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Edge-Coupled Microstrip Impedance

Welcome to our Edge-Coupled Microstrip Impedance Calculator, your specialized tool for calculating the impedance of edge-coupled microstrip lines on PCBs based on detailed operational parameters. This precision calculator assists you in determining the impedance for various edge-coupled microstrip configurations.

Click to learn more about the different types of traces.

Edge-coupled microstrips consist of two parallel traces that can effectively carry differential signals. This configuration helps reduce cross-talk and improves signal integrity in high-speed applications.

Inputs Required:

  • Trace Thickness (oz/ft², mils, cm, mm, µm, in)
  • Height (mils, cm, mm, µm, in)
  • Trace Width (mils, cm, mm, µm, in)
  • Trace Spacing (mils, cm, mm, µm, in)
  • Dielectric Constant

Outputs Provided:

  • Differential Impedance (Ohms)
  • Warnings for Values Exceeding Acceptable Ranges

PCB Design Calculators

Disclaimer: Please note that the results provided by this calculator are for estimation purposes only and should be used as a guide during the design process. We make every effort to ensure the accuracy of this tool, but it is important to verify all calculations through standard design verification processes. We are not liable for any errors in calculations or their consequences in your projects.
Diagram of a microstrip line to reference while using Microstrip Impedance Calculator.
Trace Thickness (t)
Height (h)
Trace Width (w)
Trace Spacing
Dielectric constant (εr)

* This calculator determines the impedance based on the ratio of the trace width ('w') to the height of the dielectric material ('h') between the trace and the ground plane in edge-coupled microstrip configurations. The (w/h) ratio should be maintained between 0.1 and 2.0 for accurate and reliable results. This specific range ensures that the electromagnetic fields around the coupled traces are adequately confined, maintaining stable impedance and optimal signal integrity. Values outside this range may not conform to the standard modeling assumptions used in edge-coupled microstrip designs, potentially resulting in performance issues and deviation from expected impedance values.

Edge-coupled microstrip transmission lines consist of two conductive traces running parallel on the same plane within a dielectric substrate, with a continuous ground plane on the opposite side. The impedance of an edge-coupled microstrip line depends on the width of each trace (w), the spacing between the traces (s), the thickness of the trace (t), the height above the ground plane (h), and the dielectric constant of the substrate (εr).

The calculator uses specific formulas to estimate the impedance of your edge-coupled microstrip line accurately:

  1. Logarithmic Function for Coupled Impedance:

    • Z0,coupled = (174 / √(εr + 1.41)) × log((5.98 × h) / (0.8 × w + t)) × (1 - 0.48 × exp(-0.96 × s / h))
    • This function calculates the differential impedance of the coupled traces, factoring in the trace width, thickness, and spacing to determine the effective propagation path of the electromagnetic waves. The calculation adjusts for the increased width due to the fringing fields where the electric field lines spread out around the edges of the traces, effectively increasing their width.
  2. Dielectric Constant and Propagation Effects:

    • The dielectric constant (εr + 1.41) adjusted with a square root and logarithmic modifications provides a nuanced view of how the electric field interacts with the substrate material, impacting the signal's propagation and thus the impedance calculation.

While using our Edge-Coupled Microstrip Impedance Calculator, remember that complex PCB designs often require expert guidance. If you need additional support, our team at 911EDA is ready to assist with comprehensive PCB design services and engineering solutionsLeverage our PCB design and electronic engineering expertise to enhance your project's success. Learn more about our services and how we can help bring your ideas to life by visiting our PCB Design Services and Engineering Services pages.

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