Measurement of rising part due to starting of micro gap discharge in air using distributed constant line system

Very fast voltage rising time in positive polarity and falling time in negative polarity due to starting of the gap discharge were investigated in the time domain. The gap space was set very small for voltages below 1500 V as a simulation of the CDM ESD and the gap discharge of switch devices. The measurement system consists of a distributed constant line system with a tapered coaxial electrode which has a matched impedance for the characteristic impedance of the distributed constant line system. The insertion loss of the tapered coaxial electrode was within -3 dB in the frequency range below 4.5 GHz The atmosphere around the electrode is ordinary air. This experimental system enables one to measure the high speed transients of about 100 ps due to gap discharge in the time domain. As a consequence of the experiment, the relationship between the discharge voltage and transition duration were confirmed. The voltage rise time was slowed down gradually in positive polarity, while the voltage fall time was slowed down remarkably in negative polarity for the 0.1 mm needle.