Coaxial Line Impedance (Z0) Calculator

Welcome to this engineering tutorial on the Coaxial Line Impedance (Z0) Calculator. Understanding the impedance of a coaxial line is crucial in the design and analysis of RF (Radio Frequency) and telecommunications systems. In this tutorial, we will discuss the topic, share interesting facts, explain the formula used in the calculator, provide a real-life example, and explore the practical applications of coaxial line impedance calculations.

Coaxial Line Impedance (Z0) Calculator
Dimensional units
Outer diameter (do) mm
Inner diameter (di) mm
Relative magnetic permeability (μr) (H.m-1)
Relative dielectric constant (er) (H.m-1)
Coaxial Line Impedance (Z0) Calculator Results
Inductance (L) = nH/cm
Capacitance (C) = pF/cm
Impedance (Z0) = Ohms
Propagation Delay (Tpd) = ps/cm

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Learn about Coaxial Line Impedance (Z0) and how to calculate it using the Coaxial Line Impedance Calculator. Understand the formula, its real-life applications, and the importance of impedance matching in RF and telecommunications systems

1. Coaxial Line Impedance: Ensuring Signal Integrity

Coaxial lines are widely used in various applications to transmit electrical signals with high efficiency and minimal interference. The impedance of a coaxial line, represented by Z0, plays a critical role in ensuring signal integrity and proper power transfer. Impedance matching between the source, transmission line, and load is essential for minimizing signal reflections and maximizing power transfer efficiency.

Interesting fact: Coaxial lines were invented in the early 20th century by English engineer and mathematician Oliver Heaviside. They have since become the standard transmission medium for high-frequency signals due to their superior characteristics.

2. The Formula: Calculating Coaxial Line Impedance (Z0)

The Coaxial Line Impedance Calculator uses a formula based on the physical dimensions of the coaxial line to calculate its characteristic impedance (Z0). The formula for the characteristic impedance of a coaxial line is as follows:

Z0 = 138 × log10(D/d)


  • Z0 is the characteristic impedance of the coaxial line.
  • D is the outer diameter of the outer conductor (shield).
  • d is the inner diameter of the inner conductor.

This formula allows you to calculate the characteristic impedance of a coaxial line based on its physical dimensions. The characteristic impedance determines how the coaxial line interacts with the connected devices and influences the signal transmission properties.

3. Real-Life Example: RF Transmission System

Let's explore a real-life example to understand the practical application of Coaxial Line Impedance calculations. Imagine you are designing an RF transmission system for a wireless communication network. The system requires a coaxial line to carry the RF signal from the transmitter to the antenna.

You have selected a coaxial cable with an outer diameter (D) of 10 mm and an inner diameter (d) of 2 mm. By using the Coaxial Line Impedance Calculator and plugging in these values into the formula, you can calculate the characteristic impedance (Z0) of the coaxial line:

Z0 = 138 × log10(10/2) = 138 × log10(5) = 138 × 0.69897 = 96.25486 Ω

Based on the calculation, the characteristic impedance of the coaxial line in this example is approximately 96.25486 Ω.

In the RF transmission system, this information is crucial for ensuring proper impedance matching between the transmitter, coaxial line, and antenna. By selecting components with compatible impedance values, you can minimize signal reflections, maximize power transfer efficiency, and achieve optimal system performance.

4. Practical Applications: RF and Telecommunications

The Coaxial Line Impedance (Z0) Calculator finds extensive applications in RF engineering and telecommunications. Here are some practical scenarios where knowledge of coaxial line impedance is essential:

  • Antenna Systems: Designing antenna feed lines and ensuring impedance matching for efficient signal transfer.
  • RF Transmitters and Receivers: Selecting appropriate coaxial cables and connectors to maintain impedance continuity in RF transmission and reception systems.
  • Telecommunication Networks: Optimizing impedance matching in communication lines, such as Ethernet cables and fiber optic connectors, for reliable data transmission.
  • High-Frequency Circuits: Ensuring impedance compatibility in high-frequency circuits, such as amplifiers, filters, and signal generators.

By using the Coaxial Line Impedance (Z0) Calculator, engineers and technicians can accurately determine the characteristic impedance of coaxial lines, enabling them to make informed decisions during the design, installation, and maintenance of RF and telecommunications systems.


The Coaxial Line Impedance (Z0) Calculator is a valuable tool for engineers working with RF and telecommunications systems. By understanding the formula and utilizing the calculator, professionals can determine the characteristic impedance of coaxial lines, ensuring proper impedance matching and efficient signal transmission. Impedance control is crucial for minimizing signal reflections, optimizing power transfer, and achieving reliable performance in various applications. Harness the power of the Coaxial Line Impedance (Z0) Calculator to enhance the design and functionality of your RF and telecommunications systems!