A directional-coupler-based injection device aimed at radiated susceptibility verification of antenna systems against HIRF

In this paper, a current injection method is proposed to substitute equivalently for high-level field strength radiation, when the antenna and the cable are the main coupling path. This is done by adopting differential-mode current injection, which is achieved by employing a coupling device composed of cascaded directional couplers. When the device is connected to the antenna system, the equivalent relationship between the radiated field strength and the injected voltage is analyzed. It is verified that this relationship is linear even if the EUT response is nonlinear. Therefore, linear extrapolation is employed to obtain the injected voltage which is equivalent to high-level radiated field strength. With a typical antenna system under test, the experimental results show that the proposed method is highly accurate and is fit for radiated susceptibility verification of antenna systems against high-intensity radiated field in microwave frequency band.