EMC Anechoic Chamber

EMC testing requires a controlled electromagnetic environment where radiated emissions and immunity test results are reproducible and traceable to international standards. An EMC anechoic chamber provides both RF shielding (to exclude ambient electromagnetic interference) and RF absorption (to simulate a free-space measurement environment free from reflections).

HEMU Acoustics EMC chambers are designed and constructed to comply with the critical NSA requirement of CISPR 16-1-4: the Normalised Site Attenuation (NSA) must be within ±4 dB of the theoretical free-space value at all test frequencies and antenna positions. Achieving this requires careful design of the RF absorber layout, ground plane dimensions, and shielded room geometry.

The shielded enclosure uses modular welded steel panels with conductive gaskets at all joints. Shielding effectiveness (SE) is measured to IEEE 299 at handover — typically > 100 dB at 30 MHz–18 GHz, with many facilities achieving 120 dB. RF-shielded ventilation filters, power line filters, and fibre optic penetrations maintain SE at all utilities.

Wall, ceiling, and end-wall surfaces are lined with RF absorber in a hybrid pyramidal/ferrite tile arrangement. Ferrite tiles (40 × 40 cm) on walls and ceiling provide absorption from 30 MHz to 1 GHz; pyramidal RAM (radio-absorbing material) cones extend absorption to 18 GHz and above. The reflective ground plane (polished aluminium or copper sheet) is integral to the test geometry and not lined with absorber.

Standard chamber configurations support 3 m test distance (CISPR 11, CISPR 32, ANSI C63.4) and 10 m test distance (CISPR 11 Class B, FCC Part 15). Custom configurations for 5 m, 7 m, and automotive EMC testing (CISPR 25, ISO 11452) are available.