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Calculate Differential Impedance

In this tutorial, we'll calculate the differential impedance and secondary parameters of a differential stripline transmission line. This line is located on the third layer of a sample 6-layer PCB stackup shown below. The required PCB thickness is 1.5 mm.

6-layer printed circuit board

  1. In the Calculation settings groupbox:

    • Set Target to Transmission line
    • Set Target type to Diff pair

    Then select the Edge-coupled offset stripline (ECOS-1B1A) structure.

    Select structure

  2. Define the initial calculation settings:

    • Set calculation mode to Lossless
    • Enable the Trace inverted checkbox.

    Initial settings

  3. Enter the known geometric and electrophysical parameters of the transmission line in accordance with the target PCB stackup:

  4. Set H1, Dielectric height below to 0.51 mm

  5. Set H2, Dielectric height above to 0.125 mm
  6. Set T1, Trace thickness to 0.018 mm
  7. Set W1, Trace width and W2, Upper trace width to 0.2 mm

  8. Set S1, Diff-pair trace spacing to 0.2 mm

    Transmission line parameters

  9. Click Calculate to run the calculation.

    The calculation results will be displayed in a table at the bottom of the window.

    tut-calculate-diff-pair-impedance-results

    The calculated differential impedance (Zdiff) is 79.0754 Ohm.