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EMC Laboratory
4000 Enterprise Dr.
Missouri University of Science
and Technology
Rolla, MO 65401
emclab@mst.edu
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Microstrip Impedance Calculator

Provide values for three of the four parameters H, T, W, Zo and the relative permittivity of the dielectric. Click the button corresponding to the unknown parameter to calculate its value. ( 0.1< W/H < 3.0; 1 < εr < 15 )

Select the dimension unit of the microstrip: mm mils
  
  (Dielectric thickness) : mm mils
  (Trace thickness) : mm mils
  (Trace width) : mm mils
er (Relative permittivity) :
(Characteristic impedance):

ohms

Co    (Capacitance):

pF/cm pF/inch

Tpd  (Propagation delay time):

 psec/cm psec/inch

Notes:

  • The formulas used here are taken from the Design Guide for Electronic Packaging Utilizing High-Speed Techniques (4th Working Draft, IPC-2251, February 2001).

  • Range of valid parameters specified in the Design Guide: 0.1< W/H < 3.0; 1 < εr < 15;
  • Accuracy: For typical PCB parameters (εr = 4, H = 30 mil and T = 1.37 mil), the deviation of the calculated results from results obtained using XFX, a 2D numerical field solver from Innoveda, is listed below:
Zo: 
0.1 < W/H < 0.2within 5%
0.2 < W/H < 1.5within 2%
1.5 < W/H < 2.0within 5%
2.0 < W/H < 2.7within 10%
2.7 < W/H < 3.0within 15%
Co: 
0.1 < W/H < 0.2within 10%
0.2 < W/H < 1.2within 5%
1.2 < W/H < 2.0within 10%
2.0 < W/H < 3.0within 5%