What is the oscilloscope eye diagram? How to form an oscilloscope eye diagram and how to distinguish signal quality?
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What is the oscilloscope eye diagram? How to form an oscilloscope eye diagram and how to distinguish signal quality?

Posted Date: 2024-01-21

What is the oscilloscope eye diagram? How to form an oscilloscope eye diagram and how to distinguish signal quality?

The oscilloscope eye diagram is a tool used to evaluate the quality of digital signals and is widely used in the communications industry. It is a standardized display form formed by observing and analyzing the waveform diagram of the signal. The oscilloscope eye diagram can provide information about signal stability, noise and distortion, and is used to judge the quality of the signal.

Forming an oscilloscope eye diagram requires signal sampling first, that is, converting a continuous-time analog signal into a discrete-time digital signal. When a signal is sampled, the waveform should be sampled at a high enough rate to ensure that the details and rapid changes of the signal are accurately captured. Usually, the sampling rate used by the oscilloscope eye diagram is more than twice the highest frequency of the signal, which can avoid the problem of information loss or distortion of the signal during the sampling process.

After the sampling is completed, the discrete sampling data needs to be organized into a two-dimensional matrix in an appropriate manner. This matrix is ​​called the "eye diagram", and the specific methods used include division multiplexing (TDM) and multiple input multiple output (MIMO). In the eye diagram, time domain and amplitude information are displayed on the horizontal and vertical axes respectively. By observing the eye diagram of an oscilloscope, you can intuitively understand the quality and characteristics of the signal.

The main characteristic of an oscilloscope's eye diagram is the "eye" shape it presents with an open center. This open area represents the resolution capability of each signal bit, that is, the accuracy of determining logical "0" and "1". The larger the open area, the better the signal quality. If the shape of the eye diagram is narrowed, closed, or distorted, showing some extra peaks or noise, etc., then this may be an indication of a problem with the signal quality.

By observing the eye diagram of an oscilloscope, you can tell the quality of the signal. The following are some commonly used methods to distinguish signal quality:

1. Eye height: The vertical direction of the eye diagram represents the amplitude of the signal, and the eye height represents the height of the open area. The larger the eye height, the smaller the noise and fluctuation of the signal, and the better the signal quality.

2. Eye width: The horizontal direction of the eye diagram represents the time of the signal, and the eye width represents the width of the open area. The wider the eye width, the slower the signal waveform changes, the smaller the signal transmission time jitter, and the better the signal quality.

3. Eye symmetry: The left and right symmetry of the eye diagram indicates the saturation and offset of the signal. If the eye diagram is asymmetrical from left to right, it means that the signal has saturation bias or distortion, and the signal quality is poor.

4. Eye diagram distortion: The eye diagram should be a normal rectangle in topological structure. If the shape of the eye diagram is distorted, it means that there is transmission delay or other distortion in the signal, and the signal quality may be poor.

When distinguishing signal quality, it is necessary to conduct a comprehensive analysis based on the above indicators. The most ideal oscilloscope eye diagram should have a highly open eye, equal eye widths, symmetry, and a rectangular shape without distortion. If the signal quality is poor, the eye diagram may appear closed, insufficient in height, unequal in width, poor in symmetry, and distorted.

In summary, the oscilloscope eye diagram is an important tool for evaluating digital signal quality. It displays information on signal stability, noise and distortion by observing and analyzing the waveform of the signal. By comprehensively considering indicators such as eye height, eye width, symmetry, and eye diagram shape, the quality of the signal can be judged and help engineers troubleshoot and optimize.


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