Coaxial Cable Impedance Calculator and Formula

The impedance of a coaxial cable is a critical parameter that characterizes its electrical properties. Coaxial cables are commonly used for transmitting electrical signals, including RF (radio frequency) signals.

The impedance of a coaxial cable is determined by its physical dimensions and the properties of the materials used in its construction. The characteristic impedance is essential in coaxial cables because it affects signal transmission.

When the characteristic impedance of the cable matches the impedance of the connected devices or components (e.g., antennas, transmitters, receivers), it ensures optimal power transfer and minimizes signal reflections. This is particularly critical in high-frequency applications like RF and microwave communications.

The Coaxial cable impedance Calculator calculates impedance, per Unit Length Inductance and per Unit Length Capacitance as per formula given below.

Coaxial Cable Impedance Calculator

EXAMPLE:

INPUTS:

• Outer diameter = 36
• Inner diameter = 10
• Relative permittivity = 2.2

OUTPUTS:

• Impedance = 51.8 Ohm
• Inductance (L) = 2.56 X 10^-7 H/m
• Capacitance = 9.55 X 10^-11 F/m

Coaxial Cable Impedance Formula

It’s important to note that the characteristic impedance is a fundamental property of the cable and does not change along its length. Coaxial cables are designed and manufactured with specific characteristic impedance values to meet the requirements of different applications. Common values for characteristic impedance in coaxial cables include 50 ohms and 75 ohms, which are widely used in RF and television applications, respectively.

As shown in the formula, characteristic impedance depends on outer diameter (D) of the inner conductor, inner diameter of the outer conductor, relative permittivity of the dielectric constant. Coaxial cables have a two-layered design with an inner conductor surrounded by an insulating layer, which is further encased in a metallic shield. This shielding provides excellent protection against external electromagnetic interference (EMI) and radio frequency interference (RFI), ensuring signal integrity.

Conclusion

A Coaxial cable impedance calculator serve as indispensable tools for engineers and technicians working in various fields, particularly in RF (radio frequency) and telecommunications. By understanding and applying the cable impedance formula, engineers can design, troubleshoot, and maintain RF systems with precision, ultimately leading to improved signal quality and the successful operation of wireless communication, broadcasting, and data transmission networks.