A high-efficiency wideband coupler for nanosecond-level pulsed current injection

Pulsed current injection (PCI), as a conducted vulnerability testing technique under nanosecond-level transient electromagnetic disturbance (TED), has gained great attention recently. Many kinds of TEDs, e.g., high-altitude electromagnetic pulse, very fast transient overvoltage, and electrical fast transients, have very fast rise time as well as pretty slow decay, whose frequency spectrum may cover a very wideband. Therefore, one of the challenges is that the existing inductive couplers cannot interact with the equipment under test (EUT) over the wideband efficiently, and consequently, they are inadequate to inject the proper disturbance at ports of EUT in PCI tests. To address this problem, a high-efficiency wideband PCI coupler is proposed in this paper. The coupling performance is analyzed theoretically based on the distributed-parameter model of an inductive coupler. By using the composited ferrites instead of the simplex Ni-Zn ferrites, the inductive coupling is enhanced. The capacitive coupling is also enhanced to improve the high-frequency performance by exploiting the distributed tubular winding. A PCI coupler with the dimension of 30 × 10 × 10 cm³ is built to be validated experimentally. The 3 dB bandwidth has been improved from 421 kHz-14 MHz to 77 kHz-39 MHz, which indicates that the coupler can be applied efficiently over the frequency range of interest for PCI tests.