Embedded Microstrip Calculations - National Instruments Graphical User Interface Ultiboard User Manual

Note If you chose User Defined Zo in the previous step, the Per Length Unit and the
Differential Impedance are the only values that appear in the Calculation Results area
of the PCB Differential Impedance Calculator dialog and the Results tab when you click
Calculate.

Embedded Microstrip Calculations

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4. Click Calculate. Results of the calculation appear in the Calculation
Results area. They also appear in the Results tab of the Spreadsheet
View.
5. Click Close to close the PCB Differential Impedance Calculator.
Microstrip Differential Impedance Equations
The equations used to perform the microstrip differential impedance
calculations are:
Z0 = 87/(sqrt(Er + 1.41)) * ln(5.98*H/(0.8*W+T))
Tpd = 58.35247*sqrt(Er+1.41)
C0 = Tpd/Z0
L0 = C0*Z0*Z0
Zdiff = 2*Z0*(1-0.48*exp(-0.96*S/H))
Complete the following steps to perform embedded microstrip differential
impedance calculations:
1. Select Tools»PCB Differential Impedance Calculator.
2. Select Embedded Microstrip in the Type drop-down list.
3. In the Input Data area, edit the following fields as desired.
• Input Length Unit—Select mils or millimeters.
• Dielectric Height (H1)—Refer to the figure below.
6-9
Chapter 6 PCB Calculators
NI Ultiboard User Manual