Parallel Wire Impedance Calculator
This calculator determines the characteristic impedance of a parallel wire transmission line based on conductor diameter, spacing, and dielectric constant. It’s essential for designing balanced RF lines like twin-lead cables, antennas, and low-loss feeders.
Impedance Estimator for Parallel Wire Transmission Lines
Parallel Wire Line Impedance Formula
Where:
- $$Z_0$$ = characteristic impedance (Ω)
- $$D$$ = distance between centers of the wires (m)
- $$d$$ = diameter of each wire (m)
- $$\varepsilon_r$$ = relative permittivity (dielectric constant)
This formula assumes uniform dielectric and parallel cylindrical conductors in free-space or homogenous medium.
Parallel Wire Impedance – Calculation Example
Given:
- $$D$$ = 20 mm = 0.02 m
- $$d$$ = 2 mm = 0.002 m
- $$\varepsilon_r$$ = 1 (air)
Calculation:
- $$Z_0 = \frac{120}{\sqrt{1}} \cdot \ln\left( \frac{2 \cdot 0.02}{0.002} \right) = 120 \cdot \ln(20) ≈ 120 \cdot 2.9957 ≈ 359.48~Ω$$
Parallel wire lines are used in RF communication, amateur radio, and antenna feed systems due to their low loss and ease of construction. This calculator helps designers and hobbyists determine the characteristic impedance of twin-lead or ladder lines. Proper impedance matching ensures maximum power transfer and minimal signal reflection.