SUMMARYIn order to study the cause of unwanted electromagnetic emissions under the actual operating conditions of electronic and industrial devices, it is necessary to measure the spatial distribution of the unwanted electromagnetic waves outside the devices and to identify the positions of the sources of unwanted electromagnetic waves inside the devices. The authors attempted to estimate the sources of the electromagnetic near-fields of the devices at low frequencies (less than several tens of megahertz) by placing several electromagnetic field sensors around the devices to observe the spatial distributions of the unwanted emissions. In this paper, the MUSIC method is applied to the observed vector component waveforms of the magnetic fields radiated from low-frequency current loops (magnetic dipole sources) to estimate the three-dimensional location and orientation of the sources. The effectiveness of the method and its error are evaluated by numerical simulations and experiments.