Method and apparatus for determining inter-symbol interference for estimating data dependent jitter
View Patent ↗A method and apparatus for displaying substantially noise-free segments of serial data waveforms. The method comprises the steps of dividing an acquired waveform into a plurality of waveform slices and categorizing each of the plurality of waveform slices according to at least a sequence of N bit values prior to a bit value being observed. The waveform slices in each category are then averaged resulting in an average pattern for each category. Each of the averaged patterns is then displayed on a display in an overlayed manner.
1. A method for displaying waveforms, comprising the steps of:
dividing an acquired waveform into a plurality of waveform slices;
categorizing each of said plurality of waveform slices according to at least a sequence of N bit values prior to a bit value being observed;
averaging said waveform slices in each category resulting in an average pattern for each category;
storing the average pattern for each category to a computer readable medium; and
displaying each of said averaged patterns in an overlayed manner.
2. The method of claim 1 , wherein N is in the range of 3-10.
3. The method of claim 2 , wherein N=6.
4. The method of claim 1 , wherein each of said waveforms is categorized further according to at least a sequence of P bit values following said bit value being observed.
5. The method of claim 4 wherein P=1.
6. The method of claim 1 , wherein said acquired waveform is stored in a memory upon acquisition.
7. The method of claim 1 , further comprising the step of obtaining data dependent jitter based upon a peak-to-peak variation of threshold crossing time for a specified vertical threshold.
8. The method of claim 1 , further comprising the step of characterizing an eye crossing level by observing a level at which a crossing distribution's peak-to-peak variation is narrowest.
9. The method of claim 7 , further comprising the step of re-dividing said acquired waveform into a second plurality of waveform slices in accordance with said obtained data dependent jitter, and substantially corrected for systematic intersymbol interference (ISI) induced jitter and/or noise.
10. The method of claim 9 , wherein said second plurality of waveform slices depict a substantially ISI-free jitter component associated with said acquired waveform.
11. An apparatus for displaying waveforms, comprising:
means for dividing an acquired waveform into a plurality of waveform slices;
means for categorizing each of said plurality of waveform slices according to at least a sequence of N bit values prior to a bit value being observed;
means for averaging said waveform slices in each category resulting in an average pattern for each category; and
a display for displaying each of said averaged patterns in an overlayed manner.
12. The apparatus of claim 11 , wherein N is in the range of 3-10.
13. The apparatus of claim 12 , wherein N=6.
14. The apparatus of claim 11 , wherein each of said waveforms is categorized further according to at least a sequence of P bit values following said bit value being observed.
15. The apparatus of claim 14 , wherein P=1.
16. The apparatus of claim 11 , wherein said acquired waveform is stored in memory upon acquisition.
17. The apparatus of claim 11 , further comprising means for obtaining a data dependent jitter based upon a peak-to-peak variation of threshold crossing time for a specified vertical threshold.
18. The apparatus of claim 11 , further comprising means for characterizing an eye crossing level by observing a level at which a crossing distribution's peak-to-peak variation is narrowest.
19. The apparatus of claim 17 , further comprising means for re-dividing said acquired waveform into a second plurality of waveform slices at least additionally in accordance with said obtained data dependent jitter, and substantially corrected for systematic intersymbol interference (ISI) induced jitter and/or noise.
20. The apparatus of claim 19 , wherein said second plurality of waveform slices depict a substantially ISI-free jitter component associated with said acquired waveform.