A double differential-mode current injection method based on directional couplers for HIRF verification testing of interconnected systems

In this paper, a double differential-mode current injection (DDMCI) method is proposed to achieve the equivalence with high-level field radiation, when interconnected systems are under test. With two differential-mode current injection devices involved, the equivalence of the terminal responses induced by radiation and injection at both ends can be assured. The equivalent relationships between the field strength and the two injected voltages are confirmed to be linear, even if the characteristics of the equipment under test (EUT) are both nonlinear. DDMCI can substitute for high level illumination equivalently, by the linear extrapolation of the injected voltages. The feasibility of DDMCI is verified by experiment, when the EUT responses are nonlinear and the terminal impedances change with the field strength. The method accuracy is high for frequencies up to gigahertz.