|Characteristic Impedance of Microstrip: 60-70 Ohms for w/h = 1, and 40-50 ohms for w/h = 2.||Average Propagation Delay: 2 nS / ft This is an average between microstrip and stripline.|
|Characteristic Impedance of Stripline: 0.6 times that of microstrip.||Typical Propagation Delay: 150 pS / in for Microstrip, or 180 pS / in for Stripline.|
|Characteristic Impedance of Asymmetric Stripline: 0.75 times that of microstrip.||FR-4 Epoxy Glass Dielectric Constant: Between 4.0 and 5.0 according to the composition, typically 4.5.|
|For < 2% Crosstalk:s = 4 h for Microstrip, and s = 2h for Stripline.||For Other Dielectric Materials: Characteristic impedance is proportional to one over the square root of the dielectric constant. Propagation delay is proportional to the square root of the dielectric constant.|
|Maximum Unterminated Stub Length: L(in) = tr (nS)||Dielectric Constant of Other Materials: FR-4 = 4.5, PTFE = 3.2, Polyester = 3.2.|
Note: w = width of trace, h = height of trace above the reference plane, s = spacing between traces, tr = rise time.
© 2000 Henry W. Ott
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