Resolutions of Eye Diagrams

In a schematic, define sets of analysis-specific options with the Add Solution Options selection. You can then select one of your defined option sets when you create or edit a solution setup. Using this mechanism, use the same option set in multiple analysis setups, or use different option sets in the same solution setup by editing the setup.

There are multiple ways to create an option set:

• From the Circuit menu, select Add Solution Options ....
• From the Project Manager window, expand the Project Tree. Then right-click Analysis and select Add Solution Options ... to open the Solution Setup window.
• Click Select in the Solution Options group box in a Solution Setup window.

Any of these actions opens the Solution Options window. Click the Eye Options, AMI Options, and Transient Options tabs to view the following options.

The Solution Options window controls the UI and amplitude resolutions of the generated sampled/statistical eye diagrams. And this amplitude resolution in turn controls the fineness of the eye diagram plot and measurements. The limits on these bin counts are set to 1500 which allows a finer resolution (at the possible expense of analysis time). Any eye diagram generated at a resolution higher than 1500 is sub-sampled to fit into a 1500 resolution which could potentially introduce visual and measurement artifacts.

Additionally, when combining multiple traces into a statistical eye diagram with different amplitude or UI bin resolutions, the plot tries to up-sample as many traces as needed to ensure that no trace needs to be sub-sampled. In such a case, the allowed max resolution of the composite eye is increased to 3000. For example, if the two traces (whose individual statistical eye diagrams plots are displayed in the following figures) are combined into one statistical plot.

• Assume both are set to have Amplitude resolutions of 500. Until the specified UI or Amplitude resolution in the Options is maintained at less than 1500, the trace is displayed faithfully.

• “Statistical Eye Plot 4 ” has a range of 50mV and Input_9 has an Amplitude range of 150mV. When these two are added to one plot, the composite eye diagram which superimposes both the eyes now has to fit the 50mV amplitude range of one trace into the combined 150mV Amplitude range: To avoid sub-sampling artifacts, this means that the 50mV range has to occupy at least 500 central bins in the composite eye. This means that the 150mV trace needs to be up/super-sampled to 1500 Amplitude bins (UI bins are upsampled also). In this case of mixed traces with different traces each having different Amplitude ranges, AnsysEDT super-samples the sampled eyes such that none of the constituent eyes are sub-sampled and this limit is increased on the individual eye limit of 1500 to 3000.

These limits are in place to prevent uncontrolled memory usage and users are not expected to be concerned with them. However, if these limits need to be removed (accepting the consequences for memory swell), set the ANSOFT_DISABLE_PMF_BIN_SIZE_LIMITS=1 environment variable.