System for encoding multi-bit features into sinusoidal waveforms at selected phase angles

1. A method, comprising:

receiving input digital data;

creating a modulated sinusoidal waveform by modulating a sinusoidal waveform at selected phase angles within each of a plurality of periods of the sinusoidal waveform in accordance with the input digital data;

generating an encoded analog waveform using the modulated sinusoidal waveform;

wherein the modulating includes forming a first amplitude perturbation at a first phase angle of the selected phase angles wherein the first amplitude perturbation includes a first plurality of transition features and subtends a first phase angle range about the first phase angle, the first plurality of transition features being representative of a first plurality of bit values included within the input digital data.

2. The method of claim 1 wherein the modulating includes forming a second amplitude perturbation at a second phase angle of the selected phase angles wherein the second amplitude perturbation includes a second plurality of transition features and subtends a second phase angle range about the second phase angle, the second plurality of transition features being representative of a second plurality of bit values included within the input digital data.

3. The method of claim 2 wherein the first phase angle and the second phase angle are separated by 90 degrees.

4. The method of claim 2 wherein the first phase angle range is substantially equal to the second phase angle range.

5. The method of claim 2 wherein the first phase angle range is different from the second phase angle range.

6. The method of claim 2 wherein the modulating includes forming a third amplitude perturbation at a third phase angle of the selected phase angles wherein the third amplitude perturbation includes a third plurality of transition features and subtends a third phase angle range about the third phase angle, the third plurality of transition features being representative of a third plurality of bit values included within the input digital data wherein the first phase angle and the third phase angle are separated by 180 degrees.

7. The method of claim 6 wherein the first plurality of bit values and the third plurality of bit values each consist of at least four bit values.

8. The method of claim 7 wherein the first plurality of bit values are different from the third plurality of bit values.

9. The method of claim 6 wherein the forming the third amplitude perturbation includes matching an area of the third amplitude perturbation to an area of the first data notch.

10. The method of claim 2 wherein a minimum power of the first amplitude perturbation is a first percentage of a power of the sinusoidal waveform at the first phase angle in the absence of the modulating and a minimum power of the second amplitude perturbation is a second percentage of a power of the sinusoidal waveform at the second phase angle in the absence of the modulating, the first percentage being different from the second percentage.

11. The method of claim 1 further including receiving the encoded analog waveform.

12. A system, comprising:

an input buffer for storing input digital data;

a sub-periodic modulator for encoding the input digital data in a sinusoidal waveform by modulating the sinusoidal waveform at selected phase angles within a period of the sinusoidal waveform, thereby creating a modulated sinusoidal waveform;

one or more digital-to-analog converters for generating an encoded analog waveform from a representation of the modulated sinusoidal waveform;

wherein the sub-periodic modulator is configured to form a first amplitude perturbation at a first phase angle of the selected phase angles wherein the first amplitude perturbation includes a first plurality of transition features and subtends a first phase angle range about the first phase angle, the first plurality of transition features being representative of a first plurality of bit values included within the input digital data.

13. The system of claim 12 wherein the sub-periodic modulator is further configured to form a second amplitude perturbation at a second phase angle of the selected phase angles wherein the second amplitude perturbation includes a second plurality of transition features and subtends a second phase angle range about the second phase angle, the second plurality of transition features being representative of a second plurality of bit values included within the input digital data.

14. The system of claim 13 wherein the first phase angle and the second phase angle are separated by 90 degrees.

15. The system of claim 13 wherein the first phase angle range is substantially equal to the second phase angle range.

16. The system of claim 13 wherein the first phase angle range is different from the second phase angle range.

17. The system of claim 13 wherein the sub-periodic modulator is further configured to form a third amplitude perturbation at a third phase angle of the selected phase angles wherein the third amplitude perturbation includes a third plurality of transition features and subtends a third phase angle range about the third phase angle, the third plurality of transition features being representative of a third plurality of bit values included within the input digital data wherein the first phase angle and the third phase angle are separated by 180 degrees.

18. The system of claim 17 wherein the first plurality of bit values and the third plurality of bit values each consist of at least four bit values.

19. The system of claim 18 wherein the first plurality of bit values are different from the third plurality of bit values.

20. The method of claim 17 wherein the sub-periodic modulator forms the third amplitude perturbation at least in part by matching an area of the third amplitude perturbation to an area of the first amplitude perturbation.

21. A method, comprising:

receiving input data;

creating a modulated sinusoidal waveform having amplitude perturbations of reduced power at selected phase angles within a period of the sinusoidal waveform wherein the amplitude perturbations represent the input data and wherein a first amplitude perturbation of the amplitude perturbations includes a first plurality of transition features representative of a first plurality of values included within the input data; and

generating an encoded analog waveform from a representation of the modulated sinusoidal waveform.

22. The method of claim 21 wherein the creating further includes forming a second amplitude perturbation of the amplitude perturbations wherein the second amplitude perturbation includes a second plurality of transition features representative of a second plurality of values included within the input data.

23. The method of claim 22 wherein the creating includes forming the first amplitude perturbation at a first phase angle of the selected phase angles wherein the first amplitude perturbation subtends a first phase angle range about the first phase angle and further includes forming the second amplitude perturbation at a second phase angle of the selected phase angles wherein the second amplitude perturbation subtends a second phase angle range about the first phase angle.

24. The method of claim 23 wherein the first phase angle range is substantially equal to the second phase angle range.

25. The method of claim 23 wherein the first phase angle range is different from the second phase angle range.

26. The method of claim 23 wherein the first phase angle and the second phase angle are separated by 90 degrees.

27. The method of claim 23 wherein a minimum power of the first amplitude perturbation at the first phase angle is different from a minimum power of the second amplitude perturbation at the second phase angle.