5m 길이의 USB 케이블 끝단에서 사용자 디바이스와 연결되는 제품을 개발 중인데 repeater 를 사용한 후 eye pattern 을 측정하였더니 Rise Time 에서만 Fail 이 발생되는 문제가 있음.

* 측정 결과 eye-diagram 은 margin 폭이 커서 문제없을 듯 하나 Rise Time 이 Fail 이라서 난감하다. Overall Fail.

eye pattern 을 측정하는 데에는 eye 만 중요한 것이 아니므로 아래의 parameter 들도 확인해야 한다.

## The Eye Diagram

The eye diagram shown below (TCC21 parameter) identifies key eye diagram definitions. 1. Zero Level

Zero Level is a measure of the mean value of the logical 0 of an eye diagram.

2. One Level

One Level is a measure of the mean value of the logical 1 of an eye diagram.

3. Rise Time

Rise time is a measure of the transition time of the data from the 10% level to the 90% level on the upward slope of an eye diagram.

4. Fall Time

Fall time is a measure of the transition time of the data from the 90% level to the 10% level on the downward slope of an eye diagram.

5. Eye Height

Eye height is a measure of the vertical opening of an eye diagram. An ideal eye opening would be measured from the one level to the zero level. However, noise on the eye will cause the eye to close.

The eye height measurement determines eye closure due to noise.

6. Eye Width

Eye width is a measure of the horizontal opening of an eye diagram. Ideally, the eye width would be measured between the crossing points of the eye. However, jitter may appear on the waveform and influence the eye opening.

7. Deterministic Jitter

Deterministic jitter is the deviation of a transition from its ideal time caused by reflections relative to other transitions.

8. Eye Amplitude

Eye amplitude is the difference between the logic 1 level and the logic 0 level histogram mean values of an eye diagram.

9. Bit Rate

Bit rate (data rate) is the inverse of bit period (1 / bit period).

The bit period is a measure of the horizontal opening of an eye diagram at the crossing points of the eye.

더 자세한 정보는...

http://na.tm.agilent.com/plts/help/WebHelp/Analyzing/Analyzing_Data_using_Eye_Diagrams.html

(*.219.5.64)