Reduction of EM wave reflections in a shielded room

New component level radiated emissions tests are currently being developed by the International Special Committee on Radio Interference (CISPR). These tests are likely to form the radiated emissions part of component test specifications to be introduced for the EEC Directive in EMC. It is shown that it is possible to perform these tests adequately in a shielded room with certain minor modifications. Test results show that, over a limited frequency range, such as the AM or FM broadcast bands, it is possible to reduce room reflections to 15 dB, with the possibility of further reductions to 10 dB in the future. Sweep oscillator techniques are used to examine the room characteristic, and a standard noise source generator can also be used to obtain comparisons between different chambers.<>