An unbiased data sheet
A fully compliant CISPR16 3m (3m or 3metre is the distance between the test equipment and the antenna) chamber has to perform three disciplines:
The Normalised Site Attenuation (NSA) is in relation to the EMC test chambers ability to accurately measure the emissions of an EUT (equipment under test) sometimes called a DUT (device under test) for radiated emissions at 30-1000MHz.
The NSA is carried out with a reflective floor (or ground plane) because the test is to compare (correlate) to an Open Area Test Site (OATS).
The accuracy of a compliant chamber has to be within +/-4dB
Site Voltage Standing Wave Ratio, This test is for frequencies above 1GHz and is often 1-18GHz.
The chamber is tested as a fully anechoic chamber so there are pyramidal absorbers on the floor.
The test is to detect reflections from any surface of the chamber and the transmitting antenna is almost Omni-directional so nearly the chamber’s entire inner surface is illuminated (subjected to the antennas emissions). Directional transmit antennas are not allowed.
This is a stabilised field test using a 16 point grid matrix normally 1.5m x 1.5m set at 0.8m above the floor.
Over the required frequency range the points of the matrix are compared with each other and the allowable difference is 6dB at any frequency with the option of 4 from 16 being discarded at any frequency.
The anechoic lining is normally:
100% coverage of walls and ceiling with high quality ferrite tile.
About 50% coverage of specifically designed Hybrid pyramidal absorber, this absorber system may use different pyramidal lengths and may use more than one performance type.
The floor will have high frequency pyramidal absorbers for the SVSWR.
The floor will have an area of ferrite tiles + hybrid absorbers for field uniformity measurements.
