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RF Cafe began life in 1996 as "RF Tools" in an AOL screen name web space totaling 2 MB. Its primary purpose was to provide me with ready access to commonly needed formulas and reference material while performing my work as an RF system and circuit design engineer. The World Wide Web (Internet) was largely an unknown entity at the time and bandwidth was a scarce commodity. Dial-up modems blazed along at 14.4 kbps while typing up your telephone line, and a nice lady's voice announced "You've Got Mail" when a new message arrived...

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Microstrip Substrate Equations

You can work these formulas manually, or download this great free microstrip calculator (TX Line) from NI/AWR.

Equations are given for calculating the effective width and height prior to plugging the dimensions prior to plugging them in to the equations for effective dielectric constant and then for calculating the impedance.

Here is a really nice summary of many controlled impedance line equations, by Rick Hartley.

RF / Microwave PC Board Design and Layout

Be aware that there are many microstrip impedance calculators on the Internet that give sometimes widely varying results. Be sure of which one you finally decide to use. Most claim to use some or all of these formulas these formulas, but I have discovered ones, for instance, that appear to mistakenly substitute 0.4 for 0.04 in the ε_eff formula for the W/H<1 case.

	Wavelength
	Phase

RF Cafe: Microstrip calculation equation

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