Shulou(Shulou.com)06/01 Report--

With the change of technology, users are more and more in pursuit of convenience and visual effects. In order to enhance the user experience, the amount of data of images or games is increasing. In the technical aspect, in order to maintain the overall fluency and immediacy of visual speech, the transmission efficiency and processing speed between various products must be accelerated. Speeding up the signal transmission speed will reduce the recognition rate of the receiver. In addition, the volume of electronic products is shrinking, resulting in a closer distance between the signal lines between the circuit boards, resulting in mutual interference between the signal lines and the signal lines can no longer be ignored. So how to judge the transmission quality of a product? We can use the eye chart as the basis to judge the signal quality of the product.

The formation of the eye map:

The eye map is the result of accumulating and displaying the bits of the serial signal by the way of afterglow, and the shape of the superimposed figure looks very similar to that of the eye, so it is called the eye map. Because the USB eye map represents the bit information of the serial signal completely with one graph, it has become the most important tool to measure the signal quality, so the eye map measurement is also called "signal quality test".

Analysis of eye map:

1. The width of the eye chart opening determines the time interval at which the received waveform can be sampled and reproduced without interference.

two。 The slope of the eye chart indicates the sensitivity of the system to timing jitter (or error). The larger the slope is, the more sensitive the system is to timing jitter.

3. The horizontal width of the shaded part of the left (right) corner of the eye map represents the variation range of the zero point of the signal, which is called zero distortion. The width of the eye chart opening determines the time interval at which the received waveform can be sampled and reproduced without interference.

4. The slope of the eye chart indicates the sensitivity of the system to timing jitter (or error). The larger the slope is, the more sensitive the system is to timing jitter.

5. The horizontal width of the shadow part of the left (right) corner of the eye map represents the variation range of the zero point of the signal, which is called zero distortion. In many receiving devices, the timing information is obtained from the zero position of the signal, which is very important for this kind of equipment.

6. At the sampling time, the vertical width of the shadow area represents the maximum signal distortion.

7. At the sampling time, half of the interval between the two shadow areas is the minimum noise tolerance, and misjudgment may occur if the instantaneous value of noise exceeds it.

8. The timing information in the horizontal axis corresponding to the decision threshold level is obtained by the zero position of the signal, which is very important for the zero distortion of this kind of equipment.

9. At the sampling time, the vertical width of the shadow area represents the maximum signal distortion.

10. At the sampling time, half of the interval between the two shadow areas is the minimum noise tolerance, and misjudgment may occur if the instantaneous value of noise exceeds it.

11. The horizontal axis corresponds to the decision threshold level.

Products that may need to be tested for eye maps:

The main products tested are built-in host adapters, cameras, keyboard and mouse, network devices, printers, disk drives, audio, desktop computers, media card readers, notebook computers, removable media, phones, Bluetooth, video game devices, mice, OTG devices, scanners, CD/DVD, hard drives, mobile phones, PDA, speakers, cable connectors, sockets, modems, storage devices Icano adapter, monitor, power protection, etc.

For more eye map test data, you can search for "Anxin Lab" on Baidu.

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