Shinichiro Nishizawa

Numerical study on an equivalent source model for inhomogeneous magnetic field dosimetry in the low-frequency range

A new equivalent numerical source model is proposed for efficient dosimetric investigations in the low-frequency range. This approach allows the reproduction of complicated inhomogeneous magnetic field distributions around electronic appliances with full generality (i.e., supports three-dimensional vector fields). This paper investigates the accuracy of the equivalent source model using the geometry-based numerical reference model of a current loop to simulate the magnetic field distribution of a real electronic appliance. Good agreement between the equivalent source model and the reference is obtained with regard to the magnetic field distribution and the induced electric current density in a homogeneous human body model, respectively.

Low-Frequency Dosimetry of Inhomogeneous Magnetic Fields Using the Coil Source Model and the Household Appliance

In this paper, the magnetic field properties and the dosimetry at ELF (50 Hz) are investigated using a coil model, which is prescribed in the European standard EN50366 (CENELEC) as a substitute source model for real household appliances. The accuracy of magnetic field vectors and values of the induced current density, which is achieved with the coil model, were compared with the results of two test appliances (a drilling machine and a hand mixer) obtained from the equivalent source model. It was demonstrated that the magnetic fields obtained (dominant component and strength) using the coil model and the real appliance show an agreement with each other with a maximum difference of 5 dB. The calculated induced current densities in the numerical human body models (homogeneous and anatomical body models) and the real appliances also show a good agreement with each other with a maximum difference by a factor of 1.6 (by the anatomical body model). Furthermore, the values of both field vectors and induced current density values calculated using the coil model were shown to be higher than those calculated in the case of the real appliances. Based on these results, the applicability of the coil model prescribed in EN50366 confirms that of the two applied test appliances

Magnetic Field and Dosimetric Study at Intermediate Frequency Range Using the Coil Source Model

In this paper, the magnetic field properties and the dosimetry at intermediate frequency (21 kHz) for an induction heater are investigated with the coil model, which is prescribed as substitute source model in the European standard EN50366 (CENELEC). The accuracy of the magnetic field vectors and the values of the induced current density, which are achieved with the coil model, are compared with the results of a realistic model of the induction heater obtained from the equivalent source model. It is shown that the coil model coincides well for the magnitude of the magnetic field strength around the induction heater. On the other hand, the dominant field vector of the coil model differs significantly from the real induction heater, which leads to induced current densities in the body model which are three time larger. Owing to these results, the applicability of the coil model prescribed in the EN50366 is confirmed for the induction heater.

A study of the surface current distribution on the microwave transmission line using Green's function

Abstract A method for estimating the currents on the microwave transmission line is proposed. In this method, the substrate is divided into a wire-grid model. Then the magnetic near field strength above the microwave transmission line is calculated and measured. Based on the magnetic near field strength, the magnetic field integral equation is established by applying the Green’s function and is used to estimate the currents flowing on the microwave transmission line. In this paper, the current distribution which is calculated by FDTD method with the interpolation (first order) and estimated current distribution by applying the Green’s function on the microstrip line and the coplanar line is evaluated by using the calculated magnetic field components. As a result, a good agreement between both results is observed and the validity of this method is confirmed. Furthermore, the validity of the current estimation by measuring the magnetic near fields is confirmed by comparing the current obtained from the measured magnetic fields and the calculated magnetic fields. Comparing between the measured and calculated results, a good agreement is observed between both results on the strip line area. However, differences are also observed on the dielectric substrate area.

A Study of Near Field Shielding Effect Measurement for Oval Human Phantom Model using the Conductive Material Shield

In this study, the near field human shield is investigated, which measured the shielding effect of the oval human phantom model, by locating the conductive material shield in front of the phantom model. Also the shielding effect is investigated with the FDTD (Finite Difference Time Domain) method, to confirm the validity of the measurement method. According to the results, it has been shown, that more than 30 dB of the shielding effect is observed for the small gap distances between the shield and phantom model, with the square shield length of 1.0 ¿. On the other hand, very little and also negative shielding effect observed for the square shield length of 0.25 ¿. Furthermore, due to the good agreement between the measured and calculated results, the validity of our measurement method is confirmed.

Equivalent Source Model for Electrical Appliances emitting low Frequency Magnetic Fields

A new numerical source model, which is able to reproduce the inhomogeneous magnetic field radiation of electrical appliances is proposed. The proposed new numerical source model consists of elementary magnetic dipoles, which are derived from the 3 dimensional magnetic field data around the appliance of interest. Eventually the validity of the proposed new numerical source model is confirmed.