Ki-Bok Kong

Stability and Numerical Dispersion of 3-D Simplified Sampling Biorthogonal Adi Method

We previously introduced the simplified sampling biorthogonal direction implicit (SSB-ADI) method for 2-D Maxwells equations. This paper extends it to a 3-D SSB-ADI method. Similar to the original method, the 3-D SSB-ADI method also partially uses the sampling property and compact support of the SBTD algorithm to display spatial discretization. Dispersion and stability analysis are presented. A numerical example shows that the SSB-ADI method is superior to the SB-ADI method in terms of reducing the CPU time and memory requirement of the numerical simulation.

3D Spherical Antenna Measurement System for CTIA OTA Testing and Characterizing of Mobile MIMO Terminals

This paper describes the 3D spherical antenna measurement system for a passive antenna measurement, CTIA (Cellular Telecommunications & Internet Association) OTA (Over The Air) testing and characterizing of mobile MIMO (Multiple-Input Multiple-Output) terminals. The measurements of the monopole box are performed for the calibration of the proposed measurement system. Finally, the proposed system is able to measure the experimental model of MIMO terminal with adapting the diversity antenna system.

A non-uniform one-arm spiral antenna for WBAN communication

This paper presents a non-uniform one-arm spiral antenna. The proposed antenna can be easily placed in the implant device for WBAN communication because of the compact size (Diameter: 10mm, Height: 1.035mm). The electrical length of the proposed antenna is obtained by adjusting the rate of expansion in a limited space. The characteristics of the proposed antenna have been investigated in the fluid considering the electrical property of human body. The bandwidth is 112MHz (206∼318MHz) and the measured maximum gain is −12.404dBi at 310MHz.

Analysis of Simplified SB-ADI Scheme for Two-Dimensional Maxwell's Equations

This letter represents a simplified sampling biorthogonal alternating-direction implicit (SSB-ADI) method based on the sampling biorthogonal time domain (SBTD) algorithm. Two sampling functions with different orders for sampling biorthogonal method are used to display spatial discretization. Dispersion and stability analyses are presented. It is shown through a numerical simulation that SSB-ADI reduced the CPU time and memory compared to the SB-ADI method.

A Simple Method to Reduce the Splitting Error in the LOD-FDTD Method

This paper presents a new iterative locally one-dimensional finite-difference time-domain(LOD-FDTD) method that has a simpler formula than the original iterative LOD-FDTD formula[1]. There are fewer arithmetic operations than in the original LOD-FDTD scheme. This leads to a reduction of CPU time compared to the original LOD-FDTD method while the new method exhibits the same numerical accuracy as the iterative ADI-FDTD scheme. The number of arithmetic operations shows that the efficiency of this method has been improved approximately 20 % over the original iterative LOD-FDTD method.

Design of Offset Dual-Reflector Antennas for Improving Isolation Level between Transmitter and Receiver Antennas

This paper presents the improved isolation property of the signals among transmitter and receiver antennas. The separation wall is laid at the center of the antennas to improve the isolation level between them. The introduced separation wall has serrated edges mounted on three sides, i.e., top, left and right sides. These mounted serrated edges are implemented to reduce the diffraction which may occur due to the linear edge of the wall. The Fresnel diffraction problem has been solved using analytical method in order to get the optimized structure of the serration. The Fresnel diffraction patterns due to different sizes of the serration are obtained, and their relative powers are compared to each other. The implemented antenna system with the serration wall is composed of corrugated feed horn, orthogonal mode transducer, and offset dual-reflector parabolic antennas. The effect of serration is well demonstrated by the measurement of isolation level of the antenna system. The measured results show that the serrated edges enhanced the isolation property among transmitter and receiver antennas.

Experimental investigation of 2×2 MIMO array antenna for the mobile WiMax by measuring 3D radiation patterns

This paper investigates four types of array configurations with two chip antennas by considering mutual coupling and envelop correlation coefficient from 3D radiation patterns. According to proper spacing and polarization between antennas, diversity performance may be determined. The envelop correlation coefficients calculated using scattering parameters may be inadequate because the uniform distribution of sources is assumed. The radiation-pattern-based method for the envelop correlation coefficients can include real environmental factors like angular density function.

The Simplest V-Cycle Fast Adaptive Composite Grid ADI-FDTD Method for Two-Dimensional Electromagnetic Simulations

An alternating-direction-implicit finite-difference time-domain (ADI-FDTD) method based on the fast-adaptive-composite grid ADI (FAC-ADI) scheme is introduced to reduce the truncation error generated when ADI-FDTD is derived from the Crank-Nicolson (CN) ADI scheme, and its efficiency is investigated. The relaxation equation and residual equation for FAC-FDTD are constructed by defining the error vector between the traditional ADI and CN FDTD formulas, and the iterative formulas are defined using the iterative schemes. A comparison of the computational efficiency between the FAC-ADI and ADI-FDTD is presented.