IEC 61726:2015

Overview

IEC 61726:2015 specifies the reverberation chamber (mode‑stirred chamber) method for measuring screening attenuation of cable assemblies, cables, connectors and passive microwave components. The standard defines how to expose a device under test (DUT) to an almost homogeneous, isotropic electromagnetic field inside a high‑Q shielded cavity and how to quantify the power coupled into the DUT. IEC 61726:2015 is the third edition (replacing the 1999 edition) and updates procedures in line with modern reverberation chamber design and faster measurement options.

Key topics and technical requirements

• Measurement principle: Screening attenuation is determined by comparing power induced into the DUT with the reference field in the chamber (direct power ratio or using the chamber insertion loss).
• Reverberation chamber design: Chamber must comply with IEC 61000‑4‑21 requirements; avoid perfect cubic shape; use conductive, non‑lossy materials.
• Mode stirrer: Large relative to wavelength; minimum size guidance-at least two wavelengths tip‑to‑tip at the lowest test frequency.
• Antennas: Input and reference antennas with limited resonances and minimal loss; return loss better than 6 dB recommended. Isotropic field conditions reduce directionality effects.
• Calibration and controls: Verify insertion loss of cavity, dynamic range, VSWR, and use of calibrators. The standard includes both a standard measurement and a fast measurement procedure to reduce test time.
• Frequency applicability: No theoretical upper frequency limit; practical lower frequency limit is set by chamber size (sufficient modes-e.g., ≥100 modes at lowest test frequency).
• Evaluation: Includes relation between transfer impedance/transfer functions and screening attenuation for electrically short or distributed leakage scenarios.

Applications and who uses it

• Manufacturers and test labs performing screening attenuation and EMC characterization of:
  • Waveguides, phase shifters, diplexers/multiplexers
  • Power dividers/combiners, passive microwave components
  • Cable assemblies, coaxial cables and RF connectors
• EMC engineers and compliance laboratories using reverberation chamber testing to validate shielding performance across wide microwave frequency ranges.
• R&D teams evaluating enclosure, connector and cable leakage where traditional low‑frequency methods are inadequate.

Related standards

• IEC 61000‑4‑21 - Reverberation chamber test methods (design and calibration guidance)
• IEC 61196‑1 - Coaxial communication cables (definitions and requirements)
• IEC TS 62153‑4‑1 - Introduction to electromagnetic screening measurements

Keywords: IEC 61726:2015, reverberation chamber, screening attenuation, mode‑stirred chamber, microwave components, cable assemblies, EMC testing, insertion loss, shielding measurement.