IEC 61000-4-20 relates to 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-, two-, or multi-port TEM waveguides. The frequency range depends on the specific testing requirements and the specific TEM waveguide type. The object of this standard is to describe: - TEM waveguide characteristics, including typical frequency ranges and EUT-size limitations; - TEM waveguide validation methods for EMC tests; - the EUT (i.e. EUT cabinet and cabling) definition; - test set-ups, procedures, and requirements for radiated emission testing in TEM waveguides and - test set-ups, procedures, and requirements for radiated immunity testing in TEM waveguides. IEC 61000-4-20:2010 does not intend to specify the tests to be applied to any particular apparatus or system(s). The main intention of this standard is to provide a general basic reference for all interested product committees of the IEC. For radiated emissions testing, product committees should select emission limits and test 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 standard describes test methods that are separate from those of IEC 61000-4-3. This second edition cancels and replaces the first edition published in 2003 and its amendment 1 (2006), and constitutes a technical revision. It has the status of a basic EMC publication in accordance with IEC Guide 107. The main changes with respect to the first edition of this standard and its amendment are the following: - consistency of terms (e.g. test, measurement, etc.) has been improved; - clauses covering test considerations, evaluations and the test report have been added; - references to large TEM waveguides have been eliminated; - a new informative annex has been added to deal with calibration of E-field probes.