Microstrip Impedance Calculator

The Formula

The simplified formula for calculating microstrip characteristic impedance is:

\[Z_0 \approx \frac{60}{\sqrt{\varepsilon_r}} \ln\left(\frac{8h}{w} + \frac{w}{4h}\right)\]

Where:

• Z0: Characteristic impedance (in ohms, Ω)
• εr: Dielectric constant of the substrate
• h: Height of the substrate (mm)
• w: Width of the microstrip trace (mm)

Calculation Steps

1. Gather the microstrip parameters: trace width (w), substrate height (h), and dielectric constant (εr)
2. Calculate the ratio w/h
3. Insert these values into the formula
4. Perform the calculation to get the characteristic impedance

Example Calculation

Let's calculate the characteristic impedance for a microstrip with:

• Trace width (w) = 3 mm
• Substrate height (h) = 1.6 mm
• Dielectric constant (εr) = 4.4

\[Z_0 \approx \frac{60}{\sqrt{4.4}} \ln\left(\frac{8 * 1.6}{3} + \frac{3}{4 * 1.6}\right) \approx 50.0 \Omega\]

Visual Representation

This visual shows a cross-section of the microstrip structure with the calculated impedance based on our example.