The investigation research of the electrostatic discharge ESD was carried out from the viewpoint of EMC in order to clarify the mechanism of the EMI with the ESD by the EMC investigation expert committee. The transient electromagnetic noise by the ESD has the wideband frequency spectra which reach the microwave band. Therefore, the grasp of the frequency spectra of the phenomenon and generation of electromagnetic wave are very difficult. As a result of the investigation, following results were obtained. (1) A knowledge on the ESD was consolidated, and common recognition was confirmed as an EMC problem. (2) The measuring methods of transient current up to 12GHz and transient electromagnetic field up to 3GHz were established. (3) Basic data of polarity characteristics of the impulse electromagnetic wave were obtained.

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The paper concerns calibration of generators for simulation of the Human-Metal Electrostatic Discharge (ESD) according to the IEC 61000-4-2 standard. It is shown that analysis of the ESD pulse in the frequency domain can be an indication if omitting the frequency considerations in calibration of ESD guns is acceptable. The calibration setup consists of a target (current converter), attenuator, coaxial cable and a wideband, single shot oscilloscope. It is much easier to use only a low frequency model of such a measurement path setup than consider a high frequency model. If, however, a high frequency treatment is indispensable, then a frequency dependent transfer impedance of the measurement path and approximation of the oscilloscope frequency response with an infinite impulse response discrete time filter are adequate tools. Comparison of power spectral densities (PSD) of theoretical pulses, measured pulses as well as the measurement path noise gives a good criterion for specifying minimal bandwidth of a setup required for reliable calibration of a given ESD gun. This paper is a resume of previous papers of the authors, in which these issues were presented in details.

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The micro-gap discharge as the low voltage ESD shows very fast transition-duration of about 32 ps or less. Furthermore, the breakdown field strength in the gap was very high of about 80 MV/m in low voltage discharging of below 400V. The relationship between the breakdown field strength in the gap and the amplitude of radiated electromagnetic field was examined in experimental study. The amplitude of radiated electromagnetic field was proportion to the breakdown field strength 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 amplitude of radiated electromagnetic filed in more wideband region using spherical electrodes and a horn antenna. As a result, the amplitude of radiated electromagnetic field is proportion to the discharge voltage from 300V to 620V, and the amplitude of radiated electromagnetic field was according to the diameter of spherical electrode in 1-3GHz frequency bandwidth.

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In the present study, using a 50Ω tapered coaxial type adapter and a S-parameter technique, we measured the transfer impedance of a commercially available IEC calibration current target used for the immunity testing against electrostatic discharges (ESDs), which is being prescribed in the International Electrotechnical Commission (IEC) 61000-4-2, and thereby reconstructed the waveforms of discharge currents injected onto the target from their observed output voltages for contact and air discharges of an ESD generator. As a result, we found that the transfer impedance is almost 1+j0Ω at frequencies below 1GHz, while due to resonance phenomena occurring at frequencies around 2GHz and 5GHz, resistive and reactive components significantly change at frequencies over 1GHz, though their absolute values are slightly larger than 1Ω. This result has revealed that the reconstructed discharge currents agree well with the observed voltages with a rise time of almost 1ns for the contact discharges and air discharges with slow approach of an ESD gun with charge voltages above 2kV, while in the case for the observed voltage with a rapid rise time shorter than a hundred pico-seconds for the air discharges with fast approach, the reconstructed discharge current has a bit gentle rising slope and a slightly lower level of the first current peak.

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In this study, we measured the time variation of burst electric fields leaked from a heating device in the ion cyclotron range of high-frequency in an experimental fusion facility, and analyzed their statistical characteristics such as the amplitude probability distribution (APD) and crossing rate distribution (CRD). As a result, we found that the variation of the leaked electric field level is very irregular, far from the normal distribution. Moreover, the leaked electric field variation with time may reach 400 times in one second to cross its mode value. Although so, the maximum electric field intensity itself is much smaller than the ICNIRP safety guideline. In addition, we also evaluated the possibility of electromagnetic interference to an implanted cardiac pacemaker in the measured electromagnetic environment. We found that even in the worst case the interference voltage induced in the output of the pacemaker sensing circuit does still not exceed the threshold for a malfunction.

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To investigate the effects of built-in inductors on current rising waveform for contact discharges of electrostatic discharge generators (ESD guns), we simultaneously measured discharge currents and the resultant magnetic near-fields, and compared their results with those for an ESD gun with a metal cylinder in lieu of the inductor. As a result, we found that the magnetic near-field waveform is deformed by the distortion of the current rising waveform for an ESD gun with an inductor, while the ESD gun with a metal cylinder produces no distortion for the current rising waveform despite its rise time (400 ps) shorter than the International Electrotechnical Commission (IEC) specification so that there is no distortion for the corresponding magnetic near-field waveform. Using the Heidler's formula for typical discharge current waveform specified in the IEC, we calculated current rising waveform and the resultant induced output voltage of a magnetic probe, which shows that these results do not agree with those for the built-in inductor, while there is good agreement for the metal cylinder. This finding implies that immunity test results can be affected by the frequency characteristics of a built-in inductor inside an ESD gun, and thus that not only rise time but also current rising waveform of discharge currents should be specified for ESD immunity testing.

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The measuring method of impulse electromagnetic field by Half TEM Horn elctoromagnetic fieid generator (EM generator) and Half TEM Horn electoromagnetic field detector (EM detector) was proposed. The impulse electromagnetic field is generated between the ground plane and element of EM generator and is detected by EM detector inserted in EM generator. As a result of the TDR experiment of EM generator and EM detector, the characteristic impedance from the input to the aperture was fixed 50Ω. As a result of the experiment of impulse (Amplitude 160mV, Pulse width 63ps) response, the received electric power was proportional to the cross section of the aperture of the EM detector and the received pulse width was almost invariable to the cross section of the aperture of the EM detector. This method enables the measurement which decreases the amplitude without changing the pulse width of strong impulse electromagnetic field due to the discharge such as ESD.

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When a connector is tightened with insufficient torque, electromagnetic field radiation from interconnected devices is increased. To elucidate the mechanisms of electromagnetic field radiation due a loose contact in a connector, we investigate the high-frequency electrical elements in contact boundary of a loose connector. On the basis of this result, we show the relationship between the high-frequency electrical elements and the electromagnetic field radiation from interconnected electric devices.

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We have developed an electromagnetic field intensity distribution measurement system. It is expected that this system is very useful for the evaluation of the electromagnetic noise emitted from electric devices. In this paper, we describe measurement results of the electric field generated by electric discharge in air and near field pattern of the micro strip line.

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In this study, we considered the influences of approaching speed of the grounded electrode on characteristic of ESD from charged metal. The approaching speed ranges from 0.04mm/s to 4mm/s. The radius of curvature of the semispherical copper electrode is 10mm. From experimental results, we found that the approaching speed affected the distribution of the gap length of discharge inception. This change of the gap length led to change the shape of the discharge current waveform, the 1^st peak current and their rising speed.

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We measured the electric potential of a vertical coupling plane (VCP) for contact discharges of an ESD gun, and found that multiple discharges occur during 0-500 μs despite a 200-ns short time interval, whose mechanism can qualitatively be explained from a simple discharge circuit.

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EM wave transmission characteristics of the laminated structure consisting of metal wire grid-dielectric-metal wire grid are investigated. The transmission characteristics can be controlled by the wire grid parameters such as grid spacing.

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