Differential Microstrip Impedance Calculator
Calculate the Differential Microstrip Impedance of a Transmission Line
Note: This Calculator works for W/H < 1
Result
Differential Impedance
Ω
Single Ended Impedance
Ω
Click here to view image
Where,
Z0 = Single Ended Impedance
Zd = Differential Impedance
d = Trace Separation
w = Trace Width
t = Trace Thickness
h = Dielectric Thickness
εr = Relative Dielectric Constant
Example,
If w = 10 mil, d = 63 mil, t = 1.2 mil, h = 63 mil and εr = 4 then
Z0 = 138.88 Ω and Zd = 226.71Ω
Differential Microstrip Impedance
An edge coupled differential microstrip transmission line is constructed with two traces on the same reference plane. These lines are placed on a dielectric material of height h and there is also some coupling between the lines. It is good practice to match differential trace length and to keep the distances between the traces consistent.
As can be seen from the formula below when d decreases, while keeping h constant, differential impedance decrease. The differential impedance depends upon the D/H ratio. For this calculation, the units of d,h, t and w can be ignored as long as they have the same units (mils, mm, inches).Calculating the Differential impedance is a two-step process, first Calculate the single ended impedance Zo and then use this value to calculate the differential impedance. If you have already calculated the single ended impedance Zo, we have developed another calculator that can be used to calculate the differential impedance using Zo.