APPARATUS AND METHOD FOR DETERMINING THE SOURCE AND STRENGTH OF ELECTRO-MAGNETIC EMISSIONS

摘要

A method for operating a TEM cell to determine the characteristics of aradiation source in a circuit. The circuit is placed in the TEM cell such thatthe relative orientation of the circuit and the TEM cell is measurable. TheTEM cell provides an output signal indicative of the energy radiated by thecircuit when the circuit is operated in the TEM cell. The output signal of theTEM cell is measured for at least 6 different relative orientations of thecircuit and the TEM cell. The electric and magnetic dipole moments of aradiation source having an orientation and physical dimension associatedtherewith are determined from the measured output signals. The electric andmagnetic dipole moments determined from the measured output values arecompared to moments predicted by each of a plurality of antenna types toprovide an estimate of the orientation of the radiation source relative to thecircuit. In addition, embodiments of the present invention may also measurethe output signal of the TEM cell as a function of frequency for at least oneof the different relative orientations. This information may be used todetermine a physical dimension associated with the radiation source. In oneembodiment of the present invention, the measured output signal is evaluatedas a harmonic series. In another embodiment of the present invention, theoutput signal of the TEM cell at a predetermined frequency is measured as afunction of time to determine the modulation of the output signal.