The characteristic impedance (Z_{o}) of a microstrip transmission line can be calculated using the active calculator or the
formula at the bottom of the page.

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The calculator gives very similar results to those in Table 1 of an article at http://www.polarinstruments.com/support/cits/IPC1999.pdf

The following formula is given in the above article by Polar Instruments.

Where ε_{r} is the Relative Dielectric Constant

W is the Width of track

t is the Thickness of track (1 oz/ft2 = 0.035 mm)

h is the Thickness of dielectric

Note that the "h", for dielectric thickness in this formula is omitted in some other Polar publications.

The original source of formula is IPC-2141: Controlled Impedance Circuit Boards and High-Speed Logic Design, April 1996.

IPC have their website at: http://www.ipc.org/ContentPage.aspx?pageid=PCB-Tools-and-Calculators

This calculator is provided free by Chemandy Electronics in order to promote the FLEXI-BOX

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