Article comprising a multi-port variable capacitor

• US 6,242,989 B1
• Filed: 09/12/1998
• Issued: 06/05/2001
• Est. Priority Date: 09/12/1998
• Status: Expired due to Term

• Current Assignee: Bell Semiconductor, LLC (Hilco Inc. (d/b/a Hilco Global))
• Original Assignee: Agere Systems Guardian Corp. (Broadcom, Inc.)
• Inventors: Marcus, Matthew A., Barber, Bradley Paul, Gammel, Peter L., Bishop, David J.
• Primary Examiner(s): Pascal, Robert
• Assistant Examiner(s): Glenn, Kimberly E
• Application Number:
  US09/152,185
• Time in Patent Office: 997 Days
• Field of Search: 331/36.C, 331/177.V, 334/80, 334/81, 334/82, 334/65, 334/88, 334/78, 361/278, 361/277, 361/271, 361/287, 361/290, 361/281
• US Class Current: 331/177.00V
• CPC Class Codes: G11C 23/00 Digital stores characterised by movement of mechanical parts to effect storage, e.g. using balls; Storage elements therefor
• CPC Class Codes: H01G 5/16 using variation of distance between electrodes

Abstract

An article comprising a multi-port variable capacitor is disclosed. In one embodiment, a movable plate is suspended above at least a first and a second, fixed, electrically-isolated electrode. The first electrode is electrically connected to a bias supply, and the second electrode is electrically connected to an AC signal-carrying line. As bias is applied across the first electrode and the movable plate, an electrostatic attraction is developed therebetween that causes the movable plate to move downwardly towards the first electrode. The capacitance of the variable capacitor increases as the separation distance between the movable plate and the fixed electrodes decreases. Unlike conventional variable capacitors, in the present multi-port variable capacitors, the bias (delivered via the first electrode) and the signal (delivered via the second electrode) are electrically isolated from one another. As such, the bias (DC) and signal (AC) paths are advantageously electrically isolated. In an additional embodiment, the movable plate of the present variable capacitor is operable to tilt. The ability to tilt provides additional “signal processing” (i.e., logic) capabilities to the present multi-port variable capacitors. In additional embodiments, an article in accordance with the present teachings comprises a monolithically-integrable, tunable LC circuit, and a variable-frequency oscillator. In such LC circuits and oscillators, the multi-port variable capacitor described herein is used to tune the resonant frequency of the circuit.

Claims

1. An article comprising a multi-port variable capacitor, the multi-port variable capacitor comprising:

first and second co-planar electrically-isolated electrodes;

a plate spaced from said first and second electrodes and not co-planar therewith, said plate movable from a neutral position towards at least the first electrode when a bias voltage is applied across the first electrode and the plate, wherein, as the plate moves towards the first electrode, a first capacitance between said first electrode and the plate, and a second capacitance between said second electrode and the plate, changes; and

further wherein said article is operable to sense the change in said second capacitance.

2. The article of claim 1, further comprising supports in mechanical contact with the plate for spacing the plate from said first and second electrodes.

3. The article of claim 2, wherein said supports are resilient for imparting a restoring force to the plate.

4. An article comprising a multi-port variable capacitor, the multi-port variable capacitor comprising:

first and second co-planar electrically-isolated electrodes;

a plate spaced from said first and second electrodes and not co-planar therewith, said plate movable from a neutral position towards at least the first electrode when a bias voltage is applied across the first electrode and the plate wherein, as the plate moves towards the first electrode, a first capacitance between said first electrode and the plate, and a second capacitance between said second electrode and the plate, changes; and

supports in mechanical contact with said plate for spacing the plate from said first and second electrodes, wherein;

said supports are resilient for imparting a restoring force to said plate; and

the supports are conductive so that the voltage applied to the plate is delivered via the supports.

5. An article comprising a multi-port variable capacitor, the multi-port variable capacitor comprising:

first and second co-planar electrically-isolated electrodes;

a plate spaced from said first and second electrodes and not co-planar therewith, said plate movable from a neutral position towards at least the first electrode when a bias voltage is applied across the first electrode and the plate; and

a connection for electrically connecting an AC signal line to the second electrode,

wherein, as the plate moves towards the first electrode, a first capacitance between said first electrode and the plate, and a second capacitance between said second electrode and the plate, changes.

6. An article comprising a multi-port variable capacitor, the multi-port variable capacitor comprising:

first and second co-planar electrically-isolated electrodes;

a plate spaced from said first and second electrodes and not co-planar therewith, said plate movable from a neutral position towards at least said first electrode on application of a voltage across said first electrode and said plate; and

a fulcrum disposed between the first and second electrodes and beneath and contacting said plate, the fulcrum functionally dividing the plate into first and second segments.

7. The article of claim 6, wherein the article is a logic device, and further comprising:

a third electrode disposed beneath said plate;

a first connection for electrically connecting the first electrode to a first AC signal; and

a second connection for electrically connecting the second electrode to a second AC signal;

wherein, a third signal readable at the third electrode is dependent upon a first value of the first AC signal and a second value of the second AC signal.

8. The article of claim 7, wherein the first and second values are representative of a voltage of each of the first and second AC signals.

9. The article of claim 7, and further comprising:

a third electrode disposed between the first and second electrodes underneath the first segment of the plate; and

a fourth electrode disposed between the third and second electrodes underneath the second segment of the plate.

10. A LC circuit comprising:

a multi-port variable capacitor, said multi-port variable capacitor comprising;

first and second co-planar electrically-isolated electrodes; and

a plate spaced from said first and second electrodes and not co-planar therewith, said plate movable from a neutral position towards at least said first electrode on application of a voltage across said first electrode and said plate;

an inductor electrically connected to the multiport variable capacitor; and

a signal generator.

11. The article of claim 10, wherein the inductor and the multi-port variable capacitor are connected in series.

12. The article of claim 10, wherein the inductor and the multi-port variable capacitor are connected in parallel.

13. The article of claim 10, wherein the article is a variable-frequency oscillator, the article further comprising a negative resistance device electrically connected to the LC circuit.

14. The article of claim 13, wherein the negative resistance device is a transistor, the article further comprising a terminating network electrically connected to the transistor.

15. An article comprising a multi-port variable capacitor, the multi-port variable capacitor comprising:

a first and a second electrode, wherein said first and second electrodes are co-planar and electrically isolated from one another;

a plate disposed in superposed and spaced relation from said first and second electrodes;

supports for supporting the plate in said superposed and spaced relation, wherein said supports are resilient and conductive;

a fulcrum disposed between the first and second electrodes and beneath and contacting said plate, the fulcrum functionally dividing the plate into first and second segments;

a first connection by which a first electrical signal is connected across the plate and the first electrode; and

a second connection by which a second electrical signal is connected across the plate and the second electrode.

16. A variable-frequency oscillator, the variable-frequency oscillator having:

a load incorporating an LC circuit;

a transistor electrically connected to the load; and

a terminating network electrically connected to the transistor, wherein, said LC circuit comprises a multi-port variable capacitor the multi-port variable capacitor comprising;

a first and a second electrode, wherein said first and second electrodes are co-planar and electrically isolated from one another;

a plate disposed in superposed and spaced relation from said first and second electrodes;

supports for supporting the plate in said superposed and spaced relation, wherein said supports are resilient and conductive;

a first connection by which a first electrical signal is connected across the plate and the first electrode; and

a second connection by which a second electrical signal is connected across the plate and the second electrode.

17. A method for performing logic using a plate disposed on a fulcrum and spaced from three electrodes, comprising the steps of:

applying a first signal across the first electrode and the plate;

applying a second signal across the second electrode and the plate; and

reading a third signal from the third electrode, wherein

the third signal is determined as a function of the first and second signals.

18. The method of claim 17, wherein the third signal is determined from a truth table providing the logic state of the third signal as a function of the logic states of the first and second signals.