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Centered Stripline Calculations
© National Instruments Corporation
Embedded Microstrip Differential Impedance Equations
The equations used to perform the embedded microstrip differential
impedance calculations are:
Z0 = 56*ln(5.98*H/(0.8*W+T))/sqrt(Er*(1-exp(-1.55*H1/H)))
Tpd = 84.66667*sqrt(Er*(1-exp(-1.55*H1/H)))
C0 = Tpd/Z0
L0 = C0*Z0*Z0
Zdiff = 2*Z0*(1-0.48*exp(-0.96*S/H1))
Complete the following steps to perform centered stripline differential
impedance calculations:
1.
Select Tools»PCB Differential Impedance Calculator.
2.
Select Centered Stripline 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 Thickness (H)—Refer to the figure below.
•
Trace Thickness (T)—Refer to the figure below.
•
Trace Width (W)—Refer to the figure below.
•
Trace Spacing (S)—Refer to the figure below.
•
Relative Permittivity (epsilon r)—Refer to the figure below.
Or
If you wish to define the Characteristic Impedance (Zo) yourself, click
User Defined Zo and edit the following fields as desired:
•
Input Length Unit
•
Dielectric Thickness (H)—Refer to the figure below.
•
Trace Spacing (S)—Refer to the figure below.
•
Characteristic Impedance (Zo)—Refer to the figure below.
Select mils or millimeters.
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6-11
Chapter 6
PCB Calculators
NI Ultiboard User Manual
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