A study on the characteristics of semi-anechoic chambers below 30 MHz

Several methods for evaluating test sites for EMI measurements above 30 MHz have been regulated by the CISPR, ANSI etc. Nowadays the demand for EMI measurements below 30 MHz is increasing; however, the methods to evaluate the test sites for such EMI measurements in the low frequency have not yet been regulated. In general, a loop antenna is used for measuring magnetic fields below 30 MHz, whereas a monopole antenna is used for measuring electric fields in the frequency band. Recently, we measured the characteristics of several semi-anechoic chambers (SACs) using monopole antennas and loop antennas. In this paper, we discuss and report a study on the characteristics of two types of SACs through measurement and simulation.