Wireless Sensing System Using Open-Circuit, Electrically-Conductive Spiral-Trace Sensor

Abstract

A wireless sensing system includes a sensor made from an electrical conductor shaped to form an open-circuit, electrically-conductive spiral trace having inductance and capacitance. In the presence of a time-varying magnetic field, the sensor resonates to generate a harmonic response having a frequency, amplitude and bandwidth. A magnetic field response recorder wirelessly transmits the time-varying magnetic field to the sensor and wirelessly detects the sensor's response frequency, amplitude and bandwidth.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of an open-circuit spiral trace sensor in accordance with an embodiment of the present invention;

FIG. 2 is a schematic view of an embodiment of a magnetic field response recorder used in the present invention;

FIG. 3 is a schematic view of a spiral trace sensor whose traces are non-uniform in width;

FIG. 4 is a schematic view of a spiral trace sensor having non-uniform spacing between the traces thereof;

FIG. 5 is a schematic view of a spiral trace sensor having non-uniform trace width and non-uniform trace spacing;

FIG. 6A is a cross-sectional view of a spiral trace sensor assembly with a dielectric material disposed between the sensor's traces;

FIG. 6B is a cross-sectional view of a spiral trace sensor assembly with a dielectric material layer disposed on top of the spiral trace;

FIG. 6C is a cross-sectional view of a spiral trace sensor assembly with a dielectric material disposed between the sensor's traces and on top of the spiral trace;

FIG. 7A is a schematic view of a linear arrangement of open-circuit spiral trace sensors mutually inductively coupled and interrogated by a magnetic field response recorder; and

FIG. 7B is a schematic view of a non-linear arrangement of open-circuit spiral trace sensors mutually inductively coupled and interrogated by a magnetic field response recorder.

Claims

1. A wireless sensing system, comprising: an electrical conductor having first and second ends and shaped to form a spiral between said first and second ends, said conductor so-shaped defining an open-circuit having inductance and capacitance wherein, in the presence of a time-varying magnetic field, said conductor so-shaped resonates to generate a harmonic magnetic field response having a frequency, amplitude and bandwidth; anda magnetic field response recorder for wirelessly transmitting said time-varying magnetic field to said conductor so-shaped and for wirelessly detecting said frequency, amplitude and bandwidth.

2. A wireless sensing system as in claim 1 wherein said conductor comprises a thin-film trace.

3. A wireless sensing system as in claim 2 wherein said trace is uniform in width.

4. A wireless sensing system as in claim 2 wherein spacing between adjacent portions of said trace is uniform.

5. A wireless sensing system as in claim 2 wherein said trace is non-uniform in width.

6. A wireless sensing system as in claim 2 wherein spacing between adjacent portions of said trace is non-uniform.

7. A wireless sensing system as in claim 1 wherein said conductor is configured to affect said capacitance and inductance in a way that makes said amplitude at least 10 db more than an amplitude of ambient noise at said magnetic field response recorder.

8. A wireless sensing system as in claim 1 further comprising a dielectric material disposed between adjacent portions of said conductor.

9. A wireless sensing system as in claim 1 further comprising a dielectric material disposed on said conductor.

10. A wireless sensing system as in claim 1 further comprising a dielectric material disposed between adjacent portions of said conductor and on said conductor.

11. A wireless sensing system, comprising: a non-conductive substrate;an open-circuit electrically-conductive spiral trace deposited on said substrate, said spiral trace having inductance and capacitance that (i) allows said spiral trace to generate a harmonic magnetic field response having a frequency, amplitude and bandwidth in the presence of a time-varying magnetic field, and (ii) causes said amplitude to be at least 10 dB more than ambient noise; anda magnetic field response recorder for wirelessly transmitting said time-varying magnetic field to said spiral trace and for wirelessly detecting said frequency, amplitude and bandwidth.

12. A sensing system as in claim 11 wherein said substrate is flexible.

13. A wireless sensing system as in claim 11 wherein said spiral trace is uniform in width.

14. A wireless sensing system as in claim 11 wherein spacing between adjacent portions of said spiral trace is uniform.

15. A wireless sensing system as in claim 11 wherein said spiral trace is non-uniform in width.

16. A wireless sensing system as in claim 11 wherein spacing between adjacent portions of said spiral trace is non-uniform.

17. A wireless sensing system as in claim 11 further comprising a dielectric material disposed between adjacent portions of said spiral trace.

18. A wireless sensing system as in claim 11 further comprising a dielectric material disposed on said spiral trace.

19. A wireless sensing system as in claim 11 further comprising a dielectric material disposed between adjacent portions of said spiral trace and on said spiral trace.

20. A wireless sensing system, comprising: a non-conductive, flexible substrate;an open-circuit electrically-conductive spiral trace deposited on said substrate, said spiral trace having inductance and capacitance that (i) allows said spiral trace to generate a harmonic magnetic field response having a frequency, amplitude and bandwidth in the presence of a time-varying magnetic field, and (ii) causes said amplitude to be at least 10dB more than ambient noise;a dielectric material disposed between adjacent portions of said spiral trace and on said spiral trace wherein said spiral trace is encased by said substrate and said dielectric material; anda magnetic field response recorder for wirelessly transmitting said time-varying magnetic field to said spiral trace and for wirelessly detecting said frequency, amplitude and bandwidth.

21. A wireless sensing system as in claim 20 wherein said spiral trace is uniform in width.

22. A wireless sensing system as in claim 20 wherein spacing between adjacent portions of said spiral trace is uniform.

23. A wireless sensing system as in claim 20 wherein said spiral trace is non-uniform in width.

24. A wireless sensing system as in claim 20 wherein spacing between adjacent portions of said spiral trace is non-uniform.

25. A wireless sensing system, comprising: an arrangement of inductively, wherein said arrangement is fixed;each said sensor being an electrical conductor having first and second ends, said conductor shaped to form a spiral between said first and second ends and further shaped to define an open-circuit having inductance and capacitance;at least one said sensor directly powered and interrogated by a magnetic field response recorder wherein, in the presence of a time-varying magnetic field, said sensor resonates to generate one or more harmonic responses each having a frequency, amplitude, and bandwidth resulting from resonant responses of said inductively coupled arrangement of sensors;said responses of said arrangement of sensors correlated to the magnitude of one or more physical quantities; anda magnetic field response recorder for (i) wirelessly transmitting said time-varying magnetic field to said sensor directly powered and interrogated and (ii) for wirelessly detecting said frequencies, amplitudes and bandwidths of all said arranged sensors.

26. A wireless sensing system as in claim 25 wherein each said conductor comprises a thin-film trace.

27. A wireless sensing system as in claim 26 wherein said traces are uniform in width.

28. A wireless sensing system as in claim 26 wherein spacing between adjacent portions of said traces is uniform.

29. A wireless sensing system as in claim 26 wherein said traces are non-uniform in width.

30. A wireless sensing system as in claim 26 wherein spacing between adjacent portions of said traces is non-uniform.

31. A wireless sensing system as in claim 25 wherein said conductors are configures to affect said capacitance and inductance in a way that makes said amplitudes at least 10 dB more than an amplitude of ambient noise at said magnetic field response recorder.

32. A wireless sensing system as in claim 25 further comprising a dielectric material disposed between adjacent portions of at least one of said conductors.

33. A wireless sensing system as in claim 25 further comprising a dielectric material disposed on at least one of said conductors.

34. A wireless sensing system as in claim 25 further comprising a dielectric material disposed between adjacent portions of at least one of said conductors and on at least one of said conductors.

35. A wireless sensing system as in claim 25 wherein said arrangement of sensors is deposited on a non-conductive substrate.