• Proceedings of the KOSOMBE Conference
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• v.1997 no.11
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• pp.291-293
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• 1997

A new quadrature RF coil is designed for Breast MR Imaging. Quadrature RF coils for MRI have been useful to improve the signal-to-noise ratio (SNR) by "$\sqrt{2}$" using two orthogonal RF coils in combination. A modified Breast Quadrature coil is designed. It is a modified type of the high-pass birdcage coil. To reduce the field distortion, by using current feeding, the field pattern is optimized to achieve a quadrature circularly-polarized field pattern. The coil has been implemented for receive-only mode, and tested by phantom imaging. The experimental results show the utility of the proposed RF coil.

• Current Optics and Photonics
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• v.1 no.4
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• pp.396-401
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• 2017

In this article, we proposed hybrid polarization singularity configurations, based on the superposition of two orthogonal circularly polarized components, one of which is a light beam with two optical vortices. The topological configurations are the hybridization of lowest-order polarization singularities, but are different from high-order polarization singularities. Our numerical simulation may provide a theoretical basis for expanding the variety of polarization singularity configuration.

• ETRI Journal
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• v.32 no.3
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• pp.468-471
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• 2010

A compact square patch antenna with reconfigurable circular polarization (CP) at 2.4 GHz is proposed. Circular polarization is generated by an arc-shaped slot on the ground plane. In order to switch the CP orientation, the current flow direction of the patch is reconfigured via the PIN diodes mounted on the slot. As the slot and bias circuit are not placed on the patch side, the proposed antenna radiates a CP wave without alteration in the main beam direction. From the experimental results, the impedance and CP bandwidths of the proposed antenna have been demonstrated for up to 80 MHz and 25 MHz, respectively.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.9 no.3
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• pp.338-346
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• 1998

In-Building communication network is realized by spherical reflector installed on the ceiling and a pair of circularly polarized antennas. Before realizing the system, the scattering characteristics of a spherical conductor is computed and experimented. In this paper, the computational results using vector spherical wave equation and experimental results of the scattering characteristics of a spherical conductor are dicussed. From the results, the omnidirectional scattering level is confirmed and polarity difference over 13 dB is ensured in light region. With the base on omnidirectional scattering pattern of spherical conductor in light region, spherical reflector is effectable in as Wireless In-Building communication network.

• Journal of electromagnetic engineering and science
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• v.6 no.1
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• pp.24-29
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• 2006

In this paper, we analyzed new two-branch polarization diversity at the receiving end of a mobile link which a transmitter emits circularly polarized wave. To analyze the correlation coefficient considered by XPD(Cross Polarization Discrimination) between the two received signals, a simple theoretical model of circular polarization diversity is adopted and experimental measurements are also conducted. From both theoretical and measurement results, it can be seen that the proposed circular polarization diversity scheme is more effective than that of the conventional linear polarization diversity.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.4 no.1
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• pp.59-65
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• 2000

This paper describes the characteristics of a one dimensional narrow-wall slotted waveguide array with a single-layer linear-to-circular polarization converter consisting of a dipole array. An external boundary value Problem of one slot and three dipoles, which approximates the mutual coupling between the dipole array and an edge slot extending over three faces of a rectangular waveguide, is formulated and analyzed by the method of moments; design of polarization conversion is conducted for this model as a unit element. If every unit element has perfect circular polarization, grating lobes appear in the array pattern due to the alternating slot angle: these are suppressed in this paper by changing the dipole angle and degrading the axial ratio of the unit element. The validity of the design is confirmed by the measurements. The dipole array has negligible effects upon slot impedance; the polarization conversion for existing narrow-wall slotted arrays is realized by add-on dipole array.

• Proceedings of the KIEE Conference
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• 2003.07c
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• pp.1623-1625
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• 2003

마이크로과 방전 무전극 황전등은 마그네트온에서 발생된 마이크로파로 2-원자 황을 여기하여 방출되는 빛을 조명에 사용하는 차세대 조명기구이다. 1990년대 초반에 미국의 Fusion Lighting Inc에 의해 최초로 소개된 무전극 황전등은 방전구 회전에 의한 방전을 하였다. 기존의 방전기술은 선형편파를 이용, 필드가 중앙에 모이므로 램프를 회전시켜 방전을 유지하였다. 그에 따라 시스템 구성이 복잡해지고 램프회전 속도에 따라 방전에 영향을 주었다. 본 논문에서는 원편파를 이용하여 램프 회전에 따른 문제점을 해결하고, 원편파에 의해 발생된 회전 플라즈마 방전현상을 실험적으로 보인다. 또한 원편파 방전에 의판 분광분포 및 휘도 분석등 방전 현상을 관찰했다. 아울러 연색성이 80이상, 색온도 4900k ${\sim}$ 6827k 범위를 보였다.

• Proceedings of the KIEE Conference
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• 2003.07c
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• pp.1864-1866
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• 2003

최근 마이크로파 방전에 의한 고압 2-원자 분자인 InBr중기는 고연색성(high color rendering index, CRI)의 백색광 발광원으로 주목 받고 있다. 잘알려진 무전극 황전등은 최고 효율이 173 lm/W까지 시연되어 알려진 모든 인조 광원 중에서 가장 높은 효율을 보인 혁신적인 광원이다. 이에 비해 InBr방전등은 무전극 황전등에 비해 효율은 떨어지지만 거의 완벽한 CRI(95이상)를 보이기 때문에 차세대 projection display의 발광원으로 대두되고 있다. 본 논문에서는 원편파 마이크로파 이용하여 무전극 InBr방전등의 입력전력의 변화와 InBr의 양 변화에 대한 특성(휘도, 상관색온도, 스펙트럼, 등)에 관한 실험결과를 보고한다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.1
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• pp.85-91
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• 2010

In this paper, a new microstrip antenna using asymmetric U-shaped slotted ground is proposed for a switchable circular polarization sense. The proposed antenna is achieved a circularly polarization from orthogonal E-field distributions with 90 degree phase difference due to the asymmetrical U-shaped slot. Moreover, the circular polarization sense of the proposed antenna can be easily switchable with changing the symmetric plane of the U-shaped slots. As a result, the proposed antenna is implemented by two PIN diodes with two different bias condition for ON/OFF states. The measured axial ratios are about 1.5 dB without the dependence of the polarization sense and 3-dB axial ratio bandwidth are achieved 29 MHz with respect to about 1.2 % at 2.46 GHz operating frequency.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.46 no.7
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• pp.52-60
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• 2009

In this pater, a CP-DRA(Circularly Polarized Dielectric Resonator Antenna) using cross-slot-feed is studied to enhance the gain and axial ratio bandwidth. First, a single layer CP-DRA is studied as a reference for comparison. Then a new type of multilayer CP-DRA is proposed to enhance the gain and axial ratio bandwidth. In consideration of the antenna gain enhancement, the spacing between the elements of the multilayer CP-DRA is examined through analysis of the radiation performance of a 2$\times$2 planar amy of DRAs with a spacing of 0.7$\lambda_0$ and 1.2$\lambda_0$ using CST Microwave Studio. The measured result shows that the gain and bandwidth of the multilayer structure is approximately twice that of the single layer one. In the case of the array antenna in which the spacing between multilayer CP-DRA element is 1.2$\lambda_0$, a grating lobe is reduced, in contrast to what we can expect from a conventional antenna array. The gain is 13.4dBi and axial ratio bandwidth is 0.8GHz.