Methods and systems for filtering a signal according to a signal model and continuous wavelet transform techniques

• US 8,235,911 B2
• Filed: 10/03/2008
• Issued: 08/07/2012
• Est. Priority Date: 07/15/2008
• Status: Active Grant

• Current Assignee: Nellcor Puritan Bennett Ireland
• Original Assignee: Nellcor Puritan Bennett Ireland
• Inventors: Watson, James Nicholas, Addison, Paul Stanley
• Primary Examiner(s): Brusca, John S
• Application Number:
  US12/245,356
• Publication Number:
  US 20100016695A1
• Time in Patent Office: 1,404 Days
• Field of Search: None
• US Class Current: 600/502
• CPC Class Codes: A61B 5/14551 for measuring blood gases
• CPC Class Codes: A61B 5/7203 for noise prevention, reduction or removal
• CPC Class Codes: A61B 5/726 using Wavelet transforms

Abstract

According to embodiments, systems and methods are provided for filtering a signal. A first reference signal may be generated according to a signal model and a second reference signal may be generated by analyzing a continuous wavelet transform of a signal. The first and second reference signals may then both be applied to an input signal to filter the input signal according to the components of both of the reference signals.

Claims

1. A method for filtering an input signal, the method comprising:

receiving, by a processor, the input signal;

generating, by the processor, a first reference signal based at least in part on a signal model associated with a component of the input signal;

generating, by the processor, a second reference signal based at least in part on a continuous wavelet transform of the received input signal; and

filtering, by the processor, the received input signal using at least the first reference signal and the second reference signal.

2. The method of claim 1, wherein generating a first reference signal based at least in part on a signal model comprises:

measuring at least two signals of the same or similar type as the received input signal;

assuming some mathematical relationship exists between the two measured signals; and

minimizing the correlation between a signal portion and a noise portion of at least one of the at least two measured signals.

3. The method of claim 1, wherein generating a second reference signal based at least in part on a continuous wavelet transform of the received input signal comprises generating a scalogram of the received input signal.

4. The method of claim 1, wherein filtering the received input signal comprises filtering the received input signal in wavelet space.

5. The method of claim 1, wherein:

at least one of the first and second reference signals comprises a noise component; and

filtering the received input signal comprises applying an adaptive correlation canceller to the received input signal.

6. The method of claim 1, wherein:

at least one of the first and second reference signals comprises a signal component; and

filtering the received input signal comprises cross correlating at least one of the first and second reference signals with the received input signal.

7. The method of claim 1 further comprising combining at least some of the first reference signal with at least some of the second reference signal before filtering the received input signal.

8. The method of claim 1 further comprising determining at least one physiological parameter from the filtered input signal.

9. The method of claim 1, wherein filtering the received input signal comprises:

filtering the received input signal using the first reference signal to produce a first filtered signal; and

filtering the first filtered signal using the second reference signal to produce a twice filtered signal.

10. The method of claim 1, wherein the input signal comprises at least one photoplethysmograph (PPG) signal.

11. A system for filtering, comprising:

a sensor capable of generating an input signal; and

a processor capable of;

generating a first reference signal based at least in part on a signal model associated with a component of the input signal;

generating a second reference signal based at least in part on a continuous wavelet transform of the input signal; and

filtering the input signal using at least the first reference signal and the second reference signal.

12. The system of claim 11, wherein the processor is capable of:

measuring at least two signals of the same or similar type as the input signal;

assuming some mathematical relationship exists between the two measured signals; and

minimizing the correlation between a signal portion and a noise portion of at least one of the at least two measured signals.

13. The system of claim 11, wherein the processor is capable of generating a scalogram of the received input signal.

14. The system of claim 11, wherein the processor is capable of filtering the input signal in wavelet space.

15. The system of claim 11, wherein:

at least one of the first and second reference signals comprises a noise component; and

the processor is capable of applying an adaptive correlation canceller to the input signal.

16. The system of claim 11, wherein:

at least one of the first and second reference signals comprises a signal component; and

the processor is capable of cross correlating at least one of the first and second reference signals with the input signal.

17. The system of claim 11 wherein the processor is capable of combining at least some of the first reference signal with at least some of the second reference signal before filtering the input signal.

18. The system of claim 11 wherein the processor is capable of determining at least one physiological parameter from the filtered input signal.

19. The system of claim 11, wherein the processor is capable of:

filtering the input signal using the first reference signal to produce a first filtered signal; and

filtering the first filtered signal using the second reference signal to produce a twice filtered signal.

20. The system of claim 11, wherein the input signal comprises at least one photoplethysmograph (PPG) signal.

21. A non-transitory computer-readable medium for use in generating a reference signal, the non-transitory computer-readable medium having computer program instructions recorded thereon for:

receiving the input signal;

generating a first reference signal based at least in part on a signal model associated with a component of the input signal;

generating a second reference signal based at least in part on a continuous wavelet transform of the received input signal; and

filtering the received input signal using at least the first reference signal and the second reference signal.