IEC 61000-4-20

The EN/IEC 61000-4-20 standard describes how Immunity and Emission measurements are performed in a transverse electromagnetic (TEM) waveguides.

The exact title of this standard is: "IEC 61000-4-20: Electromagnetic compatibility (EMC) - Part 4-20: Testing and measurement techniques - Emission and immunity testing in transverse electromagnetic (TEM) waveguides"

This review is based on the Edition 2.0 2010-08 version.

Some random remarks and notes:

• It is advised to not use EUT that are larger than 1/3 of the height of the usable height of the TEM.
• For the Immunity testing, the standard describes that the Uniform Field Area in the TEM should be verified, using the procedures similar to as described in the EN 61000-4-3.

Emission

The TEM cell is a different and cost efficient method, compared to the OATS, to measure the emission patron of the EUT. This method does have a down side, calculation is needed to correlate the measurements done in the TEM cell to the OATS

For the emission tests there are 2 ways to calculate a correlation to the OATS:

1. multi pole model
2. three voltage measurements

Multi pole model

The multi pole model is currently not supported by RadiMation^®

Voltage measurements: 3-Positions

Also known as the "To Radiated Power method". In this method the EUT is placed in 3 axis (x, y and z).

$S={\sqrt {V_{x}^{2}+V_{y}^{2}+V_{z}^{2}}}$

$V_{x}$, $V_{y}$ and $V_{z}$ are the measurements done in Volt on the same frequency but in different directions.

$S$ is the Root-sum-square of the measured voltages.

$E_{max}=G_{max}*{\sqrt {{\frac {3\eta _{0}}{4\pi }}P_{0}}}$

$E_{max}$ is the maximum field in V/m

$\eta _{0}={\sqrt {\frac {\mu _{0}}{\epsilon _{0}}}}=120\pi \Omega =377\Omega$

$G_{max}$ is the geometry factor determined by the height scan of the receiving antenna.

Related standards

• EN 61000-4-3

Links

• IEC 61000-4-20

Institute of Electrical and Electronics Engineers

ElectroMagnetic Compatibility

The ability of an EUT to be immune to incoming electromagnetic interference. This is equivalent to the term susceptibility that is used by some standards.

Equipment Under Test

Open Area Test Site