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Solderless Interconnection Between Microstrip Lines Through a Thick Ground Plate
Byungje Lee 한국정보과학회 1998 Journal of Electrical Engineering and Information Vol.3 No.5
Understanding of electromagnetic coupling is an important area of research in the design and development of monolithic integrated circuits(MMICs), hybrid microwave integrated circuits(MICs) and integrated antenna arrays. The Finite Difference Time Domain(FDTD) method is developed to investigate the coupling between two microstrip lines through a circular waveguide in a thick common ground plate. Measured data along with the results obtained from Spectral Domain Moment Method(SDMM) are used to verify the solution. A parametric study illustrates the coupling behavior of the structure under investigation. It is observed that the frequency tuning and wide frequency bandwidth can be achieved by choosing appropriate geometry, and this type of transition can be significantly affected by structural parameters.
NFC Antenna Design for Low-Permeability Ferromagnetic Material
Byungje Lee,Byeongkwan Kim,Harackiewicz, Frances J.,Byeonggwi Mun,Hyunwoo Lee IEEE 2014 IEEE antennas and wireless propagation letters Vol.13 No.-
<P>A novel structure of a near-field communication (NFC) antenna for a mobile handset is proposed by changing the sequence of loop winding and modifying the inner loop structure. In general, the sintered ferrite sheets with higher relative permeability (μr ≈ 200) have been used to reduce the performance deterioration of NFC antennas due to the eddy current in the battery pack of a mobile handset. However, their costs are high, and they are considerably breakable. In this letter, we effectively enhance the performance of an NFC antenna by employing the ferrite-polymer composite with lower relative permeability (μr ≈ 55). The proposed antenna improves up to 23% more reading range and up to 65% better load modulation performance.</P>
Closely Mounted Mobile Handset MIMO Antenna for LTE 13 Band Application
Byungje Lee,Harackiewicz, Frances J.,Hyunho Wi IEEE 2014 IEEE antennas and wireless propagation letters Vol.13 No.-
<P>A compact (60 × 15 × 5 mm <SUP>3</SUP>) mobile handset multiple-input-multiple-output (MIMO) antenna for LTE 13 band (746-787 MHz) applications is proposed. The antenna consists of two symmetrical planar inverted-F antennas (PIFAs) in conjunction with a T-shaped common radiator. Without using any additional coupling elements between these closely mounted antennas, both high isolation ( > 17 dB) and low envelope correlation coefficient (ECC <; 0.05 ) are achieved. The low ECC is achieved by using diagonally orthogonal radiation patterns from optimized locations of the MIMO antenna feeds and elements. Low mutual coupling achieved by using the T-shaped common radiator gives rise to the high isolation.</P>
Isolation Enhancement between Indoor Repeater Antennas with Chip Resistor Embedded FSS
Lee, Jae-Yeong,Kim, Byeongkwan,Park, Myun-Joo,Lee, Byungje Hindawi Limited 2012 International journal of antennas and propagation Vol.2012 No.-
<P>The isolation enhancement between the donor antenna and the service antenna for indoor repeater systems is presented by using a frequency-selective surface (FSS). A unit cell of the proposed FSS consists of a quarter-wavelength resonator, a chip resistor, an FR4 substrate, and a ground plane. Applying the unit cells of the proposed FSS embedded a chip resistor on the side walls of each reflector for indoor WCDMA repeater antennas and aligning them along with the cross-polarization of each antenna, the isolation is improved by about 13 dB at the WCDMA band.</P>
Lee, Hyunwoo,Kim, Sunho,Jung, Seungho,Jo, Jonggab,Lee, Hyunyoung,Hwang, Yongseok,Lee, Byungje Elsevier 2018 Fusion engineering and design Vol.136 No.2
<P><B>Abstract</B></P> <P>An antenna using the fast wave in the lower hybrid-resonance frequency range is proposed for the significant attainment of the heating and current-drive efficiencies. For the operational stability regarding the change of the plasma load, the proposed antenna is designed as the combline-structure traveling-wave antenna. It consists of two tapered coaxial cables, two exciting straps of the folded-monopole structure, 12 radiating straps, 11 field isolators, and the Faraday shield. Regarding the vacuum load, the simulated and measured results show the wide impedance bandwidth (45 MHz, VSWR < 2) of the proposed antenna in conjunction with the traveling-wave-antenna structure and the folded-monopole exciting strap. Regarding the plasma load, the simulated results show that the proposed antenna provides the impedance bandwidth (35 MHz, VSWR < 2), and the fast wave is coupled with an input power from 51.5 − 90%. The measured and simulated coupling efficiencies are highly compatible in the Versatile Experiment Spherical Torus (VEST). According to the frequency-range changes, the simulated-variable range of the parallel refractive index (n<SUB>||</SUB>) is from 3 − 4.5 in the operational frequency band of 475–510 MHz.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The development of an efficient external-current-drive device is required. </LI> <LI> The Lower Hybrid Fast Wave can propagate into central region in higher-density plasma. </LI> <LI> The combline-type traveling-wave antenna (TWA) is proposed for the heating and current-drive efficiencies. </LI> <LI> The coupling research between the antenna and simulated plasma model is carried out. </LI> <LI> The simulation and experiment results are compared regarding the coupling efficiency. </LI> </UL> </P>
The Application of Wavelets to Measured Equation of Invariance
Byungje Lee,Youngki Cho,Jaemin Lee 한국정보과학회 1998 Journal of Electrical Engineering and Information Vol.3 No.3
The measured equation of invariance (MEI) method was introduced as a way to determine the electromagnetic fields scattered from discrete objects. Unlike more traditional numerical methods, MEI method gives local equations and sparse matrices. Therefore, the savings in storage and computing time by the MEI method over conventional methods are very substantial. In this work, Haar wavelets are applied to the measured equation of invariance (MEI) to solve two-dimensional scattering problem. We refer to "MEI method with wavelets" as "Wavelet MEI method." The proposed method leads to a significant saving in the CPU time compared to the MEI method that does not use wavelets as metrons. The results presented in this work promise that the Wavelet MEI method can give an accurate result quickly. We believe it is the first time that wavelets have been applied in conjunction with the MEI method to solve this scattering problem.
Characteristics of the Microstrip Antenna on a Biased Ferrite Substrate
Lee, Byungje 광운대학교 신기술연구소 1999 신기술연구소논문집 Vol.28 No.-
페라이트 기판으로 만들어진 마이크로스트립 안테나의 입력 임피던스 특성을 연구하였다. 입력 임피던스는 페라이트 기판으로부터 그린함수를 구한 다음 모멘트 방법을 사용해서 구할 수 있다. 바이어스제의 강도를 변화시키면서 마이크로스트립 안테나의 공진 주파수의 추이를 관찰하였다. 바이어스된 마이크로스트립 안테나의 레이더 단면적 에 대한 연구도 집중적으로 진행되었다. 본 논문에서 인가된 바이어스제의 방향은 페라이트 판과 수직일 경우와 평행할 경우이다. The characteristics of input impedance for a single microstrip fatch antenna on a biased ferrite substrate is studied. The input impedance is calculated by Method of Moments(MoM) where Green's function is formulated for ferrite substrate. The variation in resonant frequencies due to the changes in biasing strength is studied. The radar cross section(RCS) of a biased ferrite microstrip antenna was also an important part of this work. The biasing direction is normal(z) or in-plane(y) to the grounded ferrite substrate. The results come from the full-wave analysis by a computer simulation.
On some properties of vague bi-groups and fuzzy bi-functions
장이채(Lee-Chae Jang),김태균(Taekyun Kim),이병제(Byungje Lee),김원주(Won-Joo Kim) 한국지능시스템학회 2010 한국지능시스템학회논문지 Vol.20 No.3
M. Demirci[Vague groups, J. math. Anal. Appl. vol.230, pp. 142-156, 1999] studied the vague group operation on a crisp set as a fuzzy function and estabished the vague group structure on a crisp set. In this paper we consider bi-groups which are studied by A.A.A. Agboola and L.S. Akinola. And we also will define vague bi-groups and fuzzy bi-functions and we investigate some basic operations on the vague bi-group and fuzzy bi-functions.