SE CALCULATION OF SHIELDING EFFECTIVENESS

Calculating Total Shielding Effectiveness SE

SE Calculation

Electromagnetic waves are attenuated as they pass through a shield because of energy losses. These are divided into reflection loss and absorption loss.

Reflection loss: when an electromagnetic wave reaches an interface between different media, some energy is reflected, reducing transmission through the interface. This loss is represented by R.

A wave passing through a shielding layer crosses two interfaces and undergoes reflection at both. The reflection loss therefore combines the losses at the two interfaces.

Total shielding effectiveness SE is determined by:
SE = R + A + B (dB), where
R is attenuation from a single surface reflection(The formula for R depends on the wave impedance under the relevant conditions.)

Far-Field Plane-Wave Impedance

Far-Field Plane-Wave Reflection Attenuation

Near-Field Electric Wave Impedance

Near-Field Electric Reflection Attenuation

Near-Field Magnetic Wave Impedance

Near-Field Magnetic Reflection Attenuation

Reflection loss depends on wave impedance; higher wave impedance gives greater reflection loss.

A is absorption attenuation

Absorption Attenuation

B is the internal multiple-reflection correction(When A >10 dB, B can be neglected.)

Multiple-Reflection Attenuation

Changing Material Thickness

As t increases, R is unchanged, A increases, and B decreases

As t decreases, R is unchanged, A decreases, and B increases

Changing Frequency

As f increases, R decreases, A increases, and B increases

As f decreases, R increases, A decreases, and B decreases

Changing Magnetic Permeability

As μr increases, R decreases, A increases, and B increases

As μr decreases, R increases, A decreases, and B decreases

Changing Electrical Conductivity

As σr increases, R increases, A increases, and B increases

As σr decreases, R decreases, A decreases, and B decreases