Claims
- 1. A method to control a movable electrode of a variable capacitor by electrostatic force feedback comprising the steps of:
a. providing a capacitor with a movable electrode and a cooperating stationary electrode; b. providing a capacitance detection circuit with an input coupling capacitor and a bridge network means actively nulled by current feedback; c. detecting and amplifying a change in capacitance of said variable capacitor to generate a feedback control voltage; d. applying said feedback control voltage across said movable and said stationary electrodes, whereby said movable electrode is maintained at a fixed position or predetermined generatrix.
- 2. The method as claimed in claim 1 wherein said capacitor is a variable-area capacitor.
- 3. The method as claimed in claim 1 wherein said capacitor is a capacitive transducer.
- 4. The method as claimed in claim 1 wherein said movable electrode is connected to a ground potential.
- 5. The method as claimed in claim 1 wherein said stationary electrode is connected to a ground potential.
- 6. The method as claimed in claim 1 wherein said capacitor at least in part is bulk micromachined.
- 7. The method as claimed in claim 1 wherein said capacitor at least in part is surface micromachined.
- 8. A method to control by electrostatic force feedback a moveable electrode located between two cooperating capacitor electrodes that form a first and a second capacitor element of a differential capacitor comprising the steps of:
a. providing a differential capacitor with a movable electrode and two stationary electrodes; b. providing a capacitance detection circuit that includes two input coupling capacitors and a bridge network means actively nulled by current feedback; c. providing an amplifying means with an output connected to a beam steering means; d. differentially detecting and amplifying a capacitance change of said first and said second capacitor elements to generate an error signal proportional to said capacitance change; e. amplifying said error signal to provide a feedback control voltage and steering said control voltage to one said capacitor element.
- 9. The method as claimed in claim 8 wherein said capacitor is a differential variable-area capacitor.
- 10. The method as claimed in claim 8 wherein said capacitor is a differential capacitive transducer.
- 11. The method as claimed in claim 8 wherein said movable electrode of said differential capacitor is connected to a ground potential.
- 12. The method as claimed in claim 8 wherein said capacitor at least in part is bulk micromachined.
- 13. The method as claimed in claim 8 wherein said capacitor at least in part is surface micromachined.
- 14. An electrostatically force-balanced capacitive transducer comprising:
a. a variable capacitor with a first electrode connected to a ground potential and a second electrode connected to a coupling capacitor connected to a first-side node of a bridge network means actively nulled by current feedback; b. said first-side node connected to a first input of a differential integrating means and a second-side node of said bridge network connected to a second input of opposing polarity of said integrating means and an output of said integrating means connected to a voltage-controlled current sourcing means connected to said first-side node of said bridge network means, whereby a first negative feedback loop actively nulls said bridge network means; c. said output of said integrating means connected to an input of an amplifying means with finite output impedance connected to said second electrode of said transducer, thereby a second negative feedback loop electrostatically force-balances said capacitive transducer.
- 15. The electrostatically force-balanced capacitive transducer of claim 14 further including a reference capacitor connected between said second-side node of said bridge network means and said ground potential, thereby forming a balanced full-bridge network.
- 16. The electrostatically force-balanced capacitive transducer of claim 14 further including a third electrode of said transducer connected to a second coupling capacitor connected to said second-side node of said bridge network means and said amplifying means connected to a feedback steering means with a first output terminal connected to said second capacitor electrode and a second output connected to said third capacitor electrode, thereby forming a differential electrostatically force balanced capacitive transducer.
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation-in-part of divisional application Ser. No. 09/482,119, Jan. 13, 2000, of application Ser. No. 09/037,733 of Mar. 10, 1998, now U.S. Pat. No. 6,151,967. The invention of the present application references art disclosed in continuation-in-part application Ser. No. 09/834,691, filed Apr. 13, 2001, Ser. No. 09/816,551, filed Mar. 24, 20001 and Ser. No. 09/794,198, filed Feb. 27, 2001, of divisional application Ser. No. 09/482,119. Each disclosure of the foregoing applications are incorporated herein by reference. All of the applications are assigned to the same assignee as the present application.
GOVERNMENT RIGHTS
[0002] This invention was made with Government support under contract N00024-97-C-4157 from the Naval Sea Systems Command. The Government has certain rights to this invention
Continuation in Parts (5)
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Number |
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09482119 |
Jan 2000 |
US |
Child |
09866351 |
May 2001 |
US |
Parent |
09037733 |
Mar 1998 |
US |
Child |
09866351 |
May 2001 |
US |
Parent |
09834691 |
Apr 2001 |
US |
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09866351 |
May 2001 |
US |
Parent |
09816551 |
Mar 2001 |
US |
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09866351 |
May 2001 |
US |
Parent |
09794198 |
Feb 2001 |
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09866351 |
May 2001 |
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