IEC 61000-4-20:2022 focuses on emission and immunity test methods for electrical and electronic equipment using various types of transverse electromagnetic (TEM) waveguides. These types include open structures (for example striplines and electromagnetic pulse simulators) and closed structures (for example TEM cells). These structures can be further classified as one-port, two-port, or multi-port TEM waveguides. The frequency range depends on the specific testing requirements and the specific TEM waveguide type. The object of this document is to describe TEM waveguide characteristics, including typical frequency ranges and equipment-under-test (EUT) size limitations;
TEM waveguide validation methods for electromagnetic compatibility (EMC) tests;
the EUT (i.e. EUT cabinet and cabling) definition;
test set-ups, procedures, and requirements for radiated emission measurements in TEM waveguides; and
test set-ups, procedures, and requirements for radiated immunity testing in TEM waveguides.

NOTE Test methods are defined in this document to measure the effects of electromagnetic radiation on equipment and the electromagnetic emissions from the equipment concerned. The simulation and measurement of electromagnetic radiation is not adequately exact for the quantitative determination of effects for all end-use installations. The test methods defined are structured for a primary objective of establishing adequate reproducibility of results at various test facilities for qualitative analysis of effects.
This document does not intend to specify the tests to be applied to any particular apparatus or system(s). The main intention of this document is to provide a general basic reference for all interested product committees of the IEC. For radiated emission measurements, product committees select emission limits and measurement methods in consultation with CISPR standards. For radiated immunity testing, product committees remain responsible for the appropriate choice of immunity tests and immunity test limits to be applied to equipment within their scope. This document describes test methods that are separate from those of IEC 61000‑4‑3.
This third edition cancels and replaces the second edition published in 2010. This edition constitutes a technical revision. This edition includes the following significant technical changes with respect to the previous edition:

provide information on the testing of large EUTs (including cables);
apply the work on measurement uncertainties by adapting the work completed in CISPR and TC 77 (for emissions and immunity);
update the validation procedure for the test volume regarding field uniformity and TEM mode verification;
provide information concerning two-port and four-port TEM waveguides;
add a new informative annex (Annex I) dealing with transient TEM waveguide characterization; and
add information dealing with dielectric test stands for EUTs.