Radio darkroom

Ane ‍ anechoic chamber Generally, for radiation testing, the test site is divided into three types: full anechoic chamber, semi-anechoic chamber, and open field. Radiation tests conducted in these three test sites are generally considered to be consistent with the propagation of electromagnetic waves in free space.

The full anechoic chamber reduces the interference of the external electromagnetic wave signal to the test signal, and the electromagnetic wave absorbing material can reduce the multipath effect caused by the reflection of the wall and the ceiling on the test result, and is suitable for the experiments of emission, sensitivity and immunity. In actual use, if the shielding effectiveness of the shield can reach 80dB~140dB, the interference to the external environment can be neglected, and the free space can be simulated in the full anechoic chamber. Compared to the other two test sites, the full anechoic chamber has minimal floor, ceiling and wall reflections, minimal interference from the outside environment, and is unaffected by outside weather. Its disadvantage is that it is limited by cost and has limited test space.

The semi-anechoic chamber is similar to the full anechoic chamber. It is also a shielded six-sided box with electromagnetic wave absorbing material inside. The difference is that the semi-anechoic chamber uses a conductive floor and does not cover the absorbing material. The semi-anechoic chamber simulates an ideal open field situation where the field has an infinitely large conductive ground plane. In a semi-anechoic chamber, since the ground does not cover the absorbing material, a reflection path will be generated such that the signal received by the receiving antenna will be the sum of the direct path and the reflected path signal.