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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. 

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. 

5.

Click Close to close the PCB Differential Impedance Calculator. 

The equations used to perform the centered stripline differential impedance 
calculations are: 

Z0 = 60*ln(4*(2*H+T)/(0.67*3.1415926*(0.8*W+T)))/sqrt(Er)

Tpd = 84.66667*sqrt(Er)

C0 = Tpd/Z0

L0 = C0*Z0*Z0

Zdiff = 2*Z0*(1-0.347*exp(-2.9*S/(2*H+T)))

Complete the following steps to perform asymmetric stripline differential 
impedance calculations:

1.

Select Tools»PCB Differential Impedance Calculator. 

2.

Select Asymmetric Stripline in the Type drop-down list.