A microwave anechoic chamber, also called an echo free chamber, a wave absorbing chamber and an anechoic chamber. When electromagnetic waves enter the wall, ceiling and ground, most of the electromagnetic waves are absorbed, while transmission and reflection are few. Microwave also has some characteristics of light, so it is called the microwave darkroom with the help of the meaning of optical darkroom. The microwave anechoic chamber is a special room constructed by absorbing materials and metal shields. It provides the artificial "free space" condition. In the darkroom, antenna, radar and other wireless communication products and electronic products testing can avoid wave interference and improve the testing accuracy and efficiency of the tested equipment. With the development of electronic technology, the darkroom is being understood and applied by more people. Microwave anechoic chamber is the use of absorbing materials to create a closed space, which can create a pure electromagnetic environment in the dark room, in order to facilitate the exclusion of external electromagnetic interference.

The microwave anechoic chamber material can be any absorbing material, the main material is the polyurethane foam sponge SA (high frequency use). In addition, when testing the electromagnetic compatibility of the electronic products, the ferrite absorbers will be used because of the low frequency.

The main principle of the microwave anechoic chamber is to use the high permeability absorbing material to guide the electromagnetic wave according to the law of the electromagnetic wave propagating in the medium from the low magnetic direction to the high magnetic direction, and to absorb the radiant energy of the electromagnetic wave through the resonance, and then transform the energy of the electromagnetic wave into heat energy by coupling.

The microwave anechoic chamber is mainly used for radiation radio harassment (EMI) and radiation sensitivity (EMS) measurement. The size of the microwave dark room and the selection of radio frequency absorbing materials are mainly based on the size and test of the tested equipment (EUT).