The use of metal-coated plastics is increasing as shielding materials of electronic and information products due to their lightweight. In this paper, a finite-difference time-domain (FDTD) algorithm, based on the derivation of a time-domain representation of the surface impedance of an equivalent resistive film, was developed to analyze the electromagnetic penetration of pulsed electromagnetic fields through metal-coated plastics. The validity of the proposed algorithm, in both the far-field and near-field cases, was verified by comparing the calculated penetrated electromagnetic fields or shielding effectiveness with theoretical and measured ones. Good agreement between them demonstrated the usefulness of the FDTD algorithm.

This letter describes the potential attenuation mechanism of the charged human body due to walking on the polymer floor. A model is proposed for analyzing the human body potential. The validity is verified by measuring the potentials of the charged acrylic sheet.

Wireless body area networks (BANs) are attracting much attention due to their suitable for healthcare and medical applications. Unfortunately, electrostatic discharge (ESD) is a major electromagnetic (EM) noise source that can degrade wireless communication performance. In this study, we measure EM noise power in the 2.4GHz and 30MHz bands for indirect ESD testing specified in IEC 61000-4-2 standard, and derived a statistical ESD noise model from the measurement results. The ESD noise power was found to follow a lognormal distribution in both 2.4GHz and 30MHz bands. We use this ESD noise model to conduct bit error rate (BER) simulations in a communication channel with additive white Gaussian noise (AWGN) plus ESD noise at 2.4GHz and 30MHz bands. The result is that the BER performance is virtually the same in both bands, and decreases with the signal to noise power ratio (SNR). It is also shown that an error floor exists in the BER performances at both frequencies, which, if the ESD noise power is larger than the Gaussian noise, cannot be improved by increasing the SNR. Although the ESD noise power at 2.4GHz band is nearly 30dB smaller than that at 30MHz band, the signal attenuation along the human body at 2.4GHz band is much larger compared to 30MHz band. This may yield a similar SNR level at 30MHz and 2.4GHz bands in an ESD-dominated environment, so that the 2.4GHz band does not have an obvious merit for BAN applications. Since there are so many in-band interference sources at 2.4GHz band, the 30MHz band seems more promising for vital data transmission in a BAN scenario even in an ESD-dominated environment.

In this study we have employed an effective technique for dosimetric analyses of base station antennas in an underground environment. The technique combines a ray-tracing method and the finite-difference time-domain (FDTD) method to calculate the specific absorption rate (SAR) in the human body. The ray-tracing method was applied to evaluate the incident fields in relation to the exposed subject in a three-dimensional space, while the FDTD method was used to calculate the detailed SAR distributions in the human body. A scenario under an underground passage with the installation of a top-loaded monopole antenna was analyzed to investigate the relationship between the actual antenna exposure and a plane-wave exposure. The results show that the plane-wave exposure overestimated the whole-body average SAR in most cases, although this was not always true for peak SAR. The finding implies not only the usefulness of the present uniform-exposure-based reference level for the whole-body average SAR evaluation but also the necessity of modeling actual underground environment for high-precision local peak SAR evaluation.

For analyzing the transient electromagnetic fields caused by electrostatic discharge (ESD), a new ESD model is presented here. Numerical calculation is also given to explain the distinctive phenomenon being well-recognized in the ESD event.

Air discharge immunity testing for electronic equipment is specified in the standard 61000-4-2 of the International Eelectrotechnical Commission (IEC) under the climatic conditions of temperature (T) from 15 to 35 degrees Celsius and relative humidity (RH) from 30 to 60%. This implies that the air discharge testing is likely to provide significantly different test results due to the wide climatic range. To clarify effects of the above climatic conditions on air discharge testing, we previously measured air discharge currents from an electrostatic discharge (ESD) generator with test voltages from 2kV to 15kV at an approach speed of 80mm/s under 6 combinations of T and RH in the IEC specified range and non-specified climatic range. The result showed that the same absolute humidity (AH), which is determined by T and RH, provides almost the identical waveforms of the discharge currents despite different T and RH, and also that the current peaks at higher test voltages decrease as the AH increases. In this study, we further examine the combined effects of air discharges on test voltages, T, RH and AH with respect to two different approach speeds of 20mm/s and 80mm/s. As a result, the approach speed of 80mm/s is confirmed to provide the same results as the previous ones under the identical climatic conditions, whereas at a test voltage of 15kV under the IEC specified climatic conditions over 30% RH, the 20mm/s approach speed yields current waveforms entirely different from those at 80mm/s despite the same AH, and the peaks are basically unaffected by the AH. Under the IEC non-specified climatic conditions with RH less than 20%, however, the peaks decrease at higher test voltages as the AH increases. These findings obtained imply that under the same AH condition, at 80mm/s the air discharge peak is not almost affected by the RH, while at 20mm/s the lower the RH is, the higher is the peak on air discharge current.

A sub-grid finite-difference time-domain (FDTD) method was applied to analyze electromagnetic (EM) interaction between a 5 GH band antenna mounted laptop personal computer (PC) and a human body model in realistic use situations. The investigated situations were a typing and a non-typing PC users, who were simulated with a realistic whole body or half body model. It was found that the body proximity effect was mainly blocking the radiation up to 20 dB towards the body side, and the hands on the keyboard were mainly blocking the radiation up to 10 dB towards the direction at an angle to the head. It was also found that the highest EM absorption in the typing and non-typing situations occurred in the hand and in the chest, respectively, and the hands on the keyboard had a significantly blocking effect for the SAR spread to the head region. The peak SAR levels were low enough compared to the safety guidelines.

We conduct, in accordance with IEC 61000-4-2, an electrostatic discharge (ESD) test for a small size battery-operated control circuit board in a myoelectric artificial hand system to investigate the influence of the induced noises by indirect ESDs from an ESD generator to a horizontal coupling plane (HCP) and a vertical coupling plane (VCP). A photo-coupler is set between the small size control board and a motor control circuit to suppress noise in the pulse width modulation (PWM) signals. Two types of ESD noise are observed at the output pins of PWM signals. One type is the ESD noise itself (called Type A) and the other one is the ESD noise superimposed over the PWM pulses (Type B). No matter which polarity the charge voltages of the ESD generator have, both types can be observed and the Type A is dominant in the output pulses. Moreover, the ESD interference in the HCP case is found to be stronger than that in the VCP case usually. In the PWM signals observed at the photo-coupler output, on the other hand, Type A noises tend to increase for positive polarity and decrease for negative polarity, while Type B noises tend to increase at -8kV test level in the HCP case. These results suggest that the photo-coupler does not work well for ESD noise suppression. One of the reasons has been demonstrated to be due to the driving capability of the photo-coupler, and other one is due to the presence of a parasitic capacitance between the input and output of the photo-coupler. The parasitic capacitance can yield a capacitive coupling so that high-frequency ESD noises pass through the photo-coupler.

Electrostatic discharge (ESD) events due to metal objects electrified with low voltages give a fatal electromagnetic interference to high-tech information equipment. In order to elucidate the mechanism, with a 6-GHz digital oscilloscope, we previously measured the discharge current due to collision of a hand-held metal piece from a charged human body, and gave a current calculation model. In this study, based on the calculation model, a method was presented for deriving a gap potential gradient from the measured discharge current. Measurements of the discharge currents were made for charge voltages from 200 V to 1000 V. The corresponding potential gradients were estimated, which were validated in comparison with an empirical formula based on the Paschen's law together with other researcher's experimental results.

For investigating the validity of the two exclusion criteria in the ANSI safety guide revised in 1982, this paper examines numerically the specific absorption rate (SAR) in the lossy sphere simulating a human head exposed to the microwave near-fields due to a half wavelength dipole antenna. The SAR patterns on the spherical surface are calculated with respect to the antenna input powers and the frequencies.

The head tissue heterogeneity required in the spatial peak specific absorption rate (SAR) assessment for portable telephones was investigated by using the FDTD method in conjunction with an MRI-based human head model. The tissue heterogeneity of the head model was changed from one type of tissue to 17 types of tissue. The results showed that, at 900 MHz and 2 GHz, the homogeneous modeling results in an underestimate about 20% for the λ/2 monopole antenna portable telephones and an overestimate to the same extent for the λ/4 monopole or helical antenna portable telephones. A head model with a simple skin-fat-muscle-bone-brain structure seems to be sufficient to obtain a fairly accurate one-gram or ten-gram averaged spatial peak SAR value in computational dosimetry for portable telephone compliance.

An attempt to derive the lethal dose for mice was made at 2.45 GHz for whole body exposure. Based on a numerical dosimetry result and an experimental death rate investigation, the lethal dose was estimated to be a whole body averaged specific absorption rate (SAR) with a level at double the mouse's basal metabolic rate.

Measurements of contact discharge current waveforms from an ESD generator with a test voltage of 4kV are conducted with the IEC specified arrangement of a 2m long return current cable in different three calibration environments that all comply with the IEC calibration standard to identify the occurrence source of damped oscillations (ringing), which has remained unclear since contact discharge testing was first adopted in 1989 IEC publication 801-2. Their frequency spectra are analyzed comparing with the spectrum calculated from the ideal contact discharge current waveform without ringing (IEC specified waveform) offered in IEC 61000-4-2 and the spectra derived from a simplified equivalent circuit based on the IEC standard in combination with the measured input impedances of one-ended grounding return current cable with the same arrangement in the same calibration environment as those for the current measurements. The results show that the measured contact discharge waveforms have ringing around the IEC specified waveform after the falling edge of the peak, causing their spectra from 20MHz to 200MHz, but the spectra from 40MHz to 200MHz significantly differ depending on the calibration environments even for the same cable arrangement, which do not almost affect the spectra from 20MHz to 40MHz and over 200MHz. In the calibration environment under the cable arrangement close to the reference ground, the spectral shapes of the measured contact discharge currents and their frequencies of the multiple peaks and dips roughly correspond to the spectral distributions calculated from the simplified equivalent circuit using the measured cable input impedances. These findings reveal that the root cause of ringing is mainly due to the resonances of the return current cable, and calibration environment under the cable arrangement away from the reference ground tends to mitigate the cable resonances.

For investigating the pantograph discontact phenomena, this letter describes the statistical measurements of the discontact properties in the sliding-contacts. The current-dependences of the discontact and the discharge rates are elucidated.

From the standpoint of studying the biological effects of microwaves on human eyes, this paper numerically examines the specific absorption rate (SAR) inside the eyeball, using the finite-difference time-domain (FD-TD) method, which does not require very much computer storage. Two kinds of highly heterogeneous models constructed by us and Taflove's group are used to compute the SARs inside the eyeball for 1.5-GHz microwave exposure under the 1991 ANSI protection guideline. The SAR contour lines and the spatial distribution are shown inside the eyeball. Comparison is also made between the SARs for the two computation models.

The electromagnetic fields emitted from an electrostatic discharge (ESD) event occurring between charged metals cause seriously damage high-tech equipment. In order to clarify the generation mechanism of such ESD fields and also to reduce them, we previously proposed a finite-difference time-domain (FDTD) algorithm based on a delta-gap feeding method and a frequency dispersion characteristic formula (Naito's formula) of ferrite material for simulating the ESD fields due to a spark between the charged metals with ferrite core attachment. In the present study, by integrating the above FDTD algorithm and a spark-resistance formula, we simulated both of the ESD itself and the resultant fields for the metal bars with ferrite core attachment, and demonstrated that the core attachment close to the spark gap suppresses the magnetic field level. This finding was also validated via 6-GHz wide-band measurement of the magnetic near-field.

In testing the possible biological effects of electromagnetic exposure from cellular telephones in small animals such as mice, it is essential to realize a highly localized head exposure as close as possible to that due to cellular telephones in humans. In this study, a 1.5GHz exposure setup was developed which has a highly localized specific absorption rate (SAR) of 2W/kg in the mouse brain and a low whole-body averaged SAR of 0.27W/kg. The low whole-body averaged SAR was realized by using a flexible magnetic sheet attachment on the mouse holder. Its validity has been carefully examined by both numerical simulation with an anatomically based mouse model and experimental simulation with a solid mouse phantom. Good agreement was obtained between the numerical and experimental results, which confirmed the effectiveness of the magnetic sheet attachment to the mouse holder.

The very fast transients of micro-gap discharges driven by low voltage electrostatic discharging (ESDs) are investigated in the time domain. We previously developed a 12 GHz wideband measurement setup consisting of a distributed constant line system, however the observed transients due to micro-gap discharges had very fast rise times of 34 ps or less, which reached the limitation on our system. In this paper, we proposed a method for estimating wideband transients beyond the measurement limit by using the transmission loss of a high performance coaxial transmission line. The proposed method is validated by estimating an impulsive voltage waveform with rise/fall time of 16 ps from the waveform measured through a semi-rigid coaxial cable with a length of 10 m.

This letter presents a new method of estimating the discontact rate of the pantograph using the noise currents in arc discharges, which is independent of the BPF overlapped responses that give large estimation error for the previous methods. The validity is confirmed experimentally.