Iwata Sakagami

High-order FDTD and auxiliary differential equation formulation of optical pulse propagation in 2-D Kerr and Raman nonlinear dispersive media

We reformulate the existing auxiliary differential equation (ADE) technique in the context of the finite-difference time-domain analysis of Maxwells equations for the modeling of optical pulse propagation in linear Lorentz and nonlinear Kerr and Raman media. Our formulation is based on the polarization terms and allows simple and consistent implementation of such media together with the anisotropic perfectly matched layer (APML) absorbing boundary condition. The disadvantages of the ADE technique, i.e., requiring additional storage for auxiliary variables, has been overcome by adopting the high-order finite-difference schemes derived from the previously reported wavelet-based formulation. With those techniques, we demonstrate in two-dimensional setting an effective and accurate numerical analysis of the spatio-temporal soliton propagation as a consequence of the physically originated balanced phenomena between the self-focusing effect of nonlinearity and the pulse broadening effects of the temporal dispersion and of the spatial diffraction.

Effective 2-Debye-Pole FDTD Model of Electromagnetic Interaction Between Whole Human Body and UWB Radiation

We have successfully developed a human body finite difference time domain model based on efficient two-pole Debye dispersion, and analyzed for the first time the electromagnetic interaction between a whole human body and ultra wide band radiation having a wide frequency spectrum. The two-pole Debye dispersion model is obtained for 50 individual human tissue properties from Gabriels Cole-Cole data by least squares fitting over a wide frequency range from 100 MHz to 6 GHz. For validation, the model is exposed to radiation of a spread spectrum signal modulated by typical binary phase shift keying. Local energy absorption in a human body has been compared between the two-pole Debye model and a conventional model with frequency-independent permittivity and conductivity.

Generalized Two-Way Two-Section Dual-Band Wilkinson Power Divider With Two Absorption Resistors and Its Miniaturization

A generalized two-way two-section dual-band Wilkinson power divider with two absorption resistors and its size-reduced model are presented. Design equations for dual-band and arbitrary power division are derived from modified even- and odd-mode analysis. The frequency ratio of the lower and upper band frequencies must be lower than three. The channel bandwidth is presented as a function of frequency ratio with mathematical expressions. A coupled line section is introduced to reduce circuit size based on the assumptions of linear phase characteristics and equal phase velocities of the even and odd modes. Two two-way dual-band power dividers, one three-way planar dual-band power divider, and one size-reduced dual-band power divider were fabricated. Experimental results were in good agreement with predicted values.

Wilkinson Power Divider With Complex Isolation Component and Its Miniaturization

By adding a complex isolation component between two 90 ° transmission lines at an arbitrary phase angle from the input terminal, a small Wilkinson power divider provides physical separation and electrical isolation between two output ports. General design equations for the complex isolation component are derived from even- and odd-mode analysis. Parallel and series RLC circuits are chosen to realize complex isolation components, respectively. Considering the bandwidths of S22, S33, and S32, inductors in both parallel and series RLC components are omitted to get the widest bandwidths; mathematical proof and design examples are also presented in this paper. A coupled line section with a compensating capacitor is introduced to reduce the circuit size, where characteristic impedances between even and odd mode are different in the coupled line section, and their electrical lengths are also different in inhomogeneous medium. Mathematical equations and simulation examples prove that the compensating capacitor compensates the characteristic impedance difference in the homogeneous medium and the electrical length difference in the inhomogeneous medium. Finally, an experimental circuit shows good agreement with the theoretical simulation.

Compact multi-way power dividers for dual-band, wide-band and easy fabrication

A loop-type compact multi-way power divider of dual-band, wide-band or easy fabrication is presented. A two-section quarter-wavelength transformer is used at the input port. Measurements using a trial compact 5-way power divider in the case of easy fabrication showed good agreement with theoretical calculations.

Miniaturization of 3- and 5-way Bagley polygon power dividers

This paper reports the miniaturization of 3- and 5-way Bagley polygon power dividers, based on two kinds of methods. In the case of first method, a good agreement between theoretical results from traditional power dividers and results from miniaturized power dividers are shown at around center frequency and within low frequency range. The experimental results agree well with the theoretical results. In the case of second method, the theoretical results from miniaturized circuit agree better with that of traditional ones than results in the case of first method. The experiment for second case has not done yet, but the designed patterns are shown.

Compact Multi-Way Power Dividers Similar to the Bagley Polygon

Planar multi-way power dividers derived from the design of the Bagley polygon are discussed theoretically and experimentally. The design theory is explained using an equivalent circuit model seen from an input port. Compared with the Bagley polygon, less area is needed on a printed circuit board because the transmission line length between output ports can be chosen arbitrarily and the frequency characteristics can be modified using proposed dividers. The experimental results showed good agreement with theoretical results.

Exploration of Whole Human Body and UWB Radiation Interaction by Efficient and Accurate Two-Debye-Pole Tissue Models

We have developed a computationally efficient finite-difference time-domain (FDTD) model of a whole human body based on accurate 2-pole Debye dispersion dielectric tissue properties. Comprehensive FDTD analyses of the interaction between a whole human body and ultrawideband (UWB) radiation are carried out by including the proposed frequency dependent tissue models. The 2-pole Debye models have been obtained for 50 individual human tissues from Gabriels Cole-Cole data by the least squares fitting technique over the frequency range from 100 MHz to 6 GHz. A whole human body composed of the 2-pole Debye models is exposed to spread spectrum radiation. Local energy absorption in a human body is compared between the proposed model and the conventional model of frequency-independent permittivity and conductivity. Resonance states are then investigated in the human body exposed to electromagnetic nano-second pulse radiation. For the extraction of the frequency contents from the highly damped FDTD time signals, a spectrum analysis technique based on an auto-regressive (AR) model has been applied. Pulse propagation in the vicinity of the human body is also characterized by the proposed model for the wireless body area network (WBAN) application that has been proposed recently for computer assisted medical diagnostics and rehabilitation.

A new type of multi-way microwave power divider based on Bagley Polygon power divider

A new type of power divider with simple design theory is proposed based on Bagley Polygon power divider. The design theory is explained by using the equivalent circuit model. Comparing with the Bagley Polygon power divider, it takes less area on substrate board and the output ports can be neatly arranged on the board. The theoretical results are presented and discussed.

Convergence of FDTD and wavelet-collocation modeling of curved dielectric interface with the effective dielectric constant technique

The convergence of the effective dielectric constant (EDC) model of curved dielectric surfaces has been investigated precisely for the finite-difference time-domain (FDTD) as well as for the interpolet-collocation time-domain (ICTD) methods. The EDC is computed by solving the Laplace equation of static electric potential by a finite-difference (FD) method for each cell located on the interface of arbitrary dielectric media. The FD solution of the Laplace equation provides an accurate EDC for arbitrary curved interface with even high contrast of the dielectric constants. It has been demonstrated in this paper that the precisely chosen EDC allows both the FDTD and the wavelet-collocation methods to exhibit second-order convergence for the analysis of not only planar but also curved dielectric interfaces.