SURFACE ACOUSTIC WAVE BASED MICRO-SENSOR APPARATUS AND METHOD FOR SIMULTANEOUSLY MONITORING MULTIPLE CONDITIONS

• US 20100158071A1
• Filed: 01/13/2009
• Published: 06/24/2010
• Est. Priority Date: 12/23/2008
• Status: Active Grant

• Current Assignee: Honeywell International Inc.
• Original Assignee: Honeywell International Inc.
• Inventors: Gologanu, Mihal, Cobianu, Cornel, Pavelescu, Ioan
• Granted Patent: US 8,317,392 B2
• Time in Patent Office: Days
• US Class Current: 374/142
• CPC Class Codes: H03H 9/02535 of surface acoustic wave devices

Abstract

A SAW-based micro-sensor apparatus for simultaneously monitoring acceleration/vibration and temperature utilizing a sensing element configured as a SAW device (e.g., SAW resonator or SAW delay line). The SAW device can be located in different locations on a substrate with respect to a thin piezoelectric diaphragm comprising an inertial mass. The temperature-compensated acceleration/vibration can be measured utilizing a frequency difference between an acceleration sensitive SAW resonator (e.g., SAW-g) and a temperature sensitive SAW resonator (e.g., SAW-T). The temperature can be measured utilizing a frequency shift provided by the SAW-T and a temperature reference SAW resonator (e.g., SAW-R). Similarly, the phase response of different reflectors of the SAW delay line can be utilized to differentially measure the acceleration/vibration and temperature.

Claims

1. A SAW-based micro-sensor apparatus, comprising:

a piezoelectric substrate; and

at least one sensing element configured as a SAW device, wherein said SAW device is capable of being located in different positions on said piezoelectric substrate with respect to a piezoelectric diaphragm that comprises an inertial mass for monitoring a plurality of conditions, including at least one of the following conditions;

temperature-compensated acceleration/vibration and a temperature thereto.

2. The apparatus of claim 1 wherein said piezoelectric diaphragm supports said inertial mass and includes at least one bridge for assisting in a high-sensitivity acceleration detection of said plurality of conditions.

3. The apparatus of claim 1 wherein said SAW device comprises at least one SAW resonator.

4. The apparatus of claim 1 wherein said SAW device comprises at least a SAW delay line.

5. The apparatus of claim 3 wherein said at least one SAW resonator further comprises:

a temperature sensitive SAW resonator located on a stress free region above said inertial mass;

an acceleration sensitive SAW resonator located on a tensile stress region of said piezoelectric diaphragm near said inertial mass; and

a temperature reference SAW resonator located on a rim of said stress free region.

6. The apparatus of claim 5 wherein:

said temperature compensated acceleration/vibration is measured utilizing a frequency difference between said acceleration sensitive SAW resonator and said temperature sensitive SAW resonator; and

said temperature is measured utilizing a frequency shift provided by said temperature sensitive SAW resonator and said temperature reference SAW resonator.

7. The apparatus of claim 3 wherein:

said acceleration sensitive SAW resonator is located on a radial compressive stress region near said rim;

said temperature sensitive SAW resonator is located on said stress free region above said inertial mass; and

said temperature reference SAW sensor is located on a rim of said stress free region.

8. The apparatus of claim 3 wherein:

said temperature sensitive SAW resonator and said temperature reference SAW resonator are located on a rim of said stress free region; and

said acceleration sensitive SAW resonator is located on a tensile stress region of said piezoelectric diaphragm near said inertial mass.

9. The apparatus of claim 3 wherein:

said temperature sensitive SAW resonator and said temperature reference SAW resonator are located on a rim of the said stress free region; and

said acceleration sensitive SAW resonator is located on a compressive stress region of said piezoelectric diaphragm near said inertial mass.

10. The apparatus of claim 2 wherein said SAW device comprises a SAW resonator.

11. The apparatus of claim 10 wherein:

said temperature sensitive SAW resonator and said temperature reference SAW resonator are located on a rim of said stress free region; and

said acceleration sensitive SAW resonator is located on a tensile stress region, near said inertial mass of said piezoelectric diaphragm supported by said at least one bridge.

12. The apparatus of claim 10 wherein:

said temperature sensitive SAW resonator and said temperature reference SAW resonator are located on a rim on said stress free region; and

said acceleration sensitive SAW resonator is located on the compressive stress region on a mass of said piezoelectric diaphragm supported by said at least one bridge.

13. The apparatus of claim 10 wherein:

said temperature sensitive SAW resonator is located on said stress free region above said inertial mass;

said temperature reference SAW resonator is located on a stress free region on said rim and outside said piezoelectric diaphragm; and

said acceleration sensitive SAW resonator is located on a tensile stress region, near said inertial mass of said piezoelectric diaphragm supported by said at least one bridge.

14. The apparatus of claim 10 wherein:

said temperature sensitive SAW resonator is located above said inertial mass on the stress free region;

said temperature reference SAW resonator is located on said rim and on the stress free region; and

said acceleration sensitive SAW resonator is located on a compressive stress region near said inertial mass, of said piezoelectric diaphragm, which is supported by said at least one bridge.

15. The apparatus of claim 3 wherein said temperature sensitive SAW resonator, said acceleration sensitive SAW resonator and said temperature reference SAW resonator are connected electrically in parallel with one another on said substrate.

16. The apparatus of claim 4 wherein said SAW delay line further comprises:

at least one inter-digital transducer located on a stress free region above said inertial mass;

a plurality of acceleration sensitive reflectors located on a tensile stressed region of said diaphragm; and

a plurality of temperature sensitive reflectors located on said stress free region above said inertial mass region, wherein said plurality of temperature sensitive reflectors is tilted with different angles with respect to a direction of said inter-digital transducer for said temperature measurement.

19. The apparatus of claim 1 wherein said piezoelectric diaphragm supports said inertial mass and includes at least one bridge for assisting in a high-sensitivity acceleration detection of said plurality of conditions, wherein said SAW device comprises at least one SAW delay line.

20. The apparatus of claim 19 wherein:

said SAW device comprises at least one SAW delay line; and

said SAW delay line further comprises;

at least one inter-digital transducer located on a stress free region of said rim;

a plurality of acceleration sensitive reflectors located on a compressive stressed region of said diaphragm; and

a plurality of temperature sensitive reflectors located on said stress free region located on the rim, wherein said plurality of temperature sensitive reflectors is tilted with different angles with respect to a direction of said inter-digital transducer for said temperature measurement.

17. A SAW-based micro-sensor apparatus, comprising:

a piezoelectric substrate;

at least one sensing element configured as a SAW device, wherein said SAW device is capable of being located in different positions on said piezoelectric substrate with respect to a piezoelectric diaphragm that comprises an inertial mass for monitoring a plurality of conditions, including at least one of the following conditions;

temperature-compensated acceleration/vibration and a temperature thereto; and

wherein said SAW device comprises at least a SAW delay line, wherein said SAW delay line further comprises;

at least one interdigital transducer located on a stress free region above said inertial mass;

a plurality of acceleration sensitive reflectors located on a tensile stressed region of said diaphragm, and

a plurality of temperature sensitive reflectors located on said tensile stressed region of said diaphragm, wherein said plurality of temperature sensitive reflectors is tilted with different angles with respect to a direction of said inter-digital transducer for said temperature measurement.

18. A SAW-based micro-sensor apparatus, comprising:

a piezoelectric substrate;

at least one sensing element configured as a SAW device, wherein said SAW device is capable of being located in different positions on said piezoelectric substrate with respect to a piezoelectric diaphragm that comprises an inertial mass for monitoring a plurality of conditions, including at least one of the following conditions;

temperature-compensated acceleration/vibration and a temperature thereto; and

wherein said SAW device comprises at least a SAW delay line, wherein said SAW delay line further comprises;

at least one interdigital transducer located on stress free region of said rim outside the said diaphragm;

a plurality of acceleration sensitive reflectors located on a compressive stressed region of said diaphragm; and

a plurality of temperature sensitive reflectors located on said stress free region on the rim outside said piezoelectric diaphragm, wherein said plurality of temperature sensitive reflectors is tilted with different angles with respect to a direction of said inter-digital transducer for said temperature measurement.