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