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Tutorial: Real-Time Impedance and Coupling Analysis

Trying to find impedance and coupling issues in your design can be a tedious and time-consuming process. Finding these issues AFTER your design is completed can lead to a complete re-spin of your design, possibly making your project late and overbudget. Real-time Impedance and Coupling Analysis in OrCAD PCB Designer Professional allows you to quickly find and fix problematic traces throughout the design process. This tutorial will show you how easy it is to simulate and view impedance and coupling issues in your traces with no additional steps or modeling by utilizing the included workflow manager. If you would like to follow along, you can download the design files here.
 

Step 1: In OrCAD PCB Designer Professional, Open the Workflow Manager. 

You can do this by selecting Analyze Workflow Manager from the Toolbar. Make sure the Impedance Workflow is selected.


 

Step 2: Complete the Set Up for Analysis.

Under Analysis Mode select “Net Based”.

Click Select Nets. This will bring up a window where you can select specific nets or all the nets in the design. Select all the nets in the design by pressing the >> button and click OK.


 

Step 3: Run the Analysis. 

Select Start Analysis from the Analysis Workflow Manager. This will perform the analysis. The progress bar will report the status of the analysis.
 


 

Step 4: View the results.

Under View Modes select “Net Based” and “Differential Pairs”.

View the results using the Impedance Table. The Impedance table is broken down into two different views: the Summary Table and Detailed Table. The Summary Table shows the following information:

  • Net Names
  • Vias
  • No Ref
  • Color Coded Impedance Values (Ohm)
  • Minimum, Maximum, and Typical
  • Impedance Length (%)
  • Minimum, Maximum, and Typical
  • Trace Total Length
  • Trace Total Delay (nS)
  • The Detailed Table includes the following information:
  • Color Coded Impedance (Ohm)
  • Length
  • Trace Delay (pS)
  • Layer
  • Location (x;y)


 

View the results using Impedance Vision. Adjust the Imp [Ohm] bar to only view traces with problematic impedance values.


 

Step 5: Select the Coupling Workflow from the Analysis Workflow Manager Window.



 

Step 6: Complete the set up the Analysis.

Under Analysis Mode select “Net Based”.
 

Click Select Nets. This will bring up a window where you can select specific nets or all the nets in the design. Select all the nets in the design by pressing the >> button and click OK.


 

Step 7: Run the Analysis.

Select Start Analysis from the Analysis Workflow Manager. As with the Impedance Workflow, this will perform the analysis. The progress bar will report the status of the analysis.
 


 

Step 8: View the results.

Under View Modes select “Net Based” and “Worst Case”.

View the results using the Coupling Table. The Coupling Table is broken down into two different views- the Summary Table and Detailed Table. The Summary Table shows the following information:

  • Net Name
  • Max Coupling
  • Aggressor Net Name
  • Color Coded Coef (%)
  • Length (%)
  • Percentage of Length with Coupling Coefficient
  • >5%
  • 2-5%
  • Total Coupling Index (millimeter-%)
  • The Detailed Table includes the following information:
  • Victim Trace Ref
  • Aggressor Net
  • Aggressor Trace Ref
  • Coupling Coefficient
  • Length
  • Layer
  • Victim Segment
  • Aggressor Segment



 

View the results using Coupling Vision. Adjust the Coef [%] bar to only view traces with problematic coupling coefficient values.


 

Step 9: In the Coupling Vision, adjust the problem routes to incorporate additional space between traces.


 

Step 10: Run the Coupling Analysis again.
This can be done by selecting Start Analysis in the Coupling Workflow Manager. Select OK in the pop-up window to replace the analysis data and view the results.
 

The analysis has completed using the adjusted traces and the coupling issues have been resolved.
 


 

Real-Time Impedance and Coupling Analysis in OrCAD PCB Designer Professional quickly analyzes a specialized selection of nets or all the nets on your board throughout your design process. With visually compelling information about the trace impedance and coupling coefficients, you can easily identify and fix problem areas on your board before design completion, saving you time and reducing errors or even complete re-spins.

Video Tutorial