Tuya Wuren

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.

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.

Pseudolinear Circuit Theory for Sinusoidal Oscillator Performance Maximization

This paper introduces a theory for fast optimization of the circuit topology and parameters in sinusoidal oscillators. The theory starts from a system model composed of standard active and passive elements. We then include even the output load in the circuit, so that there is no longer any interaction with the outside of the system through the port. This model is thus called no-input-no-output (NINO) oscillator. The circuit is cut at an arbitrary branch, and is characterized in terms of the scalar impedance from the cut point. This is called active impedance because it is a function of not only the stimulating frequency but also the active device gain. The oscillation frequency and necessary device gain are estimated by solving impedance-domain Barkhausen equilibrium equations. This estimation works for the adjustment of circuit elements to meet the specified oscillation frequency. The estimation of necessary device gain enables us to maximize the oscillation amplitude, thanks to the inherent negative-slope nonlinearity of active devices. The active impedance is also used to derive the oscillation Q (quality) factor, which serves as a key criterion for sideband noise minimization i.e. frequency spectrum purification. As an alternative measure to active impedance, we also introduce branch admittance matrix determinant. This has the same numerical effect as the scalar impedance but can be used to formulate oscillator characteristics in a more elegant fashion, and provides a lucent picture of the physical behavior of each element in the circuit. Based on the proposed theory, we provide the tabled formulas of oscillation frequency, necessary device gain, active Q factor for a variety of typical Colpitts, Hartley, and cross-coupled twin-FET (field-effect transistor) oscillators.

A miniaturized microstrip ring resonator lowpass filter with sharp attenuation

A miniaturized circuit of a microstrip ring resonator lowpass filter with sharp attenuation is investigated in this paper. The miniaturization of the circuit is realized by using a simple specific transmission line with two open stubs. The ratio of the original ring length and miniaturized ring length is 3:2. However the miniaturized circuit is equivalent to the original circuit at three frequencies ƒ 0 , 1.5ƒ 0 and 2ƒ 0 . Thus, the width of the stopband is maintained as for the original circuit. Therefore, the filter characteristic is not distorted after miniaturization. The theoretical result of a miniaturized circuit shows a broader stopband and a sharper cut off frequency response than the original one, though it also shows smaller minimum attenuation in stopband and larger maximum attenuation in passband compared to the original one. Experimental result is shown for verification of the present study.

Parameters of Coupled-Mode Equations for a Natural Single Phase Unidirectional Transducer on a La3Ga5.5Ta0.5O14 Substrate

Parameters included in coupling-of-modes equations such as coupling coefficients, transduction coefficients and electrostatic capacitances are theoretically determined for a natural single-phase unidirectional transducer (NSPUDT) on a La3Ga5.5Nb0.5O14 substrate with Euler angles of (110°, 145°, 145°) and an electromechanical coupling coefficient larger than quartz. In the hybrid finite-element method (HFEM), used for determining these parameters, all the effects of anisotropy of the substrate, piezoelectric perturbation, mechanical perturbation and energy storage are taken into account. The electrode thickness and width dependence of the parameters and the excitation characteristics of NSPUDT are investigated in detail. The parameters obtained by the present method are compared with those obtained by the perturbation method. Furthermore, numerical results for the frequency characteristics of NSPUDT are compared to the experimental data, and the validity and usefulness of the present method are demonstrated.

PWM Power Supply Using SiC RESURF JFETs with High Speed Switching

400V/2.5A 4H-SiC JFETs, having a reduced surface field (RESURF) structure have been fabricated. Measurements on the on-resistance, blocking, and switching characteristics were carried out. It was confirmed that the JFET has fast switching characteristics. A demonstration of a Pulse Width Modulation (PWM) decoder using JFETs was carried out. The input waveform, which is pulse width modulated 20.5MHz at 4.1MHz sine wave, as able to be decoded at 4.1MHz sine wave.