rexresearch.com



Steven CUMMMER, et al.

Metamaterial Power Harvester







http://www.sciencedaily.com/releases/2013/11/131107154818.htm

Wireless Device Converts 'Lost' Energy Into Electric Power: Metamaterial Cells Provide Electric Power as Efficiently as Solar Panels



Nov. 7, 2013 — Using inexpensive materials configured and tuned to capture microwave signals, researchers at Duke University's Pratt School of Engineering have designed a power-harvesting device with efficiency similar to that of modern solar panels.

The device wirelessly converts the microwave signal to direct current voltage capable of recharging a cell phone battery or other small electronic device, according to a report appearing in the journal Applied Physics Letters in December 2013.

It operates on a similar principle to solar panels, which convert light energy into electrical current. But this versatile energy harvester could be tuned to harvest the signal from other energy sources, including satellite signals, sound signals or Wi-Fi signals, the researchers say.

The key to the power harvester lies in its application of metamaterials, engineered structures that can capture various forms of wave energy and tune them for useful applications.

Undergraduate engineering student Allen Hawkes, working with graduate student Alexander Katko and lead investigator Steven Cummer, professor of electrical and computer engineering, designed an electrical circuit capable of harvesting microwaves.

They used a series of five fiberglass and copper energy conductors wired together on a circuit board to convert microwaves into 7.3V of electrical energy. By comparison, Universal Serial Bus (USB) chargers for small electronic devices provide about 5V of power.

"We were aiming for the highest energy efficiency we could achieve," said Hawkes. "We had been getting energy efficiency around 6 to 10 percent, but with this design we were able to dramatically improve energy conversion to 37 percent, which is comparable to what is achieved in solar cells."

"It's possible to use this design for a lot of different frequencies and types of energy, including vibration and sound energy harvesting," Katko said. "Until now, a lot of work with metamaterials has been theoretical. We are showing that with a little work, these materials can be useful for consumer applications."

For instance, a metamaterial coating could be applied to the ceiling of a room to redirect and recover a Wi-Fi signal that would otherwise be lost, Katko said. Another application could be to improve the energy efficiency of appliances by wirelessly recovering power that is now lost during use.

"The properties of metamaterials allow for design flexibility not possible with ordinary devices like antennas," said Katko. "When traditional antennas are close to each other in space they talk to each other and interfere with each other's operation. The design process used to create our metamaterial array takes these effects into account, allowing the cells to work together."

With additional modifications, the researchers said the power-harvesting metamaterial could potentially be built into a cell phone, allowing the phone to recharge wirelessly while not in use. This feature could, in principle, allow people living in locations without ready access to a conventional power outlet to harvest energy from a nearby cell phone tower instead.

"Our work demonstrates a simple and inexpensive approach to electromagnetic power harvesting," said Cummer. "The beauty of the design is that the basic building blocks are self-contained and additive. One can simply assemble more blocks to increase the scavenged power."

For example, a series of power-harvesting blocks could be assembled to capture the signal from a known set of satellites passing overhead, the researchers explained. The small amount of energy generated from these signals might power a sensor network in a remote location such as a mountaintop or desert, allowing data collection for a long-term study that takes infrequent measurements.



http://scitation.aip.org/content/aip/journal/apl/103/16/10.1063/1.482447
DOI: 10.1063/1.4824473
Appl. Phys. Lett. 103, 163901 (2013)

A microwave metamaterial with integrated power harvesting functionality

Allen M. Hawkes, Alexander R. Katko1 and Steven A. Cummer
allen.hawkes@duke.edu

We present the design and experimental implementation of a power harvesting metamaterial. A maximum of 36.8% of the incident power from a 900 MHz signal is experimentally rectified by an array of metamaterial unit cells. We demonstrate that the maximum harvested power occurs for a resistive load close to 70 ohms in both simulation and experiment. The power harvesting metamaterial is an example of a functional metamaterial that may be suitable for a wide variety of applications that require power delivery to any active components integrated into the metamaterial.



Metamaterial particles having active electronic components and related methods
US2010289715

Inventor: CUMMER STEVEN A // POPA BOGDAN-IOAN

Metamaterial particles having active electronic components are disclosed. According to one aspect, a metamaterial particle in accordance with the subject matter disclosed herein can include a field sensing element adapted to sense a first field and adapted to produce a sensed field signal representative of the first field in response to sensing the first field. Further, the metamaterial particle can include an active electronic component adapted to receive the sensed field signal and adapted to produce a drive signal based on the sensed field signal. A field generating element can be adapted to receive the drive signal and adapted to produce a second field based on the drive signal.

TECHNICAL FIELD

[0003] The subject matter disclosed herein generally relates to metamaterials. More particularly, the subject matter disclosed herein relates to metamaterial particles having active electronic components and related methods.

BACKGROUND

[0004] Metamaterials are a new class of ordered composites that exhibit exceptional properties not readily observed in nature. These properties arise from qualitatively new response functions that are not observed in the constituent materials and result from the inclusion of artificially fabricated, extrinsic, low dimensional inhomogeneities, which may be referred to as "metamaterial particles". These artificial composites can achieve material performance beyond the limitations of conventional composites. To date, most of the scientific activity with regard to metamaterials has centered on their electromagnetic properties.

[0005] Metamaterials can be used to engineer electromagnetic properties of a material by embedding numerous small metamaterial particles in a host matrix. These particles can produce an electric or magnetic dipole moment in response to an applied field. Metamaterials have properties that could potentially be used to fabricate super lenses, miniaturized antennas, enhanced tunneling effect devices, and invisibility cloaks. Electric and magnetic metamaterials have been extensively analyzed theoretically, in simulations, and tested experimentally, and are currently built by putting together arrays of passive subwavelength resonant particles, such as split-ring-resonators (SRRs), omega particles, electric-field-coupled resonators (ELCs), and cut-wires.

[0006] The currents and charges in these passive, self-resonant circuits created in response to an applied electric or magnetic field near the resonant frequency are great enough to generate electric or magnetic dipole moments that are in turn great enough to substantially alter the effective permittivity or permeability of a medium composed of these particles. However, exploiting this strong response close to resonance usually means significant losses and strongly frequency dependent properties, two consequences undesirable in many potential metamaterial applications. For example, it has been shown both theoretically and experimentally that the smallest amount of loss could significantly influence the effectiveness of the evanescent wave enhancement property responsible for the super lens and enhanced tunneling effects. On the other hand, it has been shown that even modest loss tangents of 0.01 can rarely be achieved in these metamaterials. Also, due to their resonant nature, the inherent high dispersion of current metamaterials makes them useful only for narrow bandwidth applications.

[0007] Accordingly, for the reasons set forth above, it is desirable to provide metamaterial particles having reduced loss, lower dispersion, and higher bandwidth.

SUMMARY

[0008] According to one aspect, metamaterial particles having active electronic components are disclosed herein. A metamaterial particle can include a field sensing element adapted to sense a first field and adapted to produce a sensed field signal representative of the first field in response to sensing the first field. Further, the metamaterial particle can include an active electronic component adapted to receive the sensed field signal and adapted to produce a drive signal based on the sensed field signal. A field generating element can be adapted to receive the drive signal and adapted to produce a second field based on the drive signal.

[0009] According to another aspect, methods for providing a field in response to sensing another field are disclosed herein. A method in accordance with the subject matter disclosed herein can include providing a metamaterial particle comprising a field sensing element, an active electronic component, and a field generating element. At the field sensing element, a first field can be sensed, and a sensed field signal representative of the first field can be produced. At the active electronic component, the sensed field signal can be received, and a drive signal based on the sensed field signal can be produced. Further, at the field generating element, a second field can be produced based on the drive signal.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Preferred embodiments of the subject matter described herein will now be explained with reference to the accompanying drawings of which:

[0011] FIG. 1 is a schematic diagram of an exemplary metamaterial particle including an active electronic component and magnetic dipoles in accordance with an embodiment of the subject matter disclosed herein;

[0012] FIG. 2 is a schematic diagram of an exemplary metamaterial particle including an active electronic component and electric dipoles in accordance with an embodiment of the subject matter disclosed herein;

[0013] FIG. 3 is a schematic diagram of an exemplary metamaterial particle including an active electronic component, a magnetic dipole, and an electric dipole in accordance with an embodiment of the subject matter disclosed herein;

[0014] FIG. 4 is a schematic diagram of an exemplary metamaterial particle including an active electronic component, an electric dipole, and a magnetic dipole in accordance with an embodiment of the subject matter disclosed herein;

[0015] FIG. 5 is a schematic diagram of an exemplary metamaterial particle including an active electronic component, magnetic dipoles, and field amplifying elements in accordance with the subject matter disclosed herein;

[0016] FIG. 6 is a flow chart of an exemplary process for providing a field in response to sensing another field according to an embodiment of the subject matter disclosed herein;

[0017] FIG. 7 is a schematic diagram of a metamaterial particle having a field sensing element and a field generating element in accordance with the subject matter disclosed herein;

[0018] FIG. 8 is a circuit diagram of the magnetic particle shown in FIG. 6;

[0019] FIG. 9 is a graph showing effective permeability versus frequency resulting from an experiment conducted using a metamaterial particle including a 1W1000 amplifier in accordance with the subject matter disclosed herein;

[0020] FIG. 10 is a graph showing measured effective permeability versus frequency in experimental results obtained with a metamaterial particle in accordance with the subject matter disclosed herein;

[0021] FIG. 11 is a graph showing effective permeability versus frequency resulting from an experiment conducted using a metamaterial particle including a MAX2472 voltage buffer in accordance with the subject matter disclosed herein;

[0022] FIG. 12 is a graph showing theoretically achievable effective permeability in a metamaterial particle including an active electronic component in accordance with the subject matter disclosed herein;

[0023] FIG. 13 is a graph showing the magnetic susceptibility versus frequency in experiments conducted with a metamaterial particle containing field amplifying elements with the power to the amplifier turned off;

[0024] FIG. 14 is a graph showing the complex permeability versus frequency for the same metamaterial particle with the power to the amplifier turned on; and

[0025] FIG. 15 is a graph showing the transmission amplitude of a signal passing through an array of metamaterial particles in both directions.

   

    
 
 

DETAILED DESCRIPTION

[0026] Metamaterial particles are disclosed that employ active electronic components, field sensing elements and field generating elements. These metamaterial particles can overcome the inherent limitations of metamaterial particles employing only passive elements, such as loss, dispersion, and narrow bandwidth. The metamaterial particles described herein can reduce or control with greater flexibility limitations on loss and dispersion.

[0027] A metamaterial particle in accordance with the subject matter disclosed herein can include a field sensing element adapted to sense an applied field and adapted to produce a sensed field signal representative of the field in response to sensing the applied field. For example, the field sensing element can sense a magnetic or electric field and produce an electrical signal representative of the sensed field. The representative signal can be proportional to a magnitude and phase of the sensed field. Further, the metamaterial particle can include an active electronic component for receiving the sensed field signal and for producing a drive signal based on the sensed field signal. For example, the active electronic component can be an amplifier operable to produce a drive signal that is a function of the sensed field signal. A field generating element can receive the drive signal and produce another field based on the drive signal. For example, the field generating element can produce a magnetic or electric field in response to receiving the drive signal. Additional embodiments and examples of the metamaterial particles in accordance with the subject matter disclosed herein are provided hereinbelow.

[0028] As used herein, the term "active electronic component" refers to an electronic element having gain or directionality. Examples of active electronic components include any suitable semiconductor and any suitable signal or power amplifying component having an external power source such as a transistor, an operational amplifier, a parametric amplifier, a voltage amplifier, and a power amplifier. An active electronic component can be packaged in a discrete form with two or more connecting leads or metallic pads. Further, for example, an active electronic component can include at least one input and at least one output. The active electronic component can receive an input signal at an input terminal and can produce an output signal at its output terminal that is a function of the input signal. A power source can be operably connected to the active electronic component for providing power for input gain. In contrast to an active electronic component, a "passive electronic component" has neither gain nor directionality.

[0029] As used herein, the term "field" refers to one of or both a magnetic field and an electric field. A magnetic field is a field that permeates space and which exerts a magnetic force on moving electric charges and magnetic dipoles. Magnetic fields surround electric currents, magnetic dipoles, and changing electric fields. An electric field is a property that can be referred to as the space surrounding an electric charge or in the presence of a time-varying magnetic field.

[0030] As used herein, the term "field sensing element" refers to an element operable to sense a magnetic field and/or an electrical field and operable to generate a signal representative of the sensed field. Examples of a field sensing element include a magnetic dipole, such as a metallic loop, and an electric dipole, such as a pair of wires. In one example, in the presence of a magnetic field, a metallic loop can generate a current through the loop. The generated current can indicate the presence of the magnetic field. In another example, in the presence of an electrical field, a wire pair can generate a voltage difference between the wires. The generated voltage difference can indicate the presence of the electrical field.

[0031] As used herein, the term "field generating element" refers to an element operable to receive an input signal and operable to generate a magnetic field and/or an electrical field in response to the received input signal. Examples of a field generating element include a magnetic dipole, such as a metallic loop, and an electric dipole, such as a pair of wires. In one example, in response to receiving an input signal, a metallic loop can generate a magnetic field. The input to the metallic loop can be application of a voltage difference between ends of the loop. In another example, a wire pair can generate an electric field in response to receiving an input signal. The input to the wire pair can be application of a voltage difference between the wires. The generated field can be proportional to the input signal.

[0032] As used herein, the term "magnetic dipole" refers to a component having a closed circuit of electric current. For example, a magnetic dipole can be a wire loop. Application of current in the wire loop can produce a magnetic dipole moment that points through the loop. Thus, a magnetic field can be generated by application of the current. The magnitude of the magnetic dipole moment is equal to the current in the loop times the area of the loop. Conversely, application of a magnetic field through the loop can generate current in the loop. Therefore, a magnetic dipole can be used for sensing the presence of a magnetic field by detection of generated current.

[0033] As used herein, the term "electric dipole" refers to refer to a component having a spatial separation of positive and negative charge. For example, an electric dipole can be a pair of wires that are spatially separated. Application of a voltage difference to the wires can produce an electric dipole moment that points from the negative charge towards the positive charge, and has a magnitude equal to the strength of each charge times the separation between the charges. Conversely, application of an electric field between the wires can generate a voltage. Therefore, an electric dipole can be used for sensing the presence of an electric field by detection of generated voltage difference.

Examples of Metamaterial Particles

[0034] In one embodiment, a metamaterial particle in accordance with the subject matter disclosed herein can include an active electronic component, and a field sensing element and a field generating element in the form of magnetic dipoles. FIG. 1 is a schematic diagram of an exemplary metamaterial particle generally designated 100 including an active electronic component 102 and magnetic dipoles 104 and 106 in accordance with an embodiment of the subject matter disclosed herein. Referring to FIG. 1, magnetic dipole 104 can function as a field sensing element adapted for sensing a magnetic field. Magnetic dipole 104 can sense a magnetic field 108 propagating in the direction of magnetic dipole 104.

[0035] In this example, magnetic dipole 104 is a metallic loop sized smaller than the magnetic field wavelength. On application of magnetic field 108 through the loop, a current is produced in the loop that is proportional to the strength of the magnetic field. The produced current results in a voltage difference at the ends of the loop. The voltage difference is referred to herein as a sensed field signal because it represents the sensed magnetic field and can be received by active electronic component 102.

[0036] Active electronic component 102 can include an input for receiving the voltage difference present at the ends of the loop of magnetic dipole 104. Particularly, active electronic component 102 can receive as input the voltage difference produced in the loop of magnetic dipole 104. Thus, active electronic component 102 can receive a signal representative of magnetic field 108. In response to receiving the sensed field signal, active electronic component 102 can produce a drive signal that is a function of the received signal. In this example, active electronic component 102 is an amplifier configured to amplify the sensed field signal by gain G and to output a drive signal, which is the sensed field signal multiplied by gain G. Thus, in this example, the output of the active electronic component is the gain G times the input sensed field signal. Alternatively, the output of the active electronic component can be any predetermined function of the input sensed field signal. Active electronic component 102 can be powered by any suitable power source 110.

[0037] The predetermined function can include current amplification by a predetermined gain G. Alternatively, the predetermined function can include power amplification. Further, for example, the function can provide the features of a nonlinear device. In a linear active electronic component for example, the function can be represented by the equation Vout=GVin, where Vin is the voltage input into the active electronic component, Vout is the voltage output by the active electronic component, and G is the gain. In a nonlinear active electronic component for example, the function can be represented by the equation Vout=GVin<2>, where Vin, is the voltage input into the active electronic component, Vout is the voltage output by the active electronic component, and G is the gain. An active electronic component may be any suitable function that alters Vout with the aide of an external power source.

[0038] The following equations can apply to active electronic component 102 with regard to gain. An input voltage from magnetic dipole element 104 can be represented by Vsense=j[omega]AsenseB, wherein B is the propagation constant through transmission lines. The output voltage to magnetic dipole element 106 can be represented by Vout=j[omega]AsenseBG. The field produced by magnetic dipole element can be represented by the following equation:

[0000] [mathematical formula]

[0000] where m is the magnetic moment generated by metamaterial particle, j is the square root of -1 and represents a 90 degree phase shift, [omega] is 2[pi]* the signal frequency, B is the input magnetic field strength, Asense is the area enclosed by the sensing loop, Adriven is the area enclosed by the driven loop, and Zdriven is the total electrical impedance of the driven loop.

[0039] Magnetic dipole 106 is operable to receive the drive signal from active electronic component 102 and to produce another field based on the drive signal. In this example, magnetic dipole 106 is a metallic loop connected at its two ends to the output of component 102 for receiving a drive voltage difference. The drive voltage causes the flow of current through the loop for generating another magnetic field or magnetic dipole moment 112. The voltage at the ends of the loop of magnetic dipole 106 can be proportional to the current at the ends of the loop of magnetic dipole 104 by a gain factor of G due to active electronic component 102. Thus, active electronic component 102 can control the relation of the input magnetic field 108 to the output magnetic field 112 such that the output field is a function of the input field.

[0040] The provision of an active electronic component in a metamaterial particle as described herein can provide a number of benefits. For example, loss and dispersion can be controlled by controlling the phase delay through the metamaterial particles disclosed herein. Further, for example, a wide bandwidth of responses to sensed fields can be provided.

[0041] In another embodiment of the subject matter disclosed herein, a metamaterial particle can include an active electronic component, and field sensing and a field generating elements in the form of electric dipoles. FIG. 2 is a schematic diagram of an exemplary metamaterial particle generally designated 200 including active electronic component 102 and electric dipoles 202 and 204 in accordance with an embodiment of the subject matter disclosed herein. Referring to FIG. 2, electric dipole 202 can function as a field sensing element for sensing an electric field 206. Electric dipole 202 can sense an electric field 204 present in the space of electric dipole 202.

[0042] In this example, electric dipole 202 is a wire pair sized smaller than the electric field wavelength. On application of electric field 206 in the space of electric dipole 202, a voltage difference between the wires of the wire pair can be produced that is proportional to the strength of the electric field. The produced voltage difference is referred to herein as a sensed field signal because it is representative of the sensed electric field.

[0043] Active electronic component 102 can include an input for receiving the sensed field signal from electric dipole 202. Particularly, active electronic component 102 can receive as input the voltage produced in the wire pair of electric dipole 202. Thus, active electronic component 102 can receive a signal representative of electric field 206. In response to receiving the sensed field signal, active electronic component 102 can produce a drive signal that is a function of the received signal. In this example, active electronic component 102 is an amplifier configured to amplify the sensed field signal by gain G and to output a drive signal, which is the sensed field signal multiplied by gain G. Thus, in this example, the output of the active electronic component is the gain G times the input sensed field signal. Alternatively, the output of the active electronic component can be any predetermined function of the input sensed field signal. Active electronic component 102 can be powered by power source 110.

[0044] Electric dipole 204 is operable to receive the drive signal from active electronic component 102 and to produce another field based on the drive signal. In this example, electric dipole 204 is a wire pair connected to component 102 for receiving a drive voltage. The drive voltage can be applied to the wire pair of electric dipole 204 for generating another electric field or electric dipole moment 208. The voltage difference between the wire pair of electric dipole 202 can be proportional to the voltage difference between the wire pair of electric dipole 204 by a gain factor of G due to active electronic component 102. Thus, active electronic component 102 can control the relation of the input electric field 206 to the output electric field 208 such that the output field is a function of the input field.

[0045] In yet another embodiment of the subject matter disclosed herein, a metamaterial particle can include an active electronic component, and a field sensing element and a field generating element in the form of a magnetic dipole and an electric dipole, respectively. FIG. 3 is a schematic diagram of an exemplary metamaterial particle generally designated 300 including active electronic component 102, magnetic dipole 104, and electric dipole 204 in accordance with an embodiment of the subject matter disclosed herein. Referring to FIG. 3, magnetic dipole 104 can function as a field sensing element for sensing magnetic field 108, which is propagating through the metallic loop of magnetic dipole 104. On application of magnetic field 108 through the metallic loop, a current is produced in the loop that is proportional to the strength of the magnetic field. The produced current results in a voltage difference at the ends of the loop. The voltage difference is referred to herein as a sensed field signal because it represents the sensed magnetic field and can be received by active electronic component 102.

[0046] Active electronic component 102 can include an input for receiving the voltage difference present at the ends of the loop of magnetic dipole 104. The input voltage difference is a signal representative of magnetic field 108. In response to receiving the sensed field signal, active electronic component 102 can produce a drive voltage signal that is a function of the received current signal.

[0047] Electric dipole 204 is operable to receive the drive signal from active electronic component 102 and to produce electric field 208 based on the drive signal. Active electronic component 102 can control the relation of the input magnetic field 108 to the output electric field 208 such that the output electric field is a function of the input magnetic field. As a result, metamaterial particle 300 can sense a magnetic field and can generate an electric field as a function of the sensed magnetic field.

[0048] In yet another embodiment of the subject matter disclosed herein, a metamaterial particle can include an active electronic component, and a field sensing element and a field generating element in the form of a magnetic dipole and an electric dipole, respectively. FIG. 4 is a schematic diagram of an exemplary metamaterial particle generally designated 400 including active electronic component 102, electric dipole 202, and magnetic dipole 106 in accordance with an embodiment of the subject matter disclosed herein. Referring to FIG. 4, electric dipole 202 can sense electric field 206, which is present in the space of electric dipole 202. On application of electric field 206, a voltage different is produced between the wires of electric dipole 202.

[0049] Active electronic component 102 can include an input for receiving the sensed field signal in the form of voltage input from electric dipole 206. The input voltage is a signal representative of electric field 108. In response to receiving the sensed field signal, active electronic component 102 can produce a drive voltage signal that is a function of the received voltage signal.

[0050] Magnetic dipole 106 is operable to receive the drive voltage signal from active electronic component 102 and to produce magnetic field 112 based on the drive signal. In particular, active electronic component 102 applies a voltage difference at the ends of the wire loop of magnetic dipole 106 to produce the magnetic field. Active electronic component 102 can control the relation of the input electric field 206 to the output magnetic field 112 such that the output magnetic field is a function of the input electric field. As a result, metamaterial particle 400 can sense an electric field and can generate a magnetic field as a function of the sensed electric field.

[0051] The metamaterial particles described herein can be used to as a polarizing element. For example, a metamaterial particle as described herein can be used as a cross-polarizing element. Referring to FIG. 1 for example, the loops of magnetic dipoles 104 and 106 can be oriented in different directions with respect to one another such that the generated magnetic field 106 propagates in a different direction than the sensed magnetic field 108. Similarly, referring to FIG. 2 for example, the wire pairs of electric dipoles 202 and 204 can be oriented in different directions with respect to one another such that the generated electric field 206 propagates in a different direction than the sensed electric field 208. Further, the sensing dipoles can be oriented in different directions for sensing fields oriented in different directions. In addition, the field generating dipoles can be oriented in different directions for generating fields oriented in different directions.

[0052] In another embodiment of the subject matter disclosed herein, a metamaterial particle can include an active electronic component, a field sensing element, a field generating element, and elements for resonantly amplifying a sensed field and a produced field. FIG. 5 is a schematic diagram of an exemplary metamaterial particle generally designated 500 including active electronic component 102, magnetic dipoles 104 and 106, and field amplifying elements 502 and 504 in accordance with the subject matter disclosed herein. Referring to FIG. 5, magnetic dipole 104 can sense magnetic field 108. Field amplifying element 502 can be a magnetic loop having ends connected to a capacitor and positioned for resonantly amplifying magnetic field 108. Further, active electronic component 102 can amplify the signal and output an amplified signal at magnetic dipole 106 for producing magnetic field 112. Field amplifying element 504 can be a magnetic loop having ends connected to a capacitor and positioned for resonantly amplifying magnetic field 112. Thus, field amplifying elements 502 and 504 can provide amplification of the magnetic fields for supporting the amplification provided by active electronic component 102.

[0053] Metamaterial particles as disclosed herein can be utilized in a process for providing a field in response to sensing another field. FIG. 6 is a flow chart illustrating an exemplary process of providing a field in response to sensing another field according to an embodiment of the subject matter disclosed herein. In this example, reference is made to metamaterial particle 100 shown in FIG. 1, although the process may be conducted using any of the exemplary metamaterial particles described herein. Referring to FIG. 6, a metamaterial particle comprising a field sensing element, an active electronic component, and a field generating element is provided (block 600). For example, metamaterial particle 100 shown in FIG. 1 can be provided. At the field sensing element, a first field is sensed, and a sensed field signal representative of the first field is produced (block 602). For example, referring to FIG. 1, the metallic loop of magnetic dipole 104 can sense a magnetic field and a voltage difference representative of the sensed field can be generated in response to the sensed magnetic field.

[0054] At block 604, the active electronic component can received the sensed field signal and can produce a drive signal based on the sensed field signal. In FIG. 1 for example, active electronic component 102 can receive the voltage difference from the metallic loop of magnetic dipole 104. Further, active electronic component 102 can generate a drive signal that is an amplification of the received voltage difference signal. The drive signal can be output to the field generating element for producing a second field based on the drive signal (block 606). For example, active electronic component 102 can output the drive signal voltage difference to the metallic loop of magnetic dipole 106 for producing another magnetic field. The active electronic component can thereby generate a field based on another field that has been sensed.

Mathematical Analysis

[0055] In a mathematical analysis of the subject matter disclosed herein, a plane wave propagating in free space in the direction of a metamaterial particle is considered. In this analysis, reference is made to FIG. 7 where a metamaterial particle generally designated 700 having a field sensing element 702 and a field generating element 704 in accordance with the subject matter disclosed herein is shown. Field sensing element 702 and field generating element 704 are operably connected to an active electronic component (an amplifier in this example) 706 as described in further detail herein. Further, field sensing element 702 and field generating element 704 include metallic loops that are parallel to each other and are both perpendicular to an applied magnetic field (indicated by direction arrow 708) having a propagation direction (indicated by direction arrow 710) towards the field sensing and field generating elements. This arrangement makes the metamaterial particle anisotropic with a non-unity component on the diagonal of the permeability tensor in the direction perpendicular to the loops.

[0056] FIG. 8 is a circuit diagram of the magnetic particle shown in FIG. 7. Referring to FIGS. 7 and 8, to control the phase delay through the system, the metallic loops of field sensing element 702 and field generating element 704 are connected to active electronic component 706 through transmission lines of characteristic impedance Z0 and lengths I1 and I2, respectively. Amplifier 706 has input impedance Zin, output impedance Zout, and gain G. The metallic loop of field sensing element 702 has an interior area Ai and inductance L. The voltage picked up by the sensing loop of area Ai and inductance Li satisfies the following equation (1):

[0000]
Vin=-j[omega][mu]0HAi (1)

[0000] where H is the externally applied magnetic field, and the loop is substantially smaller than the wavelength of magnetic field 708. It is noted that in equation (1), the magnetic coupling between the metallic loops is neglected. However, this is justified by the experimental data discussed in the Experimental Results section below. Given these parameters, it can be shown that, assuming no magnetic coupling between the metallic loops, the voltage Vout across the driven loop of area Ao and inductance Lo is given by the following equation (2):

[0000] [mathematical formula]

[0000] where [beta]1 and [beta]2 are the propagation constants through the two transmission lines, and where

[0000] [mathematical formula]

[0057] From these equations, it follows that the currents through the field sensing and field generating loops are iin=Vin/j[omega]Li (this expression is valid when the inductive impedance is larger than the transformed input impedance) and iout=Vout/j[omega]L0, respectively. Therefore, the magnetic moment generated in metamaterial particle is m=iinAi+ioutA0, and assuming that the metamaterial particle has volume Vuc, it follows that the effective relative permeability of a metamaterial made of arrays of such metamaterial particles is provided by the following equation (5):

[0000] [mathematical formula]

[0000] where Geff is the equivalent gain of the system defined as Geff=[nu]out/[nu]in.

[0058] Equations (2)-(5) can be used as design equations for the metamaterial particle shown in FIG. 1. In the following discussion, [mu]r' and [mu]r'' are the real and imaginary parts of [mu]r. If zero losses are needed in a metamaterial made of such metamaterial particles, [mu]r'' should equal 0, which means, from equation (5), that Geff must be real, or, equivalently, Vout and Vin must be either in phase or 180 degrees out of phase. A closer look at equation (2) reveals that this occurs periodically in frequency because Vout varies periodically with frequency due to the delay in the transmission lines and the phase distortions of the amplifier. Moreover, if the amplitude ¦G¦ is approximately constant with frequency in the band of interest, as it usually happens in practice with most amplifiers, then the amplitude ¦Vout¦ varies slowly with frequency, which means that [mu]r' oscillates around 1 with minima and maxima at frequencies where, again, Vout and Vin are in phase or 180 degrees out of phase, and where [mu]r'' 0. This feature is demonstrated by experiments described in the following Experimental Results section.

Experimental Results

[0059] Experiments were conducted using a metamaterial particle having a field sensing element and a field generating element in accordance with the subject matter disclosed herein. In particular, experiments were conducted on a metamaterial particle in accordance with the embodiment shown in FIG. 7. Referring to FIG. 7 for illustrative purposes, a microstrip transmission line was used to excite transverse electromagnetic (TEM) modes to below 900 MHz inside it. Two circular metallic loops 702 and 704 of radius 1.8 cm oriented parallel to each other and the axis of the microstrip are placed inside a waveguide 712. The distance between loops 702 and 704 was 6 cm. Subminiature version A (SMA) cables 1 m long entering the microstrip through two holes drilled through the waveguide walls were used to connect the two loops to an AR 1W1000 microwave amplifier (active electronic component 706) placed outside waveguide 712. The amplifier has a 30+-1.5 dB gain between 1 MHz and 1 GHz, 50[Omega] input and output impedances, has linear phase distortions, and can handle purely inductive loads. Since frequencies below 900 MHz are of interest, the sensing and driven loops are smaller than [lambda]/8, and the effective medium approximation assumed here holds. An AGILENT(R) 8720A network analyzer (commercially available from Agilent Technologies, Inc., of Santa Clara, Calif.) was used to measure the reflected and transmitted waves through the waveguide. A single field sensing/field generating loop configuration was provided in the experiments so only one metamaterial particle is considered to fill the transverse section of the waveguide. Under these assumptions, the procedure described in the article "Determination of Effective Permittivity and Permeability of Metamaterials From Reflection and Transmission Coefficients," Smith et al., Phys. Rev., B 65, 195104 (2002), the disclosure of which is incorporated herein by reference in its entirety, was used to retrieve the effective permeability of such a medium. The result is plotted in the solid lines shown in FIG. 9.

[0060] FIG. 9 is a graph showing effective permeability versus frequency for this experiment. The frequencies with almost no dispersion and zero loss are identified by the shadowed regions in FIG. 9. The permeability follows closely the expected theoretical predictions (indicated by dotted lines), which validates equations (1)-(5). Moreover, it is noted that the important features expected theoretically, namely, [mu]r' oscillates around 1, with maxima and minima occurring at frequencies where [mu]r'' is approximately zero. Thus, for example, at around 602 MHz, the dispersion is almost zero (d[mu]r'/d[omega] 0) as well as the loss ([mu]r'' 0). Notice that, according to the design equations, in the regions where the amplifier is linear, the response of the active cell is also linear, therefore, the Kramers-Kronig relations must apply. As a result, at the frequencies where there is anomalous dispersion (i.e. d[mu]r'/d[omega]<0)), there must be either loss, or gain, which is in agreement with the retrieved permeability. FIG. 10 is another graph showing measured effective permeability versus frequency in experimental results obtained with a metamaterial particle in accordance with the subject matter disclosed herein.

[0061] Another experiment was conducted with a different amplifier to ensure a good match between the theoretical and experimentally retrieved permeability is not a coincidence. The AR 1W1000 amplifier was replaced with a MINI-CIRCUITS(R) ZHL2010 microwave amplifier (commercially available from Scientific Components Corporation, of Brooklyn, N.Y.) in series with a MAXIM(R) MAX2472 voltage buffer (commercially available from Maxim Integrated Products, Inc., of Sunnyvale, Calif.). Another exemplary amplifier that may be used is the MINI-CIRCUITS(R) high directivity monolithic amplifier VNA-28 (0.5-2.5 GHz) available from Scientific Components Corporation. The gain of this system was, again, about 30 dB. The output impedance given in the datasheets and measured with the network analyzer was (91-j182) [Omega], and was slowly varying with frequency, thus it was approximated as being constant throughout the frequency band of interest. The capacitive component of this impedance together with the inductance of the driven loop was expected to create resonant features in the retrieved permeability. Moreover, these features were expected to be periodic because of the linear phase distortions of the amplifier and buffer, and the length of the cables, as discussed above. Indeed, the experimentally retrieved permeability presented in FIG. 11 clearly shows these features. FIG. 11 is a graph showing effective permeability versus frequency for this experiment. Moreover, the good agreement between the experiment and the theoretical predictions further verify the validity of equations (2)-(5).

[0062] These equations facilitate the design of a metamaterial particle that could be used to generate a metamaterial having negative effective permeability. Thus, assuming that the field sensing and field generating loops are kept unchanged, in order to increase the magnetic moment generated in response to an applied magnetic field, it follows from equation (5) that either the concentration of unit cells is increased by decreasing Vuc, or increasing Vout. From equation (2), the latter can be achieved by increasing the amplifier gain, G, its input impedance, Zin, or by decreasing the output impedance, Zout. Thus, assuming a unit cell occupying a volume three times smaller than in the previous experiments, and a miniature amplifier placed inside the cell next to the two loops and having a gain of 40 dB, 200[Omega] input impedance, 50[Omega] output impedance, and same linear phase distortions as AR 1W1000, it follows from equation (5) that the relative permeability shown in FIG. 12 can be achieved. It is noted that the oscillatory behavior in this case is caused only by the phase distortions of the amplifier which explains the bigger period. It follows from equations (2) and (5) that the frequency at which zero losses and essentially no dispersion is achieved can be tuned by changing the phase delay through the amplifier (i.e., the phase of G) to bring Vout and Vin in phase at the desired frequency.

[0063] Further, experiments were conducted on metamaterial particles in accordance with the diagram shown in FIG. 5. FIG. 13 is a graph showing the effective magnetic susceptibility of one particle with the power to the amplifier off. The FIG. 13 graph is thus the response of the passive elements of the system and shows the type of material response that can be obtained with passive particles. FIG. 14 is a graph showing the effective magnetic permeability with the power on when the particle acts as an active metamaterial. In FIG. 14, the permeability variation with frequency is completely different, showing that a different class of response can be obtained with active metamaterials. Moreover, the FIG. 14 graph shows that a magnetic permeability much smaller than 1 can be achieved at a frequency where the losses (i.e., the imaginary part of the permeability) is zero. This type of response can be obtained by use of active metamaterials.

[0064] In accordance with the subject matter disclosed herein, an array of metamaterial particles may be arranged together. In one experiment, five identical metamaterial particles, each containing field sensing elements and an active component were arranged in an array. These particular particles contained magnetic field sensing elements and electric field driven elements as shown in FIG. 3. FIG. 15 is a graph showing the transmission amplitude of a signal passing through this array in both directions. The transmitted signal is strongly attenuated and the array is effectively opaque. This demonstrates another way in which active metamaterials can be engineered to have properties different than those that can be obtained with passive metamaterials.

[0065] In conclusion, an architecture for active metamaterial particles are disclosed that employ a field sensing element, an active electronic component, and a field generating element that produces the electric or magnetic dipole moment material response. Full design equations for the specific case of an active magnetic metamaterial are disclosed herein that were derived and validated through single metamaterial particle experimental measurements. This active magnetic metamaterial particle exhibits dispersion and loss characteristics that are dramatically different from those found in passive resonant metamaterials, including frequencies where the permeability is less than unity yet with zero loss and near zero dispersion. By controlling the amplifier characteristics, most importantly the phase, a very wide set of metamaterial characteristics can be achieved through this active cell approach.

[0066] In one application, numerous metamaterial particles disclosed herein can be embedded in a host matrix for controlling the electromagnetic properties of the material. The metamaterial particles can produce an electric and/or magnetic dipole moment in response to an applied field and, therefore, produce engineered permittivity or permeability, respectively, of the material. The metamaterial particles can be smaller than a wavelength of the applied field.

[0067] The subject matter and the experimental results disclosed herein demonstrate a metamaterial particle including an active electronic component and related methods. As described herein, a field sensing element (e.g., a metallic loop to sense a magnetic field, and a wire to sense an electric field) can generate a voltage proportional to a local electric or magnetic field. An active electronic component (e.g. an amplifier), which can be contained inside or outside a metamaterial, amplifies this voltage and controls its phase. The amplifier can driver a field generating element (e.g. a metallic loop to generate a magnetic dipole moment, and a wire to generate an electric dipole moment), which collectively produces an electromagnetic response in the metamaterial. Combinations of different field sensing and field generating elements can enable the production of almost any class of electromagnetic material response, including anisotropic response, off-diagonal response (if the sensing and driven elements are not oriented in the same way), and magnetoelectric response (if the field sensing and field generating elements are of different types).

[0068] Because the metamaterial particles described herein are not limited to the specific electromagnetic response of passive components, the metamaterial particles described herein can yield a metamaterial whose properties are essentially constant over a significant band of frequencies. The active electronic component enables the phase difference between the sensed field and the generated field to be controlled, thereby enabling easy design of metamaterials with lossless and strong response or negative response, or metamaterials with significant gain or loss in specific frequency ranges. In contrast, resonator-based passive metamaterials are unavoidably lossy and must have properties that change strongly with frequency (i.e. narrowband). Removing these limitations improves the prospect of functional metamaterial applications significantly.

[0069] Further, hybrid active-passive metamaterials can be provided in accordance with the subject matter disclosed herein. Such hybrid metamaterials can include both active and passive components. Passive metamaterials can generate a strong material response very efficiently, but they can be very lossy. This loss can be offset by embedding active elements along with resonant passive elements. Modest power is needed to produce a net magnetic or electric dipole moment to cancel the phase-quadrature response of the passive element without significantly modifying its in-phase response (which is responsible for the real part of the effective permittivity or permeability). Such a hybrid metamaterial can be lossless and also suitable for applications not possible with passive, lossy metamaterials.

[0070] It will be understood that various details of the presently disclosed subject matter may be changed without departing from the scope of the presently disclosed subject matter. Furthermore, the foregoing description is for the purpose of illustration only, and not for the purpose of limitation.



Wide Angle Impedance Matching Using Metamaterials in a Phased Array Antenna System
US7889127


A phased array antenna system may include a sheet of conductive material with a plurality of aperture antenna elements formed in the sheet of conductive material. Each of the plurality of aperture antenna elements is capable of sending and receiving electromagnetic energy. The phased array antenna system may also include a wide angle impedance match (WAIM) layer of material disposed over the plurality of aperture antenna elements formed in the sheet of conductive material. The WAIM layer of material includes a plurality of metamaterial particles. The plurality of metamaterial particles are selected and arranged to minimize return loss and to optimize an impedance match between the phased array antenna system and free space to permit scanning of the phased array antenna system up to a predetermined angle in elevation.

FIELD

[0002] The present invention relates to antennas, antenna arrays and the like, and more particularly to wide angle impedance matching (WAIM) using metamaterials in a phased array antenna system.

BACKGROUND OF THE INVENTION

[0003] Currently existing phased array antenna systems when scanned at wide elevation angles, such as past sixty degrees from an angle normal or perpendicular to the face of the array, experience severe reflections that can prevent detectable signals from being transmitted or received. Isotropic dielectric materials have been used for impedance matching of phased array antennas in attempts to improve at large scan angles but improvements have been limited.

BRIEF SUMMARY OF THE INVENTION

[0004] In accordance with an embodiment of the present invention, a phased array antenna system may include a sheet of conductive material with a plurality of aperture antenna elements formed in the sheet of conductive material. Each of the plurality of aperture antenna elements is capable of sending and receiving electromagnetic energy. The phased array antenna system may also include a wide angle impedance match (WAIM) layer of material disposed over the plurality of aperture antenna elements formed in the sheet of conductive material. The WAIM layer of material includes a plurality of metamaterial particles. The plurality of metamaterial particles are selected and arranged to minimize return loss and to optimize an impedance match between the phased array antenna system and free space to permit scanning of the phased array antenna system up to a predetermined angle in elevation and all azimuthal angles.

[0005] In accordance with another embodiment of the present invention, a communications system may include a transceiver to transmit and receive electromagnetic signals and a tracking and scanning module coupled to the transceiver. A phased array antenna system may be coupled to the tracking and scanning module. The phased array antenna system may include a sheet of conductive material with a plurality of aperture antenna elements formed in the conductive sheet. Each of the plurality of aperture antenna elements may be capable of sending and receiving electromagnetic energy. The phased array antenna system may also include a wide angle impedance match (WAIM) layer of material disposed over the plurality of aperture antenna elements formed in the sheet of conductive material. The WAIM layer of material includes a plurality of metamaterial particles. The plurality of metamaterial particles are selected and arranged to minimize return loss and to optimize an impedance match between the phased array antenna system and free space to permit scanning of the phased array antenna system up to a predetermined angle in elevation.

[0006] In accordance with another embodiment of the present invention, a method for widening an angular scanning range of a phased array antenna system may include forming a wide angle impedance match (WAIM) layer of material. Forming the WAIM layer of material may include selecting and arranging a plurality of metamaterial particles to minimize return loss and to optimize an impedance match between the phased array antenna system and free space to permit scanning of the phased array antenna system up to a predetermined angle in elevation. The method may further include disposing the WAIM layer of material on a plurality of aperture antenna elements formed in a sheet of conductive material to form the phased array antenna system.

[0007] Other aspects and features of the present invention, as defined solely by the claims, will become apparent to those ordinarily skilled in the art upon review of the following non-limited detailed description of the invention in conjunction with the accompanying figures.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0008] The following detailed description of embodiments refers to the accompanying drawings, which illustrate specific embodiments of the invention. Other embodiments having different structures and operations do not depart from the scope of the present invention.

[0009] FIG. 1 is a perspective view of an example of a phased array antenna system with a wide angle impedance match (WAIM) feature using metamaterials in accordance with an aspect of the present invention.

[0010] FIG. 2 is an example of a wide angle impedance match (WAIM) layer of material using metamaterials in accordance with an aspect of the present invention.

[0011] FIG. 3 is an example of a magnetic metamaterial particle in accordance with an aspect of the present invention.

[0012] FIG. 4 is an example of an electric metamaterial particle in accordance with an aspect of the present invention.

[0013] FIG. 5 is an example of a communications system including a phased array antenna system with a WAIM feature using metamaterials in accordance with an aspect of the present invention.

 


DETAILED DESCRIPTION OF THE INVENTION

[0014] The following detailed description of embodiments refers to the accompanying drawings, which illustrate specific embodiments of the invention. Other embodiments having different structures and operations do not depart from the scope of the present invention.

[0015] FIG. 1 is a perspective view of an example of a phased array antenna system 100 with a wide angle impedance match (WAIM) feature 102 using metamaterials in accordance with an aspect of the present invention. The phased array antenna system 100 may include a sheet of conductive material 104. A plurality of aperture antenna elements 106 or radiating apertures may be formed in the conductive sheet 104. The aperture antenna elements 106 may collectively send and/or receive electromagnetic energy and, as described herein, may be controlled to scan to a large angle [theta] of radiation propagation relative to a normal or perpendicular angle relative to a front face 108 of the phased array antenna system 100 as illustrated by the dashed or broken line 110.

[0016] The aperture antenna elements 106 may be uniformly arranged to form the phased array antenna system 100. The aperture antenna elements 106 may be uniformly spaced from one another by a distance X and may have a predetermined opening size or diameter D. The distance X and opening size D will be a function of the operating parameters of the phased array antenna system 100, such as operating frequency and wavelength.

[0017] Each of the plurality of aperture antenna elements 106 may be fed by a waveguide 112. The aperture antenna elements 106 may be substantially circular in shape or may be formed in other shapes depending upon the desired radiation characteristics or other properties. Each of the waveguides 112 may have a cross-section corresponding to the shape of the aperture antenna elements 106. The waveguides 112 may couple the apertures elements 106 to a communications system (not shown in FIG. 1) similar to that described with reference to FIG. 5 to transmit and receive electromagnetic signals.

[0018] One or more wide angle impedance match (WAIM) layers 114 and 116 of material may be disposed over the plurality of aperture antenna elements 106 formed in the sheet 104 of conductive material. Each of the WAIM layers 114 and 116 may include a plurality of metamaterial particles 120. The plurality of metamaterial particles 120 may be selected and arranged in a predetermined order or pattern substantially completely across each of the WAIM layers 114 and 116 similar to that illustrated in FIG. 2 to optimize an impedance match between the phased array antenna system 100 and free space 122 beyond the antenna array system 100 and to substantially minimize reflection or return loss of electromagnetic signals to permit scanning the phased array antenna system up to a predetermined angle in elevation. The dots represent additional metamaterial particles. As described herein properties of the WAIM layer or layers 114 and 116 may be selected, adjusted or tuned to provide substantially minimized return loss at an angle of scan [theta] of at least about 80 degrees to the normal 110 of the front face 108 of the phased array antenna system 100.

[0019] Also referring to FIG. 2, FIG. 2 is an example of a wide angle impedance match (WAIM) layer 200 of material using metamaterials 202 in accordance with an aspect of the present invention. The metamaterials 202 are arranged in a predetermined uniform pattern to minimize return loss and to optimize an impedance match between the phased array antenna system, such as system 100 in FIG. 1 and free space 122, to permit scanning a radiating wave or electromagnetic signal in the wide angle of at least about 80 degrees from the normal 110.

[0020] As determined by the geometry, orientation, topology and physical parameters of the metamaterial elements, the metamaterials 120 (FIG. 1) or 202 (FIG. 2) may be selected to have different electrical and magnetic properties. The plurality of metamaterials 120 and 202 may include magnetic metamaterials particles and electric metamaterial particles. The magnetic metamaterial particles provide or elicit a predetermined magnetic response when energized or when radiating or receiving electromagnetic energy. The electric metamaterial particles provide or elicit a predetermined electrical response when energized or when radiating or receiving electromagnetic energy. Referring also to FIGS. 3 and 4, FIG. 3 is an example of a magnetic metamaterial particle 300 in accordance with an aspect of the present invention, and FIG. 4 is an example of an electric metamaterial particle 400 in accordance with an aspect of the present invention. The exemplary magnetic metamaterial particle 300 illustrated in FIG. 3 is a split ring resonator (SRR). The exemplary electric metamaterial particle 400 illustrated in FIG. 4 is an electric inductor-capacitor resonator (ELC). The configurations or structures of the metamaterial particles 300 and 400 in FIGS. 3 and 4 are merely examples and other forms of magnetic and electric metamaterial particles or other subwavelength particles that elicit a specific magnetic and electric response as described herein to provide impedance matching and a large scan angel [theta] may also be used.

[0021] The magnetic metamaterial particles 300 and the electric metamaterial particles 400 may be periodically arranged in a predetermined pattern or order relative to one another similar to that illustrated in FIG. 2 to provide the optimum impedance match between the phased array antenna system 100 and free space 122 for wide angle scanning of the radiation wave or beam. For example, the magnetic metamaterial particles 300 and the electric metamaterial particles 400 may be interwoven to optimize the impedance match and provide the wide angle scanning. In another embodiment, a combination of interwoven arrays of two disparate magnetic particles may be co-arranged with interwoven arrays of two disparate electric particles in order to achieve at least two independent magnetic permeabilities and two independent electric permittivities in perpendicular directions of three-dimensional space. A material without the same magnetic permeability or electric permittivity in all three spatial dimensions is known as anisotropic. This invention refers to an anisotropic WAIM layer made up of subwavelength metamaterial elements.

[0022] The metamaterial particles 300 and 400 may be arranged in different patterns in the plurality of WAIM layers 114 and 116 to provide different operating characteristics and wide angle scanning. The WAIM layers 114, 116 and 200 may also have varying thicknesses "T" as illustrated in FIG. 2 which may be adjusted to providing varying operating characteristics. The metamaterial particles 300 and 400 may be formed on the surface 204 of the WAIM layer 200 or may be embedded within the WAIM layer 200 and may be arranged in a selected orientation to provide the desired operating characteristics of optimum impedance matching and wide angle scanning. The WAIM layer 200 may be formed from a dielectric material and the metamaterial particles 202 from a conductive material, such as copper, aluminum or other conductive material. The metamaterials may be formed or embedded in the WAIM layer 200 using similar techniques to that used in forming semiconductor materials, such as photolithography, chemical vapor deposition, chemical etching or similar methods.

[0023] The selection and arrangement of the metamaterials 300 and 400 permit formation of an anisotropic WAIM layer of material wherein the material parameters may be different in different directions with the layer of material to provide optimum impedance matching and minimum return loss or reflection of the electromagnetic signal. In accordance with an aspect of the present invention, the selection and arrangement of the metamaterial particles 300 and 400 permit the permittivity in different directions ([epsilon]x, [epsilon]y, [epsilon]z) with the WAIM layer and the permeability in different directions ([mu]x, [mu]y, [mu]z) to be controlled to optimize the impedance match between the phased array antenna system 100 and the free space 122 and thereby to permit wider angle scanning of the phased array 100 of at least about 80 degrees than has been previously been achievable with other material layers, such as isotropic dielectric layers and the like. The geometry and dimensions of the elements in the WAIM layer 200 or layers 114 and 116 may also be varied to adjust or tune the material characteristics, such as permittivity and permeability. There is no limit to the number of metamaterial WAIM layers used to provide optimum matching for the antenna.

[0024] In accordance with one aspect of the present invention, the permittivities ([epsilon]x, [epsilon]y, [epsilon]z) in different directions or orientation and the permeabilities ([mu]x, [mu]y, [mu]z) in different directions or orientations in the WAIM layer may be determined by calculating the active element admittance that provide the minimum amount of reflected power or in other words, provides the maximum ratio of radiated (transmitted) power (PT) to input power (PI) at all scan angles theta ([theta]). This ratio may be expressed as equation 1.

[0000]
PT/PI=(1-[Gamma]([theta]<2>)cos [theta] Eq. 1

[0025] The permittivity and permeability of each element array in the WAIM can be determined by quantitatively observing its response to an incoming plane wave of light at the design frequencies. The process is typically done using commercially available software that solve for electromagnetic scattering parameters, such as Ansoft HFSS (High Frequency Structure Solver) available from Ansoft of Pittsburgh, Pa., CST Microwave Studio available from Computer Simulation Technology of Framingham, Mass., or similar software. The electromagnetic scattering matrix retrieved from a simulation of the physical model of the element array is mathematically processed using an "inverse-problem" approach so as to extract the permittivity (electric) or permeability (magnetic) parameters that would elicit the response indicated in the scattering matrix of the element array. This process can also be done experimentally.

[0026] FIG. 5 is an example of a communications system 500 including a phased array antenna system 502 with a WAIM feature 504 using metamaterials in accordance with an aspect of the present invention. The phased array antenna system 502 and WAIM feature 504 may be similar to the phased array antenna system 100 in FIG. 1 and may include a sheet of conductive material 505 with a plurality of aperture antenna elements formed therein and WAIM feature or layer 504. Similar to that previously described, the WAIM feature or layer 504 may include a plurality of metamaterial particles similar to those shown in FIGS. 3 and 4. The metamaterial particles may be selected and arranged to optimize the impedance match between the phase array antenna system 502 and free space 506 to permit scanning of a radiation wave 508 to a wide angle [theta] relative to a norm (illustrated by broken or dashed line 510) from a face 512 of the phased array 502. The wide angle [theta] may be at least about 80 degrees relative to the norm 510.

[0027] The communication system 500 may also include a tracking and scanning module 514 to control operation of the phased array antenna elements for scanning the radiation beam 508. The tracking and scanning module 514 may control phase shifters associated with feed waveguides (not shown in FIG. 5) similar to waveguides 112 illustrated in FIG. 1 to control the scanning of the radiation beam 508 through the wide angle [theta] between about 0 degrees normal to the array face 512 and about 80 degrees or more.

[0028] The communications system 500 may also include a transceiver 516 to generate communications signals for transmission by the phased array antenna system 502 to a remote station 518 or other object and to receive communications signals received by the phased array antenna system 502.

[0029] The flowcharts and block diagrams in the Figures illustrate the architecture, functionality, and operation of possible implementations of systems and methods according to various embodiments of the present invention. In this regard, each block in the flowchart or block diagrams may represent a module, segment, or portion of code, which comprises one or more executable instructions for implementing the specified logical function(s). It should also be noted that, in some alternative implementations, the functions noted in the block may occur out of the order noted in the figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved. It will also be noted that each block of the block diagrams and/or flowchart illustration, and combinations of blocks in the block diagrams and/or flowchart illustration, can be implemented by special purpose hardware-based systems which perform the specified functions or acts, or combinations of special purpose hardware and computer instructions.

[0030] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and/or "comprising," and "includes" and/or "including" when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.

[0031] Although specific embodiments have been illustrated and described herein, those of ordinary skill in the art appreciate that any arrangement which is calculated to achieve the same purpose may be substituted for the specific embodiments shown and that the invention has other applications in other environments. This application is intended to cover any adaptations or variations of the present invention. The following claims are in no way intended to limit the scope of the invention to the specific embodiments described herein.





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