In this work, micromagnetic simulations of writing and reading processes in a perpendicular system including a single pole head and recording media with soft underlayer (SUL) have been performed. The noise contribution from the recording layer increased with increasing grain size distribution of the recording layer but that from soft underlayer remained almost a constant at a given linear density. Details of the noise from the soft underlayer will be discussed. Also thermal decay over a long time scale of the recorded bits was investigated by the Langevin equation and the time-temperature scaling method. It was found that at the linear density of 1058 kfci narrower grain size distribution in the recording layer even in the same average grain size is very important in the point of thermal decay than expectation.

The tectonic activities that precede significant earthquakes release electromagnetic (EM) waves that can be used as earthquake precursors. We have been observing EM radiation in the ELF (extremely low frequency) band at about 40 observation stations in Japan for predicting significant earthquakes. The recorded signals contain, however, several noise components generated from the ionosphere, human activity, and so on. Most background noise in observed signal is attributed to lightning in the tropics. This paper proposes method based on PCA (principal component analysis) to extract signals from large data sets. The good performance of the proposed method is confirmed.

So far, a lot of analyses have been performed on the edge-guide mode isolator with one short edge. However, the detailed characteristics such as the influence of shape of a metal strip and the thickness of a ferrite substrate have not been revealed. This paper clarifies the influence of the structure on the frequency response both experimentally and numerically. The numerical analysis is performed by the FDTD method. The numerical results indicate that the frequency response does not depend on the thickness of ferrite substrate but does on the shape of the metal strip. Furthermore, based on the numerical results, the experiment is carried out on the prototype isolator. All the results provide a theory of the optimum design on the isolator.

An analysis method based on the FD-TD and radiation mode expansion methods and its simulation tool are developed for calculating circuit characteristics and parameter values of passive MMIC (Monolithic Microwave Integrated Circuits) elements having multilayer structure. For straight multilayer microstrip lines and coplanar waveguides, it is possible to calculate characteristic impedance, effective permittivity, transverse field distribution of guided modes, etc. For various multilayer microstrip and coplanar waveguide elements, it is possible to calculate scattering parameters, radiated power, radiation patterns, etc. As an example of application of the present technique, effects of inclusion of lower permittivity layer in the substrate on transmission and radiation characteristics are investigated for right-angled microstrip bends.

We developed a phase controlled magnetron (PCM) with high DC-RF conversion efficiency and with phase control to steer a microwave beam in order to realize the final space Solar Power Station (SPS) system. For the PCM, we use injection locking technique and PLL feedback to anode current. We can stabilize and control a frequency and a phase of a microwave of the PCM. However, we have a power loss after the PCM for the SPS use because of a size of the antenna (> km) and of a microwave power (> GW). In order to decrease power loss after PCM, we newly propose a concept of "sub phase shifter" which can change only 1 or 2 bits of a phase and has low loss. We can keep high beam collection efficiency when we control a beam to a twice larger direction in the SPS system. With this concept, we developed a PCM array called SPORTS (Space Power Radio Transmission System) in FY2000 and FY2001 in Kyoto University.

Microwave Power Transmission (MPT) technology is one of the most essential parts for Solar Power Station/Satellite (SPS). We study on application of magnetrons as DC-RF converters for the MPT transmitting system. Magnetrons cost much cheaper, have much higher DC-RF efficiency over 70% and much lighter system weight per 1 watt RF output than semiconductor amplifiers although they have wider bandwidth of the fundamental frequency and spurious noises in various frequencies. Spurious noises are radiated from the transmitting system and interfere in the other communication systems both in space and on the Earth. The objective of this study is the improvement of the spurious noises generated from magnetrons. Experimentally, magnetrons driven by DC stabilized power supply had not only narrower bandwidth of the fundamental frequency but also lower spurious noise levels when filament current is turned off than when it is turned on. Some spurious noises are probably caused by the intermodulation between the low frequency spurious noises, which frequency is below 1 GHz, and the fundamental or the harmonics. We also verified that the harmonics levels of the measured magnetron in our measurement system were below -70 dBc, which are comparable to or better than those of some semiconductor amplifiers, and that the harmonics were not improved greatly when the filament current was turned off because the source of the harmonics is the distortion of the fundamental.

This paper newly proposes a hollow ferrite waveguide which consists of a microstrip line loaded on two ferrite slabs with adjacent air gap. Dispersion relation of magnetostatic surface wave in the waveguide is derived by the two dimensional analysis, and reciprocal behavior for parallel bias magnetic field and nonreciprocal behavior for antiparallel bias magnetic field are shown. Propagation characteristic of magnetostatic surface wave in the hollow ferrite waveguide are experimentally demonstrated under both parallel and antiparallel bias magnetic field directions. Strong nonreciprocal behavior in the hollow guide was found for case of antiparallel bias field configuration. These experimental results are mostly in agreement with the dispersion diagram. A nonreciprocal four port junction is demonstrated as an application of the hollow ferrite waveguide.

In this study, the frequency and spatial properties of undesired electromagnetic radiation distribution around a simple printed circuit board (PCB) model, which only has the mismatching printed line (PL) and ground, are estimated. Finite difference time domain (FDTD) modeling is developed for the analysis space, which is 500 400 51 mm3 in size, around the PCB. As the driving clock pulse has a very wide frequency bandwidth, ranging from kHz to GHz, basic and precise investigation of the noise emission mechanism from the basic model is performed. The results of the magnetic field Hx on the PCB as determined by FDTD simulation, and those of the experiment, driven by a clock pulse, agree well. The results show that although this approach is basic and simple, it becomes clear that the frequency and spatial characteristics of the electric and magnetic field near the PCB are influenced by the wavelength of the frequency and appling the driving clock pulse, and the low-frequency component of the electromagnetic distribution around the PCB is larger than the high-frequency components. It is suggested that the low-frequency noise problem should be carefully considered.

In this paper, we describe our study on a novel high-frequency magnetic field probe based both on the BiRIG rotation magnetization (RM) phenomenon and the third-generation optical probing scheme. First, we explain our experimental investigation on RF sensitivity and frequency response of the RM-based Faraday effect in a commercially available Bi-substituted rare-earth iron garnet plate. Second, we report on the implementation of fiber-optic magneto-optic (MO) probe heads with bandwidths of 10 GHz or broader, which have been brought about by careful arrangement of the magnetization axis of a single-domain crystal and the highly sensitive fiber-edge optical probing scheme. Third, we describe a few RF magnetic field distribution measurements carried out successfully over GHz-band microstrip line circuits. The results of the study imply the substantial potential of the present MO probe head for the RF current visualization.

We have thoroughly investigated the effect of on-chip decoupling capacitors on the simultaneous switching noise (SSN) and the radiated emission. Furthermore, we have successfully demonstrated an efficient design method for on-chip decoupling capacitors on an 8-bit microcontroller without increasing the die size, which results in more than 10 dB of suppressed radiated emission.

As a new material, silver (Ag) coated fabric has been developed, and its use for shielding electromagnetic radiation is expected. In this paper, seven kinds of Ag coated fabrics, woven, knitted and nonwoven by Ag coated fibers, are prepared, and placed over a PCB with a microstrip line, which is used as a noise source. By measuring the input impedance of the microstrip line, the distance between the PCB and the fabric is fixed to 8 mm to reduce the coupling paths. The shielding effect SE of those fabrics was compared by measuring the magnetic near-field with a small shielded-loop probe. In the results, the resonance frequency is dependent on the fabric's length, as well as the case of a copper sheet. Comparing the texture, the SE of woven and nonwoven fabrics is larger than the knitted fabric. Comparing with the copper sheet, the SE of the fabrics is smaller below 200 MHz, but elsewhere is almost the same.

To estimate the electromagnetic noise radiated from a printed circuit board (PCB) driven by a switching device, the finite difference time domain (FDTD) simulation method implementing the switching transistor is developed. The electric and magnetic field distributions on the signal line driven by a switching transistor are calculated or measured. These calculated and measured results show good agreement. The electric and magnetic field noises at typical impedance conditions modeled for the switching condition, i.e., the ON or OFF state of the transistor, are estimated by the FDTD calculation. The variation of the radiation noise when the switching transistor is turned ON or OFF is large at 216 MHz, whose input impedance of the signal line is small. It is speculated that the noise radiation at the 10 Ω signal source impedance condition that is modeled for the ON condition shows good agreement with the noise distributions at the driving condition.

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.

This letter presents a Monte-Carlo FDTD technique to determine the scattered field from a perfectly conducting fractal surface from which the useful information on the incoherent pattern tendency could be observed. A one-dimensional fractal surface was generated by the bandlimited Weierstrass function. In order to verify the numerical results by this technique, these results are compared with those of Kirchhoff approximations, which show a good match between them. To investigate the incoherent pattern tendency involved, the dependence of the fitting curve slope on the different D and is discussed for the bistatic and back scattering case, respectively.

The Neural Network (NN) is applied to recognize basic PCB configurations using its magnetic near-field spectra and radiated far-field emission. The learning process is accomplished by using the computed spectra of the radiated field from PCBs having different configurations. The anomaly is detected through the monitoring of the spectra's amplitude frequency by injecting a voltage pulse at the PCB configuration. The trained NN is then applied to the identification of PCB layouts from radiated emission measurements. The trained NN can identify all of those PCB configurations from the magnetic near-field spectra and the radiated far-field EMI. Moreover, the calculated results of the NN are compared with the actual far-field measurements and other models for evaluation. Finally, the NN used for predicting far-field emission from their magnetic near-field measurement is proposed. Experiments show that the NN can predict the far-field spectra from the magnetic near-field spectra.

MRAM-writing circuitry to compensate for the thermal variation of the magnetization-reversal current is proposed. The writing current of the proposed circuitry is designed to decrease in proportion to an increase in temperature. This technique prevents multiple-write failures from degrading 1 Gb MRAM yield where the standard deviation of magnetization-reversal current variation from other origins is less than 5%.

The effect of a conductive sheet placed over a PCB with a microstrip line on electromagnetic noise shielding is investigated. As a typical conductive sheet, a copper sheet is used, and is not grounded. First, the input impedance of the microstrip line and the magnetic field when varying the distance between the PCB and the conductive sheet are measured, and the distance that does not affect the signal transmission is set at 8 mm. Second, the effect of the conductive sheet size on the magnetic field radiation is discussed by measurements and FDTD modeling, and the magnetic near-field distribution around the PCB is visualized by using the FDTD calculation. A conductive sheet whose width is larger than the PCB width should be effective for suppression of the magnetic near-field noise radiation just above a PCB.

Recently, a new approach was presented to determine the high-frequency response of on-chip passives and interconnects. The method solves the electric scalar and magnetic vector potentials in a prescribed gauge. The latter one is included by introducing an additional independent scalar field, whose field equation needs to be solved. This additional field is a mathematical aid that allows for the construction of a gauge-conditioned, regular matrix representation of the curl-curl operator acting on edge elements. This paper reports on the convergence properties of the new method and shows the first results of this new calculation scheme for VLSI-based structures at high frequencies. The high-frequent behavior of the substrate current, the skin effect and current crowding is evaluated.

In this paper, we investigate the electron-hole energy states and energy gap in three-dimensional (3D) InAs/GaAs quantum rings and dots with different shapes under external magnetic fields. Our realistic model formulation includes: (i) the effective mass Hamiltonian in non-parabolic approximation for electrons, (ii) the effective mass Hamiltonian in parabolic approximation for holes, (iii) the position- and energy-dependent quasi-particle effective mass approximation for electrons, (iv) the finite hard wall confinement potential, and (v) the Ben Daniel-Duke boundary conditions. To solve the 3D nonlinear problem without any fitting parameters, we have applied the nonlinear iterative method to obtain self-consistent solutions. Due to the penetration of applied magnetic fields into torus ring region, for ellipsoidal- and rectangular-shaped quantum rings we find nonperiodical oscillations of the energy gap between the lowest electron and hole states as a function of external magnetic fields. The nonperiodical oscillation is different from 1D periodical argument and strongly dependent on structure shape and size. The result is useful to study magneto-optical properties of the nanoscale quantum rings and dots.

This paper presents a framework for modeling and mixed-mode simulation of circuits/interconnects and electromagnetic (EM-) radiations. The proposed framework investigates the signal integrity in VLSI chips, packages and wiring boards at the GHz-band level, and verifies the electromagnetic interference (EMI) and the electromagnetic compatibility (EMC) of high-speed systems. In our framework, the frequency characteristics of interconnects and EM-radiations are extracted by the full-wave FDTD simulation. The macromodels of interconnects are synthesized as SPICE subcircuits, and the impulse responses of EM-radiations are stored in the database. Once the macromodels are synthesized, the circuit simulation with the consideration of EM-effects can be performed by using SPICE. The EM-field distributions can be also easily calculated by taking convolutions of pre-simulated EM impulse responses and the SPICE results.