Adaptive noise rejection system and method

• US 6,594,364 B2
• Filed: 11/15/2001
• Issued: 07/15/2003
• Est. Priority Date: 06/28/2000
• Status: Expired due to Fees

• Current Assignee: Esion-Tech LLC
• Original Assignee: Esion-Tech LLC
• Inventors: Linder, Frank X
• Primary Examiner(s): Isen, Forester W.
• Assistant Examiner(s): Pendleton, Brian T.
• Application Number:
  US09/999,476
• Publication Number:
  US 20020041691A1
• Time in Patent Office: 607 Days
• Field of Search: 381/94.1, 381/94.2, 381/71.1, 381/71.14
• US Class Current: 381/71.14
• CPC Class Codes: G10L 2021/02085 Periodic noise
• CPC Class Codes: G10L 21/02 Speech enhancement, e.g. noise reduction or echo cancellation reducing echo effects in line transmission systems H04B3/20; echo suppression in hands-free telephones H04M9/08
• CPC Class Codes: G10L 21/0208 Noise filtering
• CPC Class Codes: H03G 3/345 Muting during a short period of time when noise pulses are detected, i.e. blanking H03G3/348 takes precedence

Abstract

An adaptive noise rejection method and apparatus. An information signal having an information component and a repetitive noise component having a varying characteristic frequency is delayed the information signal by a reference delay time that is equal that is equal to a predetermined number of periods of the characteristic frequency to form a delayed information signal. The delayed information signal is subtracted from the information signal to form a processed information signal in which the information component is substantial and the noise component is negligible. The amplitude of the noise component of the processed information signal is constantly monitored. The delay of the information signal is varied as the characteristic frequency of the noise component changes so as to maintain the amplitude of the noise component of the processed information signal at a predetermined level.

Claims

1. A storage medium encoded with machine-readable computer program code for processing an information signal, comprising:

means for causing a computer to receive an information signal having an information component and a repetitive noise component having a varying characteristic frequency;

means for causing the computer to delay the information signal by a reference delay time that is equal to a predetermined number of periods of the characteristic frequency to form a delayed information signal;

means for causing the computer to process the information signal and the delayed information signal to form a processed reference information signal in which the information component is substantial and the noise component is negligible;

means for causing the computer to determine the amplitude of the noise component of the processed reference information signal; and

means for causing the computer to vary the delay of the information signal as the characteristic frequency of the noise component changes in order to maintain the noise component of the processed reference information signal at a predetermined level.

2. The storage medium encoded with machine-readable computer program code for processing an information signal according to claim 1 wherein the means for causing the computer to delay the information signal further comprises means for causing the computer to simultaneously provide (i) a second delayed information signal that is delayed, with respect to the information signal, by an amount of time that is less than the reference delay time, and (ii) a third delayed information signal that is delayed, with respect to the information signal, by an amount of time that is greater than the reference delay time.

3. The storage medium encoded with machine-readable computer program code for processing an information signal according to claim 2 wherein the means for causing the computer to process the information signal and the delayed information comprises:

means for causing the computer to process the second delayed information signal with the received information signal to provide a second processed signal; and

means for causing the computer to process the third delayed information signal with the received information signal to provide a third information signal.

4. The storage medium encoded with machine-readable computer program code for processing an information signal according to claim 3 wherein the means for causing the computer to vary the delay of the information signal comprises:

means for causing the computer to determine the amplitude of the noise component of the second processed signal;

means for causing the computer to determine the amplitude of the noise component of the third information signal;

comparing the amplitude of the noise component of the reference processed information signal with the noise components of the second and third processed information signals;

means for causing the computer to maintain the current reference delay time if the amplitude of the noise component of the referenced processed information signal is relatively lower than the amplitudes of the noise components of both the second and third processed information signals;

means for causing the computer to decrease the reference delay time if the amplitude of the noise component of the second processed information signal is relatively lower than the amplitude of the noise components of both the referenced processed information signal and the third processed information signal; and

means for causing the computer to increase the reference time delay if the amplitude of the noise component of the third processed information signal is relatively lower than the amplitude of the noise components of both the referenced processed information signal and the second processed information signal.

5. The storage medium encoded with machine-readable computer program code for processing an information signal according to claim 3 wherein the means for causing the computer to determine the amplitude of the noise component comprises means for causing the computer to detect the amplitude of the noise component of the reference processed information signal.

6. The storage medium encoded with machine-readable computer program code for processing an information signal according to claim 5 wherein the means for causing the computer to determine the amplitude of the noise component of the second processed information signal comprises means for causing the computer to detect the amplitude of the noise component of the second processed information signal.

7. The storage medium encoded with machine-readable computer program code for processing an information signal according to claim 6 wherein the means for causing the computer to determine the amplitude of the noise component of the third processed information signal comprises means for causing the computer to detect the amplitude of the noise component of the third processed information signal.

8. The storage medium encoded with machine-readable computer program code for processing an information signal according to claim 3 further comprising means for causing the computer to filter the reference, second and third processed information signals to remove the information component before the computer varies the delay of the information signal.

9. The storage medium encoded with machine-readable computer program code for processing an information signal according to claim 1 wherein means for causing the computer to process the information signal comprises means for causing the computer to subtract the delayed information signal from the received information signal.

10. The storage medium encoded with machine-readable computer program code for processing an information signal according to claim 3 wherein the means for causing the computer to process the second delayed information signal with the received information signal comprises means for causing the computer to subtract the second delayed information signal from the received information signal.

11. The storage medium encoded with machine-readable computer program code for processing an information signal according to claim 3 wherein the means for causing the computer to process the third delayed information signal with the received information signal comprises means for causing the computer to subtract the third delayed information signal from the received information signal.

12. The storage medium encoded with machine-readable computer program code for processing an information signal according to claim 1 wherein the received information signal is an analog signal and wherein the means for causing the computer to receive the information signal comprises means for causing the computer to convert the analog information signal into a digital information signal.

13. The storage medium encoded with machine-readable computer program code for processing an information signal according to claim 1 further comprising means for causing the computer to convert the reference processed information signal into a processed analog signal.

14. The storage medium encoded with machine-readable computer program code for processing an information signal according to claim 3 further comprising means for causing the computer to filter the reference, second and third processed information signals to remove the information component.

15. The storage medium encoded with machine-readable computer program code for processing an information signal according to claim 14 wherein the means for causing the computer to filter the reference, second and third processed information signals to remove the information component comprises means for causing the computer to input the reference, second and third processed information signals into respective band pass filters, each filter having a pass band and a center frequency, the means for causing the computer to vary the delay of the information signal comprises means for causing the computer to vary the center frequency of the pass bands of the filters to match the characteristic frequency of the noise component.

16. A method of rejecting RF noise introduced into an information signal, comprising the steps of:

a) receiving an RF signal having an information component and a repetitive RF noise component having a varying characteristic frequency;

b) delaying the RF signal by a reference delay time that is equal to a predetermined number of periods of the characteristic frequency to form a delayed RF signal;

c) processing the RF signal and the delayed RF information signal to form a processed reference RF signal in which the information component is substantial and the RF noise component is negligible;

d) determining the amplitude of the RF noise component of the processed reference RF signal; and

e) varying the delay of the RF signal as the characteristic frequency of the RF noise component changes in order to maintain the amplitude of the RF noise component of the processed RF reference signal at a predetermined level.