Wireless sensor antenna configuration

• US 20070131032A1
• Filed: 12/13/2005
• Published: 06/14/2007
• Est. Priority Date: 12/13/2005
• Status: Active Grant

• Current Assignee: Honeywell International Inc.
• Original Assignee: Honeywell International Inc.
• Inventors: Liu, James
• Granted Patent: US 7,377,168 B2
• Time in Patent Office: Days
• US Class Current: 73/579
• CPC Class Codes: G01N 2291/0255 (Bio)chemical reactions, e.g. on biosensors
• CPC Class Codes: G01N 2291/0256 Adsorption, desorption, surface mass change, e.g. on biosensors
• CPC Class Codes: G01N 2291/02863 Electric or magnetic parameters
• CPC Class Codes: G01N 2291/0423 Surface waves, e.g. Rayleigh waves, Love waves
• CPC Class Codes: G01N 27/025 a current being generated within the material by induction
• CPC Class Codes: G01N 27/725 by using magneto-acoustical effects or the Barkhausen effect
• CPC Class Codes: G01N 29/022 Fluid sensors based on microsensors, e.g. quartz crystal-microbalance [QCM], surface acoustic wave [SAW] devices, tuning forks, cantilevers, flexural plate wave [FPW] devices microdevices per se B81B
• CPC Class Codes: G01N 29/2412 using the magnetostrictive properties of the material to be examined, e.g. electromagnetic acoustic transducers [EMAT]; investigating the presence of flaws using eddy currents G01N27/90, magnetostrictive transducers B06B1/08, measuring magnetostrictive properties G01R33/18
• CPC Class Codes: G01N 29/2462 Probes with waveguides, e.g. SAW devices
• CPC Class Codes: G01N 29/34 Generating the ultrasonic, sonic or infrasonic waves , e.g. electronic circuits specially adapted therefor
• CPC Class Codes: G01N 29/36 Detecting the response signal , e.g. electronic circuits specially adapted therefor

Abstract

Many sensors could be used in a passive wireless mode. These include RLC, acoustic wave and magneto-elastic sensors. These types of sensors are designed to exhibit a change in fundamental frequency when exposed to environmental factors such as temperature, pressure, or chemicals. An interrogation circuit can inductively couple to the sensor and measure the change in fundamental frequency. The change can be used to measure the environmental factor. Sensor sensitivity and inductive coupling efficiency can be competing design constraints. A driver, electrically connected to the sensor and inductively coupled to the interrogation circuit, can relax the constraints. The driver, however, can introduce noise into the sensor. The sensor can be shielded using physical and geometric techniques to reduce the noise.

Claims

1. A system comprising:

a sensor comprising an acoustic wave device electrically connected to a spiral inductor wherein the sensor has a fundamental frequency that changes in response to environmental factors such as temperature, pressure, or chemicals;

an interrogation circuit that measures the fundamental frequency wherein the interrogation circuit is inductively coupled to the spiral inductor, and wherein the interrogation circuit comprises a grid dip oscillator; and

a shield inhibiting inductive coupling to the acoustic wave device.

2. The system of claim 1 wherein the spiral inductor and the acoustic wave device are coplanar and wherein the shield is a guard ring surrounding the spiral inductor.

3. The system of claim 2 wherein the acoustic wave device is a surface acoustic wave device;

4. The system of claim 2 wherein the acoustic wave device is a bulk acoustic wave device;

5. The system of claim 1 wherein the spiral inductor and the acoustic wave device are coplanar and wherein the shield is a guard ring surrounding the acoustic wave device.

6. The system of claim 5 wherein the acoustic wave device is a surface acoustic wave device;

7. The system of claim 5 wherein the acoustic wave device is a bulk acoustic wave device;

8. The system of claim 1 wherein the shield comprises a conductive material enclosing the acoustic wave device.

9. A system comprising:

a sensor comprising an RLC sensor and electrically connected to a spiral inductor, wherein the sensor has a fundamental frequency that changes in response to environmental factors such as temperature, pressure, or chemicals;

an interrogation circuit that measures the fundamental frequency wherein the interrogation circuit is inductively coupled to the spiral inductor, and wherein the interrogation circuit comprises a grid dip oscillator; and

wherein the placement of the RLC sensor in relation to the spiral inductor and the interrogation circuit produces a geometric shield inhibiting inductive coupling to the acoustic wave device.

10. The system of claim 9 wherein the RLC sensor is rotated and displaced laterally in relation to the spiral inductor and the interrogation circuit.

11. The system of claim 10 wherein the RLC sensor comprises a PTC or NTC type resistor;

12. The system of claim 10 wherein the RLC sensor is a resistive pressure sensor;

13. The system of claim 10 wherein the RLC sensor is a capacitive pressure sensor;

14. The system of claim 10 wherein the RLC sensor is an inductive pressure sensor;

15. The system of claim 9 wherein a fundamental period is a distance inversely related to the fundamental frequency and wherein the geometric shield comprises placing the acoustic wave device more than 4 fundamental periods from the spiral inductor and from the interrogation circuit.

16. A method comprising:

providing a sensor comprising a passive sensor electrically connected to a spiral inductor wherein the sensor has a fundamental frequency that changes in response to environmental factors such as temperature, pressure, or chemicals;

shielding the passive sensor from inductive coupling; and

measuring the fundamental frequency with an interrogation circuit inductively coupled to the spiral inductor wherein the interrogation circuit comprises a grid dip oscillator.

17. The system of claim 16 wherein shielding comprises:

rotating the passive sensor in relation to the spiral inductor and the interrogation circuit; and

laterally displacing the passive sensor from the spiral inductor and the interrogation circuit.

18. The system of claim 17 wherein the passive sensor comprises a surface acoustic wave device.

19. The system of claim 17 wherein the passive sensor is a RLC sensor.

20. The system of claim 17 wherein the passive sensor comprises a magneto-elastic or magneto-strictive type device.

21. The system of claim 16 wherein shielding comprises surrounding the spiral inductor with a guard ring wherein the spiral inductor and the acoustic wave device are coplanar.

22. The system of claim 16 wherein shielding comprises surrounding the passive sensor with a guard ring wherein the spiral inductor and the acoustic wave device are coplanar.

23. The system of claim 16 wherein shielding comprises enclosing the passive sensor in a shield comprising conductive material.