Time-domain measurements of transient field coupling through slots

Recent advancements in the field of communications technology include the use of high speed data transmissions with extremely wide frequency bandwidth. This technology is widely employed in ultra-wideband (UWB) communication systems which can produce significant EM emissions at microwave frequencies. A key element in assessing the vulnerability of equipment to UWB signals involves an understanding on the phenomenon of transient electromagnetic energy coupling into cavity-like objects. When the wavelength of microwave sources is comparable to the size of the ports of entry (slots, apertures, seams, cracks, protruding connectors, etc.), the latter is no longer below the cut-off frequency, allowing significant amount of microwave energy to penetrate into internal susceptible electronics. In fact, these coupling paths can be highly resonating at certain microwave frequencies making EM shielding a challenging task. This paper examines the coupling effects of transient UWB signals into a rectangular shielded enclosure with two different slot sizes, through physical measurements using a time-domain technique