Data dithering apparatus and method
View Patent ↗A waveform having an amplitude that varies to thereby represent corresponding data values is dithered to further shape the waveform so that use of the dithered waveform to create a corresponding FSK signal will result in a signal having a smoothed frequency domain profile. In various embodiments, the waveform amplitude is varied with respect to periodicity of variation, extent of variation, and duration of variation.
1. A method comprising the steps of:
providing data elements comprising at least one parameter having a representative amplitude that varies in correspondence with information values that correlate to the data;
for at least one of the data elements, varying the amplitude by a relatively small amount to provide an amplitude-irregular data element;
using the amplitude-irregular data element to provide a corresponding frequency shift keyed signal having a smoothed frequency domain profile.
2. The method of claim 1 wherein the at least one parameter comprises a voltage level.
3. The method of claim 1 wherein the at least one parameter comprises a current level.
4. The method of claim 1 wherein the representative amplitude varies between approximately 5 volts as corresponds to a logical “1” and approximately −5 volts as corresponds to a logical “0”.
5. The method of claim 1 wherein the relatively small amount comprises no more than approximately 4.0% greater and 4.0% less than a given representative amplitude.
6. The method of claim 5 wherein the representative amplitude varies between approximately 5 volts as corresponds to a logical “1” and approximately −5 volts as corresponds to a logical “0” and the relatively small amount comprises approximately 0.2 volts greater and less than the representative amplitude.
7. The method of claim 1 wherein, for at least one of the data elements, varying the amplitude by a relatively small amount to provide an amplitude-irregular data element includes so varying the amplitude for a plurality of the data elements.
8. The method of claim 7 wherein so varying the amplitude for a plurality of the data elements comprises so varying the amplitude for substantially all of the data elements.
9. The method of claim 1 wherein varying the amplitude by a relatively small amount includes varying the amplitude a plurality of times by a relatively small amount for a single one of the data elements.
10. The method of claim 9 wherein varying the amplitude a plurality of times by a relatively small amount for a single one of the data elements includes varying the amplitude at least 3 times by a relatively small amount for a single one of the data elements.
11. The method of claim 10 wherein varying the amplitude at least 3 times by a relatively small amount for a single one of the data elements includes varying the amplitude at least 4 times by a relatively small amount for a single one of the data elements.
12. The method of claim 1 wherein varying the amplitude by a relatively small amount to provide an amplitude-irregular data element includes varying the amplitude by a relatively small amount to provide an amplitude-irregular data element having an average amplitude value that is at least approximately equal to the representative amplitude for such data element.
13. The method of claim 1 wherein varying the amplitude by a relatively small amount to provide an amplitude-irregular data element includes varying the amplitude by a relatively small amount for varying amounts of time to provide an amplitude-irregular data element.
14. The method of claim 13 wherein varying the amplitude by a relatively small amount for varying amounts of time includes varying the amplitude by a relatively small amount for at least pseudo-randomly varying amounts of time.
15. An FSK transmitter including:
a data source having an output that provides data elements comprising at least one parameter having a representative amplitude that varies in correspondence with information values that correlate to the data;
a data element dithering unit having an input operably coupled to receive the data elements and an output that provides dithered data elements wherein the at least one parameter has a dithered amplitude;
a parameter controlled oscillator having an input operably coupled to receive the dithered data elements and an output that provides a signal having a frequency that varies as a function, at least in part, of the dithered data elements.
16. The FSK transmitter of claim 15 wherein the parameter comprises voltage.
17. The FSK transmitter of claim 16 wherein the parameter controlled oscillator comprises a voltage controlled oscillator.
18. The FSK transmitter of claim 15 wherein the data elements comprises non-return-to-zero data elements.
19. The FSK transmitter of claim 15 wherein the dithered amplitude of a dithered data element has an average value that is at least approximately equal to the representative amplitude as corresponds to the dithered data element.
20. The FSK transmifter of claim 15 wherein the data element dithering unit includes dithering means for dithering the representative amplitude of a given data element by a dithering amplitude that comprises a relatively small fraction of the representative amplitude.
21. The FSK transmitter of claim 20 wherein the dithering amplitude comprises no more than approximately 4.0% of the representative amplitude.
22. The FSK transmitter of claim 20 wherein the dithering means further dithers the representative amplitude of a given data element a plurality of times.
23. The FSK transmitter of claim 22 wherein the dithering means further dithers the representative amplitude of a given data element both above and below the representative amplitude.
24. The FSK transmitter of claim 20 wherein the dithering means dithers the representative amplitude of a given data element at a dithering rate that exceeds a symbol rate for the data source.