Metamaterial-based phase shifting element and phased array
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.
1. A phase shifting element configured to receive an input signal having a radio wave frequency and an input phase, and configured to generate 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 three-layer structure including:
an upper patterned metamaterial structure configured to have a fixed capacitance, and configured such that said metamaterial structure resonates at said radio wave frequency,
a backplane layer that is electrically isolated from the upper patterned metamaterial structure, and
a dielectric layer disposed between and coupled to the upper patterned metamaterial structure and the backplane layer; 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,
wherein said variable capacitor includes a first terminal connected to said metamaterial structure and a second terminal connected to a fixed potential,
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.
2. A phase shifting element configured to receive an input signal having a radio wave frequency and an input phase, and configured to generate 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,
wherein said metamaterial structure comprises a three-layer structure including:
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 the variable capacitor is mounted on said first metal layer such that said first metal layer is disposed between said variable capacitor 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.
3. The phase shifting element of claim 2 , wherein the first metal layer structure comprises a patterned planar structure defining one or more open regions.
4. The phase shifting element of claim 3 , wherein the first metal layer structure comprises:
a peripheral frame portion including an outer peripheral edge;
one or more radial arms, each radial arm having a first end thereof 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 entirely surrounded by and spaced from said peripheral frame portion by way of said one or more open regions.
5. The phase shifting element of claim 2 , wherein said dielectric layer comprises a lossless dielectric material.
6. The phase shifting element of claim 2 ,
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 thereof,
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 of said variable capacitor.
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.