Metamaterial-Based Phase Shifting Element and Phased Array

• US 20160013531A1
• Filed: 07/14/2014
• Published: 01/14/2016
• Est. Priority Date: 07/14/2014
• Status: Active Grant

• Current Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Original Assignee: Palo Alto Research Center, Inc. (Xerox Holdings Corp.)
• Inventors: Casse, Bernard D., Volkel, Armin R., Liu, Victor, Tuganov, Alexander S.
• Granted Patent: US 9,972,877 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: H01P 1/184 Strip line phase-shifters H01P1/181, H01P1/185, H01P1/19 take precedence
• CPC Class Codes: H01Q 21/065 Patch antenna array
• CPC Class Codes: H01Q 21/08 the units being spaced along or adjacent to a rectilinear path waveguide fed H01Q21/0037
• CPC Class Codes: H01Q 3/36 with variable phase-shifters
• CPC Class Codes: H01Q 3/46 Active lenses or reflecting arrays

Abstract

A metamaterial-based phase shifting element utilizes a variable capacitor (varicap) to control the effective capacitance of a metamaterial structure in order to control the phase of a radio frequency output signal generated by the metamaterial structure. The metamaterial structure is configured to resonate at the same radio wave frequency as an incident input signal (radiation), whereby the metamaterial structure emits the output signal by way of controlled scattering the input signal. A variable capacitance applied on metamaterial structure by the varicap is adjustable by way of a control voltage, whereby the output phase is adjusted by way of adjusting the control voltage. The metamaterial structure is constructed using inexpensive metal film or PCB fabrication technology including an upper metal “island” structure, a lower metal backplane layer, and a dielectric layer sandwiched therebetween. The varicap is connected between the island structure and a base metal structure that surrounds the island structure.

Claims

1. A phase shifting element for receiving an input signal having a radio wave frequency and an input phase, and for generating an output signal having said radio wave frequency and having an output phase determined by an applied phase control signal, the phase shifting element comprising:

a metamaterial structure configured to have a fixed capacitance, and configured such that said metamaterial structure resonates at said radio wave frequency; and

a variable capacitor configured to generate a variable capacitance that varies in accordance with said applied phase control signal, said variable capacitor being coupled to said metamaterial structure such that an effective capacitance of said metamaterial structure is altered by a corresponding change in said variable capacitance, whereby said metamaterial structure generates said output signal at said output phase determined by said applied phase control signal.

2. The phase shifting element of claim 1, wherein said phase control signal comprises a direct-current phase control voltage, and wherein the variable capacitor is configured such that:

when said phase control voltage is applied across said variable capacitor and has a first voltage level, said variable capacitor generates said variable capacitance at a first capacitance level such that said metamaterial structure generates said output signal at an associated first output phase, and

when said applied phase control voltage is increased from said first voltage level to a second voltage level, said variable capacitor generates said variable capacitance at a second capacitance level such that said metamaterial structure generates said output signal at an associated second output phase, said second output phase being greater than said first output phase.

3. The phase shifting element of claim 1,

wherein said variable capacitor includes a first terminal connected to said metamaterial structure and a second terminal,

wherein said phase shifting element further comprises a conductive structure connected to one of said metamaterial structure and said first terminal of said variable capacitor such that, when said phase control signal is applied to said conductive structure and said second terminal is connected to a ground potential, said variable capacitor generates said associated variable capacitance having a capacitance level that is proportional to said phase control signal.

4. The phase shifting element of claim 1, wherein said metamaterial structure comprises:

a first metal layer structure connected to said variable capacitor;

an electrically isolated second metal layer structure; and

a dielectric layer sandwiched between said first and second metal layer structures,

wherein said first and second metal layer structures are cooperatively configured such that said metamaterial structure resonates at said radio wave frequency and has said fixed capacitance.

5. The phase shifting element of claim 4, wherein said dielectric layer comprises a lossless dielectric material.

6. The phase shifting element of claim 4,

wherein said first metal layer structure is disposed on an upper dielectric surface of said dielectric layer,

wherein said phase shifting element further comprises a third metal layer structure disposed on said upper dielectric surface and spaced from said first metal layer structure, and

wherein said variable capacitor includes a first terminal connected to said first metal layer structure and a second terminal connected to said third metal structure.

7. The phase shifting element of claim 6,

wherein said third metal layer structure defines an opening disposed inside an inner peripheral edge,

wherein said first metal layer structure is disposed inside said opening such that an outer peripheral edge of said first metal layer structure is separated from the inner peripheral edge of said third metal layer structure by a peripheral gap, and

wherein said first, second and third metal layer structures are cooperatively configured such that said metamaterial structure resonates at said radio wave frequency and has said fixed capacitance.

8. The phase shifting element of claim 7, wherein said third metal layer structure and said first metal layer structure comprise a single metal.

9. The phase shifting element of claim 7, further comprising a metal via structure extending through the dielectric layer and contacting the first terminal.

10. The phase shifting element of claim 7, wherein said inner peripheral edge defining said at least one opening in said third metal layer structure and said outer peripheral edge of said first metal layer structure comprise concentric square shapes such that a width of said peripheral gap remains substantially constant around the entire perimeter of said first metal layer structure.

11. The phase shifting element of claim 4, wherein the first metal layer structure comprises a patterned planar structure defining one or more open regions.

12. The phase shifting element of claim 11, wherein the first metal layer structure comprises:

a peripheral frame portion including said outer peripheral edge;

one or more radial arms, each radial arm having a first end integrally connected to the peripheral frame portion and extending inward from the peripheral frame toward a central region of said metamaterial structure; and

an inner structure integrally connected to second ends of the one or more radial arms, said inner structure being spaced from said peripheral frame portion by way of said one or more open regions.

13. A phase shifting apparatus for generating an output signal at an output phase determined by a phase control signal, said apparatus comprising:

a signal source configured to generate a first signal having a radio wave frequency and a first phase;

a phase shifting element including;

a metamaterial structure configured to have a fixed capacitance, and configured such that said metamaterial structure resonates at said radio wave frequency, and

a variable capacitor configured to generate a variable capacitance that varies in accordance with an applied phase control voltage, said variable capacitor being coupled to said metamaterial structure such that an effective capacitance of said metamaterial structure is altered by a corresponding change in said variable capacitance; and

a control circuit configured to generate said phase control voltage applied to said variable capacitor at a voltage level determined in accordance with said phase control signal, whereby said metamaterial structure generates said output signal at said output phase determined by said phase control signal.

14. The phase shifting apparatus of claim 13, wherein said metamaterial structure comprises:

a first metal layer structure connected to said variable capacitor;

an electrically isolated second metal layer structure; and

a dielectric layer sandwiched between said first and second metal layer structures,

wherein said signal source is disposed over the first metal layer structure such that said first metal layer structure is disposed between said signal source and said dielectric layer, and

wherein said first and second metal layer structures are cooperatively configured such that said metamaterial structure resonates at said radio wave frequency and has said fixed capacitance.

15. The phase shifting apparatus of claim 14,

wherein said first metal layer structure is disposed on an upper dielectric surface of said dielectric layer,

wherein said phase shifting element further comprises a third metal layer structure disposed on said upper dielectric surface and spaced from said first metal layer structure, and

wherein said variable capacitor includes a first terminal connected to said first metal layer structure and a second terminal connected to said third metal structure.

16. The phase shifting apparatus of claim 15,

wherein said third metal layer structure defines an opening disposed inside an inner peripheral edge,

wherein said first metal layer structure is disposed inside said opening such that an outer peripheral edge of said first metal layer structure is separated from the inner peripheral edge of said third metal layer structure by a peripheral gap, and

wherein said first, second and third metal layer structures are cooperatively configured such that said metamaterial structure resonates at said radio wave frequency and has said fixed capacitance.

17. The phase shifting apparatus of claim 16,

wherein the control circuit is mounted below the electrically isolated second metal layer structure, and

wherein the phase shifting apparatus further comprises a metal via structure extending from the control circuit through the dielectric layer and contacting the first terminal of the variable capacitor.

18. A phased array system for generating an emitted beam, said apparatus comprising:

a signal source configured to generate a first signal having a radio wave frequency and a first phase;

a phase shifting element array including;

a plurality of metamaterial structures, each said metamaterial structure configured to have an associated fixed capacitance such that said each metamaterial structure resonates at said radio wave frequency, and

a plurality of variable capacitors configured to respectively generate associated variable capacitances that vary in accordance with associated applied phase control voltages, each said variable capacitor being coupled to an associated said metamaterial structure such that an effective capacitance of said associated metamaterial structure is altered by a corresponding change in the variable capacitance generated by said each variable capacitor in accordance with an associated applied phase control voltages; and

a control circuit configured to generate a plurality of phase control voltages, each phase control voltage being applied to an associated variable capacitor of said plurality of variable capacitors, said plurality of phase control voltages having a plurality of voltage levels such that said plurality of metamaterial structures respectively generate output signals at a plurality of different output phases, wherein said plurality of different output phases are respectively coordinated such that said output signals cumulatively generate said emitted beam.

19. The phased array system of claim 18, wherein said plurality of metamaterial structures are arranged in a one-dimensional array, whereby changes in said plurality of phase control voltages cause said beam to change direction in a region defined by a two-dimensional plane.

20. The phased array system of claim 18, wherein said plurality of metamaterial structures are arranged in a two-dimensional array such that said metamaterial structures are aligned in a plurality of rows and a plurality of columns, whereby changes in said plurality of phase control voltages cause said beam to change direction in an area defined by a three-dimensional region.