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Optimum Array Configuration to Improve Null Steering Time for Mobile CRPA Systems
Hosung Choo,Seung Mo Seo,Jong-Chul Hyun,Gangil Byun 한국전자파학회JEES 2016 Journal of Electromagnetic Engineering and Science Vol.16 No.2
This paper proposes an optimum array configuration to improve null steering time for mobile controlled reception pattern antenna (CRPA) systems. The proposed array consists of a single reference element at the center and nine auxiliary elements arranged in a circular array. The array radius and the vertical positions of the center element are optimized using a genetic algorithm in conjunction with a constrained least-mean-square algorithm. The results demonstrate that the proposed array is suitable for mobile CRPA systems without significant side nulls in satellite directions.
Design of a Small Array Antenna with an Extended Cavity Structure for Wireless Power Transmission
Hosung Choo,Jun Hur 한국전자파학회JEES 2020 Journal of Electromagnetic Engineering and Science Vol.20 No.1
This paper proposes a design of a small array antenna with an extended cavity structure for wireless power transmission. The proposed array element consists of a square radiating loop, which is designed to resonate at 5.8 GHz, and an extended cavity structure to reduce the mutual coupling between adjacent elements. We derive the optimal element number in a limited space by considering the input power for each element, fabrication cost, and aperture efficiency of the system. To verify the suitability of the proposed a small array with an extended cavity structure, a 2 × 2 downscaled array antenna is fabricated and measured in a full anechoic chamber. The results confirm that the proposed antenna element with an extended cavity structure is suitable for wireless power transmission systems; the proposed array has a transmission efficiency of about 1% at a distance of 2 m when the array is applied to both transmitting and receiving antennas.
CHOO, Jaeyul,CHO, Chihyun,CHOO, Hosung 'Institute of Electronics, Information and Communi 2014 IEICE TRANSACTIONS ON COMMUNICATIONS - Vol.eb97 No.5
<P>This paper designs tag antennas to satisfy three key goals: mounting on very small objects, extending the reading range with planar structures, and maintaining stable performance on various materials. First, the size of the tag is reduced up to 17% compared to the half-wavelength dipole without a large reduction in bandwidth and efficiency by introducing an inductively coupled feed structure. Second, the reading range is increased to 1.68 times that of the reference dipole tags while maintaining the planar structure using circular polarization characteristics. Finally, a stable reading range is achieved with a deviation in the reading range of only 30% of that of commercial tags on various objects by employing the capacitively-loaded and T-matching network.</P>
Jaeyul Choo,Jeongki Ryoo,Hosung Choo 한국전자파학회JEES 2011 Journal of Electromagnetic Engineering and Science Vol.11 No.1
In this letter, we propose a novel tag antenna that has low performance degradation with nearby dielectric material. We obtained a stable reading performance and a broad matching bandwidth on nearby dielectric materials by employing a T-matching network with thick line width and capacitively slot-loaded arms. We then built the proposed antenna and measured the tag sensitivity to examine the reading characteristics with nearby dielectric materials. The measured results clearly demonstrate stable tag sensitivity with various nearby dielectric materials, such as foam, acrylic-plastic, glass, and ceramic plates. To more closely observe the antenna characteristics with nearby dielectric materials, we also examined the impedance variation and surface current distribution with respect to the dielectric constant of nearby target objects, which ranged from 1×ε? to 16×ε?.
Design of vertical lines for vehicle rear window antennas
Kang, Woojoon,Choo, Hosung Wiley Subscription Services, Inc., A Wiley Company 2010 MICROWAVE AND OPTICAL TECHNOLOGY LETTERS Vol.52 No.6
<P>In this article, we propose the design of a rear on-glass antenna for a commercial sedan. We focus on optimizing the vertical lines of the antenna and propose the optimum design parameters to maximize the matching bandwidth and improve the average vertical gain for the entire FM radio band. The detailed design parameters are determined using the Pareto genetic algorithm with an EM simulation tool. The optimized rear on-glass antenna was built and installed on a commercial sedan. The measurement results showed a matching bandwidth of about 15%, an average bore-sight gain of about −2.86 dBi in the entire FM band, and an average gain of about −14 dBi along the azimuth direction. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1445–1449, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25184</P>
Jun Hur,Hosung Choo,Jong-Eon Park 대한전기학회 2018 Journal of Electrical Engineering & Technology Vol.13 No.4
Eigenvalue distributions for a periodic metal-insulator-metal waveguide, classified into the point spectrum and the discretized continuous spectrum (DCS), are investigated as functions of frequencies, gap widths, and periods. Muller’s method is suggested for solving exact eigenvalues, and we propose the scheme for finding proper initial values in the Muller’s method by considering only Re(εr) in the dispersion equation. We then find that anti-crossing behavior, repulsive effect between the point spectrum and the DCS, becomes stronger when the real parts of the roots in the point spectrum have smaller values. Finally, we examine the transmittances of a single subwavelength slit for real metals using the mode matching technique. The transmittances in real metals similarly follow those of the perfect electric conductor (PEC) at low frequencies, while the patterns at higher frequencies begin to differ from the PEC.
Hur, Jun,Choo, Hosung,Park, Jong-Eon The Korean Institute of Electrical Engineers 2018 Journal of Electrical Engineering & Technology Vol.13 No.4
Eigenvalue distributions for a periodic metal-insulator-metal waveguide, classified into the point spectrum and the discretized continuous spectrum (DCS), are investigated as functions of frequencies, gap widths, and periods. Muller's method is suggested for solving exact eigenvalues, and we propose the scheme for finding proper initial values in the Muller's method by considering only ${\Re}e({\varepsilon}_r)$ in the dispersion equation. We then find that anti-crossing behavior, repulsive effect between the point spectrum and the DCS, becomes stronger when the real parts of the roots in the point spectrum have smaller values. Finally, we examine the transmittances of a single subwavelength slit for real metals using the mode matching technique. The transmittances in real metals similarly follow those of the perfect electric conductor (PEC) at low frequencies, while the patterns at higher frequencies begin to differ from the PEC.
Optimum Placement of DF Antenna Elements for Accurate DOA Estimation in a Harsh Platform Environment
Byun, Gangil,Hosung Choo,Hao Ling IEEE 2013 IEEE transactions on antennas and propagation Vol.61 No.9
<P>This paper presents a systematic approach to the optimum placement of direction finding (DF) antennas in a harsh platform environment. A circular array with omni-directional elements is considered for azimuthal direction of arrival (DOA) estimation based on the multiple signal classification (MUSIC) algorithm. The element positions are optimized by the use of a genetic algorithm (GA) in conjunction with the FEKO electromagnetic simulator. The proposed approach is first tested with a generic platform shape. It is then extended to a more realistic military aircraft model with a strong scattering object. The optimized results show a significant performance improvement over the uniform circular array in both platform environments.</P>
Antenna polarisation adjustment for microstrip patch antennas using parasitic elements
Gangil Byun,Hosung Choo IET 2015 Electronics letters Vol.51 No.14
<P>A novel and simple approach to adjust the polarisation properties of a microstrip patch antenna in the entire axial ratio (AR) range is proposed. The proposed antenna consists of a radiating patch and a parasitic strip separated into two parts, and the separated strip is placed at the outer perimeter of the patch for capacitive coupling. This structure enables the antenna to induce opposite-direction currents on the strip, which allows flexible polarisation adjustment by moving the separated positions of the strip. For evaluation, two antennas with linear and circular polarisations are fabricated, and their performance is measured in a full anechoic chamber. The results prove that the proposed approach is suitable for flexible AR adjustment without a significant degradation of the matching characteristics and the design complexity.</P>
The Effects of Substrate, Metal-line, and Surface Material on the Performance of RFID Tag Antenna
Chihyun Cho,Hosung Choo,Ikmo Park 한국전자파학회JEES 2007 Journal of Electromagnetic Engineering and Science Vol.7 No.1
We investigated the effects of substrate, metal-line, and surface material on the performance of radio frequency identification (RFID) tag antenna using a tag antenna with a meander line radiator and T-matching network. The results showed that readability of the tag antenna with a thin high-loss substrate could be increased so that it was similar to that of a low-loss substrate if the substrate was very thin. The readability of the tag antenna decreased significantly when the metal line was thinner than the skin depth. The readability of the tag also decreased drastically when the tag was attached to high-permittivity high-loss target objects.