System for reducing signal interference in modulated signal communication

• US 20060092328A1
• Filed: 11/03/2005
• Published: 05/04/2006
• Est. Priority Date: 11/03/2004
• Status: Active Grant

• Current Assignee: Dragerwerk AG & Company KGaA (FPS Vermögensverwaltung GmbH)
• Original Assignee: Draeger Medical Systems Incorporated (Dragerwerk AG)
• Inventors: Bernstein, Michael, Anderson, Ralph
• Granted Patent: US 7,623,990 B2
• Time in Patent Office: Days
• US Class Current: 348/571
• CPC Class Codes: A61B 5/14551 for measuring blood gases
• CPC Class Codes: G01N 2021/3144 for oxymetry
• CPC Class Codes: G01N 2021/3181 using LEDs
• CPC Class Codes: G01N 21/35 using infrared light G01N21/39 takes precedence
• CPC Class Codes: H04N 5/21 Circuitry for suppressing or minimising disturbance, e.g. moiré or halo

Abstract

A system for reducing signal interference in modulated signal communication includes a measurement processor. The measurement processor measures amplitudes of noise components of a received amplitude modulated signal prior to demodulation. The measurement processor also identifies a frequency of a noise component having an amplitude larger than the amplitude of another noise component. A carrier frequency generator generates a carrier frequency substantially at a harmonic of the identified noise component. The carrier frequency is used to generate and demodulate the amplitude modulated signal.

Claims

1. A system for reducing signal interference in modulated signal communication, comprising:

a measurement processor for,

measuring amplitudes of noise components of a received amplitude modulated signal prior to demodulation, and

identifying a frequency of a noise component having an amplitude larger than the amplitude of another noise component; and

a carrier frequency generator for generating a carrier frequency substantially at a harmonic of said identified noise component for use in generating and demodulating said amplitude modulated signal.

2. The system of claim 1 further comprising:

a demodulator for demodulating a received signal modulated at said noise component harmonic carrier frequency to provide a demodulated signal; and

a compensation processor for processing said demodulated signal and subtracting a DC component associated with said noise component from said processed demodulated signal.

3. The system of claim 2 further comprising an analog-to-digital converter (ADC) for analog-to-digital conversion of said received signal modulated at said noise component harmonic carrier frequency prior to demodulation.

4. The system of claim 1 wherein said measurement processor measures said received amplitude modulated signal and identifies noise components by at least one of:

(a) amplitude, (b) frequency, (c) harmonic content, and (d) waveform morphology.

5. The system of claim 1 wherein said identified noise component frequency is of a noise component being at least one of:

(a) substantially the largest amplitude noise component in said received amplitude modulated signal, and (b) substantially the largest, or equally largest, amplitude noise component in said received amplitude modulated signal.

6. The system of claim 1 wherein said measurement processor identifies multiple noise components of substantially equal amplitude, said substantially equal amplitude being larger than another noise component.

7. The system of claim 6 wherein said multiple noise components being substantially the largest, or equally largest, amplitude noise components in said received amplitude modulated signal.

8. The system of claim 6 further comprising a decision processor for inhibiting said carrier frequency generator from generating a carrier frequency substantially at said harmonic of said identified noise component, in response to said identification of multiple noise components of substantially equal amplitude.

9. The system of claim 1 wherein said modulated signal communication is for patient medical parameter monitoring.

10. The system of claim 1 further comprising:

a light emitting diode (LED);

a photo-detector sensor for providing an output voltage signal in response to light generated by said LED;

a modulator for modulating a carrier frequency at said noise component harmonic for transmission using said LED; and

a demodulator for demodulating a signal modulated on said noise component harmonic carrier frequency received by said photo-detector sensor and transmitted using said LED, to provide a demodulated signal.

11. The system of claim 10 further comprising an LED drive unit for at least one of:

(a) changing the amplitude of LED drive power, and (b) reducing to zero LED drive power, during identifying and measuring noise components.

12. The system of claim 10 further comprising a modulation processor that adjusts at least one of:

(a) modulation frequency, (b) modulation drive pattern, and (c) type of modulation of said LED.

13. The system of claim 10 further comprising a modulation processor that adjusts LED modulation frequency to substantially match the frequency of a harmonic of the identified noise component signal.

14. The system of claim 10 further comprising a compensation processor for processing said demodulated signal and subtracting a DC component associated with said noise component from said processed demodulated signal.

15. The system of claim 10 wherein said sensor output voltage signal is provided by at least one of:

(a) amplification, (b) filtering, and (c) buffering of a signal provided by a photo-detector device.

16. The system of claim 10 wherein said system is for patient blood oxygen saturation parameter monitoring.

17. The system of claim 10 wherein said light generated by said LED is detected by said photo-detector device following transmission through patient blood and tissue.

18. The system of claim 10 wherein said LED comprises a red and an infra-red LED and said system performs measurements and compensation of sensor output voltage in a first mode in response to light provided by said red LED and in a second mode in response to light provided by said infra-red LED.

19. A method for reducing signal interference in modulated signal communication, comprising the activities of:

measuring amplitudes of noise components of a received amplitude modulated signal prior to demodulation;

identifying a frequency of a noise component having an amplitude larger than another noise component;

generating a carrier frequency substantially at a harmonic of said identified noise component; and

employing said generated carrier frequency substantially at said harmonic of said identified noise component in generating and demodulating said amplitude modulated signal.

20. A tangible storage medium incorporating machine readable instructions for performing the activities of claim 19.