Coplanar Stripline Impedance Calculator (CPS)
Calculate the characteristic impedance of a coplanar stripline (CPS), or estimate conductor width for a target impedance. Enter the substrate and two-strip dimensions shown in the cross-section below.
Use the units printed beside each field. On a small screen, scroll the calculator horizontally to see all inputs and results.
Inputs and units
- er
- Relative permittivity of the substrate.
- s (mm)
- Strip spacing shown in the cross-section.
- h (mm)
- Substrate thickness.
- f (MHz)
- Operating frequency.
- w (mm)
- Conductor width used by Analyze.
- Zo (Ω)
- Target characteristic impedance used by Synthesis.
How to use this calculator
Use Analyze when conductor width is known. Use Synthesis to estimate conductor width for the target Zo while keeping substrate and spacing inputs fixed. Read the returned width in millimetres.
Worked example
For er = 2.6, s = 1 mm, h = 0.6 mm, f = 1000 MHz and w = 0.5 mm, Analyze returns approximately 234.10 ohms. Entering 234.099 ohms as the Synthesis target returns approximately 0.5 mm for the conductor width. The quarter-wavelength result is approximately 59.58 mm.
Reading the results
Read impedance in ohms and synthesized dimensions in millimetres. Effective permittivity and velocity factor describe the propagation estimate; the quarter-wavelength output is in millimetres.
Before using the result in a design
Match the strip pair and dielectric geometry to the drawing. The estimate does not replace a full model of launches, bends, nearby metal or the complete balanced circuit.
Blank fields use the tool’s built-in example defaults; always enter and check your actual design values.
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