Non-contact measurement system for accurate measurement of frequency and amplitude of mechanical vibration

• US 7,848,896 B2
• Filed: 06/02/2008
• Issued: 12/07/2010
• Est. Priority Date: 05/31/2007
• Status: Active Grant

• Current Assignee: University of Florida Research Foundation, Incorporated (State University System of Florida)
• Original Assignee: University of Florida Research Foundation, Incorporated (State University System of Florida)
• Inventors: Li, Changzhi, Lin, Jenshan
• Primary Examiner(s): Nghiem; Michael P
• Application Number:
  US12/131,721
• Publication Number:
  US 20080300805A1
• Time in Patent Office: 918 Days
• Field of Search: 702/54, 702/56, 702/150, 702/75, 702/76, 702/79, 702/159, 735/70, 736/57, 324/318, 324/633
• US Class Current: 702/56
• CPC Class Codes: G01H 9/00 Measuring mechanical vibrations or ultrasonic, sonic or infrasonic waves by using radiation-sensitive means, e.g. optical means

Abstract

A non-contact detection technique of measuring both the frequency and the amplitude of periodic movement using a property of nonlinear phase modulation is provided. In one embodiment, the technique can utilize a 22-40 GHz radar sensor. Embodiments do not require calibration of signal amplitude for accurate measurement of movement amplitude. In addition, self-verification is possible. Furthermore, embodiments can provide measurements of frequency and amplitude using a very simple architecture. The method can be used to detect movements with amplitudes larger than 0.335 of the carrier wavelength for a fixed carrier frequency system and 0.214 of the minimum carrier wavelength for a frequency tunable system.

Claims

1. A method for non-contact measurement of a periodic movement of a target, comprising:

transmitting a radio frequency (RF) signal towards the target, wherein upon incidence of the radio frequency (RF) signal on the target a reflected radio frequency (RF) signal is produced;

receiving the reflected radio frequency (RF) signal;

down-converting the received radio frequency (RF) signal to a baseband signal;

determining one harmonic of the baseband signal having an order n, where n is an integer; and

determining an additional harmonic of the baseband signal having an order n+2;

determining a model, wherein the model comprises a model ratio of the n+2 order harmonic and the n order harmonic as a function of model movement amplitude;

determining an amplitude of a periodic movement of the target from the n+2 order harmonic of the baseband signal and the n order harmonic of the baseband signal, wherein determining the amplitude of the periodic movement of the target comprises;

calculating a measured ratio, wherein the measured ratio is a ratio of the n+2 order harmonic of the baseband signal and the n order harmonic of the baseband signal; and

determining the amplitude of the periodic movement by comparing the measured ratio to the model and selecting the model movement amplitude corresponding to the measured ratio, wherein the amplitude of the periodic movement of the target is the selected model movement amplitude corresponding to the measured ratio.

2. The method according to claim 1, wherein the frequency of the radio frequency (RF) signal is 9 GHz or higher.

3. The method according to claim 1, wherein the frequency of the radio frequency (RF) signal is between 22 GHz and 40 GHz.

4. The method according to claim 1, wherein the target is a human or animal, wherein the periodic movement is due to the target'"'"'s breathing movement.

5. The method according to claim 1, wherein the target is a human or animal, wherein the periodic movement is due to the target'"'"'s heart movement.

6. The method according to claim 1, further comprising:

determining a frequency of the periodic movement of the target.

7. The method according to claim 6, wherein the target is a human or animal, wherein the periodic movement is due to the target'"'"'s breathing movement, wherein the frequency of the period movement of the target is the target'"'"'s breathing rate.

8. The method according to claim 6, wherein the target is a human or an animal, wherein the periodic movement is due to the target'"'"'s heart movement, wherein the frequency of the period movement of the target is the target'"'"'s heart rate.

9. The method according to claim 1, wherein the model is based on a non-linear Doppler phase modulation effect in the reflected radio frequency (RF) signal.

10. The method according to claim 1, wherein the radio frequency (RF) signal is a single tone radio frequency (RF) signal.

11. The method according to claim 10, wherein the radio frequency (RF) signal has no modulation.

12. The method according to claim 10, wherein the periodic movement of the target is sinusoidal.

13. The method according to claim 10, wherein the periodic movement of the target is a series of sinusoids.

14. The method according to claim 1, wherein the model is determined theoretically.

15. The method according to claim 1, wherein the model is determined experimentally.

16. The method according to claim 1, wherein the ratio of the n+2 order harmonic and the n order harmonic in the model is H_n+2/H_n, wherein the ratio of the n+2 order harmonic and the n order harmonic in the measured ratio is H_n+2/H_n.

17. The method according to claim 1, wherein the ratio of the n+2 order harmonic and the n order harmonic in the model is H_n/H_n+2, wherein the ratio of the n+2 order harmonic and the n order harmonic in the measured ratio is H_n/H_n+2.

18. The method according to claim 1, wherein the model is dependent on the wavelength of the radio frequency (RF) signal.

19. The method according to claim 1, wherein n is odd.

20. The method according to claim 1, wherein n is even.

21. The method according to claim 1, wherein m≧

0.214λ

, where m is the amplitude of the periodic movement of the target, where λ

is the wavelength of the radio frequency (RF) signal.

22. The method according to claim 21, wherein n=1, wherein 0.214λ

≦

m≦

0.290λ

.

23. The method according to claim 21, wherein n=2, wherein 0.335λ

≦

m≦

0.489λ

.

24. The method according to claim 21, wherein n=3, wherein 0.455λ

≦

m≦

0.677λ

.

25. The method according to claim 21, wherein n=4, wherein 0.575λ

≦

m≦

0.859λ

.

26. The method according to claim 21, wherein n=5, wherein 0.694λ

≦

m≦

1.039λ

.

27. A system for non-contact measurement of a periodic movement of a target, comprising:

a means for transmitting a radio frequency (RF) signal towards the target, wherein upon incidence of the radio frequency (RF) signal on the target a reflected radio frequency (RF) signal is produced;

a means for receiving the reflected radio frequency (RF) signal from the target;

a means for down-converting the received radio frequency (RF) signal to a baseband signal;

a means for determining one harmonic of the baseband signal having an order n, where n is an integer; and

a means for determining an additional harmonic of the baseband signal having an order n+2;

a means for determining an amplitude of a periodic movement of the target from the n+2 order harmonic of the baseband signal and the n order harmonic of the baseband signal, wherein the means for determining the amplitude of the periodic movement of the target comprises;

a means for calculating a measured ratio, wherein the measured ratio is a ratio of the n+2 order harmonic of the baseband signal and the n order harmonic of the baseband signal; and

a means for determining the amplitude of the periodic movement by comparing the measured ratio to a model, wherein the model comprises a model ratio of the n+2 order harmonic and the n order harmonic as a function of model movement amplitude, and selecting the model movement amplitude corresponding to the measured ratio,

wherein the amplitude of the periodic movement of the target is the selected model movement amplitude corresponding to the measured ratio.

28. A system for non-contact measurement of a periodic movement of a target, comprising:

a radio frequency (RF) transmitter, wherein the radio frequency (RF) transmitter is adapted to transmit a radio frequency (RF) signal towards the target, wherein upon incidence of the radio frequency (RF) signal on the target a reflected radio frequency (RF) signal is produced;

a radio frequency (RF) receiver, wherein the radio frequency (RF) receiver is adapted for receiving the reflected radio frequency (RF) signal from the target;

a mixer, wherein the mixer down-converts the received radio frequency (RF) signal to a baseband signal; and

a signal processing device, wherein the signal processing device;

determines one harmonic of the baseband signal having an order n, where n is an integer;

determines an additional harmonic of the baseband signal having an order n+2;

determines an amplitude of a periodic movement of the target from the n+2 order harmonic of the baseband signal and the n order harmonic of the baseband signal, wherein determining the amplitude of the periodic movement of the target comprises;

calculating a measured ratio, wherein the measured ratio is a ratio of the n+2 order harmonic of the baseband signal and the n order harmonic of the baseband signal; and

determining the amplitude of the periodic movement by comparing the measured ratio to a model, wherein the model comprises a model ratio of the n+2 order harmonic and the n order harmonic as a function of model movement amplitude, and selecting the model movement amplitude corresponding to the measured ratio,

wherein the amplitude of the periodic movement of the target is the selected model movement amplitude corresponding to the measured ratio.

29. The system according to claim 28, wherein the radio frequency (RF) signal is a single tone radio frequency (RF) signal.

30. The system according to claim 28, wherein the ratio of the n+2 order harmonic and the n order harmonic in the model is H_n+2/H_n, wherein the ratio of the n+2 order harmonic and the n order harmonic in the measured ratio is H_n+2/H_n.

31. The system according to claim 28, wherein the ratio of the n+2 order harmonic and the n order harmonic in the model is H_n/H_n+2, wherein the ratio of the n+2 order harmonic and the n order harmonic in the measured ratio is H_n/H_n+2.

32. The system according to claim 28, wherein the model is dependent on the wavelength of the radio frequency (RF) signal.

33. The system according to claim 28, wherein the frequency of the radio frequency (RF) signal is 9 GHz or higher.

34. The system according to claim 28, wherein the frequency of the radio frequency (RF) signal is between 22 GHz and 40 GHz.

35. The system according to claim 28, wherein the signal processing device determines a frequency of the periodic movement of the target.

36. The system according to claim 28, wherein the model is based on a non-linear Doppler phase modulation effect in the reflected radio frequency (RF) signal.

37. The system according to claim 28, wherein the radio frequency (RF) signal has no modulation.

38. The system according to claim 28, wherein the model is determined theoretically.

39. The system according to claim 28, wherein the model is determined experimentally.

40. The system according to claim 28, wherein n is odd.

41. The system according to claim 28, wherein n is even.

42. The system according to claim 28, wherein m≧

0.214λ

, where m is the amplitude of the periodic movement of the target, where λ

is the wavelength of the radio frequency (RF) signal.

43. The system according to claim 28, wherein n=1, wherein 0.214λ

≦

m≦

0.290λ

.

44. The system according to claim 28, wherein n=2, wherein 0.335λ

≦

m≦

0.489λ

.

45. The system according to claim 28, wherein n=3, wherein 0.455λ

≦

m≦

0.677λ

.

46. The system according to claim 28, wherein n=4, wherein 0.575λ

≦

m≦

0.859λ

.

47. The system according to claim 28, wherein n=5, wherein 0.694λ

≦

m≦

1.039λ

.