5.6 Eye pattern

An eye pattern is the display that results from measuring a system' s response to baseband signals in a prescribed way.

Figure 1 Eye pattern

Figure 1 describe the eye pattern that results for binary binary pulse signalling. The width of the opening indicates the time over which sampling for detection might be performed. The optimum sampling time corresponds to the maxmum eye opening, yielding the greatest protection against noise. If there were no filtering in the system then the system would look like a box rather than an eye. In figure 1, $D_A$ , the range of amplitude differences of the zero crossings, is a measure of distortion caused by ISI.

$J_T$ , the range of amplitude differences of the zero crossing , is a measure of the timmung jitter. $M_N$ is a measure of noise margin. $S_T$ is mesuare of sensity-to-timing error.

In general, the most frequent use of the eye pattern is for qualitatively assessing the extent of the ISI. As the eye closes, ISI is increase; as the eye opens, ISI is decreaseing.