Creating an Eye Diagram

眼图，，，，common in telecommunications, is a way of plotting the rising and falling edges of a digital signal in the same plot, creating an “eye”-like design. When combined with persistence, these plots are extremely useful for analyzing the properties of these most-important parts of these signals. Oscilloscopes are commonly used to create these plots, by using a clock signal synchronous to the signal of interest to trigger captures of that signal. Let’s看一看在如何创建一个 波形，我们的免费测试和测量软件。

您为什么要或需要眼图？

眼图using persistenceallows you to quickly identify how noisy a signal is.  It does this byrepeatedlytracing the measured signal path and layer将其登上相同阴谋over and over. Ideally，，，，a clean signal会有很瘦线，这意味着您的系统非常一致。如果您有更广阔的路径，这表明were一些不一致/distortions in the data， 如jitter (rising and falling edges occurring slightly earlier or later than expected），，，，降低率的差异，意外的过冲，来自串扰等来源的额外噪音，more。Many of these问题具有可以看到的特征模式乍看上去经过an engineer with a trained eye (pun intended).

在波形中设置眼图

可以轻松地为某些信号创建眼图波形，通过测量感兴趣的信号和与时钟同步的时钟信号，并触发重复捕获时钟边缘。范围仪器的持久视图如前所述，这些重复捕获层，并绘制每个数据点发生的频率。

设置眼睛模式的触发因素取决于您正在分析的协议类型，如果是编码或单独的时钟，或者数据速率是单个或双重的。  For single data rate signals, you likely want to trigger captures centered on the clock edge (whether rising or falling) that the digital interface uses to sample the data. For double data rate signals, triggering on either edge is the way to go. Even though WaveForms currently doesn’t support the recovery of encoded clocks, persistence is still handy for analyzing these signals, and either edge triggers are still likely to get you the consistency required, even if the resulting plot will be centered on the edges of the signal of interest rather than centering on the middle of the eye.

最新的波形测试版， 波形Beta 3.18.23，添加“Top透明option到范围仪器的p持久看法，，，，有助于区分这data captured from multiple channels within the diagram。，，，，the system colors这绘制数据点都通过这ir frequency, as normalfor the Persistence view，，，，and with the color representing the channel。只有数据点比选定的顶部设置百分比由频道颜色;to show the pathmost commonly taken。

为了模拟通信系统，我们使用了单独的设备（ Digital Discovery）以不同的驱动强度和振荡速率（影响上升时间和降落时间）以及一个模拟发现专业人物来生成信号，以测量信号。使用两个设备来确保使用相同时钟的仪器不会生成和消耗数据信号 - 我们正在模拟的系统将在传输的任一端具有多个时钟源，因此我们也应该使用。

Here are a couple examples of signals generated by the Digital Discovery’s pattern generator:

现在，让我们看看一些捕获！