In this article, we propose and implement a novel technique to locate electromagnetic interference (EMI) sources using the concept of time-reversal (TR) cavity. We show in an intuitive manner that reflections from the surfaces of a cavity can emulate an infinite number of sensors in the TR method. In order to locate EMI sources, the equipment under test (EUT) is placed in a rectangular metallic cavity, of suitable dimensions according to the considered frequency band and the EUT size, equipped with a simple monopole or dipole antenna. We demonstrate that by using only one sensor, we are able to locate EMI sources by taking advantage of the focusing properties of a TR cavity. The entropy criterion is applied to obtain the focusing time slice in which the maximum electric field determines the location of the EMI source. Both 2- and 3-D numerical simulation schemes are deployed to demonstrate the ability of the proposed technique. The validity of numerical simulations is tested against frequency-domain measurements. Compared with the conventional EMI tests in anechoic chambers and scanning methods, the proposed technique represents a simpler and cost-effective test method requiring only one sensor (a monopole or dipole antenna).
