Temperature compensation mechanism for a micromechanical ring resonator

• US 6,859,113 B2
• Filed: 08/29/2003
• Issued: 02/22/2005
• Est. Priority Date: 11/02/1999
• Status: Expired due to Term

• Current Assignee: ETA SA Fabriques d'Ebauches
• Original Assignee: ETA SA Fabriques d'Ebauches
• Inventors: Kück, Heinz, Platz, Rainer, Giousouf, Metin
• Primary Examiner(s): Nguyen, Minh
• Application Number:
  US10/650,811
• Publication Number:
  US 20040041643A1
• Time in Patent Office: 543 Days
• Field of Search: 331/108.C, 331/108.D, 331/116.R, 331/116.M, 331/154, 735/041.7, 735/041.8, 735042-5048, 735/041.3, 361/283.1
• US Class Current: 331/154
• CPC Class Codes: G01C 19/5712 the devices involving a micromechanical structure
• CPC Class Codes: H03B 5/30 with frequency-determining element being electromechanical resonator

Abstract

A time base including a resonator (4) and an integrated electronic circuit (3) for driving the resonator into oscillation and for producing, in response to the oscillation, a signal having a determined frequency. The resonator is an integrated micromechanical ring resonator supported above a substrate (2) and adapted to oscillate in a first oscillation mode. The ring resonator includes a free-standing oscillating structure (6). Electrodes (100, 120; 130, 150) are positioned under the free-standing oscillating structure in such a way as to drive and sense a second oscillation mode in a plane substantially perpendicular to the substrate and having a resonant frequency which is different from the resonant frequency of the first oscillation mode, a frequency difference between the resonant frequencies of both oscillation modes being used for compensating for the effect of temperature on the frequency of the signal produced by the time base.

Claims

1. A time base comprising a resonator and an integrated electronic circuit for driving said resonator into oscillation and for producing, in response to said oscillation, a signal having a determined frequency, said resonator being an integrated micromechanical ring resonator supported above a substrate and adapted to oscillate, according to a first oscillation mode, around an axis of rotation substantially perpendicular to said substrate, said ring resonator comprising:

a central post extending from said substrate along said axis of rotation;

a free-standing oscillating structure connected to said central post and including an outer ring coaxial with said axis of rotation and connected to said central post by means of a plurality of spring elements; and

electrodes disposed around said outer ring and connected to said integrated electronic circuit,

wherein said electrodes are positioned under said free-standing oscillating structure in such a way as to drive and sense a second oscillation mode in a plane substantially perpendicular to said substrate and having a resonant frequency which is different from the resonant frequency of said first oscillation mode, a frequency difference between the resonant frequencies of both oscillation modes being used for compensating for the effect of temperature on the frequency of the signal produced by said time base.

2. The time base according to claim 1, wherein said second oscillation mode is a tilting oscillation mode.

3. The time base according to claim 2, wherein said electrodes disposed under the free-standing oscillating structure for driving and sensing the ring resonator tilting oscillation comprise at least one driving electrode disposed on a first side of the free-standing oscillating structure and at least one sensing electrode disposed on an opposite side of the free-standing oscillating structure.

4. The time base according to claim 1, wherein said second oscillation mode is a vertical oscillation mode parallel to said axis of rotation.

5. The time base according to claim 4, wherein said electrodes disposed under the free-standing oscillating structure for driving and sensing the ring resonator vertical oscillation comprise one pair of diametrically opposed driving electrodes and one pair of diametrically opposed sensing electrodes.

6. The time base according to claim 1, wherein said electrodes comprise a first set of electrodes, disposed around said outer ring, and a second set of electrodes positioned under said free-standing oscillating structure.

7. In a time base comprising a resonator, a method for driving said resonator into oscillation, said resonator being an integrated micromechanical ring resonator supported above a substrate and comprising:

a central post extending from said substrate along an axis of rotation substantially perpendicular to said substrate;

a free-standing oscillating structure connected to said central post and including an outer ring coaxial with said axis of rotation and connected to said central post by means of a plurality of spring elements; and

electrodes disposed around said outer ring,

said method comprising a step of driving said ring resonator into oscillation, according to a first oscillation mode, around said axis of rotation,

wherein said method further comprises the steps of;

providing said electrodes under said free-standing oscillating structure so as to drive and sense a second oscillation mode of said ring resonator in a plane substantially perpendicular to said substrate and having a resonant frequency which is different from the resonant frequency of said first oscillation mode, and

measuring a frequency difference between the resonant frequencies of the first and second oscillation modes for compensating for the effect of temperature on the frequency of a signal produced by the time base.

8. The method according to claim 7, wherein said second oscillation mode is a tilting oscillation mode.

9. Method according to claim 7, wherein said second oscillation mode is a vertical oscillation mode parallel to said axis of rotation.