SELECTABLE CAPACITANCE CIRCUIT
First Claim
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1. A voltage-controlled capacitor comprising:
- a substrate assembly with an input terminal, a control terminal, and a voltage reference terminal;
voltage reference lines disposed on the substrate assembly, wherein at least one of the voltage reference lines is coupled to the voltage reference terminal;
a mechanical conductor membrane spaced above the substrate assembly and coupled directly or indirectly to one or more of the voltage reference lines at opposing ends of the mechanical conductor membrane so that the opposing mechanical conductor membrane is anchored at two or more ends and so that the mechanical conductor membrane is AC coupled to the one or more voltage reference lines, wherein at least a portion of the mechanical conductor membrane is movable to and from a first position a first distance from a surface of the substrate assembly and a second position a second distance from the surface of the substrate assembly;
one or more posts disposed between the substrate assembly and the mechanical conductor membrane and disposed between the two or more ends anchoring the mechanical conductor membrane, where the one or more posts support the mechanical conductor membrane;
a signal conductor disposed on the substrate assembly, where the signal conductor is DC coupled to the control terminal, wherein a voltage on the control terminal at least partially controls the position of the mechanical conductor membrane;
a layer of dielectric material disposed between a top surface of the signal conductor and the mechanical conductor membrane, where a gap exists between at least one of (a) the mechanical conductor membrane and the layer of dielectric material or (b) the layer of dielectric material and the signal conductor when the mechanical conductor membrane is in the first position, and substantially no gap exists when the mechanical conductor membrane is in the second position; and
a coupling capacitor with a first terminal and a second terminal, where the first terminal is coupled to the input terminal and where the second terminal is coupled to the signal conductor.
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Abstract
A voltage-controlled capacitor and methods for forming the same are described. A mechanical conductor membrane of the voltage-controlled capacitor is movable to and from a first position and a second position. An amount of capacitance can vary with the movement of the mechanical conductor membrane. A microelectromechanical systems (MEMS) voltage-controlled capacitor can be used in a variety of applications, such as, but not limited to, RF switches and RF attenuators.
83 Citations
20 Claims
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1. A voltage-controlled capacitor comprising:
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a substrate assembly with an input terminal, a control terminal, and a voltage reference terminal; voltage reference lines disposed on the substrate assembly, wherein at least one of the voltage reference lines is coupled to the voltage reference terminal; a mechanical conductor membrane spaced above the substrate assembly and coupled directly or indirectly to one or more of the voltage reference lines at opposing ends of the mechanical conductor membrane so that the opposing mechanical conductor membrane is anchored at two or more ends and so that the mechanical conductor membrane is AC coupled to the one or more voltage reference lines, wherein at least a portion of the mechanical conductor membrane is movable to and from a first position a first distance from a surface of the substrate assembly and a second position a second distance from the surface of the substrate assembly; one or more posts disposed between the substrate assembly and the mechanical conductor membrane and disposed between the two or more ends anchoring the mechanical conductor membrane, where the one or more posts support the mechanical conductor membrane; a signal conductor disposed on the substrate assembly, where the signal conductor is DC coupled to the control terminal, wherein a voltage on the control terminal at least partially controls the position of the mechanical conductor membrane; a layer of dielectric material disposed between a top surface of the signal conductor and the mechanical conductor membrane, where a gap exists between at least one of (a) the mechanical conductor membrane and the layer of dielectric material or (b) the layer of dielectric material and the signal conductor when the mechanical conductor membrane is in the first position, and substantially no gap exists when the mechanical conductor membrane is in the second position; and a coupling capacitor with a first terminal and a second terminal, where the first terminal is coupled to the input terminal and where the second terminal is coupled to the signal conductor. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. A capacitor having a selectable capacitance comprising:
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a substrate assembly; a signal conductor on the substrate assembly, wherein the signal conductor forms a first electrode for the capacitor; a layer of dielectric material covering at least an upper surface of the signal conductor; and one or more mechanical conductor membranes spaced above the substrate assembly such that the signal conductor is disposed between the substrate assembly and the one or more mechanical conductor membranes, where the one or more mechanical conductor membranes form a second electrode for the capacitor, wherein at least two or more portions of the one or more mechanical conductor membranes are at least partially independently movable from a low capacitance position and a high capacitance position such attainable positions include a low capacitance position for at least a selected two portions of the mechanical conductor membranes, a high capacitance position for the selected two portions of the mechanical conductor membranes, and an intermediate capacitance configuration in which one of the selected two portions is in the high capacitance position and the other is in the low capacitance position, wherein the selected position is at least partially determined by a voltage on the signal conductor. - View Dependent Claims (15, 16, 17)
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18. A capacitor having a selectable capacitance, the capacitor comprising:
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at least two electrodes spaced apart by a gap; and means for adjusting the gap to select the capacitance. - View Dependent Claims (19, 20)
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Specification