SELECTABLE CAPACITANCE CIRCUIT

• US 20110085278A1
• Filed: 12/17/2010
• Published: 04/14/2011
• Est. Priority Date: 09/27/2004
• Status: Active Grant

• Current Assignee: Snaptrack Incorporated (Qualcomm, Inc.)
• Original Assignee: Qualcomm MEMS Technologies Incorporated (Qualcomm, Inc.)
• Inventors: Floyd, Philip D.
• Granted Patent: US 8,078,128 B2
• Time in Patent Office: Days
• US Class Current: 361/277
• CPC Class Codes: G02B 26/001 based on interference in an adjustable optical cavity interference filters G02B5/28; devices or arrangements using multiple reflections in spectrometry or monochromators G01J3/26
• CPC Class Codes: G09G 2300/06 Passive matrix structure, i.e. with direct application of both column and row voltages to the light emitting or modulating elements, other than LCD or OLED
• CPC Class Codes: G09G 3/346 based on modulation of the reflection angle, e.g. micromirrors micromirrors devices per se G02B26/0833
• CPC Class Codes: G09G 3/3466 based on interferometric effect
• CPC Class Codes: G09G 3/3473 based on light coupled out of a light guide, e.g. due to scattering, by contracting the light guide with external means
• CPC Class Codes: H01G 5/18 due to change in inclination, e.g. by flexing, by spiral wrapping
• CPC Class Codes: H01G 5/40 Structural combinations of variable capacitors with other electric elements not covered by this subclass, the structure mainly consisting of a capacitor, e.g. RC combinations

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.

Claims

1. A capacitor having a selectable capacitance comprising:

a signal conductor;

a first mechanical conductor membrane coupled to a first bias configured to control positioning of the first mechanical conductor membrane relative to the signal conductor; and

a second mechanical conductor membrane coupled to a second bias configured to control positioning of the second mechanical conductor membrane relative to the signal conductor independent of the positioning of the first mechanical conductor membrane,

wherein a capacitance is defined by a combination of the positioning of the first mechanical conductor membrane and the positioning of the second mechanical conductor membrane.

2. The capacitor of claim 1, further comprising:

a substrate assembly; and

a layer of dielectric material coupled to the signal conductor.

3. The capacitor of claim 2, further comprising:

a first plurality of posts disposed between the substrate assembly and the first mechanical conductor membrane and disposed between two or more ends anchoring the first mechanical conductor membrane, where the first plurality of posts support the first mechanical conductor membrane; and

a first second of posts disposed between the substrate assembly and the second mechanical conductor membrane and disposed between two or more ends anchoring the second mechanical conductor membrane, where the second plurality of posts support the second mechanical conductor membrane.

4. The capacitor of claim 3, wherein the first plurality of posts have a first height that is greater than a second height of the second plurality of posts.

5. The capacitor of claim 3, wherein the first plurality of posts have a first spacing distance that is greater than a second spacing distance of the second plurality of posts.

6. The capacitor of claim 1 wherein the signal conductor comprises a non-transparent material.

7. The capacitor of claim 1 wherein a material for the signal conductor comprises at least one of silver, copper, gold, aluminum, or combinations thereof.

8. The capacitor of claim 1 wherein a material for the signal conductor has a resistivity of less than 1×

10<sup>−

6</sup> ohm-meters (Ω

-m).

9. The capacitor of claim 1 wherein a material for the signal conductor has a resistivity of less than 0.1×

10<sup>−

6</sup> ohm-meters (Ω

-m).

10. The capacitor of claim 1, wherein the signal conductor has a thickness in the range of 0.5 to 5 micrometers.

11. The capacitor of claim 1, wherein a plurality of signal conductors and a plurality of mechanical conductor membranes are arranged in rows and columns.

12. A capacitor having a selectable capacitance comprising:

means for conducting a signal;

a first means for adjusting capacitance coupled to a first means for controlling positioning of the first capacitance adjusting means relative to the conducting means; and

a second means for adjusting capacitance coupled to a second means for controlling positioning of the second capacitance adjusting means relative to the conducting means independent of the positioning of the first capacitance adjusting means,

wherein a capacitance is defined by a combination of the positioning of the first capacitance adjusting means and the positioning of the second capacitance adjusting means.