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# Microstrip Transmission Line Width

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#### Antenna (^.^)

##### Member level 3
Hello,

Could anyone assist in telling me how to find the width of a microstrip transmission line?
I know there are formulas and some calculators online but they all seem to require some initial width anyway.

Thanks!!

Microstrip line usually related with impedance. Also some parameters like substrate height, frequency and dielectric constant. I suggest using following.
https://www.emtalk.com/mscalc.php
for more accurate u can use

Hello,

Could anyone assist in telling me how to find the width of a microstrip transmission line?
I know there are formulas and some calculators online but they all seem to require some initial width anyway.

Thanks!!

many closed form formulas..depends on which characteristic impedance you are trying to implement

Impedance is chiefly dependent on track width to gap ratio and dielectric constant,D.

• Thinner boards allow smaller tracks at the same ratio and impedance.
• D tends to have a 10% minimum tolerance.
• Track widths have an etch-back tolerance equal to thickness of copper.
• Impedance testing by TDR method is done at fab shop on test coupons at additional expense for better results and D codes adjusted in Gerber file.
• Slight variations exist due to dielectric constant reducing with rising f , conductor skin effects and gap to wavelength ratio at EHF.

hamid did you verify all calculators give the same results?

SunnySkyguy it is assumed we want to synthesis a 50-ohm microstrip transmission line,
consider er = 4.4, h (height) = 1.6 mm, freq = 1000 MHz, and t (thickness of trace) = 0.001 mu m.

W = 3.045654296875 mm

**broken link removed** gave me Z0 = 50.1 ohm

https://chemandy.com/calculators/microstrip-transmission-line-calculator-hartley27.htm gave me Z0 = 50.22 ohm