1. What is Coaxial Cable Impedance?

The characteristic impedance of a coaxial cable is a key parameter that determines how electrical signals propagate through the cable. It's determined by the physical dimensions of the cable and the dielectric material between the conductors.

2. How Does the Calculator Work?

The calculator uses the coaxial impedance formula:

Where:

• \( Z \) — Characteristic impedance (ohms)
• \( D \) — Inner diameter of outer conductor (mm)
• \( d \) — Outer diameter of inner conductor (mm)
• \( \epsilon_r \) — Relative permittivity of dielectric (dimensionless)

Explanation: The impedance depends on the ratio of the conductor diameters and the dielectric material's properties. Common values are 50Ω (RF systems) and 75Ω (video systems).

3. Importance of Impedance Calculation

Details: Proper impedance matching is crucial for minimizing signal reflections and maximizing power transfer in RF and high-frequency applications.

4. Using the Calculator

Tips: Enter diameters in millimeters (must have D > d), and relative permittivity (≥1). Typical ε_r values: ~2.3 for polyethylene, ~2.1 for PTFE.

5. Frequently Asked Questions (FAQ)

Q1: What are common coaxial impedance values?
A: 50Ω is standard for RF systems, 75Ω for video/CATV, and 93Ω for some computer networks.

Q2: Why does impedance matter?
A: Mismatched impedance causes signal reflections, leading to power loss and signal distortion.

Q3: How does dielectric affect impedance?
A: Higher permittivity lowers impedance for the same conductor dimensions.

Q4: What's the relationship between D/d ratio and impedance?
A: Higher D/d ratio gives higher impedance (logarithmic relationship).

Q5: Can I use this for other transmission lines?
A: This formula is specific to coaxial cables. Other geometries (twin-lead, microstrip) have different formulas.