising:
a source configured to produce an incident electromagnetic wave;
a reflector antenna arranged to receive the incident electromagnetic wave, the reflector antenna having a first plurality of scattering elements, wherein the reflector antenna is responsive to reflect a portion of the incident electromagnetic wave to produce a first radiation field;
a scattering antenna configured to receive at least a portion of the first radiation field, the scattering antenna having a second plurality of scattering elements, each of the scattering elements in the second plurality of scattering elements having an individual electromagnetic response to an incident electromagnetic wave; and
wherein the scattering antenna includes a waveguide supportive of a discrete set of modes, and wherein the scattering antenna is configured to produce a first set of radiation field patterns corresponding to the set of modes.

25. An apparatus comprising:
a source configured to produce an incident electromagnetic wave;
a reflector antenna arranged to receive the incident electromagnetic wave, the reflector antenna having a first plurality of scattering elements, wherein the reflector antenna is responsive to reflect a portion of the incident electromagnetic wave to produce a first radiation field;
a scattering antenna configured to receive at least a portion of the first radiation field, the scattering antenna having a second plurality of scattering elements, each of the scattering elements in the second plurality of scattering elements having an individual electromagnetic response to an incident electromagnetic wave;
a detector operably connected to the scattering antenna; and
circuitry operably connected to the detector and configured to reconstruct an image of a scene that is substantially within the first radiation field using a compressive imaging algorithm.

26. The apparatus of claim 25 wherein each scattering element in the first plurality of scattering elements has an adjustable individual electromagnetic response, and wherein the circuitry is operably connected to the first plurality of scattering elements to provide a set of adjustments selected according to the compressive imaging algorithm.

27. The apparatus of claim 25 wherein each scattering element in the second plurality of scattering elements has an adjustable individual electromagnetic response, and wherein the circuitry is operably connected to the second plurality of scattering elements to provide a set of adjustments selected according to the compressive imaging algorithm.

28. The apparatus of claim 25 wherein the incident electromagnetic wave has a frequency, and wherein the circuitry is operably connected to the source to vary the frequency of the incident electromagnetic wave according to the compressive imaging algorithm.