Shigeki Minegishi

Measurement of very fast voltage rise curve due to gap discharge using coupled transmission lines in distributed constant system

A measurement method of very-fast-voltage rise curves due to gap discharge using the coupled transmission lines was examined to discuss a electromagnetic noise source from a viewpoint of electromagnetic compatibility (EMC). The measurement system consists of a distributed constant line system, because the voltage transients were very rapid. A characteristic of the gap electrode, which has a matched impedance for the distributed constant line system, was investigated in the frequency range below 5 GHz. The voltages of power source in experiment were 510 V and 800 V because the Paschens law holds stability in air condition. As a consequence of the experiment with this measurement system, the measurement method made it possible to observe the very fast rise curves of about 100 ps.

Frequency spectra of the arc current due to opening electric contracts in air

Frequency spectra of the electromagnetic noise due to arc current caused by Ag contacts upon opening in air at atmospheric pressure are described. To take into consideration the fast transients and high-frequency discharge phenomena at the contacts, a distributed constant model consisting of relay contacts and a coaxial distributed constant line is introduced. An experiment carried out under conditions of low circuit current (3.84 A) and low source voltage (48 V) is reported. The results indicate that the frequency spectra of the arc currents depends on the length and terminal conditions of the line connected to the contacts. >

12GHz measurement of transition duration and breakdown field due to low voltage ESD

Transition duration of voltage and current rise time due to small gap discharge as the low voltage ESD was investigated in time domain. The measurement system was improved on the band width from 6GHz to 12GHz using the coaxial electrode system. Also, the sensing system was changed from the coupled transmission lines to an E-field sensor and a Hfield sensor. The insertion loss of the experimental system was within about -3dB in frequency range below 12GHz. As a consequence of the experiment using the system, voltage and current rise time of transition duration were shown 32 ps or less. The rise times were changed in configuration of electrodes, source polarity and discharging voltage. Besides, breakdown field was examined to corroborate the very fast transition durations of about 32ps. The breakdown field was very high of about 8×107 V/m in low voltage discharging of below 350V.

A measurement of very fast transition durations due to gap discharge in air using distributed constant line system

Very fast transition durations (rising time in positive polarity and falling time in negative polarity) due to starting of gap discharge were investigated in time domain. The gap space was set very small for voltages below 1500 V as a simulation of the charged device model (CDM) electrostatic discharge (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 time domain. As a consequence of the experiment, the relationship between the discharge voltage and transition duration was 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.

A method for measuring transients caused by interrupting current using a transmission line terminated in its characteristics impedance

A measurement method of transients caused by interrupting a current is described. In consideration of the fast transients and high-frequency discharge phenomena due to interrupting the current, a transmission-line system was introduced. It consists of a coaxial switch, coaxial cables as transmission lines on the right and left sides of the switch, and termination resistors. When the current is interrupted by the switch, the waveform across the termination resistor is measured by an oscilloscope. The impedance-matching technique for the cables was employed to minimize the effects of reflected waves. That is, the resistors were designed to match the characteristic impedance of the cables. The characteristics of the system were measured by a network analyzer. The VSWR of the system was within 1.33 in the frequency range below 500 MHz. The time-domain measurement using a transmission-line system terminated in its characteristic impedance clears up the process of the complicated transients caused by interrupting current. >

Measurements of characteristics of electromagnetic radiation caused by electrostatic discharges in metal sphere gap at voltages less than 1 kV

In this study, the characteristics of Electromagnetic (EM) radiation caused by Electrostatic Discharges (ESDs) from metal spheres charged to voltages less than 1 kV are examined experimentally. Our experimental system consists of a pair of spherical electrodes of different diameters, a 1-18 GHz-band-width horn antenna and a 20-GHz-bandwidth digitizing oscilloscope. Polarization, waveform duration and peaks of antenna-received voltages from the EM field radiation are measured in order to clarify the EM radiation mechanism. The ratio of the received voltages between the antenna arrangements of the field polarization parallel and perpendicular to the spark pass is 18 to 20 dB. The polarities of the antenna-received voltages are the same as those of the charge voltages across the gap. Moreover, the waveform duration and the first peaks increase with an increase in the diameters of the spherical electrodes. Consequently, we find that the polarization, waveform duration and first peaks of the EM field radiation can be explained by a dipole antenna structure, which makes the spark part of the spherical electrodes a feeding point on the straight line passing through the centres of the two spheres.

Information leakage from cryptographic hardware via common-mode current

Recently, it has been known that electromagnetic radiation from electrical device leaks internal information. That is, electromagnetic radiation contains information. Especially, it causes serious problem for cryptographic modules if electromagnetic radiation contains secret information. Therefore many studies have been made on power/electromagnetic analysis attacks, which extract secret keys from cryptographic modules by analyzing waveforms of currents, voltage or electromagnetic field. The attacks assume that the waveforms should contain the information leakage in some way. However, there are few studies discussing about “mechanisms” of the information leakage via electromagnetic field. In this paper, we will give the leakage model caused by common-mode currents, which are one of dominant factors of radiation. If the common-mode currents contain the secret information, it might be possible to obtain the information from far field. In order to verify the leakage model, we implement cryptographic hardware on an FPGA board, and reveal the secret information from common-mode currents measured by using EMC measurement techniques.

Influence of electrode approach speed in variation characteristics of the impulsive ESD noise

Impulsive electromagnetic noise is caused by ESD. Especially, micro gap discharge of less than 1kV produces GHz band width electromagnetic noise. It is thought ESD noise has possibility that affects to various electrical systems. To solve EMC problems, we elucidated a mechanism which ESD noise occurs. We found out the amplitude of electromagnetic noise depended on the size of electrode and applied voltage of the electrode in a previous study. Therefore, we mainly measured the amplitude of electromagnetic noise when we changed the approach speed of electrode by this experiment. Then, the average amplitude and the dispersion of the amplitude tended to increase with the approach speed became fast. On the other hand, the difference between the intermediate value of the amplitude and the average value tended to decrease with the approach speed of electrode became fast. Furthermore, we discovered these changes make logarithmic change by approximating them.

Influence of electrode size for electromagnetic radiation due to micro gap discharge in spherical electrode

Relation between discharge voltage and amplitude of electromagnetic radiation was examined in experimental study. The amplitude of electromagnetic radiation was proportion to the voltage gradient at the gap in the resonance experimental system using the discharge electrode with dipole configuration. In this time, we present an improved experimental system to measure the radiated electromagnetic waves in the frequency range from 1 GHz to 3 GHz using a pear of spherical electrode and a horn antenna. As a result, the amplitude of received voltage is proportion to the discharge voltage (charged voltage of the electrode) from 300V to 620V, and the received voltage is proportion to the diameter of spherical electrodes.

Directivity and polarization of electromagnetic radiation in low voltage ESD using spherical electrode

Directivity of electromagnetic field radiation in low voltage ESD (Electrostatic discharge) using a pair of spherical electrode was examined in experimental study. In addition to that, polarization effect of electromagnetic field radiation in a pair of spherical electrode investigates for clarify the radiation factors due to low voltage discharge below 1 kV. The experimental system consists of a pair of spherical electrodes, a horn antenna and wideband digitizing oscilloscopes. The ratio of directivity between front value and side value is about 18 dB in received voltage. Polarization of received voltage is clearly seen in electromagnetic radiation from a pair of spherical electrode. As a result, the EM field radiation looks like radiation from dipole antenna structure which makes the spark part of spherical electrodes a feeding point on the straight line passing through the tow sphere centers.