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Microstrip Impedance Calculator

Welcome to our Microstrip Impedance Calculator, a specialized tool designed specifically for calculating the impedance of microstrip lines on PCBs based on your unique specifications. This focused calculator helps you accurately determine microstrip impedance for your circuit design needs.

Click to learn more about the different types of traces.

Microstrip traces are commonly used for high-speed signal routing in PCB design. They offer good impedance control and are easier to fabricate compared to other trace types.

Inputs Required:

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

Outputs Provided:

  • Target 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 the Microstrip Impedance Calculator.
Inputs:
Trace Width (w)
Trace Thickness (t)
Height (h)
Dielectric constant (εr)
Results:

* This calculator determines the optimal trace width based on the ratio of the trace width ('w') to the height of the dielectric material ('h') between the trace and the ground plane. For accurate and reliable results, the (w/h) ratio should be between 0.1 and 2.0. This range ensures the electrical field around the trace is properly confined, maintaining stable impedance and signal integrity. Values outside this range might not align with standard PCB design assumptions, potentially leading to performance issues.

Microstrip transmission lines consist of a conductive trace printed on a dielectric substrate with a continuous ground plane on the opposite side. The impedance of a microstrip line depends on its width (w), the thickness of the trace (t), and the height (h) above the ground plane, along with the dielectric constant of the substrate (εr).

The calculator uses a specific formula to estimate the impedance of your microstrip line accurately:

  1. Logarithmic Function:

    • Z0 = (87 / √(εr + 1.41)) × log((5.98 × h) / (0.8 × w + t))
    • This function calculates the effective width of the microstrip. It accounts for the increase in trace width due to the fringing fields, where the electric field lines spread out around the edges of the trace, effectively increasing its width.
  2. Square Root and Scaling Factors:

    • √(εr + 1.41)
    • This part of the formula helps approximate the effective dielectric constant, taking into account the non-ideal behaviors of the substrate material.
    • The scaling factor of 87 is used to align the result with the standard impedance units of Ohms. This factor helps balance the microstrip line's capacitive and inductive properties, ensuring your circuit meets its required performance characteristics.

While using our 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 expertise in PCB design and electronic engineering 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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