• Journal of the Korean Institute of Telematics and Electronics A
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• v.28A no.11
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• pp.866-873
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• 1991

In this paper the electric and magnetic field distributions in a TEM cell used for EMC testing are analyzed numerically. The fields are distorted with the increase of frequency. These distortions are due to higher order modes and resonances and cause the bandwidthe limitations in the uae of TEM cels. The upper frequency is lower modes however, are reflected at some points through the tapered ends of the cell. Higher order modes however, are reflected at some points within the tapered region where it becomes too small to support the modes, The first two TE mode(TE$_{01}$ and TE$_{10}$) cutoff frequencies and the first six TE$_mnp$ resonant ferquencies are identified in a TEM cell (1x0 6x2m,w=0.72m) from field patterns and the results are consistent with others' data. The circumferential wall currents to support resonances are shown. For the large cell it is desired to extend the usable frequency range above the cutoff frequency of the first higher order mode. This study proposes an attempt to expand the frequency bandwidth by a resonance suppression.

• Proceedings of the KIPE Conference
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• 2002.07a
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• pp.228-232
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• 2002

In this paper, In order to solve the problem is proposed using a new type of electronic ballast that the traditional magnetic ballasts operated at 50-60Hz have been suffered from noticeable flicker, high loss, large crest factor and heavy weight which is composed of rectifier, active power corrector, series resonant half bridge inverter, micro-controller and piezoelectric transformer for driving for driving T5 fluorescent lamp were manufactured. The proposed electronic ballast operated at high frequency (about 75kHz) shows a input power factor of more than 0.995, total harmonic distortion of less than $12\%$ and lamp current crest factor of less than 1.5, respectively. Output power and efficiency showed 28w and $85\%$, respectively. Accordingly, it is considered that the ballast using piezoelectric transformer can replace the typical electronic ballast.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.16 no.2 s.107
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• pp.183-189
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• 2006

In mobile phones of multimedia era, microspeakers of high qualify sound are essential parts to generate human voice in speaker phone and MP3 song player. In this paper, two types of microspeakers, outer permanent magnet (PM) and combined PM type, are analyzed using electromagnetic, mechanical and their coupling analysis. For performance comparison, voice coil diameter is chosen as a design parameter to change excitation position and magnet volume for both types. For combined PM type, sound pressure level (SPL) is improved due to increased PM volume compared to outer PM type. Also, with the decreased voice coil diameter for combined PM type, the 1st resonant mode of the diaphragm is more efficiently excited due to concentrative excitation, resulting in lower and broader frequency range. Therefore, it can be said that the combined PM type microspeakers are more advantageous for high performance microspeaker which are essential for multimedia era.

• Nuclear Engineering and Technology
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• v.38 no.4
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• pp.327-342
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• 2006

Radiation therapy is an important part of cancer treatment in which cancer patients are treated using high-energy radiation such as x-rays, gamma rays, electrons, protons, and neutrons. Currently, about half of all cancer patients receive radiation treatment during their whole cancer care process. The goal of radiation therapy is to deliver the necessary radiation dose to cancer cells while minimizing dose to surrounding normal tissues. Success of radiation therapy highly relies on how accurately 1) identifies the target and 2) aim radiation beam to the target. Both tasks are strongly dependent of imaging technology and many imaging modalities have been applied for radiation therapy such as CT (Computed Tomography), MRI (Magnetic Resonant Image), and PET (Positron Emission Tomogaphy). Recently, many researchers have given significant amount of effort to develop and improve imaging techniques for radiation therapy to enhance the overall quality of patient care. For example, advances in medical imaging technology have initiated the development of the state of the art radiation therapy techniques such as intensity modulated radiation therapy (IMRT), gated radiation therapy, tomotherapy, and image guided radiation therapy (IGRT). Capability of determining the local tumor volume and location of the tumor has been significantly improved by applying single or multi-modality imaging fur static or dynamic target. The use of multi-modality imaging provides a more reliable tumor volume, eventually leading to a better definitive local control. Image registration technique is essential to fuse two different image modalities and has been In significant improvement. Imaging equipments and their common applications that are in active use and/or under development in radiation therapy are reviewed.

• Journal of Magnetics
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• v.16 no.2
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• pp.108-113
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• 2011

The electron spin resonance lineshape (ESRLS) function for the electron spin resonance linewidth (ESRLW) of $Cr^{3+}$ (S = 3/2) in ferroelectric lithium niobate single crystals doped with 0.05 wt% of Cr, is obtained by using the projection operator technique (POT), developed by Argyres and Sigel. The ESRLS function is calculated to be axially symmetric about the c - axis and analyzed by using the spin Hamiltonian $H_{SP}={\mu}_B(B{\cdot}{^\leftrightarrow_{g}}{\cdot}S)+S{\cdot}{^\leftrightarrow_{D}}{\cdot}S$ with the parameters g = 1.972 and D = $0.395\;cm^{-1}$. In the ca plane, the linewidths show a strong angular dependence, whereas in the ab plane, they are independent of the angle. This result implies that the resonance center has an axial symmetry along the c - axis. Further, from the temperature dependence of the linewidths that is shown, it can be seen that the linewidths increase as the temperature increases, at a frequency of v = 9.27GHz. This result implies that the scattering effect increases with increasing temperature. Thus, the POT is considered to be more convenient to explain the scattering mechanism as in the case of other optical resonant systems.

• Journal of Power Electronics
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• v.16 no.6
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• pp.2202-2211
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• 2016

In certain applications, such as IPT-based EV charger (IPTEC), any variation in alignment and distance between pickup and charger primary leads to a change in leakage and magnetic impedance magnitudes. The power transmission capacity is not always at the maximum level because of these variations. This study proposes a new low-cost tracking method that achieves the Maximum Inductive Power Transmission Capacity (MIPTC). Furthermore, in the proposed method, the exchange of information between load and source is not required. For an application such as IPTEC, the load detected by the IPTEC varies continuously with time because of the change in state of the charge. This load variation causes a significant variation in IPT resonant circuit voltage gain. However, the optimized charging output voltage should be kept constant. From the analysis of the behavior of the IPT circuit at different working frequencies and load conditions, a MIPTC operation point that is independent of load condition can be identified. Finally, the experimental results of a developed prototype IPT circuit test show the performance of the proposed method.

• Journal of the Institute of Electronics and Information Engineers
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• v.53 no.1
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• pp.22-26
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• 2016

In this paper, using the globular structure designed and implemented for the transmitter and the receiver resonant wireless power transfer(WPT). The coil of the transmitter was proposed to emit a magnetic energy in three-dimensional space by winding a ball shape. Each side of the transmitter has been designed to obtain a high Q value by a spiral structure. This solves the problem that the transfer efficiency decreases rapidly depending on the location in the conventional WPT. The resonance frequency is used 6.78 MHz and the distance between the trasnitter and the receiver is 200 mm. The transfer efficiency of the proposed WPT system is higher than 40% at all direction.

• Proceedings of the KIPE Conference
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• 2001.07a
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• pp.584-588
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• 2001

A conventional power supply to drive a microwave oven has ferro-resonant transformer and high voltage Capacitor(HVC). Though it is simple, transformer is bulky, heavy and has low-efficiency. To improve this defect a high frequency inverter type power supply has been investigated and developed in recent years. But, because of additional control circuit and switching device, inverter-type power supply is more expensive than conventional one. In this study, A new pulse power supply for Microwave Oven using novel HVC embedded high frequency transformer is proposed for down-sizing, cost reduction, and efficiency emprovement of Inverter type power supply. Also, equivalent circuit model is derived by impedance measurements. And the operation of proposed pulse power supply is verified by simulations and experimental results.

• Proceedings of the KIPE Conference
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• 2017.07a
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• pp.429-430
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• 2017

본 논문은 Integrated Magnetics(IM)을 적용한 3-레벨 LLC 공진형 컨버터를 제안한다. 제안된 3-레벨 LLC 공진형 컨버터는 스위치 내압이 입력전압의 절반으로 보장되므로 스위칭 손실을 대폭 저감할 수 있어 고주파수 구동에 유리하다. 이에 따라 제안 회로는 리액티브 소자 저감에 유리하나, 회로 동작 상 2개의 공진 인덕터와 1개의 트랜스포머가 요구되는 단점이 있다. 이를 위해 본 논문에서는 자화 인덕터로 공진 인덕터를 대체하는 동시에 모든 자기 소자를 하나로 통합할 수 있는 새로운 IM을 제안하고 그 타당성 검증을 위해 인덕턴스 모델을 통한 이론적 분석과 350W-800kHz급 시작품 제작을 통한 실험결과를 제시한다.

• Proceedings of the KIPE Conference
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• 2017.07a
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• pp.84-85
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• 2017

본 논문은 LLC 공진형 컨버터의 고전력밀도를 위한 IM(Integrated Magnetics)을 제안한다. 일반적으로 컨버터의 전력밀도는 사용되는 변압기, 인덕터와 같은 자기소자에 의해 결정되므로, 평판형 자기소자(Planar Magnetics)는 고 전력밀도화에 매우 적합하다. 하지만 LLC 공진형 컨버터에 평판형 자기소자를 적용할 경우 높은 자기 결합도에 의해 공진을 위한 충분한 누설 인덕턴스를 얻을 수 없다. 따라서 공진동작을 위한 추가적인 인덕터의 사용이 필수적이며, 전력밀도는 감소하게 된다. 반면, 제안방식은 자기소자 내부에 형성되는 두 개의 자화 인덕터를 공진 인덕터로 사용하기 때문에 공진동작에 필요한 누설 인덕터가 필요하지 않다. 또한, 이러한 두 개의 자화 인덕터는 하나의 자기소자에 집적화 할 수 있으므로 고 전력밀도에 유리한 구조를 갖는다. 더불어, 공진동작에 필요한 모든 파마리터가 설계자의 의도대로 설계가능하기 때문에 컨버터 최적설계가 매우 유리하다. 제안방식의 타당성을 확인하기 위하여 자기소자 모델을 통한 효율분석 및 350W-800kHz 시작품에 대한 실험결과를 제시한다.