QCD’s Automated S-Parameter ChecklistQCD’s Automated S-Parameter Checklist

S-PARAMETER DATA

Most signal integrity engineers work with S-parameter files on a daily basis - creating, combining and including them into simulations used to make design decisions. However, the quality of S-parameter data varies widely and typical metrics of causality, passivity and reciprocity don’t always flag problems that impact simulation accuracy.

Because S-parameter data is frequency-domain and system simulations are performed in the time-domain, finding flaws and inconsistencies in S-parameter data can be difficult. Even when issues are traced back to a particular S-parameter model, documenting and explaining the issue to the person who created the data can be difficult. Thus, system designers are often forced to run simulations with data they don’t really trust.

When S-parameter data doesn’t accurately represent real world hardware, prototypes can end up failing in the lab, or extra margin can be left on the table, resulting in systems that deliver less performance than they could.

VALIDATING S-PARAMETER QUALITYSiSoft’s S-parameter checklist provides an automated approach to validating S-parameter models and predicting how they will perform in time-domain simulations. It combines standard metrics with automated frequency and time-domain test benches to examine the model from multiple perspectives, highlighting inconsistencies in how the model behaves. The checklist helps designers make targeted corrections to data and document the results of validation tests for reports and presentations. Where data has been corrected, the checklist allows original and updated data to be compared side by side, so that designers can decide whether the degree of change is acceptable, or the source data needs to be regenerated. Either way, SiSoft’s S-parameter checklist gives system designers confidence in the models they work with and the results of their system simulations.

BENEFITS● Saves time by identifying model issues up front

in the design process

● Saves time by correcting simple problems without requiring model regeneration

● Creates clear documentation for tests performed and issues found

● Increases confidence in system simulation results

QCD’s Automated S-Parameter ChecklistQCD’s Automated S-Parameter Checklist (continued)

GRAPHICAL, GUIDED PROCESS The S-parameter checklist steps designers through the validation process, providing guidance on what to look for and what is considered acceptable. The user’s screen is divided into four areas:

● A process list indicating which step the designer is currently working on

● Instructions on what to look for and behavior that is considered acceptable / not acceptable

● Plots of the data being reviewed, where designers can pan and zoom as needed

● A notes section, where designers indicate which tests passed or failed, optionally making detailed notes and observations for inclusion in test documentation

Designers can use the process step list to jump back and forth, comparing behavior between different views. Once the designer has stepped through all the parts of the process, test results, results plots and detailed notes can be exported for inclusion in project level reports and presentations.

CHECKLIST PROCESS STEPSThe checklist automatically creates test benches and simulation results, guiding the designer through the following process steps:

● Visual inspection of source data

● Metrics: passivity, causality, reciprocity, delay, frequency spacing

● Insertion loss (rectangular and polar plots)

● Return loss and crosstalk

● Time-Domain Transmissometry (TDT)

● Time-Domain Reflectometry (TDR)

CORRECTING AND EDITING DATAAutomated corrections for passivity, causality and reciprocity can be applied through the checklist GUI and the effects of those corrections can be reviewed before deciding to accept them. Missing DC points, a common problem with S-parameter data, can be added either through automated extrapolation or created from user defined input. S-parameter data can also be edited directly—usually to remove a few data points that are inconsistent with the rest of the model after careful analysis of the different checklist plots.

At any point in the editing process, designers can revert to the original model and start over. This allows multiple correction strategies to be tested quickly to identify the best approach. The behavior of the updated model can always be compared to the original model to let designers assess whether the changes are acceptable. Once the model behaves satisfactorily, users can save the validated model, which will not only provide better results in QCD but will provide more consistent results in other tools as well.

To learn more about SiSoft’s products, contact sales@sisoft.com or visit our website at www.sisoft.com.

Signal Integrity Software, Inc.6 Clock Tower Place, #250, Maynard, MA 01754Phone: 978.461.0449 Fax: 978.461.5092

Copyright © 2015 Signal Integrity Software, Inc. SiSoft, Quantum Channel Designer, Quantum-SI, Core-to-Core, TransferNet, and High-Speed Design Closure are trademarks of Signal Integrity Software, Inc.All other trademarks are the property of their respective owners. SC-9/15

QCD’s Automated S-Parameter ChecklistQCD’s Automated S-Parameter Checklist (continued)

DOCUMENTATIONThroughout the checklist process, designers can indicate whether tests pass, fail or produce unusual results that should be investigated further. When complete, the checklist process generates a PowerPoint report that includes all the screen shots along with a list of which tests passed/failed and any notes that were entered. This report can then be forwarded to a model creator highlighting issues that need verification/correction, or it can just be a record of the tests performed on the model.

INTEGRATES SEAMLESSLY WITH QCD S-PARAMETER MANAGEMENT

The S-parameter checklist complements QCD’s existing capabilities for creating and manipulating S-parameters to provide a complete environment for managing S-parameter data. S-parameter capabilities supplied with every copy of QCD include:

● S-parameter port map / port name editor

● S-parameter slicing capability (create smaller .sNp’s from larger ones)

● S-parameter splicing (create composite .sNp’s from THRU, NEXT, FEXT data)

● S-parameter concatenation (create a single .sNp from a QCD schematic)

● S-parameter Resampling / Truncation