Time domain delay measurement apparatus and associated method

• US 5,700,952 A
• Filed: 11/28/1995
• Issued: 12/23/1997
• Est. Priority Date: 11/28/1995
• Status: Expired due to Term

• Current Assignee: Sawtek Incorporated (Qorvo, Inc.)
• Original Assignee: Sawtek Incorporated (Qorvo, Inc.)
• Inventors: Andersen, Jorgen W.
• Primary Examiner(s): Williams, Hezron E.
• Assistant Examiner(s): MILLER, ROSE MARY
• Application Number:
  US08/563,393
• Time in Patent Office: 756 Days
• Field of Search: 73/597, 73/599, 73/19.03, 73/24.06, 73/24.04, 73/31.06, 73/54.24, 73/54.41, 73/61.79, 73/64.53, 374/119, 310/313 B, 310/313 D, 310/313 R
• US Class Current: 73/19.03
• CPC Class Codes: G01H 5/00 Measuring propagation velocity of ultrasonic, sonic or infrasonic waves , e.g. of pressure waves
• CPC Class Codes: G01P 5/247 Sing-around-systems

Abstract

An embodiment of a sensing apparatus includes an ultrasonic delay sensor having a delay related to the sensed quantity; and a time domain analysis circuit for recirculating pulses through the ultrasonic delay sensor or device and for generating the output signal related to the sensed quantity. In particular, the time domain analysis circuit may include a pulse generator for generating a series of input pulses to the ultrasonic delay sensor; a pulse detector for detecting a series of output pulses after propagation through the ultrasonic delay sensor; and a pulse recirculating circuit for causing the pulse generator to generate the series of input pulses based upon respective previously detected output pulses from the pulse detector. The apparatus also preferably includes circuits for suppressing the undesirable reflections generated by the ultrasonic delay sensor. For example, random phase switching may be used for randomly switching phases of the series of input pulses to the ultrasonic delay sensor to thereby reduce undesired reflections. In addition, a fixed delay may be operatively connected between the pulse detector and the pulse generator. Also time diversity matching to the ultrasonic delay device may also be used to suppress the effects of undesired reflections. Method aspects of the invention are also disclosed.

Claims

1. A sensing apparatus for generating an output signal related to a sensed quantity, said sensing apparatus comprising:

an ultrasonic delay sensor having a delay related to the sensed quantity; and

time domain analysis means operatively connected to said ultrasonic delay sensor for recirculating pulses therethrough and for generating the output signal related to the sensed quantity, said time domain analysis means comprising

pulse generator means for generating a series of input pulses to said ultrasonic delay sensor,

pulse detector means for detecting a series of output pulses after propagation through said ultrasonic delay sensor, and

pulse recirculating means for causing said pulse generator means to generate the series of input pulses based upon respective previously detected output pulses from said pulse detector means.

2. A sensing apparatus according to claim 1 wherein said ultrasonic delay sensor generates undesired multiple reflections from pulses propagating therethrough, and wherein said time domain analysis means further comprises reflection suppression means for suppressing effects of the undesired reflections generated by said ultrasonic delay sensor.

3. A sensing apparatus according to claim 2 wherein said reflection suppression means further comprises random phase switching means cooperating with said pulse generator means for randomly switching phases of the series of input pulses to said ultrasonic delay sensor to thereby reduce effects of the undesired reflections.

4. A sensing apparatus according to claim 2 wherein said reflection suppression means further comprises a fixed delay operatively connected between said pulse detector means and said pulse generator means to thereby reduce effects of the undesired reflections.

5. A sensing apparatus according to claim 2 wherein said reflection means further comprises time diversity matching means operatively connected between said pulse generator means and said ultrasonic delay sensor for providing a substantial conjugate match therebetween during a time interval of each pulse and providing a relatively large mismatch at other times.

6. A sensing apparatus according to claim 1 further comprising:

at least one other ultrasonic delay sensor having a delay related to another sensed quantity; and

time division multiplex means for successively connecting said time domain analysis means to each of the plurality of ultrasonic delay sensors so that said time domain analysis means generates a plurality of output signals related to corresponding sensed quantities.

7. A sensing apparatus according to claim 1 wherein the ultrasonic delay sensor is a surface acoustic wave (SAW) sensor.

8. A sensing apparatus according to claim 1 wherein the ultrasonic delay sensor is a surface acoustic wave (SAW) vapor sensor, and wherein said time domain analysis means further comprises vapor concentration output means for generating the output signal related to vapor concentration sensed by said SAW vapor sensor.

9. A sensing apparatus according to claim 8 wherein said vapor concentration output means further comprises sensor calibration means for calibrating the output signal therefrom.

10. A sensing apparatus according to claim 1 wherein the ultrasonic delay sensor is an ultrasonic delay pressure sensor, and wherein said time domain analysis means further comprises pressure output means for generating the output signal related to pressure sensed by said ultrasonic delay pressure sensor.

11. A sensing apparatus according to claim 1 wherein the ultrasonic delay sensor is an ultrasonic delay particulate sensor, and wherein said time domain analysis means further comprises particulate output means for generating the output signal related to a particulate sensed by said ultrasonic delay particulate sensor.

12. A sensing apparatus according to claim 1 wherein said time domain analysis means further comprises time base means for generating a time base signal having a predetermined time base period.

13. A sensing apparatus according to claim 12 wherein said time domain analysis means further comprises counting means for determining a number of time base periods occurring during a measurement defined by a predetermined number of pulse recirculations.

14. A sensing apparatus according to claim 12 further comprising integration means cooperating with said time base means for generating an interpolation signal based upon an integration relative to a last time period of said time base during the measurement defined by the predetermined number of pulse recirculations.

15. An apparatus for generating output signals related to sensed quantities from a plurality of ultrasonic delay sensors, said apparatus comprising:

time domain analysis means for recirculating pulses through an ultrasonic delay sensor and for generating an output signal related to a respective sensed quantity; and

time division multiplex means for successively connecting said time domain analysis means to each of the plurality of ultrasonic delay sensors so that said time domain analysis means generates a plurality of output signals related to corresponding sensed quantities.

16. An apparatus according to claim 15 wherein said time domain analysis means comprises:

pulse generator means for generating a series of input pulses to said ultrasonic delay sensor;

pulse detector means for detecting a series of output pulses after propagation through said ultrasonic delay sensor; and

pulse recirculating means for causing said pulse generator means to generate the series of input pulses based upon respective previously detected output pulses from said pulse detector means.

17. An apparatus according to claim 16 wherein each of the ultrasonic delay sensors generates undesired multiple reflections from pulses propagating therethrough, and wherein said time domain analysis means further comprises reflection suppression means for suppressing effects of the undesired reflections generated by a connected ultrasonic delay sensor.

18. An apparatus according to claim 17 wherein said reflection suppression means further comprises random phase switching means cooperating with said pulse generator means for randomly switching phases of the series of input pulses to the connected ultrasonic delay sensor to thereby reduce effects of the undesired reflections.

19. An apparatus according to claim 17 wherein said reflection suppression means further comprises a fixed delay operatively connected between said pulse detector means and said pulse generator means to thereby reduce effects of the undesired reflections.

20. An apparatus according to claim 17 wherein said reflection suppression means further comprises time diversity matching means operatively connected between said pulse generator means and each ultrasonic delay sensor for providing a substantial conjugate match therebetween during a time interval of each pulse and providing a relatively large mismatch at other times.

21. An apparatus according to claim 16 wherein said time domain analysis means further comprises a time base having a predetermined time base period.

22. An apparatus according to claim 21 wherein said time domain analysis means further comprises counting means for determining a number of time base periods occurring during a measurement defined by a predetermined number of pulse recirculations.

23. An apparatus according to claim 15 wherein each of the ultrasonic delay sensors is a surface acoustic wave (SAW) vapor sensor, and wherein said time domain analysis means further comprises vapor concentration output means for generating the plurality of output signals related to vapor concentration sensed by corresponding SAW vapor sensors.

24. An apparatus for generating an output signal related to a delay of at least one ultrasonic delay device, said apparatus comprising:

pulse generator means for generating a series of input pulses to the ultrasonic delay device;

pulse detector means for detecting a series of output pulses after propagation through the ultrasonic delay device;

pulse recirculating means for causing said pulse generator means to generate the series of input pulses based upon respective previously detected output pulses from said pulse detector means; and

output means operatively connected to said pulse detector means for generating the output signal related to the delay of the ultrasonic delay device based upon detected recirculated pulses.

25. An apparatus according to claim 24 wherein the ultrasonic delay device generates undesired multiple reflections from pulses propagating therethrough, and further comprising reflection suppression means for suppressing effects of the undesired reflections generated by the ultrasonic delay device.

26. An apparatus according to claim 25 wherein said reflection suppression means further comprises random phase switching means cooperating with said pulse generator means for randomly switching phases of the series of input pulses to the ultrasonic delay device to thereby reduce effects of the undesired reflections.

27. An apparatus according to claim 25 wherein said reflection suppression means further comprises a fixed delay operatively connected between said pulse detector means and said pulse generator means to thereby reduce effects of the undesired reflections.

28. An apparatus according to claim 25 wherein said reflection suppression means further comprises time diversity matching means operatively connected between said pulse generator means and said ultrasonic delay sensor for providing a substantial conjugate match therebetween during a time interval of each pulse and providing a relatively large mismatch at other times.

29. An apparatus according to claim 24 wherein the ultrasonic delay sensor is a surface acoustic wave (SAW) vapor sensor, and wherein said output means further comprises means for generating the output signal related to vapor concentration sensed by the SAW vapor sensor.

30. An apparatus according to claim 24 further comprising a time base operatively connected to said output means and having a predetermined time base period.

31. An apparatus according to claim 30 wherein said time domain analysis means further comprises counting means for determining a number of time base periods occurring during a measurement defined by a predetermined number of pulse recirculations.

32. An apparatus for generating an output signal related to delay of at least one ultrasonic delay device of a type generating undesired multiple reflections from pulses propagating therethrough, said apparatus comprising:

pulse generator means for generating a series of input pulses to said ultrasonic delay device;

pulse detector means for detecting a series of output pulses after propagation through said ultrasonic delay device;

pulse recirculating means for causing said pulse generator means to generate the series of input pulses based upon respective previously detected output pulses from said pulse detector means;

random phase switching means cooperating with said pulse generator means for randomly switching phases of the series of input pulses to the ultrasonic delay device to thereby reduce effects of the undesired reflections; and

output means operatively connected to said pulse detector means for generating the output signal related to the delay of the ultrasonic delay device based upon detected recirculated pulses.

33. An apparatus according to claim 32 further comprising a fixed delay operatively connected between said pulse detector means and said pulse generator means to thereby further reduce effects of the undesired reflections.

34. An apparatus according to claim 32 further comprising time diversity matching means operatively connected between said pulse generator means and said ultrasonic delay device for providing a substantial conjugate match therebetween during a time interval of each pulse and providing a relatively large mismatch at other times.

35. An apparatus according to claim 32 wherein the ultrasonic delay device is a surface acoustic wave (SAW) vapor sensor, and wherein said output means further comprises means for generating the output signal related to vapor concentration sensed by the SAW vapor sensor.

36. An apparatus according to claim 32 further comprising a time base having a predetermined time base period.

37. An apparatus according to claim 36 wherein said output means further comprises counting means for determining a number of time base periods occurring during a measurement defined by a predetermined number of pulse recirculations.

38. An apparatus for generating an output signal related to delay of at least one ultrasonic delay device of a type generating undesired multiple reflections from pulses propagating therethrough, said apparatus comprising:

pulse generator means for generating a series of input pulses to said ultrasonic delay device;

pulse detector means for detecting a series of output pulses after propagation through said ultrasonic delay device;

pulse recirculating means for causing said pulse generator means to generate the series of input pulses based upon respective previously detected output pulses from said pulse detector means;

a fixed delay operatively connected between said pulse detector means and said pulse generator means to thereby reduce effects of the undesired reflections; and

output means operatively connected to said pulse detector means for generating the output signal related to the delay of the ultrasonic delay device based upon detected recirculated pulses.

39. An apparatus according to claim 38 further comprising time diversity matching means operatively connected between said pulse generator means and said ultrasonic delay device for providing a substantial conjugate match therebetween during a time interval of each pulse and providing a relatively large mismatch at other times.

40. An apparatus according to claim 38 wherein the ultrasonic delay device is a surface acoustic wave (SAW) vapor sensor, and wherein said output means further comprises means for generating the output signal related to vapor concentration sensed by the SAW vapor sensor.

41. An apparatus according to claim 38 further comprising a time base having a predetermined time base period.

42. An apparatus according to claim 41 wherein said output means further comprises counting means for determining a number of time base periods occurring during a measurement defined by a predetermined number of pulse recirculations.

43. An apparatus for generating an output signal related to delay of at least one ultrasonic delay device, said apparatus comprising:

pulse generator means for generating a series of input pulses to said ultrasonic delay device, said pulse generator means further comprising time diversity matching means for providing a substantial conjugate match with the ultrasonic delay device during a time interval of each pulse and providing a relatively large mismatch at other times;

pulse detector means for detecting a series of output pulses after propagation through the ultrasonic delay device;

pulse recirculating means for causing said pulse generator means to generate the series of input pulses based upon respective previously detected output pulses from said pulse detector means; and

output means operatively connected to said pulse detector means for generating the output signal related to a delay of the ultrasonic delay device based upon detected recirculated pulses.

44. An apparatus according to claim 43 wherein the ultrasonic delay device is a surface acoustic wave (SAW) vapor sensor, and wherein said output means further comprises means for generating the output signal related to vapor concentration sensed by said SAW vapor sensor.

45. An apparatus according to claim 43 further comprising a time base having a predetermined time base period.

46. An apparatus according to claim 44 wherein said output means further comprises counting means for determining a number of time base periods occurring during a measurement defined by a predetermined number of pulse recirculations.

47. A method for measuring delay of an ultrasonic delay device, the method comprising the steps of:

recirculating pulses through the ultrasonic delay device by detecting a series of output pulses after propagation through the ultrasonic delay device, and generating a series of input pulses to the ultrasonic delay device based upon respective previously detected output pulses; and

generating an output signal related to the delay of the ultrasonic delay device based upon time domain analysis of the recirculated pulses.

48. A method according to claim 47 further comprising the step of suppressing effects of undesirable reflections generated by the ultrasonic delay device.

49. A method according to claim 48 wherein the step of suppressing effects of undesirable reflections comprises randomly switching phases of the series of input pulses to the ultrasonic delay device.

50. A method according to claim 48 wherein the step of suppressing effects of undesirable reflections comprises inserting a fixed delay in a pulse recirculating path.

51. A method according to claim 48 wherein the step of suppressing effects of undesirable reflections further comprises the step of providing a substantial conjugate match between a pulse generator and the ultrasonic delay device during a time interval of each pulse and providing a relatively large mismatch at other times.

52. A method according to claim 47 further comprising the step of time division multiplexing a plurality of ultrasonic delay devices.

53. A method according to claim 47 wherein the ultrasonic delay device is a surface acoustic wave (SAW) sensor, and further comprising the step of generating the output signal related to a quantity sensed by the SAW sensor.

54. A method according to claim 53 further comprising the step of calibrating the output signal for the SAW sensor.

55. A method according to claim 47 further comprising the step of generating a time base signal having a predetermined time base period.

56. A method according to claim 55 further comprising the step of determining a number of time base periods occurring during a measurement defined by a predetermined number of pulse recirculations.

57. A method according to claim 56 further comprising the step of generating an interpolation signal based upon an integration relative to a predetermined time period of the time base signal.