A preliminary study of fields in mode-stirred chambers

It is likely that there will be increased use of mode-stirred chambers for EMC testing. They provide a possible mechanism for overcoming one of the main drawbacks of screened rooms, namely the poor field uniformity. However, their operation is still, largely, poorly understood due to the general complexity that such a system involves. The behaviour of the fields within the room as the mode-stirrer revolves are fundamental to building up this understanding. From a knowledge of field distributions and changes in field distributions, an understanding of the mechanisms of coupling to equipment under test will be made easier. The purpose of the paper is to present a method of developing that initial understanding of the modal behaviour using the transmission-line modelling (TLM) method. Previous work has validated TLM as a useful tool in the development of an understanding of fields in screened rooms and the present work is extended to a discussion of the strengths of TLM for this purpose.