Tunable impedance surface and method for fabricating a tunable impedance surface
AssigneeRaytheon Company
InventorsDaniel Sievenpiper, Thomas Dougherty, John Drab, Solomon Robinson
Life of this patent
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Abstract
A tunable impedance surface includes a varactor. The varactor comprises a bottom electrode formed on a surface of a substrate. First and second ferroelectric elements are on top of the bottom electrode and electrically connected to one another through the bottom electrode. A first top electrode is on top of and electrically connected to the first ferroelectric element and a second top electrode is on top of and electrically connected to the second ferroelectric element.
Claims35
A varactor, comprising:
- a bottom electrode formed on a surface of a substrate;
- first and second ferroelectric elements on top of the bottom electrode and electrically connected to one another through the bottom electrode;
- a first top electrode on top of and electrically connected to the first ferroelectric element;
- a second top electrode on top of and electrically connected to the second ferroelectric element.
A tunable impedance surface for steering a radio frequency beam, the tunable impedance surface comprising a solid state monolithic device, said device comprising:
- a substrate;
- a ground plane arranged at a bottom surface of the substrate;
- a plurality of conductive elements arranged on a top surface of the substrate and spaced from said ground plane by a distance less than a wavelength at a frequency of the RF beam;
- a plurality of variable capacitance structures arranged for controllably varying the capacitance between at least adjacent ones of said plurality of elements, wherein the variable capacitance structures comprise a ferroelectric material which locally changes its permittivity in response to a set of bias signals.
An electronically scanned antenna comprising:
- at least one radiator element;
- a tunable impedance surface located for illumination by the at least one radiator element, wherein the tunable surface comprises a solid state monolithic device, said device comprises a first plurality of conductive elements connected to corresponding bias lines and a second plurality of conductive elements connected to a ground plane, wherein the first plurality of conductive elements are connected to corresponding, neighboring ones of the second plurality of conductive elements by a respective varactor comprising a ferroelectric material;
- a controller for controlling bias voltages applied to the bias lines, wherein the varactor comprises barium strontium titanate (BST).
A method for fabricating a tunable surface, comprising:
- depositing a bottom electrode layer on a surface of a substrate;
- depositing a ferroelectric layer over the bottom electrode layer;
- depositing a top electrode layer over the ferroelectric layer;
- patterning the top electrode layer to form a plurality of top electrode pairs;
- patterning the ferroelectric layer to form a plurality of ferroelectric element pairs under corresponding, respective top electrode pairs, respectively;
- patterning the bottom electrode layer to form a plurality of bottom electrodes, wherein each bottom electrode is under and in electrical contact with a corresponding one of the plurality of ferroelectric element pairs;
- wherein the plurality of bottom electrodes, corresponding ones of the plurality of ferroelectric element pairs and corresponding, respective top electrode pairs define a plurality of varactors, each comprising two ferroelectric elements connected in series through the bottom electrode.
A method for fabricating a tunable surface, comprising:
- depositing a bottom electrode layer on a surface of a substrate;
- depositing a ferroelectric layer over the bottom electrode layer;
- depositing a top electrode layer over the ferroelectric layer;
- patterning the top electrode layer to form a plurality of top electrode pairs;
- patterning the ferroelectric layer to form a plurality of ferroelectric element pairs under corresponding, respective top electrode pairs, respectively;
- patterning the bottom electrode layer to form a plurality of bottom electrodes, wherein each bottom electrode is under and in electrical contact with a corresponding one of the plurality of ferroelectric element pairs.
An electronically scanned antenna for steering a beam of microwave or millimeter wave energy, comprising:
- a substrate;
- a ground plane disposed on a back surface of the substrate;
- a periodic metallic pattern fabricated on a front surface of the substrate;
- a set of varactors formed on the front surface and comprising a ferroelectric material, said material comprising barium strontium titanate (BST);
- a set of control lines connected to the periodic metallic pattern to apply a set of bias voltages to the set of varactors;
- a circuit for supplying the bias voltages to the set of control lines.
Dependencies are inferred from the claim text.