The calculator allows you to put out a preliminary calculation of the symmetrical strip line characteristic impedance. Existing calculators use different calculation formulas and are mainly designed to calculate a "sandwich" of two PCBs with a strip line in the middle. This calculator allows you to calculate, among other things, an air-filled strip line. Such a line can be used to make a matching or a balancing device (balun) for antennas (example).
The main limitation of the calculation is that the width of the ground plane conductor must be at least an order of magnitude greater than the width of the strip. Otherwise, electromagnetic simulators must be used to calculate the characteristic impedance of a symmetrical strip line. For example, ANSYS 2DExtractor. The project file of such a calculation, which was used to verify this calculator, can be downloaded from our website. You can use it as a calculation template by editing the variables in Design properties and Optimetrics setup.
Javascript source code:
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The calculator is based on ©1994-2003 Daniel R. McMahill's source codes.
Limitations and features of antenna calculations
At zero strip thickness, the calculation can be done using exact formulas, where K() is a complete elliptic integral of the first kind:
In practice, such a calculation is applicable only if the thickness of the strip is at least three orders of magnitude less than the distance between the "grounds". Otherwise, the following approximate calculation formula is used:
The formula has an accuracy of 1.5% provided w / h ≥ 0.35 (1 - h / t);
Related links:
- Symmetric Stripline Analysis/Synthesis Calculator - the prototype of this calculator;
- Symmetric Stripline Impedance Calculator - despite the same calculation formulas, for some reason it computes incorrectly;
- Microstrip characteristic impedance calculator;
- Coplanar waveguide impedance calculator;
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