Deficiency of anechoic/semi-anechoic chambers

There is a perceived problem with the anechoic chamber facility, i.e., significant deviations from the "standard" open site attenuation performance have been observed at the lower end of the frequency range. The possible mechanisms leading to the observed behaviour are described and the analysis presented confirms the expected performance of such a chamber. The modelling approach, using both free-space electromagnetic radiation theory and a new representation of Dyadic Green's function for screened chamber, is straightforward and computationally efficient. The results indicate that a typical 10-m chamber facility will not perform satisfactory between about 10 MHz and 60 MHz, the exact frequencies being dependant on lining material performance. Based on this analysis, some general remedies are suggested.<>