• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.6
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• pp.610-616
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• 2010

In this paper, particle swarm optimization(PSO) is applied for the design of frequency selective surface based artificial magnetic conductor. An equivalent circuit model for this artificial magnetic conductor(AMC) with Jerusalem Cross arrays was derived and then PSO was applied for obtaining the optimized geometrical parameters with desired resonant frequency. The resonant frequency and the reflection phase characteristics from the optimization were compared to the results from commercial software for verifying the validity of this paper. The procedure presented in this paper can be applied to design the AMC with different frequency selective surface and also can be used for the design of microwave circuits like the AMC ground planes.

• Journal of the Korean Magnetics Society
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• v.25 no.1
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• pp.22-26
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• 2015

In this paper, a magneto-inductive wave generated in a chain of LC resonators fabricated with Ni-Zn ferrite cores and chip capacitors is presented. RF signal propagates to neighbor resonator one by one as a consequence of the magnetical coupling between two resonators in the device. The magnetical coupling is due to the mutual inductances along the chain of resonators. So, the signal amplitude (${\approx}$ coupling intensity) is dependent of the mutual inductance which can be adjusted by applied magnetic field. In order to demonstrate the device, some experiments have been carried out systemically. The transmission characteristics of a magneto-inductive wave could be controlled by applied external magnetic field. The device composed of 5 resonators; the center frequencies were estimated to be 32 MHz and 38 MHz with the external magnetic flux density of 75 Oe and 222 Oe, respectively. We expect that the reported results could open a promising way to a high variety of applications in one- and two-dimensional functional devices, such as transducers, delay lines, power dividers and couplers.

• Proceedings of the KIPE Conference
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• 2012.07a
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• pp.623-624
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• 2012

공진기 공진주파수와 인버터 스위칭 주파수를 최적화하는 이론에 대해 설명한다. 제안된 방법론을 이용하여 1차측 끼리 혹은 2차측 끼리 자기적으로 결합된 경우의 주파수 조절에 대해 설명한다.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.29 no.12
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• pp.992-995
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• 2018

The wireless charging of body-embedded medical instruments and wireless power transfer to various inside dielectric-materials is still a future technology that has not yet been achieved. This paper proposes methods for controlling the capacitance of the resonators and installing air pockets on the top and bottom sides of the resonators for optimal design, which considered efficiency and resonant frequency in accordance with the electromagnetic characteristics of the dielectric medium. In future, the results of this research will be utilized as the basic research data to design and restore resonant frequency of resonators embedded in various dielectric environments.

• Journal of the Korean Magnetics Society
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• v.14 no.1
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• pp.1-6
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• 2004

To construct the non-contact temperature detection systems, LC resonance type sensors composed of temperature sensitive ferrite inductors and capacitors were used, and their wireless temperature detection performances were investigated. The temperature was wirelessly detectable using the fabricated LC resonance sensors with a transmitter and receiver, because their inductances and resonance frequencies were changed according to the temperature dependance of permeability of the ferrites. The sensitivity of the system was decreased with the distance i between transmitter and receiver as a ratio of the l$^6$.

• Korean Journal of Optics and Photonics
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• v.2 no.4
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• pp.197-202
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• 1991

The real time autocorrelator has been developed in order to measure the pulse widths of ultrashort laser pulses using the SHG method. The scanning range of the autocorrelator is 142 ps, and inserting a delay block in one arm of the autocorrelator, the scanning range can be extended to 250 ps. The shortest pulse width was measured to be 20 ps, when the cavity length was well matched to the RF frequency of the mode-locker, and broadened to be 39 ps and 47 ps as the cavity length was detuned.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.1561-1562
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• 2015

본 논문에서는 자기공명 방식 무선전력전송 시스템의 공진기 재질에 따른 전송 특성을 분석하였다. 12.74MHz의 공진 주파수를 갖는 무선전력전송 시스템을 구현하여 공진 코일에 초전도 코일을 적용하였으며, 비교를 위해 구리를 이용한 공진 코일을 제작하였다. 이 때 network analyzer를 이용하여 S-parameter $S_{11}$을 측정하였다. 실험결과, 초전도 공진 코일을 적용하였을 때 구리코일보다 반사계수가 높은 것을 확인할 수 있었다.

• Proceedings of the KIPE Conference
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• 2012.07a
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• pp.627-628
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• 2012

기존 자기공진형태에서 사용되는 루프 형태의 코일 대신에 코어를 사용한 다이폴 형태의 코일을 1차 측과 2차 측에 사용해 코일의 부피를 줄이 면서도 먼 거리까지 자기장을 보낼 수 있는 자기유도방식의 무선 전력 시스템을 구성 하였다. 각 코일에 사용된 코어의 형상은 코어 내부에서 자기장이 균일하게 분포 될 수 있도록 최적화 되었으며 5m 거리에서 209W의 전력을 전달하고, 최대 16%의 효율을 달성 하였다.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.27 no.2
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• pp.163-169
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• 2016

In this paper, we miniaturized the loop and coil in magnetic resonance wireless power transfer(MR-WPT) system for application to the small mobile device. The proposed disk type double coil resonator was designed to cause resonance at 6.87 MHz. It is composed of thin copper on both-side of acrylic substrate structured 2 mm width, 1 mm pitch and 8 turns. The outer radius of spiral coil pattern is 9 cm. And the proposed loop was made of the copper wire 5 mm diameter of cross-section. The size of loop is 10 cm diameter. For resonance at 6.87 MHz, the capacitor with 3,300 pF was connected in series on the loop. We rearranged the resonators and organized several WPT systems which is rearranged by resonators. The highest transfer efficiency of miniaturized WPT system was 35.67 %. This proposed design of spiral double coil will contribute to make resonator smaller for appling small and thin mobile device.

• Journal of the Korean Magnetics Society
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• v.20 no.6
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• pp.228-233
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• 2010

The microwave permeability was measured in order to analyze the thickness dependence of loss properties in CoFeHfO thin films with varying thickness of t = 57~1368 nm. A single resonance peak (P1) at 2.95 GHz was appeared in the samples with thickness less than 405 nm, while second resonance peak (P2) at 547MHz was additionally appeared in the samples with thickness greater than 405 nm. The P2 was originated by the angle distribution of the easy axis, which was confirmed from the measured results of the change of imaginary permeability with applied magnetic field in the sample of 1368 nm thickness and low field torque curves. If the second peaks can be reduced by minimizing the angle distribution of the easy axis, the CoFeHfO thin films with thickness greater than 400 nm can be used for the compact microwave devices operated at up to 2 GHz ranges.