Radiation characteristics of transient electromagnetic field due to low voltage ESD in spherical electrode

Radiation characteristics of transient electromagnetic field caused by ESDs (electrostatic discharges) in spherical electrode were examined by experimental study. The experimental system consists of a pair of spherical electrode, a 1-18 GHz bandwidth horn antenna and a 20 GHz bandwidth digitizing oscilloscope. Diameter of the electrodes is 19.0 mm, 25.4 mm, 30.0 mm, 50.0 mm, and 100.0 mm. Discharge voltage is less than 700 V in this experiment. Transient EM waveforms caused by ESDs were measured in order to clarify an EM radiation mechanism and characteristics. As a result, transition duration of the received voltage was found to be related to some extent to the size of the electrode. From this, one of the excitation factors due to EM radiation from the electrode elements are mentioned the current path length of the electrodes. Furthermore, polarization characteristics affected by the size of the electrodes. From this fact, as the excitation element of electromagnetic radiation, current path direction on the electrode is also important has been shown. It is possible from these results, the excitation mechanism of electromagnetic radiation is considered as a dipole elements formed by the current path on the electrode and excitation current by the discharge between the electrodes.