A deep interpretation of jitter
If the data rate of the system is increased, the jitter amplitude measured in a few seconds will remain roughly the same, but when measured in a fraction of the time of the bit period, it will increase proportionately with the data rate, resulting in bit errors. Therefore, the related jitter should be reduced as much as possible in the system to improve the overall system performance.
Jitter describes the horizontal fluctuation of a signal, that is, the short-term deviation of a signal from its ideal time position at a particular moment.
1. Interpretation of intersection points
The crossover ratio of the general standard signal is 50%, which means that the signal "1" and "0" each account for half of the level. To measure the correlation ratio, use the statistical method shown in the figure. The cross level is the average calculated according to the center window of the vertical statistics of the cross point, and its proportion equation is as follows (where the 1 and 0 level is the average value of 20% in the middle of the eye map, that is, the conversion from 40% to 60%
2.Effect
The ability of a signal 1 or 0 to transmit mass varies with the proportion of the crossing points. As shown in the figure, the figure on the left is the eye map with different cross-proportional relationships, corresponding to the relevant 1 and 0 pulse signals on the right. At the same time, we can also understand the relationship between the width of different pulse signal time and the cross proportion of the graph.
3.Summarize
For general signals, the average distributed signal levels 1 and 0 are the most common. It is generally required that the eye-image cross ratio is 50%, that is, the same signal pulse length 1 and 0 is used as the standard to verify the relevant parameters. Therefore, the relative amplitude loss analysis caused by the deviation of different 1 and 0 signal levels can be effectively measured according to the distribution of the eye cross ratio relationship. For example, if the eye cross ratio is too large, that is, too many 1 level signals are transmitted, the signal error, shielding and its limits will be verified according to this cross ratio relationship. The eye cross ratio is too small, that is, the transmission of too many 0 level signals, generally easy to cause the receiver signal is not easy to extract the frequency from it, resulting in failure to synchronize, resulting in synchronization loss. It is equivalent to a square wave, resulting in a frequency mismatch, and less than 50% of the square wave proportion..
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