Apparatus and method for system identification

• US 20070114443A1
• Filed: 11/13/2006
• Published: 05/24/2007
• Est. Priority Date: 11/10/2005
• Status: Active Grant

• Current Assignee: In-Situ Incorporated
• Original Assignee: TauTheta Instruments, LLC
• Inventors: Baltz, Nathan, Danielson, J.D. Sheldon
• Granted Patent: US 7,791,028 B2
• Time in Patent Office: Days
• US Class Current: 250/458.100
• CPC Class Codes: G01N 2021/6432 Quenching
• CPC Class Codes: G01N 21/6408 with measurement of decay time, time resolved fluorescence
• CPC Class Codes: G01N 21/6428 Measuring fluorescence of fluorescent products of reactions or of fluorochrome labelled reactive substances, e.g. measuring quenching effects, using measuring "optrodes" in vivo A61B5/00; immunoassay G01N33/53
• CPC Class Codes: G01N 21/645 Specially adapted constructive features of fluorimeters

Abstract

Methods and apparatus for system identification operate by computing phase and amplitude using linear filters. By digitally processing the linearly filtered signals or data, the phase and amplitude based on measurements of the input and output of a system, are determined.

Claims

1. A method for system identification comprising:

exciting a system by directing a first waveform to the system;

detecting a second waveform emitted from the system; and

analyzing at least one signal corresponding to the detected waveform emitted from the system by linearly filtering the at least one signal.

2. The method of claim 1, wherein the system includes a luminescent probe and the first waveform includes light.

3. The method of claim 1, wherein the system includes a sample with electrical impedance characteristics and the first waveform includes electricity.

4. The method of claim 1, wherein the system includes a sample with magnetic characteristics and the first waveform includes magnetic energy.

5. The method of claim 1, wherein analyzing the at least one signal includes determining the phase shift between the first waveform directed to the system and the second waveform emitted from the system.

6. The method of claim 1, wherein analyzing the at least one signal includes determining amplitude ratio of the waveform emitted from the system.

7. The method of claim 1, wherein analyzing the at least one signal includes sampling and linearly filtering the at least one signal, and transforming the sampled at least one signal into a real portion and an imaginary portion.

8. The method of claim 1, wherein analyzing the at least one signal includes applying at least a modified Goertzel algorithm to the at least one signal.

9. The method of claim 1, wherein linearly filtering the at least one signal includes processing the at least one signal in a second order linear filter.

10. The method of claim 9, wherein the second order linear filter includes an infinite impulse response filter.

11. A method for analyzing light emissions from a luminescent sample comprising:

providing excitation light to a luminescent sample;

detecting emitted luminescence from the luminescent sample;

analyzing the emitted luminescence by linearly filtering the output corresponding to the detected emitted luminescence.

12. The method of claim 11, wherein analyzing the emitted luminescence includes determining the phase shift between the excitation light and the emitted luminescence.

13. The method of claim 11, wherein analyzing the emitted luminescence includes determining the amplitude ratio of the emitted luminescence.

14. The method of claim 12, wherein determining the phase shift of the emitted luminescence includes:

determining the phase of a first waveform representative of the luminescent sample, based on the output corresponding to the detected emitted luminescence, determining the phase of a second waveform, representative of a reference and, calculating the difference between the phase of the first waveform and the second waveform.

15. The method of claim 11, wherein analyzing the output includes passing the output through at least one linear filter and determining the phase of the waveform corresponding to the detected luminescence emitted from the luminescent sample.

16. The method of claim 15, wherein analyzing the output includes sampling and linearly filtering the at least one signal, and transforming the samples of the linearly filtered at least one signal into at least one of phase or amplitude.

17. The method of claim 11, wherein analyzing the output includes applying at least a modified Goertzel algorithm to the output.

18. The method of claim 15, wherein the at least one linear filter includes a second order linear filter.

19. The method of claim 18, wherein the second order linear filter includes an infinite impulse response filter.

20. An apparatus for system identification comprising:

a source of a first waveform for exciting a system;

a detector for detecting a second waveform emitted from the system;

a converter for converting the second waveform into output signals corresponding to the second waveform; and

, a linear filter component for analyzing at least one output signal corresponding to the second waveform.

21. The apparatus of claim 20, additionally comprising:

a processor in communication with the linear filter component, the processor programmed to determine a phase shift between the first waveform and the second waveform.

22. The apparatus of claim 20, additionally comprising:

a processor in communication with the linear filter component, the processor programmed to determine an amplitude ratio between the first waveform and the second waveform.

23. The apparatus of claim 20, wherein the linear filter component includes at least one linear filter and control logic for applying a modified Goertzel algorithm to the at least one signal corresponding to the second waveform.

24. The apparatus of claim 23, wherein the at least one linear filter includes a second order linear filter.

25. The apparatus of claim 24, wherein the second order linear filter includes an infinite impulse response filter.

26. The apparatus of claim 20, wherein the source includes an electric source and the detector includes at least one electrode.

27. The apparatus of claim 20, wherein the source includes a light emitting diode.

28. The apparatus of claim 20, wherein the detector includes at least one photodiode.

29. A luminescent light measurement apparatus comprising:

an excitation light source configured to transfer excitation light;

a luminescent probe configured to transfer emission light in response to the excitation light; and

a detector system configured to detect the emission light and generate at least one signal corresponding to the emission light, comprising;

a linear filter component for processing the signal; and

,

a processor in communication with the linear filter component for determining the phase shift between the excitation light and the emission light.

30. The apparatus of claim 29, wherein the linear filter component includes at least one linear filter and control logic.

31. The apparatus of claim 29, wherein the at least one linear filter component is configured for applying at least a portion of a modified Goertzel algorithm to the at least one signal.

32. The apparatus of claim 30, wherein the at least one linear filter includes a second order linear filter.

33. The apparatus of claim 32, wherein the second order linear filter includes an infinite impulse response filter.

34. The apparatus of claim 29, wherein the excitation light source includes at least one light emitting diode.

35. The apparatus of claim 29, wherein the detector system additionally comprises:

at least one photodiode to detect the emission light.

36. A down-converting apparatus for system identification, comprising:

a. a source of a first periodic waveform for exciting a system;

b. a detector for detecting a second periodic waveform in response to the first periodic waveform exciting the system;

c. a generator for generating a third periodic waveform;

d. a mixing unit for mixing at least two of the first periodic waveform, the second periodic waveform and the third periodic waveform to generate down converted fourth and fifth periodic waveforms; and

,

e. at least one linear filter component for analyzing at least one signal corresponding to each of the down converted fourth and fifth periodic waveforms.

37. The apparatus of claim 36, wherein said at least one linear filter component includes two linear filter components, including first and second linear filter components, the first linear filter component for analyzing at least one signal corresponding to the down converted fourth periodic waveform, and, the second linear filter component for analyzing at least one signal corresponding to the down converted fifth periodic waveform.

38. The apparatus of claim 37, additionally comprising:

a processor in communication with the first and second linear filter components, the processor programmed to determine a phase shift between the down converted fourth periodic waveform and the down converted fifth periodic waveform.

39. The apparatus of claim 37, additionally comprising:

a processor in communication with the first and second linear filter components, the processor programmed to determine an amplitude ratio between the amplitude of the down converted fourth periodic waveform and the down converted fifth periodic waveform.

40. The apparatus of claim 37, wherein each of the linear filter components includes at least one linear filter and control logic for applying at least a modified Goertzel algorithm to the waveforms inputted into the linear filter component.

41. The apparatus of claim 40, wherein the at least one linear filter includes a second order linear filter.

42. The apparatus of claim 41, wherein the second order linear filter includes an infinite impulse response filter.

43. The apparatus of claim 36, additionally comprising:

programmable modules for producing square waves for the first and third periodic waveforms.

44. The apparatus of claim 36, additionally comprising:

direct digital synthesis engines for producing sine wave functions for the first and third periodic waveforms.

45. The apparatus of claim 36, wherein the source is an electronic source.

46. The apparatus of claim 36, wherein the source is a light emitting diode.

47. The apparatus of claim 36, wherein the mixing unit comprises at least one differential amplifier and at least one multiplexing switch.

48. The apparatus of claim 36, wherein the mixing unit includes two mixers.

49. The apparatus of claim 36, wherein the detector includes at least one electrode.

50. The apparatus of claim 36, wherein the detector includes at least one photodiode.

51. A method for analyzing down-converting waveforms for system identification, comprising:

a. exciting a system by transferring a first periodic waveform to the system;

b. detecting a second periodic waveform in response to the first periodic waveform exciting the system;

c. generating a third periodic waveform;

d. mixing at least two of the first periodic waveform, the second periodic waveform and the third periodic waveform to generate down converted fourth and fifth periodic waveforms; and

,

e. analyzing at least one signal corresponding to each of the down converted fourth and fifth periodic waveforms by linearly filtering the at least one signal corresponding to each of the down converted fourth and fifth periodic waveforms.

52. The method of claim 51, wherein the system includes a luminescent probe and the first periodic waveform includes light.

53. The method of claim 51, wherein the system includes a sample with electrical impedance characteristics and the first periodic waveform includes electricity.

54. The method of claim 51, wherein the system includes a sample with magnetic characteristics and the first waveform includes magnetic energy.

55. The method of claim 51, additionally comprising:

analyzing the output from the linearly filtered at least one signal to determine the phase shift between the down converted fourth periodic waveform and the down converted fifth periodic waveform.

56. The method of claim 51, additionally comprising:

analyzing the output from the linearly filtered at least one signal to determine an amplitude ratio between the amplitude of the down converted fourth periodic waveform and the down converted fifth waveform.

57. The method of claim 51, wherein analyzing the at least one signal includes sampling and linearly filtering the at least one signal, and transforming the sampled and linearly filtered at least one signal into a real portion and an imaginary portion.

58. The method of claim 51, wherein analyzing the at least one signal includes applying at least a portion of a modified Goertzel algorithm to the at least one signal.

59. The method of claim 57, wherein linearly filtering the at least one signal includes processing the at least one signal in a second order linear filter.

60. The method of claim 59, wherein the second order linear filter includes an infinite impulse response filter.