A controlled electrically small antenna for the evaluation of radiated emission testing

The use of screened rooms for spurious radiated emission measurements has been common practice for many years. At low frequencies the rooms cannot be made anechoic due to the depth of radio absorbent material (RAM) required, and the measurements are affected by cavity and other resonances associated with the propagation mechanisms operating in the room. Measurement uncertainties of ±30 dB or more have been observed. The authors are involved in a study of the feasibility of reducing these measurement errors to an acceptable level. In order to carry out the study, an electromagnetically representative device-under-test (DUT) has been developed. The authors describe the design philosophy of the DUT. They also present some preliminary results of experiments carried out to investigate the effects the position of the DUT inside the screened room has on its operation with reference to its operation on an open field test site