Patent Application
20240204405
Example embodiments generally relate to metasurface technology and, in particular, relate to dynamically controllable metasurfaces.
Innovation in the area of metamaterials continues to accelerate with new properties and associated applications being regularly developed. Metamaterials, which are engineered materials that exhibit properties not found in naturally occurring materials, are typically constructed of constituent components that can be repeated to form a sheet, which may be referred to as a metasurface. Such metamaterials are often developed to have properties that generate or affect electromagnetic fields, and thereby exhibit an electromagnetic field response to a reflected, transmitted, or absorbed electromagnetic field. In this regard, some metamaterials have been designed to exhibit a response that blocks, absorbs, enhances, or even bends electromagnetic waves. As such, metamaterials can offer solutions and achieve benefits that were simply unavailable through the use of conventional materials. While numerous metamaterials and associated metasurfaces have been developed or used in a variety of applications, there continues to be a desire and need to expand dynamic control of the behavior of metasurfaces.
Although some early implementations of metamaterials and metasurfaces have matured, new concepts in the field has continued to fuel innovation. As more technologies emerge from the ever-branching development process, dynamic metasurfaces have excelled as a promising means to dexterously manipulate electromagnetic waves. While passive metasurfaces have found homes in several applications, e.g., microwave imaging and infrared lenses, their dynamic counterparts have been shown to provide added flexibility, enabling them to adapt for situation specific demands.
According to some example embodiments, a metasurface system is provided that may include a metasurface device including at least one metasurface unit cell, a control interface operably coupled to the metasurface device, and control circuitry configured to output a control signal for delivery to the metasurface unit cell to control operation of the metasurface unit cell. The metasurface unit cell may include a first metasurface sub-cell configured to exhibit a first resonant electromagnetic field (EMF) response and a second metasurface sub-cell configured to exhibit a second resonant EMF response. The first metasurface sub-cell may include a first patterned layer and a first variable impedance element operably coupled to the first patterned layer. The first variable impedance element may be configured to, in response to receipt of a first control signal based on a control signal from the control circuitry, change a first impedance of the first metasurface sub-cell based on the first control signal to change the first EMF response. The second metasurface sub-cell may include a second patterned layer and a second variable impedance element. The second variable impedance element may be configured to, in response to receipt of a second control signal based on a control signal from the control circuitry, change a second impedance of the second metasurface sub-cell based on the second control signal to change the second EMF response. The first metasurface sub-cell and the second metasurface sub-cell may be disposed in a cascaded configuration such that first EMF response and the second EMF response couple to exhibit an integrated EMF response for the metasurface unit cell.
According to some example embodiments, a metasurface unit cell for a metasurface device is provided. The metasurface unit cell may include a first metasurface sub-cell configured to exhibit a first resonant electromagnetic field (EMF) response and a second metasurface sub-cell configured to exhibit a second resonant EMF response. The first metasurface sub-cell may include a first patterned layer and a first variable impedance element operably coupled to the first patterned layer. The first variable impedance element may be configured to, in response to receipt of a first control signal, change a first impedance of the first metasurface sub-cell based on the first control signal to change the first EMF response. The second metasurface sub-cell may include a second patterned layer and a second variable impedance element, the second variable impedance element being configured to, in response to receipt of a second control signal, change a second impedance of the second metasurface sub-cell based on the second control signal to change the second EMF response. The first metasurface sub-cell and the second metasurface sub-cell may be disposed in a cascaded configuration such that first EMF response and the second EMF response couple to exhibit an integrated EMF response for the metasurface unit cell.
According to some example embodiments, a method for exhibiting an electromagnetic field (EMF) response from a metasurface unit cell is provided. The method may include receiving a first control signal at a first variable impedance element of a first metasurface sub-cell of the metasurface unit cell and receiving a second control signal at a second variable impedance element of a second metasurface sub-cell of the metasurface unit cell. The method may further include independently modifying a first EMF response exhibited by the first metasurface sub-cell based on the first control signal, and independently modifying a second EMF response exhibited by the second metasurface sub-cell based on the second control signal. The method may also include exhibiting an integrated EMF response by the metasurface unit cell based on coupling of the first EMF response with the second EMF response due to the first metasurface sub-cell and the second metasurface sub-cell being disposed in a cascaded configuration. The integrated EMF response may be controllably tuned by the first control signal and the second control signal to a desired magnitude and phase.
Having thus described some example embodiments in general terms, reference will now be made to the accompanying drawings, which are not necessarily drawn to scale, and wherein:
Some non-limiting, example embodiments now will be described more fully hereinafter with reference to the accompanying drawings, in which some, but not all example embodiments are shown. Indeed, the examples described and pictured herein should not be construed as being limiting as to the scope, applicability or configuration of the present disclosure. Rather, these example embodiments are provided so that this disclosure will satisfy applicable legal requirements. Like reference numerals refer to like elements throughout. As used herein, operable coupling should be understood to relate to direct or indirect connection that, in either case, enables functional interconnection of components that are operably coupled to each other.
Following from the background above, some example embodiments described herein include a dynamic metasurface that is configured to be tuned for target applications to exhibit an electromagnetic field (EMF) response that is tailored for magnitude and phase. As used herein, an EMF response may be a reflection, transmission, or absorption of electromagnetic energy, where the metasurface operates to contribute to the EMF response. In this regard, a unit cell of a metasurface device may include, according to some example embodiments, two dynamic metasurface sub-cells structured in a cascaded configuration, and the sub-cells may operate, separately, as resonators to affect fields that couple to achieve desired response properties (e.g., reflection, transmission, or absorption properties) and a desired electromagnetic field (EMF) response. According to some example embodiments, a cascaded configuration may be one where the sub-cells are aligned and physically coupled to each other, and, possibly also physically coupled to a common substrate, a common ground plane, a common printed circuit board (PCB), or the like. To be dynamic, the metasurface sub-cells may include variable impedance elements that can be controlled to modify the response properties of the metasurface device. Such variable impedance elements may be controlled, for example, to change capacitance or inductance to realize a modification to the impedance of the metasurface sub-cell. While a number of components may be used to implement such a controlled variable impedance, according to some example embodiments, a varactor diode or varicap may be used. In this regard, by changing the voltage biasing of the varactor diode, the capacitance of the varactor diode may be changed, thereby changing the impedance of the metasurface sub-cell and the sub-cell's response properties.
As such, control circuitry may be implemented to control the impedance of the variable impedance elements (e.g., via provision of control signals to be used, for example, as biasing voltages) to exhibit desired response properties for the metasurface device. According to some example embodiments, the coupling of the fields from the cascaded sub-cells and the ability to control of the impedance of the sub-cells may permit both the magnitude and phase to be independently tuned, which is particularly useful in communications modulations methods.
While, according to some example embodiments, a unit cell of a metasurface device may include two cascaded, dynamic sub-cells, example embodiments of a metasurface device may have any number of cells structured as cascaded layers of cells. In other words, a plurality of a two-dimensional metasurfaces included of metasurface cells according to some example embodiments, may be constructed in a cascaded configuration and controlled to output a desired EMF response for the metasurface device. According to some example embodiments, a connectivity interface may be implemented in support of a certain control scheme. In this regard, for example, a control scheme may be implemented with an associated connectivity interface to permit each, individual cell to be controlled. Alternatively, according to some example embodiments, a control scheme may be implemented with an associated connectivity interface that supports control of the cells on a cell or sub-cell layer basis. In other words, a connectivity interface may be structured to electrically connect common nodes for each of the unit cells on a given cell layer, and, as such, each cell on that cell layer may be controlled in the same manner. Alternatively, according to some example embodiments, a control scheme and connectivity interface may be implemented that causes, for example, all cells (regardless of position or layer) of the metasurface device to operate in a common manner. As such, a variety of control schemes may be implemented, which may include the schemes that individually control cells differently, schemes that define groups of cells as super cells that are controlled in a common manner or in a uniquely coordinated manner, schemes that define cells as function of their spatial positioning, such as rings or loops of cells, concentric or nested rings or loops of cells, or the like. In this regard, it is understood that by having cells with individual addressability provides the most flexibility for implementing control schemes and even control schemes that may change as a function of time. However, to minimize cost of construction, for example, the structure of the connectivity interface 130 may be designed to implement the control schemes that are appropriate for a specific application. In other words, given a particular application, it may be determined that a more simplified control scheme and connectivity interface may be sufficient for the application and therefore certain costs and complexities of the metasurface device may be avoided.
According to some example embodiments, the implementation of a metasurface system that includes a metasurface device and control circuitry that is capable of tuning both a phase and magnitude response of the device may be used in a variety of contexts. In this regard, the metasurface system may be configured to operate in the radio-frequency (RF) spectrum as, for example, a communications device. Moreover, reconfigurable intelligent surfaces can be realized that are valuable for microwave imaging, beam steering reflectarrays, tunable RF lenses, wireless power transfer, and next-generation adaptive antennas.
Some example embodiments of metasurface devices described herein may operate to manipulate electromagnetic fields by leveraging a metal patterned layer that relies on subwavelength patterning to realize a tailored EMF response. Moreover, while bulk material properties of a two-dimensional (2D) metasurface have a clear impact on the operation of a metasurface device, the surface impedance or a collection of polarizabilities or susceptibilities of the metasurface device may also have a significant impact on the operation of the device. Accordingly, such a description of the metasurface may be used to facilitate, for example, a more simplified approach to both modeling and fabrication. According to some example embodiments, a hybrid modeling and fabrication approach may be used where several cell layers of 2D metasurfaces, as described herein, are cascaded to provide more robust control while avoiding the complications of volumetric fabrication. Such cascaded metasurfaces, according to some example embodiments, may also be implemented as Huygens' metasurfaces to balance electric and magnetic dipole moments and create a robust physics layer that brings electromagnetic equivalence principles into practice.
According to various example embodiments, the inclusion of multiple controllable sub-cells of a metasurface cell may create additional degrees of freedom for the behavior of a metasurface device. Using these degrees of freedom in implementation of example embodiments, the phase and magnitude response of a metasurface can be separately tuned. Due to the inherent coupling of the magnitude and phase in a passive resonator implementation, significant design constraints arise when attempting to perform such tuning in a passive implementation. Moreover, such passive implementations do not provide any dynamic capability for in situ modification of the response of a metasurface. Given their passive nature, such passive resonator implementations are also subject to Kramers-Kronig relations, which fundamentally limit the device's bandwidth performance. Accordingly, the added versatility of, for example, a multilayered dynamic metasurface device, according to some example embodiments, is well suited to address the need for magnitude and phase tuning, while also allowing for thin and convenient form factor construction.
As mentioned above, according to some example embodiments, a metasurface device may be constructed that is built on cascaded, dynamic metasurfaces having a unit cell that includes two sub-cell layers and, therefore, two tunable resonances. The two resonances of the unit cell may be separately controlled by a control signal provided to each of the sub-cells. In some example embodiments, each sub-cell may receive a control signal, which may be individual to the sub-cell or shared with a number of sub-cells. According to some example embodiments, respective desired voltages may be applied based on the control signals, which may be modified (similar to a knob implementation) to allow for enhanced control over magnitude and phase response. The control signals, according to some example embodiments, may be modulated or analog signals for dynamically controlling the sub-cells. According to some example embodiments, to provide improved control over the response magnitude, a series resistor may be included in the variable impedance elements of one of the sub-cell layers (as further described below), which may enable the ability to modify the response phase of the metasurface without affecting the response magnitude (and vice versa). Such behavior is favorable for a wide array of applications, e.g., holography and communications.
As such, according to some example embodiments, a cascaded dynamic metasurface with multiple control points is described that can provide augmented capabilities. By including multiple controls within a single metasurface or metasurface device, more degrees of freedom can be leveraged, and the increased degrees of freedom can be optimized, for example, jointly with the static geometry, to provide added functionality. According to some example embodiments, a system with a plurality of cascaded dynamic sub-cells is provided, where each dynamic sub-cell layer possesses tunable elements, referred to herein as variable impedance elements. Such tunable elements may operate in collaboration with, for example, patch-like elements that can be tuned with, for example, a varactor diode. According to some example embodiments, a resistor may also be included to add asymmetry in any resonance loss provided by each layer. Additionally, in consideration of the structure, response properties of the metasurface can be monitored to implement an ability to independently tune a magnitude and a phase from the single, in some cases, electrically thin surface. Tuning the magnitude and phase separately, a widely sought-after behavior, can be implemented, as described herein, in multiple communications modulation methods including phase-shift keying and 16-point quadrature amplitude modulation.
Having described some aspects of example embodiments, reference is now made to
Accordingly, based on the number of individual control signals required for a given implementation, the control circuitry 20 may be configured to output the respective control signals to the control interface 30 for delivery to the metasurface device 40. According to some example embodiments, the control circuitry 20 may be configured to receive inputs, for example, from a communications interface or a user interface and perform responsive actions, based on the inputs, such as provide outputs in the form of control signals to the metasurface device 40. The control circuitry 20 may be electronic circuitry configured to selectively output control signals for use in operating the metasurface device 40 for a given application. The control circuitry 20 may be disposed on a common board or within a common housing with the metasurface device 40. Although not shown in
According to some example embodiments, the control circuitry 20 may be embodied as a single integrated circuit including processing circuitry with one or more processors 22 (or processor cores) and memory 24. The control circuitry 20 may be embodied as a circuit chip (e.g., an integrated circuit chip, such as a field programmable gate array (FPGA), an application specific integrated circuit (ASIC), or the like) configured (e.g., with hardware, software, or a combination of hardware and software) to perform operations described with respect to the control circuitry 20 provided herein. According to some example embodiments, the control circuitry 20 may be configured to execute instructions stored in the memory or otherwise accessible to the control circuitry 20. As such, whether configured by hardware or by a combination of hardware and software, the control circuitry 20 may represent an entity (e.g., physically embodied in circuitry—in the form of control circuitry) capable of performing operations according to example embodiments while configured accordingly. Thus, for example, when the control circuitry 20 is embodied by or includes an ASIC, FPGA, or the like, the control circuitry 20 may be specifically configured hardware for conducting the operations described herein. Alternatively, as another example, when the control circuitry 20 is embodied as an executor of software instructions, the instructions may specifically configure the control circuitry 20 to perform the operations described herein. According to some example embodiments, the control circuitry 20 may include one or more physical packages (e.g., chips) including materials, components, wires, or the like on a structural assembly (e.g., a baseboard). Further, in some example embodiments, the control circuitry 20 may be a configuration of components including some analog components, such as, for example, analog filters and modulators. Further, operational amplifiers and other passive components, such as resistors and capacitors, may also be included to support the operation and functionalities performed by the control circuitry 20 as described herein. According to some example embodiments, the control circuitry 20 may be configured to perform signal conditioning and processing using either analog or digital techniques.
In some example embodiments, the memory 24 of the control circuitry 20 may include one or more non-transitory memory devices such as, for example, volatile or non-volatile memory that may be either fixed or removable. The memory may be configured to store information, data, applications, instructions or the like for enabling, for example, execution of procedures and the like to carry out various functions in accordance with example embodiments. For example, the memory 24 could be configured to buffer input data for processing by, for example, the processing circuitry of the control circuitry 20. Additionally or alternatively, the memory 24 may be configured to store instructions for execution by the control circuitry 20. Among the contents of the memory, applications may be stored for execution by the control circuitry 20 in order to carry out the functionality associated with a given application.
Referring now to
The example metasurface unit cell 100 may be, for example, a component of the metasurface device 40, which may, according to some example embodiments, have one or more metasurface unit cells arranged in a variety of structural configurations. In this regard, according to some example embodiments, the metasurface unit cell 100 may be a dual-resonance unit cell that operates based on the coupling of two resonance fields that result from the cascaded metasurface sub-cells 101 and 102. According to some example embodiments, the metasurface sub-cells may be considered cascaded because the sub-cells are stacked with one over the other in an overlapped configuration. According to some example embodiments, the metasurface sub-cells 101 and 102 may be cascaded such that a patterned layer of each of the sub-cells is disposed on different parallel planes. Further, according to some example embodiments, the patterned layers of each of the metasurface sub-cells of the metasurface unit cell 100 may be aligned such that a center line 190 that passes through a centroid 191 of the patterned layer 110 of the metasurface unit cell 100 and a centroid of the patterned layer 150 of the metasurface unit cell 100 may be perpendicular to respective planes of the patterned layer 110 and the patterned layer 150. As such, the cascaded metasurface sub-cells 101 and 102 may be aligned and parallel with each other to exhibit interacting EMF responses that allow for control of both the magnitude and phase of the integrated, overall EMF response of the metasurface unit cell 100. According to some example embodiments, the metasurface sub-cells 101 and 102 may be constructed, for example, on opposite sides of a printed circuit board (PCB).
The metasurface unit cell 100 may therefore include a metasurface sub-cell 101 (e.g., a first metasurface sub-cell), a metasurface sub-cell 102 (e.g. a second metasurface sub-cell), a connectivity interface 130, a spacer layer 160, and a ground plane 170. The metasurface sub-cell 101 may include a patterned layer 110 (e.g., first patterned layer) and a dielectric layer 120 (e.g., first dielectric layer). The metasurface sub-cell 102 may include a dielectric layer 140 (e.g., second dielectric layer) and a patterned layer 150 (e.g., second patterned layer). With respect to the example embodiment of the metasurface unit cell 100, the layers from top to bottom, as best seen in
Accordingly, the metasurface sub-cell 101 and the metasurface sub-cell 102 may be constructed or disposed on the spacer layer 160 and the ground plane 170. In this regard, the spacer layer 160 and the ground plane 170 may embody a backplane or substrate for the metasurface sub-cells 101 and 102. The spacer layer 160 may include a dielectric material that has sufficient insulating properties, based on the type of material used and the thickness of the material used, to isolate the ground plane 170 from, for example, the patterned layer 150 of the metasurface sub-cell 102 and the other components of the metasurface sub-cell 101 and the metasurface sub-cell 102. The ground plane 170 may operate as a convenient current sink and as a backplane shielding element for certain EMF emissions. According to some example embodiments, the ground plane 170 may be formed as a conductive sheet that spans the base of the metasurface unit cell 100. The ground plane 170 may, according to some example embodiments, be formed of a metal, such as, for example, copper.
As mentioned above, the metasurface unit cell 100 may include the metasurface sub-cell 101 and the metasurface sub-cell 102. In the example embodiment of the metasurface unit cell 100, the metasurface sub-cell 101 includes a patterned layer 110, a plurality of variable impedance elements (e.g., variable impedance elements 112 and 114), and a dielectric layer 120. The patterned layer 110 may be, for example, an etched, stamped, or cut layer of metal having a desired architecture for exhibiting an EMF response in the form of a resonance field for the metasurface sub-cell 101. According to some example embodiments, the patterned layer 110 may be formed of copper, aluminum, gold, a conductive alloy, a conductive composite material, or the like. According to some example embodiments, the architecture of the patterned layer 110 may include two electrically separate regions or portions that are electrically connected via the variable impedance elements.
In this regard, the patterned layer 110 may include an outer portion 111 and an inner portion 115. According to some example embodiments, the outer portion 111 may be a perimeter conductive band or trace for the patterned layer 110. While the outer portion 111 is shown as being a rectangular perimeter band in
According to some example embodiments, the outer portion 111 or the inner portion 115 may include a plurality of leads that extend from one of the portions to the other of the portions to facilitate connectivity of the variable impedance elements between the outer portion 111 and the inner portion 115. In this regard, the metasurface sub-cell 101 may include a plurality of variable impedance elements. In the example embodiment of metasurface sub-cell 101, four variable impedance elements 112, 114, 116, and 118 are included. As shown in
As mentioned above, the variable impedance elements 112, 114, 116, and 118 may be controllable to modify an impedance of the element and thereby change the impedance and EMF response of the metasurface sub-cell 101. The variable impedance elements 112, 114, 116, and 118 may include one or more components that are collectively configured to perform the functionality of impedance modification. In this regard, according to some example embodiments, each variable impedance elements 112, 114, 116, and 118 may include a variable reactance element that is configured to controllably modify the capacitance or inductance of the variable reactance element. In this regard, according to some example embodiments, the variable reactance element may be controlled via a control connection (e.g., a gate connection) as a three terminal element. Alternatively, the variable reactance element may be two terminal element that is controlled via, for example, voltage biasing (e.g., reverse biasing) across the two terminals. In this regard, for example, according to some example embodiments, each variable impedance element 112, 114, 116, and 118 may include a varactor diode or a varicap. The varactor diode may have a controllable capacitance based on voltage biasing provided to the varactor diode as a control signal (e.g., from the control circuitry 20). According to some example embodiments, the implementation of varactor diodes may be beneficial due to an ability to tune the capacitance while drawing minimal current, which can support the feasible construction and operation of large arrays of metasurface cells operating at relatively high frequencies. In this regard, according to some example embodiments, the capacitance of the varactor diode may vary as a function of the reverse voltage biasing that is applied to the varactor diode. As such, the changes to the capacitance of the varactor diode result in changes to the impedance of the metasurface sub-cell 101, thereby modifying the resonance of the metasurface sub-cell 101 and the EMF response of the metasurface sub-cell 101.
Use of a varactor diode is just one example of a component that may be included in, or embodied by, a variable impedance element, such as variable impedance elements 112, 114, 116, and 118, to change the impedance of the device. According to some example embodiments, the variable impedance element may include other components that facilitate the ability to dynamically change the impedance of the device. In this regard, for example, a liquid crystal device may be included in some example embodiments. Additionally or alternatively, a p-i-n diode may be included in a variable impedance element in some example embodiments. Moreover, a phase change material may be additionally or alternatively included for changing impedance according to some example embodiments. In some example embodiments, a piezo device may additionally or alternatively included according to some example embodiments. According to some example embodiments, the variable reactance element may be a switchable device that may be controlled to introduce a binary (two states) or a non-binary (many states) change to the impedance (i.e., reactance or resistance) of the device. In this regard, for example, a micro-electromechanical system (MEMS) device may be employed to control impedance. As such, according to some example embodiments, combinations of active and passive components may be included in a variable impedance device. For example, a switching element (e.g., a switch, transistor, selector, multiplexer, etc.) having two or more connectivity states may switchably introduce static or variable reactance or resistance devices into electrical connection to introduce different impedance states.
According to some example embodiments, the variable impedance elements 112, 114, 116, and 118 may include components that have resistive properties. According to some example embodiments, the variable impedance elements 112, 114, 116, and 118 may include or be embodied by a variable resistor that may be controlled to change the impedance of the metasurface sub-cell 101 as a change in resistance. According to some example embodiments, rather than a continuous change variable resistor, a variable resistor may be included that supports discrete, step value changes as a “lump” resistance change to support tuning. In this regard, according to some example embodiments, a control signal may include component control signals to thereby control particular components of a variable impedance element (e.g., a first component control signal for a varactor of a variable impedance element and a second component control signal for a variable resistor of the same variable impedance element). In some example embodiments, the variable impedance elements 112, 114, 116, and 118 may include a fixed-value resistor connected, for example, in series with a variable reactance element. The incorporation of the fixed-value resistor may be determined based on a desired EMF response for the metasurface unit cell 100 in consideration of the effects of the EMF response provided by the metasurface sub-cell 102. As such, due to the coupling of the fields resulting from the metasurface sub-cell 101 and the metasurface sub-cell 102, the component selection may be interrelated, requiring consideration of their aggregate operational effects.
The dielectric layer 120 of the metasurface sub-cell 101 may be formed of a dielectric material that, for example, is an insulator to the patterned layer 110 and may separate the patterned layer 110 from the connectivity interface 130. The dielectric layer 120 may include a material and have a thickness that supports the operation of the metasurface sub-cell 101. In this regard, the dielectric layer 120 may be configured to affect the EMF response of the metasurface sub-cell 101 and the metasurface sub-cell 102.
With respect to the metasurface sub-cell 102, the dielectric layer 140 may be structured in a same or similar manner as the dielectric layer 120, but positioned, for example, between the connectivity interface 130 and the patterned layer 150. Similar to the dielectric layer 120, the dielectric layer 140 may operate as insulator to the patterned layer 150 and may separate the patterned layer 150 from the connectivity interface 130. Additionally, the dielectric layer 140 may be configured to affect the EMF response of the metasurface sub-cell 102 and the metasurface sub-cell 101 similar to the dielectric layer 120.
The patterned layer 150 may be structured in a similar manner to the patterned layer 110. According to some example embodiments, the patterned layer 150 may be shaped in the same manner as the patterned layer 110. However, according to some example embodiments, the patterned layer 150 may be shaped differently to exhibit a desired resonance and EMF response for the metasurface sub-cell 102. Accordingly, the material and shape options for the patterned layer 150 may be same as those for the patterned layer 110 described above. In this regard, according to some example embodiments, the patterned layer 150 may include an outer portion 151 and an inner portion 155. Notably, with respect to the example embodiment of the patterned layer 150, the area of the inner portion 155 may be, for example, larger than the area of the inner portion 115, as best seen in
Similar to the metasurface sub-cell 101, the metasurface sub-cell 102 may also include a plurality of variable impedance elements that may connected between the outer portion 151 and the inner portion 155. Similar to the patterned layer 110, the patterned layer 150 may include leads or traces that facilitate connecting the variable impedance elements between the outer portion 151 and the inner portion 155. In the example embodiment of metasurface sub-cell 102, four variable impedance elements 152, 154, 156, and 158 are included. As shown in
Similar to the variable impedance elements of the metasurface sub-cell 101, the variable impedance elements 152, 154, 156, and 158 may be controllable to modify an impedance of the element and thereby change the EMF response of the metasurface sub-cell 102. The variable impedance elements 152, 154, 156, and 158 may include one or more components that are collectively configured to perform the functionality of impedance modification. In this regard, according to some example embodiments, each variable impedance element 152, 154, 156, and 158 may include a variable reactance element that is configured to controllably modify the capacitance or inductance of the variable reactance element. In this regard, according to some example embodiments, the variable reactance element may be controlled via a control connection (e.g., a gate connection) as a three terminal element. Alternatively, the variable reactance element may be two terminal element that is controlled via, for example, voltage biasing (e.g., reverse biasing). In this regard, for example, according to some example embodiments, each variable impedance element 152, 154, 156, and 158 may include a varactor diode or a varicap. As mentioned above, the varactor diode may have a controllable capacitance based on voltage biasing provided to the varactor diode as a control signal (e.g., from the control circuitry 20). In this regard, according to some example embodiments, the capacitance of the varactor diode may vary as a function of the reverse voltage biasing that is applied to the varactor diode. As such, the changes to the capacitance of the varactor diode may result in changes to the impedance of the metasurface sub-cell 102, thereby modifying the resonance of the metasurface sub-cell 102 and the EMF response of the metasurface sub-cell 102.
Use of a varactor diode is just one example of a component that may be included in, or embodied by, a variable impedance element, such as variable impedance elements 152, 154, 156, and 158, to change the impedance of the device. According to some example embodiments, the variable impedance element may include other components that facilitate the ability to dynamically change the impedance of the device. In this regard, for example, a liquid crystal device may be included in some example embodiments. Additionally or alternatively, a p-i-n diode may be included in a variable impedance element in some example embodiments. Moreover, a phase change material may be additionally or alternatively included for changing impedance according to some example embodiments. In some example embodiments, a piezo device may additionally or alternatively included according to some example embodiments. According to some example embodiments, the variable reactance element may be a switchable device that may be controlled to introduce a binary (two states) or a non-binary (many states) change to the impedance (i.e., reactance or resistance) of the device. In this regard, for example, a micro-electromechanical system (MEMS) device may be employed to control impedance. As such, according to some example embodiments, combinations of active and passive components may be included in a variable impedance device. For example, a switching element (e.g., a switch, transistor, selector, multiplexer, etc.) having two or more connectivity states may switchably introduce static or variable reactance or resistance devices into electrical connection to introduce different impedance states.
According to some example embodiments, the variable impedance elements 152, 154, 156, and 158 may include components that have resistive properties. According to some example embodiments, the variable impedance elements 152, 154, 156, and 158 may include or be embodied by a variable resistor that may be controlled to change the impedance of the metasurface sub-cell 101 as a change in resistance. According to some example embodiments, rather than a continuous change variable resistor, a variable resistor may be included that supports discrete, step value changes as a “lump” resistance change to support tuning. In this regard, according to some example embodiments, a control signal may include component control signals to thereby control particular components of a variable impedance element (e.g., a first component control signal for a varactor of a variable impedance element and a second component control signal for a variable resistor of the same variable impedance element). In some example embodiments, the variable impedance elements 152, 154, 156, and 158 may include a fixed-value resistor connected, for example, in series with a variable reactance element. The incorporation of the fixed-value resistor may be determined based on a desired EMF response for the metasurface unit cell 100 in consideration of the effects of the EMF response provided by the metasurface sub-cell 101. As such, due to the coupling of the fields resulting from the metasurface sub-cell 102 and the metasurface sub-cell 101, the component selection and operation may be interrelated, requiring consideration of the aggregate effects.
According to some example embodiments, the variable impedance elements of the metasurface sub-cell 101 may be the same or different from the variable impedance elements of the metasurface sub-cell 102. In this regard, according to some example embodiments, the variable impedance elements 112, 114, 116, and 118 may be, for example, single component devices embodied as a varactor diode. However, the variable impedance elements 152, 154, 156, and 158 may be different and need not be embodied by or include a varactor diode. In the example embodiments of the metasurface unit cell 100, the variable impedance elements 152, 154, 156, and 158 may be embodied as a varactor diode connected in series with a fixed-value resistor. As can be best seen in
In addition to the other design parameters described herein, the distance 105 may be a design parameter for the metasurface unit cell 100. In this regard, according to some example embodiments, a desired wavelength or range of wavelengths may be targeted for the operation of the metasurface unit cell 100 and the EMF response of the metasurface unit cell 100. The distance 105 between the metasurface sub-cell 101 and the metasurface sub-cell 102 may be factor that affects the EMF response. More specifically, according to some example embodiments, the distance 105 between the patterned layer 110 and the patterned layer 150 may be a factor that affects the EMF response. According to some example embodiments, the distance 105 may be selected to cause coupling between the EMF response exhibited by the metasurface sub-cell 101 and the metasurface sub-cell 102. According to some example embodiments, the distance 105 may cause near-field coupling between the metasurface sub-cell 101 and the metasurface sub-cell 102. Moreover, the distance 105 may be a function of the desired wavelength or range of wavelengths (e.g., one-quarter the length of the desired wavelength or one-quarter the length of a center wavelength).
As mentioned above, the metasurface unit cell 100 may also include a connectivity interface 130. In general, the connectivity interface 130 may be configured to provide electrical connectivity between the control circuitry 20 and the metasurface unit cell 100 for the delivery of control signals via the control interface 30. According to some example embodiments, the connectivity interface 130 may include one or more layers of connection traces and interlayer vias to form electrical connections between inputs, outputs, and components of the metasurface unit cell 100. In this regard, according to some example embodiments, the metasurface unit cell 100 may include a printed circuit board (PCB). The top surface of the PCB may include the patterned layer 110 with the variable impedance elements 112, 114, 116, and 118 affixed thereto, which is disposed on the dielectric layer 120 as the top dielectric layer of the PCB. The bottom surface of the PCB may include the patterned layer 150 with the variable impedance elements 152, 154, 156, and 158 affixed thereto, which is disposed on the dielectric layer 140 as the bottom dielectric layer of the PCB. The connectivity interface 130 may be disposed in one or more layers between the top dielectric layer and the bottom dielectric layer of the PCB. For simplicity of the drawings, the individual, discrete connectivity paths between the various components is not specifically shown. However, one of ordinary skill in the art would understand that single and multilayer PCB design can be used to route connections to various components on a board to support operation of the device that include the board.
The connectivity interface 130 may therefore operate to deliver control signals to desired connection points on the patterned layer 110 and the patterned layer 150. More specifically, the connectivity interface 130 may be configured to deliver control signals to the variable impedance elements to control the operation of the variable impedance elements to tune the EMF response of the metasurface unit cell 100. As such, where the variable impedance elements are, for example, three terminal elements, the connectivity interface 130 may be configured to deliver signals to a control terminal of the three-terminal variable impedance element. However, in example embodiments where the variable impedance elements are two terminal devices, the connectivity interface 130 may be configured to deliver control signals in the form of, for example, a voltage biasing across the two-terminal variable impedance element.
The example embodiment of metasurface unit cell 100 includes two-terminal variable impedance elements and therefore the connectivity interface 130 may be configured to connect to the patterned layer 110 and patterned layer 150 to apply a desired bias voltage across the variable impedance elements. In this regard, according to some example embodiments, for each control signal that is provided to the metasurface unit cell 100, the control circuitry 20 may output the respective control signal and the control interface 30 may include a conductor that delivers the respective control signal to the connectivity interface 130 for isolated delivery to one or more components of the metasurface unit cell 100. Moreover, as used herein, the application of a control signal may be a signal that is applied across two terminals of a component to, for example, apply a voltage bias to the component. Accordingly, a first potential may be applied by the connectivity interface 130 to the inner portion 115 through the via 132 (and connection point 113) and a second potential may be separately applied to the outer portion 111 either by a trace disposed on the patterned layer 110 or through the via 131 by the connectivity interface 130. As such, a control signal in the form of a voltage bias across the variable impedance elements 112, 114, 116, and 118 may be applied using the connectivity interface 130. Moreover, a third potential may be applied by the connectivity interface 130 to the inner portion 155 through the via 134 (and connection point 153) and a fourth potential may be separately applied to the outer portion 151 either by a trace disposed on the patterned layer 150 (which may be connected through a via to the patterned layer 110) or through the via 133 by the connectivity interface 130. As such, a control signal in the form of a voltage bias across the variable impedance elements 152, 154, 156, and 158 may be applied using the connectivity interface 130. As mentioned above, according to some example embodiments, the same control signal may be applied to the patterned layer 110 and the patterned layer 150, but the differences in the configurations of the metasurface sub-cell 101 and the metasurface sub-cell 102 may result in differing EMF responses from the respective sub-cells. As such, for example, if the variable impedance elements 152, 154, 156, and 158 include a fixed-resistance that is not included in the variable impedance elements 112, 114, 116, and 118, then the difference in the structures may result in a desired EMF response for the metasurface unit cell 100, while simplifying the architecture of the connectivity interface 130. Therefore, according to some example embodiments, to apply a desired voltage bias to both the variable impedance elements 112, 114, 116, and 118 and the variable impedance elements 152, 154, 156, and 158, a first potential may be applied to both the inner portion 115 and the inner portion 155 through, for example, vias 132 and 134, respectively, of the connectivity interface 130. Similarly, a second potential may be applied to both the outer portion 111 and the outer portion 151 through, for example, connection traces on the patterned layer 110 and/or the patterned layer 150 or through the vias 131 and 133, respectively, of the connectivity interface 130. In this manner, the same control signal may be leveraged for both the metasurface sub-cell 101 and metasurface sub-cell 102.
Referring specifically to
Now referring to
The control signals provided by the control circuitry 20 may be conditioned in a number of different ways. For example, the control circuitry 20 may configured to output the control signals as modulated signals with, for example, a DC offset. Further, according to some example embodiments, the control signals may be provided in association with a binary phase-shift keying (BPSK) approach, a quadrature phase shift keying (QPSK) approach, or a 16-point quadrature amplitude modulation approach.
With reference to
Having described some example embodiments involving the metasurface unit cell 100 in isolation,
In this regard,
According to some example embodiments, the control circuitry 20 may be connected to the outer portion 111, the outer portion 211, the outer portion 151, and the outer portion 251 via a first conductor of the control interface 30 and connected to the connectivity interface 130 via a second conductor of the control interface 30. As such, to operate the metasurface device 104, the control circuitry 20 may be configured to provide a control signal in the form of a bias potential on the first conductor and a bias potential on the second conductor. Moreover, in the example embodiment shown in
According to some example embodiments, the variable impedance elements 212, 214, 252, and 254 may be controlled by control signals delivered via the connectivity interface 130 and the vias 231, 232, 233, and 234. According to some example embodiments, the control circuitry 20 may implement a control scheme for the metasurface device 104 that includes common control of the cell 100 and the cell 200. As such, the same control signal (e.g., a first control signal) may control the operation of the variable impedance elements 112, 114, 212, and 214, based on the structure of the connectivity interface 130. Similarly, according to some example embodiments, the same control signal may control the operation of the variable impedance elements 152, 154, 252, and 254, based on the structure of the connectivity interface 130. Further, according to some example embodiments, the same control signal may be leveraged to provide control to all of the variable impedance elements 112, 114, 212, 214, 152, 154, 252, and 254 based on the structure of the connectivity interface 130. Accordingly, the control circuitry 20 may be configured to implement layer control of the cells 100 and 200, since both cells may be commonly controlled and the cells are disposed on a common cell layer. Such an example configuration provides a simplified approach to biasing the variable impedance elements in a coordinated manner using minimal control signals that may be shared across numerous cells. Moreover, the connectivity interface 130 may provide for cell layer level control across an entire layer of cells (e.g., dual-resonance cells) that may be disposed in a side-by-side fashion, as further described with respect to example embodiments of
Now referring to
Similar to the example embodiment of
In this regard, with reference to
As indicated by the conductors of the control interface 30, according to some example embodiments, each of the cell layers 420, 430, and 440 may be separately controlled by a respective control signal. As such, the EMF response from each of the cell layers 420, 430, and 440 may be different, even though the architectures of the cell layers 420, 430, and 440 may, for example, be the same. As described above, the combination of EMF responses from the sub-cells and cells of the metasurface device 410 may combine to exhibit a desired EMF response for the device 410. As an alternative to cell layer-based control, the control interface 30 and the connectivity interfaces 130 may be configured to permit any configuration for delivery of control signals. For example, each cell 450 of the metasurface device 410 may be individually addressable for delivery of a control signal. Alternatively, any combination of cells 450 may be connected in such as a manner as to be controlled together.
Now with reference to
Based on the forgoing, a metasurface unit cell 100 and associated control circuitry 20 have been described that, according to some example embodiments, enable in situ control of an EMF response exhibited by the metasurface unit cell 100 and a metasurface device 40 with respect to both magnitude and phase in real time. Conventional solutions offer magnitude-only or phase-only responses, and such conventional solutions may also incorporate an internal air gap that creates an undesirable increase in thickness and a high degree of losses. In contrast, some example embodiments described herein may be constructed to have a thickness that is less than 1/30 of the target wavelength, which can provide a single effective interface with reduced angular sensitivity. Moreover, in some example embodiments, only two biasing voltages may be required for controlling the metasurface unit cell 100, whereas some conventional solutions required more signals and biasing to perform lesser functionality. Additionally, as a contrast to some conventional solutions, the operation of some example embodiments may work in concert with a cooperative receiver, rather than directly on the incident signal, to deliver complex waveforms that, for example, emulate analog modulation.
Moreover, according to some example embodiments, a dynamic cascaded metasurface is provided that is configured to independently control a magnitude and phase for an EMF response. In this regard, some example embodiments are configured to dynamically tune two sub-cells independently for exhibiting a desired EMF response. According to some example embodiments, by changing, for example, only capacitances via the control of varactor diodes, continuous control of the resonance and loss of both fundamental modes can be realized. In this regard, the modification of sub-cell resonances can result in variation of the response magnitude and phase of the surface (e.g., the metasurface unit cell 100), and the control signals may operate to adjust the behavior of constituent components to achieve a desired response.
According to some example embodiments, the metasurface unit cell 100 may operate based on two degrees of freedom associated with respective control signals that support voltage biasing to control two resonant responses. Such biasing operates to control the impedance of a respective sub-cell, where the sub-cells may employ, for example, patch architectures and are cascaded or stacked. In this regard, when the two resonant modes are provided by the sub-cells of a metasurface unit cell with slightly different frequencies, the effects of the resonances may compound. Where the spectral response is dominated by one resonant mode, the EMF response may be primarily governed by that same resonant mode. However, when neither resonant mode is clearly dominant, the effects of both resonant modes may contribute to the response of the metasurface unit cell 100.
Referring now to
A coupled mode theory (CMT) model may be used to for independently coupling the two resonances to the incident wave, where each resonance is defined by a characteristic resonance frequency and absorption loss. Because the two sub-cells may be positioned in a subwavelength thickness, transmission-line theory can offer a valid approximation. However, in the absence of a more complex model, such a transmission-line model can lead to complex transcendental equations for the coupling coefficients, and may overlook some effects such as evanescent coupling between the sub-cells. As such, further abstraction may be performed using CMT. While some of details may be lost in such as refined framework, the model may still provide insights into the interplay between resonance frequencies that generalize beyond the specific unit-cell design and even into other domains of wave physics.
In this regard, a model for metasurface unit cell 100 may include two resonances that independently couple to the plane-wave radiation with strength K, and have a respective resonance frequency (ω0∓Δω/2) and absorption rates (γ0 and γ0+Δγ), respectively. The term Δω may capture a difference in resonance frequencies between the two modes, and Δγ may account for any difference in absorption. It is acknowledged that such a simplified model may not consider some effects, such as direct coupling between sub-cells and phase accumulation through the substrate (e.g., the spacer layer 160 and the ground plane 170). However, such a model can be useful due to its simplicity and ability to build intuition in the results.
The effect of various system parameters can be realized by adding contributions from each by sequentially adding the parameters one by one. Using this approach it is shown that when Δω=0 and Δγ=0, the model operates to provide a single resonance. As ω0 is varied relative to the incident frequency ω, the reflected signal undergoes a phase shift, but also an amplitude dip from passing through resonance. However, a one-to-one relationship still exists between amplitude and phase. When a constant Δω is introduced and ω0 is again varied, a phase shift of about 4π occurs resulting in about two amplitude points for each reflection phase. If the two resonant frequencies can be independently tuned, a solid area of the complex response, and this case reflection, map may be filled, including some amplitude bands where a full 2π of phase may be available. Finally, more absorption may be added to the second mode, and the two resonances may be independently varied. As a result, the maximum amplitude, where full phase coverage is available, increases.
Based on the foregoing, for the metasurface unit cell 100, the metasurface sub-cell 102 may include a variable impedance element with a varactor and a resistor to permit the sub-cell 102 to be varactor-tuned with the resistor in series with the varactor. For a resistance in series with a capacitance, as the capacitance increases, a redshift of the resonances occurs and current flows more freely through the resistor under radio frequency (RF) illumination. As a result, the power dissipation increases for a given voltage. In contrast with a p-i-n diode, which can be switched discretely between conductive and resistive states, use of a varactor-resistor series combination may allow for a continuous tuning of the effective losses. The inclusion of the resistance may increase the relative change in loss compared to the induced resonance shift by the capacitance change, thereby allowing more control over the amplitude.
For the metasurface unit cell 100, each dynamic sub-cell 101 and 102 may include, according to some example embodiments, a patterned layer (e.g., patterned layer 110 and patterned layer 150) with a square patch (e.g., inner portion 115 and inner portion 155) at a center and a thin metallic mesh around a perimeter (e.g., outer portion 111 and outer portion 151). The mesh and the patch may be connected on each side of the square shape with thin metal strips in line with a varactor diode on each side. A patterned layer for one of the sub-cells may also include a lumped resistor added between the strips and the mesh. According to some example embodiments, the bias voltage between the perimeter mesh and the patch may determine the effective capacitance of the varactor diode, and thus the resonance properties of the unit cell (i.e., the EMF response) may be modified in this manner. Since the varactor diode may consistently be in reverse bias, according to some example embodiments, a minimal steady-state current may flow through the resistor (e.g., resistor 53) due to a DC component of the biasing voltage. In between the two dynamic patterned layers 110 and 150, separated by the dielectric layers, the connectivity interface 130 may include, for example, a metallic grid (e.g. trace 180) rotated at 45 degrees, as shown in
According to some example embodiments, the resistance value for the resistors 53, 55, 57, and 59 (
As the capacitance (C2) of the metasurface sub-cell 102 is increased, a corresponding increase in current flow may occur (e.g., resistors 53, 55, 57, and 59) and the loss at resonance may increase to a point of reaching critical damping (perfect absorption) and then overdamping (phase going through zero instead of wrapping around ±π). Again, increasing C2 may also redshift the resonance slightly. As such, the metasurface device 40 may be brought back to resonance by then decreasing the capacitance (C1) in the metasurface sub-cell 101, as shown in
Since a direct relationship exists between the varactor diode's capacitance and the applied voltage, a C→V conversion may be performed based on characteristic information for the varactor diode, for example, provided in a data sheet for the varactor diode. This conversion may allow for improved comparisons with experimental results. For such a comparison, the graphs 1000 and 1010 of
Additionally, experimentation has been performed in a communications context using a number of differing modulation techniques with the metasurface unit cell 100. Results of such experimentation is shown in
Now referring to
Having described some example embodiments in the foregoing description, some additional example embodiments will now be described that are based the foregoing description. According to some example embodiments, a metasurface system is provided that may include a metasurface device including at least one metasurface unit cell, a control interface operably coupled to the metasurface device, and control circuitry configured to output a control signal for delivery to the metasurface unit cell to control operation of the metasurface unit cell. The metasurface unit cell may include a first metasurface sub-cell configured to exhibit a first resonant electromagnetic field (EMF) response and a second metasurface sub-cell configured to exhibit a second resonant EMF response. The first metasurface sub-cell may include a first patterned layer and a first variable impedance element operably coupled to the first patterned layer. The first variable impedance element may be configured to, in response to receipt of a first control signal based on a control signal from the control circuitry, change a first impedance of the first metasurface sub-cell based on the first control signal to change the first EMF response. The second metasurface sub-cell may include a second patterned layer and a second variable impedance element. The second variable impedance element may be configured to, in response to receipt of a second control signal based on a control signal from the control circuitry, change a second impedance of the second metasurface sub-cell based on the second control signal to change the second EMF response. The first metasurface sub-cell and the second metasurface sub-cell may be disposed in a cascaded configuration such that first EMF response and the second EMF response couple to exhibit an integrated EMF response for the metasurface unit cell.
Additionally, according to some example embodiments of the metasurface system, the metasurface unit cell may also include a connectivity interface operably coupled to first patterned layer and the second patterned layer to deliver the first control signal to the first patterned layer and the second control signal to the second patterned layer. Additionally, according to some example embodiments, via the connectivity interface, the first control signal may be applied as a first voltage bias across the first variable impedance element, and, via the connectivity interface, the second control signal is applied as a second voltage bias across the first variable impedance element.
Additionally or alternatively, according to some example embodiments of the metasurface system, the first variable impedance element may include a first variable reactance element, and the second variable impedance element may include a second variable reactance element and a resistive element.
Additionally or alternatively, according to some example embodiments of the metasurface system, the first variable impedance element may include a first varactor diode configured to change a first capacitance of the first varactor diode in response to the first control signal to thereby change the first impedance of the first metasurface sub-cell. Additionally, the second variable impedance element may include a second varactor diode configured to change a second capacitance of the second varactor diode in response to the second control signal to thereby change the second impedance of the second metasurface sub-cell.
Additionally or alternatively, according to some example embodiments of the metasurface system, the control circuitry may be configured to adjust the first control signal and the second control signal to independently change the first EMF response and the second EMF response to tune both a magnitude and a phase of the integrated EMF response exhibited by the metasurface unit cell.
Additionally or alternatively, according to some example embodiments of the metasurface system, a first centroid of the first patterned layer of the metasurface unit cell may be aligned with a second centroid of the second patterned layer, such that an center line through the first centroid and the second centroid is perpendicular to planes of the first patterned layer and the second patterned layer.
Additionally or alternatively, according to some example embodiments of the metasurface system, the metasurface device may include a plurality of metasurface cells including the metasurface unit cell. Further, the plurality of metasurface cells may be arranged in a first metasurface cell layer and a second metasurface cell layer. The first metasurface cell layer and the second metasurface cell layer may be disposed in a cascaded configuration such that the layers are physically coupled together and aligned. Additionally, the connectivity interface may include a dedicated electrical connection to each sub-cell of each metasurface cell within the plurality of metasurface cells. Further, via the control interface, the control circuitry may be configured to provide a dedicated control signal to each sub-cell of each metasurface cell within the plurality of metasurface cells via the dedicated electrical connections of the connectivity interface. Additionally or alternatively, the connectivity interface may include a first electrical connection that is electrically connected to each first metasurface sub-cell of each metasurface cell within the first metasurface cell layer, and a second electrical connection that is electrically connected to each second metasurface sub-cell of each metasurface cell within the first metasurface cell layer. Further, via the control interface, the control circuitry may be configured to provide the first control signal to the first electrical connection and the second control signal to second electrical connection, and, via the connectivity interface, each metasurface cell of the first metasurface cell layer may be commonly controlled by the first control signal and the second control signal.
Additionally or alternatively, according to some example embodiments of the metasurface system, the first patterned layer may include a first central patch portion and a first outer portion, wherein the first variable impedance element is electrically connected between the first central patch portion and the first outer portion. Additionally, the second patterned layer includes a second central patch portion and a second outer portion. Additionally, the second variable impedance element may include a variable reactance element and a resistive element. The variable reactance element and the resistive element may be electrically connected in series between the second central patch portion and the second outer portion.
According to some example embodiments, a metasurface unit cell for a metasurface device is provided. The metasurface unit cell may include a first metasurface sub-cell configured to exhibit a first resonant electromagnetic field (EMF) response and a second metasurface sub-cell configured to exhibit a second resonant EMF response. The first metasurface sub-cell may include a first patterned layer and a first variable impedance element operably coupled to the first patterned layer. The first variable impedance element may be configured to, in response to receipt of a first control signal, change a first impedance of the first metasurface sub-cell based on the first control signal to change the first EMF response. The second metasurface sub-cell may include a second patterned layer and a second variable impedance element, the second variable impedance element being configured to, in response to receipt of a second control signal, change a second impedance of the second metasurface sub-cell based on the second control signal to change the second EMF response. The first metasurface sub-cell and the second metasurface sub-cell may be disposed in a cascaded configuration such that first EMF response and the second EMF response couple to exhibit an integrated EMF response for the metasurface unit cell.
Additionally, according to some example embodiments of the metasurface unit cell, the metasurface unit cell may further include a connectivity interface operably coupled to first patterned layer and the second patterned layer to deliver the first control signal to the first patterned layer and the second control signal to the second patterned layer. The connectivity layer may be configured to receive a control signal, route the control signal to the first patterned layer as the first control signal, and route the control signal (i.e., the same control signal) to the second patterned layer as the second control signal.
Additionally or alternatively, according to some example embodiments of the metasurface unit cell, via the connectivity interface, the first control signal may be applied as a first voltage bias across the first variable impedance element, and, via the connectivity interface, the second control signal may be applied as a second voltage bias across the first variable impedance element.
Additionally or alternatively, according to some example embodiments of the metasurface unit cell, the first variable impedance element may include a first variable reactance element, and, the second variable impedance element may include a second variable reactance element and a resistive element.
Additionally or alternatively, according to some example embodiments of the metasurface unit cell, the first variable impedance element may include a first varactor diode configured to change a first capacitance of the first varactor diode in response to the first control signal to thereby change the first impedance of the first metasurface sub-cell. Additionally, the second variable impedance element may include a second varactor diode configured to change a second capacitance of the second varactor diode in response to the second control signal to thereby change the second impedance of the second metasurface sub-cell.
Additionally or alternatively, according to some example embodiments of the metasurface unit cell, the first control signal may independently change the first EMF response and the second control signal may independently change the second EMF response to tune both a magnitude and a phase of the integrated EMF response exhibited by the metasurface unit cell.
Additionally or alternatively, according to some example embodiments of the metasurface unit cell, a first centroid of the first patterned layer of the metasurface unit cell may be aligned with a second centroid of the second patterned layer such that an center line through the first centroid and the second centroid is perpendicular to planes of the first patterned layer and the second patterned layer.
Additionally or alternatively, according to some example embodiments of the metasurface unit cell, the first patterned layer may include a first central patch portion and a first outer portion, and the first variable impedance element may be electrically connected between the first central patch portion and the first outer portion. Additionally, the second patterned layer may include a second central patch portion and a second outer portion, and the second variable impedance element may include a variable reactance element and a resistive element, and, the variable reactance element and the resistive element may be electrically connected in series between the second central patch portion and the second outer portion.
According to some example embodiments, a method for exhibiting an electromagnetic field (EMF) response from a metasurface unit cell is provided. The method may include receiving a first control signal at a first variable impedance element of a first metasurface sub-cell of the metasurface unit cell and receiving a second control signal at a second variable impedance element of a second metasurface sub-cell of the metasurface unit cell. The method may further include independently modifying a first EMF response exhibited by the first metasurface sub-cell based on the first control signal, and independently modifying a second EMF response exhibited by the second metasurface sub-cell based on the second control signal. The method may also include exhibiting an integrated EMF response by the metasurface unit cell based on coupling of the first EMF response with the second EMF response due to the first metasurface sub-cell and the second metasurface sub-cell being disposed in a cascaded configuration. The integrated EMF response may be controllably tuned by the first control signal and the second control signal to a desired magnitude and phase.
Many modifications and other embodiments of the metasurface device set forth herein will come to mind to one skilled in the art to which these inventions pertain having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the inventions are not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Moreover, although the foregoing descriptions and the associated drawings describe exemplary embodiments in the context of certain exemplary combinations of elements and/or functions, it should be appreciated that different combinations of elements and/or functions may be provided by alternative embodiments without departing from the scope of the appended claims. In this regard, for example, different combinations of elements and/or functions than those explicitly described above are also contemplated as may be set forth in some of the appended claims. In cases where advantages, benefits or solutions to problems are described herein, it should be appreciated that such advantages, benefits and/or solutions may be applicable to some example embodiments, but not necessarily all example embodiments. Thus, any advantages, benefits or solutions described herein should not be thought of as being critical, required or essential to all embodiments or to that which is claimed herein. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.
This application claims priority to and the benefit of prior-filed, co-pending U.S. Provisional Application No. 63/432,425 filed on Dec. 14, 2022, the entire contents of which are incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| 63432425 | Dec 2022 | US |
