Generation of Standard Fields in Shielded Enclosures

In this paper a method for calibrating loop antennas in a shielded enclosure is analyzed. The scheme considered involves the generation of a known field in the vicinity of the loop by an energized wire mounted near the ceiling of the enclosure. The published formulas for computing the field are based upon simplifying approximations which result in large inaccuracies in many cases. To extend the usefulness of the method new formulas are developed with which the field can be predicted with better than 1 per cent accuracy in the low and medium frequency ranges for most installations. The results can be applied over most of the high frequency region with a possible reduction of accuracy. A method is presented for estimating the error in this region. Finally, the passible limitation of the method at very low frequencies is discussed.