Shoji Mochizuki

Novel iteration procedures of a hybrid method combining MoM and scattered-field FDTD method for electromagnetic dosimetry

Health effects of human-body exposure to the near field of a mobile communication device have been investigated with knowledge of the electromagnetic power absorption in human heads during cellular-telephone use. One of the most powerful numerical calculation methods for biological electromagnetic compatibility (Bio-EMC) problems is the finite-difference time-domain (FDTD) method. However accurate models of curved structures, which are closely related to the antenna characteristics, are difficult to realize in the FDTD method. Because recent devices have more complex antennas, it is not easy to precisely evaluate dose characteristics in the human body exposed to the near field from such devices by only using the FDTD method. The objective of this study is to establish a numerical hybrid method combining the advantage of different numerical calculation methods such as the MoM/FDTD method proposed in the literature in order to accurately analyze the complex Bio-EMC problem. In this paper, novel iteration procedures are introduced into the previously reported hybrid MoM/FDTD method. We also show the validity of application of this method to Bio-EMC problems.

Effects of Ear Shape and Head Size on Simulated Head Exposure to a Cellular Phone

The dependence of the specific absorption rate (SAR) on ear shape and head size have been investigated using human-head and cellular-phone models. Cubical and realistic head models were used. Various ear shapes were used with the cubical head model whereas a low-loss thin ear or a lossy realistic ear was used with the realistic head models. The SAR distribution depends significantly on the shape of the ear, regardless of the head model. The effects of the head size have been investigated using a 90th-percentile head model and a Japanese-average head model. The head size has considerably less effect than the ear shape. The measurement results have been validated by numerical calculation, and support the use of the specific anthropomorphic mannequin (SAM) standard head model.

A new iterative MoM/FDTD analysis for EM scattering by a loop antenna

The health concern posed by human-body exposure to near field of wireless communication devices has been raised recently with the rapid growth of cellular-telephone use. Our previously proposed hybrid formulation (Mochizuki et al. (2003)) is applied to a one-wavelength square loop antenna with a lossy dielectric sphere to demonstrate the validity and the flexibility of our method. The computed results such as antenna input impedance, field and specific absorption rate (SAR) in the scatterer are then compared with those obtained by the conventional FDTD method. It is found that the proposed hybrid formula seems to have fast convergence and only a few iterations are needed.

Development of a millimeter-wave exposure setup for rabbit eyes

Safety guidelines for human exposure to millimeter waves are based on ocular effects (ICNIRP, Health Physics, vol.74, p.494-522, 1999; IEEE C95.1, 1999). Few biological studies on ocular effects of millimeter waves have, however, been reported (Rosenthal, et al., 1976; Kues, H.A., et al., 1999; Chalfin, et al., 2002; Mic, 1908). Because various millimeter-wave applications will be available for public use in the near future, it is necessary to increase our biological knowledge of the ocular effects of millimeter-wave exposure. The paper describes the development of a setup to investigate the effect of millimeter-wave exposure on rabbit eyes.