• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.11 no.7
• /
• pp.1211-1217
• /
• 2000

The three-dimensional finite-difference time-domain (FDTD) method and the two-dimensional quasi-static formulation have been used to calculate the characteristic impedance and the microwave effective index of coplanar waveguide structures on Lithium Niobate ($LiNBO_3$) single crystal substrates with a yttria-stabilized zirconia (YSZ) or $SiO_2$ buffer layer. The results shown can be a good source to predict the modulator characteristics. The effects of the thin buffer layer and anisotropy of the $LiNBO_3$ crystal (x-cut and z-cut) are discussed. The comparison between the FDTD and quasi-static results shows good agreement. In this paper, the efficient modeling technique of the FDTD method for the coplanar waveguide (CPW) structures based on an anisotropic substrate with a thin buffer layer is developed.

• Resources Recycling
• /
• v.13 no.6
• /
• pp.26-30
• /
• 2004

Input impedance of the inverted L antenna which is modified from a monopole antenna varies to very high input impedance value when the ratio of vertical height to horizontal length is reduced. So its impedance matching becomes very difficult. In this paper, we analyzed the input impedance variation range depending on the ratio of vertical height to horizontal length in the normal and ferrite thin film added configuration for the input impedance control. For the exact analysis involving the permittivity, permeability and conductivity of ferrite material, FDTD numerical method is used.

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.37 no.6
• /
• pp.396-396
• /
• 2000

Three-Dimensional FDTD method is applied to analyze the dielectric resonator coupled with two microstrip lines. We model accurately the curved surface using Noriaki model. The frequency resolution is 106.46 MHz by the conventional FFT However it is not sufficient for determining its resonant frequency. So we introduce the Pad approximation and Stoer-Bulirsch method in order to have the high frequency resolution degree, 1.00 MHz. All results are compared with the measured data. As a result, we acquire the very precise result through the Pad approximation. And sinusoidal wave is applied. From the plot of the electric and magnetic field distribution, it is shown that the resonant mode is $TE_{01{\delta}}$ mode.

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.37 no.6
• /
• pp.36-43
• /
• 2000

Three-Dimensional FDTD method is applied to analyze the dielectric resonator coupled with two microstrip lines. We model accurately the curved surface using Noriaki model. The frequency resolution is 106.46 MHz by the conventional FFT However it is not sufficient for determining its resonant frequency. So we introduce the Pad approximation and Stoer-Bulirsch method in order to have the high frequency resolution degree, 1.00 MHz. All results are compared with the measured data. As a result, we acquire the very precise result through the Pad approximation. And sinusoidal wave is applied. From the plot of the electric and magnetic field distribution, it is shown that the resonant mode is TE$_{01{\delta}}$ mode.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.11 no.3
• /
• pp.437-444
• /
• 2000

In this paper, we propose a method that directly converts 3D CAD files for handheld phones designed by a commercial CAD S/W, PATRAN, to FDTD modeling with 1mm resolution. To qualify the accuracy of this method, we compared the calculation of radiation pattern using 3D transient far zone transformation with the measured results by gain comparison method in anechoic chamber and the difference is less than 0.5 dB. The calculation of magnetic field distributions on the front of handheld phones has been done to find a factor contributes to SAR. The result showed up the H-field in the width direction of the phone gives more dominant effect than the field in the length or inside to the front direction.

• Proceedings of the Korean Institute of Resources Recycling Conference
• /
• 2004.12a
• /
• pp.43-51
• /
• 2004

Input impedance of the inverted L antenna which is modified from a monopole antenna varies to very high input impedance value when the ration of vertical height to horizontal length is reduced. So its impedance matching becomes very difficult. In this paper, we analyzed the input impedance variation range depending on the ratio of vertical height to horizontal length in the normal and ferrite thin film added configuration for the input impedance control. For the exact analysis involving the permittivity, permeability and conductivity of ferrite material, FDTD numerical method is used.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.23 no.1
• /
• pp.141-149
• /
• 2009

In this paper, quasi-static FDTD method is implemented by FORTRAN programming, and it is used for analysis of body induced current in middle frequencies. The quasi-static FDTD program is validated by comparing the calculation result with analytic solution of the test model, to which it is difficult to apply conventional FDTD. It is confirmed that the time-step is reduced by $5.68{\times}10^6$ times. Using validated numerical technique, body induced current distribution in high resolution 3-D human model is calculated for 20[kHz] magnetic field exposure and 1[MHz] electric field exposure. Also, the effect of grounding condition of both feet on the distribution and amplitude of the induced current is analyzed. It is expected that this research can be applied to various fields including safety assessment of body induced current and development of diagnosis devices using bio-electricity.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.2 no.4
• /
• pp.653-660
• /
• 1998

The purpose of this paper is to analyze the electromagnetic field characteristics of microstrip array antenna with the FDTD(finite difference-time domain method). Finite difference equations of Maxwell's equations are defined in rectangular coordinate systems. To simulate the unbounded problem like a free space, the Mur's absorbing boundary condition is also used. After modeling the microstrip array antenna with the grid structure, the transient response of the field distribution is depicted in the time domain.

• Journal of the Optical Society of Korea
• /
• v.13 no.2
• /
• pp.286-293
• /
• 2009

In this paper, we present an optimal shape design method for a dielectric microlens which is used to focus an incoming infrared plane wave in wideband, by exploiting the finite difference time domain (FDTD) technique and the topology optimization technique. Topology optimization is a scheme to search an optimal shape by adjusting the material properties, which are design variables, within the design space. And by introducing the adjoint variable method, we can effectively calculate a derivative of the objective function with respect to the design variable. To verify the proposed method, a shape design problem of a dielectric microlens is tested when illuminated by a transverse electric (TE)-polarized infrared plane wave. In this problem, the design variable is the dielectric constant within the design space of a dielectric microlens. The design objective is to maximally focus the incoming magnetic field at a specific point in wideband.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.11 no.3
• /
• pp.474-483
• /
• 2000

In this paper, the planar LTS and Vibaldi antenna operating at 28 GHz for LMDS is optimized by finite difference time domain(FDTD) method and then fabricated and measured. We designed LTS and Vivaldi antenna with corrugation structure for reducing sidelobe, then these antenna are optimized by FDTD, and then fabricated and measured. In a results of the measured values, sidelobe level of LTS and Vivaldi antenna with corrugation structure is 4 dB lower than that of LTS and Vivaldi antenna.