Selectable capacitance circuit

• US 20060077617A1
• Filed: 08/30/2005
• Published: 04/13/2006
• 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 7,653,371 B2
• Time in Patent Office: Days
• US Class Current: 361/278
• 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: Y10T 29/49124 On flat or curved insulated base, e.g., printed circuit, etc.

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. An apparatus having a selectable amount of capacitance, the apparatus comprising:

at least two electrodes at least one of which is controllably movable with respect to the other to provide adjustability of a gap defined between the at least two electrodes, wherein at least one of the electrodes carries an RF signal; and

a plurality of posts disposed between the at least two electrodes, wherein the plurality of posts are configured to tension at least one of the electrodes.

2. The apparatus as defined in claim 1, further comprising a circuit configured to selectively apply a DC bias between two electrodes, at least one of which is the movable electrode, such that the circuit adjusts a size of the gap between the two electrodes.

3. The apparatus as defined in claim 1, further comprising:

a display;

a processor that is in electrical communication with said display, said processor being configured to process image data; and

a memory device in electrical communication with said processor.

4. The apparatus of claim 3, further comprising a driver circuit configured to send at least one signal to said display.

5. The apparatus of claim 4, further comprising a controller configured to send at least a portion of said image data to said driver circuit.

6. The apparatus of claim 3, further comprising an image source module configured to send said image data to said processor.

7. The apparatus of claim 6, wherein said image source module comprises at least one of a receiver, transceiver, and transmitter.

8. The apparatus of claim 3, further comprising an input device configured to receive input data and to communicate said input data to said processor.

9. A capacitor having a selectable amount of capacitance, the capacitor comprising:

means for carrying an RF signal, the carrying means having a controllably adjustable gap; and

means for tensioning at least part of the carrying means.

10. The capacitor as defined in claim 9, wherein the carrying means comprises at least two electrodes, at least one of which is movable with respect to the other.

11. The capacitor as defined in claim 9, wherein the tensioning means comprises one or more posts disposed adjacent to a movable portion of the carrying means.

12. The capacitor as defined in claim 9, wherein the carrying means comprises a deformable membrane.

13. The capacitor as defined in claim 12, wherein the carrying means additionally comprises a circuit configured to selectively apply a DC bias.

14. The capacitor as defined in claim 13, wherein the carrying means comprises a plurality of gaps between a conductive line configured to carry an RF signal and a conductive membrane.

15. The capacitor as defined in claim 13, wherein the carrying means further comprises:

means for selecting a DC bias; and

means for applying the DC bias to the at least two electrodes.

16. The capacitor as defined in claim 15, wherein the selecting means comprises a processor or a logic circuit.

17. The capacitor as defined in claim 16, wherein the applying means comprises a switch.

18. A method of selecting capacitance, the method comprising:

adjusting a gap between at least two electrodes, wherein at least one of the electrodes carries an RF signal; and

tensioning at least one of the electrodes.

19. The method as defined in claim 18, wherein adjusting the gap further comprises:

selecting a DC bias; and

applying the DC bias to the at least two electrodes.

20. The method as defined in claim 18, wherein adjusting the gap comprises adjusting a plurality of gaps between a conductive line configured to carry the RF signal and a plurality of electrodes.

21. A method of manufacturing a capacitor having a selectable capacitance, the method comprising:

forming a first electrode;

forming a second electrode such that it is movable with respect to the first electrode to provide adjustability of a gap defined between the first electrode and the second electrode; and

forming a plurality of posts configured to tension at least the second electrode, wherein the posts are disposed between the electrodes.

22. The method as defined in claim 21, further comprising forming the first electrode from a non-transparent material.

23. A capacitor produced in accordance with the method defined in claim 21.

24. An RF device, comprising:

a first conductor for carrying an RF signal; and

a deformable membrane spaced apart from the first conductor, the deformable membrane configured to selectively filter the RF signal, the deformable membrane having at least three discrete actuatable positions for selectively filtering the RF signal.

25. The RF device as defined in claim 24, wherein the deformable membrane comprises a unitary membrane.

26. The RF device as defined in claim 24, wherein the deformable membrane comprises two or more separate membranes.

27. An RF device, comprising:

means for carrying an RF signal; and

means for filtering the RF signal, the filtering means being deformable to at least one of three discrete actuatable positions to selectively filter the RF signal.

28. The RF device as defined in claim 27, wherein the carrying means comprises a conductive line.

29. The RF device as defined in claim 28, wherein the filtering means comprises two or more at least partially independently actuatable portions of one or more deformable membranes.

30. The RF device as defined in claim 29, wherein the filtering means is configured such that the at least two actuatable portions are independently actuatable.

31. A method of filtering an RF signal, the method comprising:

carrying the RF signal in a conductive line; and

selectively filtering the RF signal using a deformable membrane having at least three discrete actuatable positions for selectively filtering the RF signal, wherein the deformable membrane is adjacent to the conductive line.

32. The method as defined in claim 31, wherein selectively filtering comprises actuating two or more at least partially independently actuatable portions of one or more deformable membranes.

33. A method of manufacturing an RF device having a selectable capacitance, the method comprising:

forming a first conductor for carrying an RF signal; and

forming a deformable membrane spaced apart from the first conductor, the deformable membrane configured to selectively filter the RF signal, the deformable membrane having at least three discrete actuatable positions for selectively filtering the RF signal.

34. The method as defined in claim 33, further comprising:

forming a substrate assembly;

forming the first conductor on the substrate assembly;

forming a layer of dielectric material covering at least an upper surface of the first conductor; and

forming the deformable membrane spaced above the substrate assembly such that the first conductor is disposed between the substrate assembly and the deformable membrane.

35. The method as defined in claim 34, wherein the deformable membrane corresponds to a single continuous segment of a mechanical conductor membrane.

36. The method as defined in claim 34, further comprising forming at least two or more segments of the deformable membrane, wherein the separate segments are DC isolated from one another and coupled to separate biases for independent control of the separate segments.

37. An RF device produced in accordance with the method defined in claim 33.