A tool designed to calculate the skin-depth of different materials to allow RF energy through it.

Inputs

(μΩ cm)
 
 

Output

(μm)

Overview

Skin depth refers to the property of a material to allow RF energy through it. It can be computed if the material's resistivity, relative permeability, and the frequency of the RF signal is known. To use this calculator, just select the material type and the signal frequency. The resistivity and relative permeability of the chosen material will be automatically given. 

Equations 

$$\sigma = \sqrt{\frac{\rho}{\pi f_{o} \mu_{r} \mu_{o}}}$$

Where:

$$\sigma$$ = skin depth

$$\rho$$ = resistivity

$$f_{o}$$ = signal frequency

$$\mu_{r}$$ = relative permeability

$$\mu_{o}$$ = permeability of free space = 4π x 10-7

Applications

Skin depth is the measure of how evident the skin effect is on a conductor. Skin effect is a phenomena wherein the current flows through the surface (i.e. skin) instead of uniformly through the conductor. Skin effect is much more evident in higher frequencies. Thus, skin depth is a function of frequency.

The skin effect and skin depth theories might be better appreciated with a real-world example. Have you ever wondered what would happen if WiFi or Bluetooth signals are allowed to propagate through copper wires instead of through air? WiFi and Bluetooth operate at 2.4 GHz. Using the calculator, the skin depth is 1.331 micrometer. This means the WiFi or Bluetooth signals would hardly exist on the surface of the conductor thus radiating themselves easily through the air. 

Further Reading

Textbook - Introduction to Conductance and Conductors

Textbook - Skin and Proximity Effects of AC Current

Worksheet - Fundamentals of Radio Communication

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