Single sideband voice signal tuning method

• US 20080153441A1
• Filed: 12/20/2006
• Published: 06/26/2008
• Est. Priority Date: 12/20/2006
• Status: Active Grant

• Current Assignee: ICOM Incorporated
• Original Assignee: ICOM America Incorporated (ICOM Incorporated)
• Inventors: Gibbs, John A.
• Granted Patent: US 7,826,561 B2
• Time in Patent Office: Days
• US Class Current: 455/184.1
• CPC Class Codes: G10L 25/69 for evaluating synthetic or decoded voice signals

Abstract

Method for tuning a Single Sideband receiver including processing the signal in the time domain, converting the signal to the frequency domain, processing the signal in the frequency domain, converting the modified signal from the frequency domain to a correlation domain, processing the signal in the correlation domain and analyzing the processed signal from the correlation domain to determine a receiver tuning error.

Claims

1. A method for tuning a Single Sideband receiver, comprising:

obtaining an audio signal;

processing the signal in the time domain;

converting the signal to the frequency domain;

processing the signal in the frequency domain to modify the signal;

converting the modified signal from the frequency domain to a correlation domain;

processing the signal in the correlation domain; and

analyzing the processed signal from the correlation domain to determine a receiver tuning error.

2. The method of claim 1, further comprising filtering the signal prior to processing in the time and frequency domains.

3. The method of claim 1, wherein the step of processing the signal in the time or frequency domain comprises spectral flattening of the signal.

4. The method of claim 3, wherein the step of spectral flattening of the signal in the time domain comprises center clipping the signal.

5. The method of claim 4, wherein the signal is center clipped in the time domain by determining a level at which to clip the signal based on a root mean squared (RMS) or mean absolute deviation criteria.

6. The method of claim 4, wherein the signal is center clipped in the time domain, the step of processing the signal in the time domain comprising windowing the center clipped signal and optionally zero-padding the windowed, center clipped signal.

7. The method of claim 6, wherein the step of windowing the center clipped signal comprises selecting the length of the window based on an initial estimate of the pitch of the signal.

8. The window of claim 6, wherein the step of windowing the center clipped signal comprises utilizing a triangular window.

9. The window of claim 6, wherein the step of windowing the center clipped signal comprises using overlap processing entailing taking a new time record at predetermined intervals.

10. The method of claim 3, further comprising converting the signal to magnitude to remove time information.

11. The method of claim 10, further comprising center clipping the signal magnitude in the frequency domain to remove unwanted noise.

12. The method of claim 11, further comprising zero-padding the center clipped magnitude in the frequency domain to improve resolution in the correlation domain.

13. The method of claim 1, wherein the step of processing the signal in the correlation domain comprises correcting for processing of the signal in the time domain.

14. The method of claim 13, wherein the processing of the signal in the time domain comprises windowing the signal, the correction for processing of the signal in the time domain constituting correction for undesired effects resulting from the time domain processing of the signal.

15. The method of claim 13, wherein the step of processing the signal in the correlation domain further comprises fitting the signal to a curve using a parabolic regression of at least 5 points.

16. The method of claim 15, wherein the step of processing the signal in the correlation domain further comprises determining the location of the peak magnitude of the signal in the correlation domain and calculating the pitch and the offset frequency based thereon.

17. The method of claim 1, wherein the step of processing the signal in the correlation domain further comprises determining the location of a peak magnitude of the signal in the correlation domain and calculating the pitch and offset frequency based thereon.

18. The method of claim 17, wherein the step of analyzing the processed signal from the correlation domain to determine a pitch and offset frequency comprises determining whether the peak magnitude is above a threshold indicative of a voiced sound and if not, disregarding the processed signal.

19. The method of claim 18, wherein the step of analyzing the processed signal from the correlation domain to determine the receiver tuning error further comprises forming a cost function from the processed signal from the correlation domain when the peak magnitude is above the threshold, the cost function being formed such that voiced sounds far from estimated receiver tuning error contribute a larger error.

20. The method of claim 19, wherein the cost function is a least squares estimate of the receiver tuning error.

21. The method of claim 19, wherein the cost function is a least squares estimate of the receiver tuning error weighted by the ratio of the correlation peak power to total processed power.

22. The method of claim 19, wherein the step of analyzing the processed signal from the correlation domain to determine a receiver tuning error further comprises determining whether a statistically significant difference is present between a first and a second estimate of the receiver tuning error derived from the cost function and if so, considering the first estimate as the receiver tuning error.

23. The method of claim 22, wherein when a statistically significant difference is not present between a first and a second estimate of the receiver tuning error, additional received voiced signals are processed.

24. The method of claim 22, wherein the step of analyzing the processed signal from the correlation domain to determine the receiver tuning error further comprises determining whether a set number of received voiced signals have been processed and only when the set number of received voiced signals have been processed, determining whether a statistically significant difference is present between a first and a second estimate of the receiver tuning error.

25. The method of claim 1, wherein the obtaining of the voice signals and the processing of the voice signals is performed simultaneously such that as one voice signal is being processed, another voice signal is being obtained.