静電気試験機の校正用電流検出変換器に対する伝達インピーダンスのFDTDシミュレーション

Abstract

Transient electromagnetic fields caused by electrostatic discharges (ESDs) are known to cause a serious failure in high-tech information devices. From this perspective, an international standard for ESD testing or IEC 61000-4-2 has been specified, in which a detailed waveform of the discharge current to be injected onto equipment under test (EUT) by an ESD-gun is prescribed, and is also required for contact discharges onto a calibration current target called Pellegrini target, which is specially designed so that the waveform of an injected current and its observed voltage coincides. However, the coincidence relationship should not hold at high frequencies due to parasitic components which the target has. In this study, we constructed an FDTD model of the Pellegrini target, and calculated its transfer impedance by simulating the injected current onto the target and the corresponding output voltage in combination with an FDTD model being previously developed for an ESD-gun. As a result, we found that the target has a transfer impedance of almost 1-j0 Ω at less than a few hundred MHz, though it has resonance phenomena around 2-3 GHz, which was validated by measuring scattering parameters of the target through a transmission line with a network analyzer. Using the FDTD-calculated transfer impedance, we reconstructed injected current waveforms for contact and air discharges of an ESD-gun from their observed voltages to reveal that the injected current waveform is almost identical to the observed voltage waveform for the contact discharge, while the injected currents for the air discharges have smaller peaks and longer rise times than the observed voltages do due to the presence of resonance properties of the transfer impedance.