Anechoic chambers

In the early days, the electromagnetic interference test was conducted in an ideal test site—Open Area Test Site (OATS). An OATS is an area characterized by cleared level terrain and the presence of ground plane. To meet the validation requirements, a metallic ground plane is recommended. Such a test site shall be free of buildings, electric lines, fences, trees, etc. and free from underground cables, pipelines etc.. Generally, military requirements for conduction and radiation are 6dB below the limitation, commercial requirements for conducted emissions are 20 dB below the limitation, and radiated emissions are 10dB below the limitation. Different electromagnetic compatibility standards and specifications have different dimensional requirements for OATS. With the rapid development of electrical, electronic equipment and radio communication, it is really difficult to find an OATS that is not affected by electromagnetic environment. In addition, the test conditions of the open area test site might be limited by the weather, intrusion of strong external signals such as radio, or regional radar may shield the EUT from transmitting and cause the receiver overloaded etc.. Currently OATS is used to calibrate antennas than for products testing.
After the 1950s, people began to use shielded rooms instead of OATS for EMC test. The typical structure is welded or bolted steel structure. The shielded room can also be composed of wire mesh or even conductive wallpaper. However, due to the strong emission of the metal wall of the shielded room and the multiple resonance effects of the metal surface, the error is increased, and lacking of the repeatability and accuracy. For this reason, we installed absorbers on the other five inner surfaces of the shielded room except the ground to eliminate the reflection and resonance effects of the electromagnetic wave, which is a current semi anechoic chamber.
Compared with OATS, the semi anechoic chamber is immune to outside weather and ambient noise; in addition, it does not affect the operation of other electronic devices in sensitivity test. Because of this superiority, the semi anechoic chamber has been used as the best substitute for OATS.
To meet the unique requirements for each customer, RFT can provide turnkey solutions for the following EMC anechoic chambers:
3m full anechoic chamber
3m semi anechoic chamber
5m semi anechoic chamber
10m semi anechoic chamber
CISPR-25 semi anechoic chamber
MIL-STD anechoic chamber
Compact full anechoic chamber