• 대한화학회지
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• 제36권2호
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• pp.329-334
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• 1992

단백질 수용액 중의 초음파흡수 mechanism을 규명하기 위하여 pH 7의 소혈청 albumin(BSA)수용액의 초음파흡수 측정을 주파수 100 kHz에서 1600 MHz에 걸쳐 행하였다. 측정방법은 plano-concave 공명법(0.1${\sim}$10 MHz)과 고분해능 Bragg 반사법(120${\sim}$1600 MHz)을 사용하였다. pH7에서의 초음파흡수스펙트럼은 Davidson-Cole 분포식의 거울상인 분포함수를 사용한 완화곡선과 일치하였다. 이 완화현상을 BSA 분자의 수화평행에 의한 것으로 해석하였다.

• 한국자기학회지
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• 제11권3호
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• pp.109-113
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• 2001

Presently, an inductor adapted at MMIC (Monolithic Microwave Integrated Circuit) which is used for cellular phone or PHS operates at quasi-microwave range over 800 MHz. However, a W-CDMA (Wideband Code Division Multiple Access) will use about 2 GHz range. Therefore magnetic film device should be compatible up to 2 GHz. We have deposited Co-Pd-Al-O system film using rf sputtering method which is expected up to 2 GHz, and investigated the effect of Pd content and magnetic field annealing. When Pd composition is 19%, Hk was 118 Oe, and ${\mu}$′showed flat frequency characteristics up to 1.5 GHz. The Q factor (=${\mu}$′/${\mu}$") was 23.3 at 1 GHz, 6.7 at 1.5 GHz and 1.5 at 2 GHz, respectively. Resonance frequency was 2 GHz. Therefore Co-Pd-Al-O thin film could be used at over 1 GHz, and also expected as an inductor material for wide band CDMA type cellular phone.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2003년도 하계종합학술대회 논문집 I
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• pp.629-632
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• 2003

This paper has been studied analysis and design of microstrip Rotman lens operating over wide band and wide steering angle by the contour integral method along with the segmentation method. All mutual coupling, internal reflections between ports with exponential taper are taken into account. Equally spaced ports are designed and realized which gives less amplitude ripple at array ports. The measured results of 12 input and 12 output lens show $\pm$1.8 dB insertion loss deviation over 6~18GHz wide frequency range and beam steering accuracy less than 1$^{\circ}$ over $\pm$53$^{\circ}$ angle and agrees well with the analysis results.

• KIEE International Transactions on Electrophysics and Applications
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• 제3C권5호
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• pp.194-198
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• 2003

A wide-band E-plane notch phased array antenna having bandwidths of 3:1 and a scan volume of $\pm$ 45 is designed considering the active element pattern (AEP) with analysis of the full structure of E-plane notch phased array antenna. Using the numerical E-plane waveguide simulator as an infinite linear array in the broadside angle, the active reflection coefficient (ARC) of the unit element is optimized in the design frequency range. To evaluate the convergence of the AEP, the simulation of full array as changing the number array is investigated, and the minimum numbers of array that have characteristics similar to the AEP of an infinite array are determined.

• Journal of electromagnetic engineering and science
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• 제9권1호
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• pp.25-31
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• 2009

This paper describes CMOS VCO circuit design procedures and techniques for multi-band/multi-standard RF transceivers. The proposed techniques enable a 4 GHz CMOS VCO to satisfy all requirements for Quad-band GSMIEDGE and WCDMA standards by achieving a good trade-off among important specifications, phase noise, power consumption, modulation performance, and chip area efficiency. To meet the very stringent GSM T/Rx phase noise and wide frequency range specifications, the VCO utilizes bond-wire inductors with high-quality factor, an 8-bit coarse tune capbank for low VCO gain(30$\sim$50 MHz/V) and an on-chip $2^{nd}$ harmonic noise filter. The proposed VCO is implemented in $0.13{\mu}m$ CMOS technology. The measured tuning range is about 34 %(3.17 to 4.49 GHz). The VCO exhibits a phase noise of -123 dBc/Hz at 400 kHz offset and -145 dBc/Hz at 3 MHz offset from a 900 MHz carrier after LO chain. The calculated figure of merit(FOM) is -183.5 dBc/Hz at 3 MHz offset. This fully integrated VCO occupies $0.45{\times}0.9\;mm^2$.

• 한국산업융합학회 논문집
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• 제22권5호
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• pp.491-497
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• 2019

Dissimilar friction welding were produced using 15 mm diameter solid bar in superalloy(Alloy718) to chrome molybdenum steel(SCM440) to investigate their mechanical properties. Consequently, optimal welding conditions were n=2000 rpm, HP=60 MPa, UP=120 MPa, HT=10 sec and UT=10 sec when the metal loss(Mo) is 3.5 mm. Acoustic Emission(AE) technique was applied to analyze the dissimilar friction welding of Alloy718 and SCM440. The relationship between the AE parameters and dissimilar friction welding of both material was discussed. In the case of heating time of 6 sec, 10 sec, 14 sec and 20 sec, 5 AE events per 0.5 seconds and energy about $2.7{\times}10^{10}$ were exhibited in heating time. In upsetting time, resulting in various numbers of events per second and very low energy. The frequency range of the signal generated during the heating time was about 200 kHz. However, the upsetting time resulted in a wide range of signals from very low frequency to high frequency of 500 kHz due to rapid plasticity of the material.

• 전력전자학회논문지
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• 제14권2호
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• pp.168-175
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• 2009

본 논문은 에어포일 베어링을 적용한 45,000[rpm]/22[kW]급 초고속 영구자석형 동기전동기의 센서리스 제어을 위한 개선된 알고리즘을 제안한다. 에어포일 베어링이 적용된 전동기를 정지상태에서 초기 기동시 부터 고속영역까지 전 속도 영역에 걸쳐 센서리스 알고리즘을 구현하기 위하여 반복 적응자속관측기를 제안하여 회전자의 회전각 및 속도를 실시간으로 추정하여 센서리스 제어 알고리즘을 구현하였다. 기존 적응자속관측기의 주파수 응답특성을 개선하고 넓은 속도 범위에서 안정된 응답을 얻기 위하여 속도에 따른 회전자의 추정 위치각과 실제 회전각과의 오차를 시뮬레이션을 통하여 분석한 후 안정된 위상지연 특성을 나타내는 반복 횟수를 얻고 전류제어 주기 내에서 관측기를 반복 수행하여 적응자속관측기의 동특성 성능을 개선하는 알고리즘을 제안하였다. 또한 제안된 반복 적응 자속관측기를 적용한 센서리스 알고리즘의 타당성을 입증하기 위하여 실험을 통하여 검증하였다.

• 대한전자공학회논문지SD
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• 제40권6호
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• pp.408-420
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• 2003

이 논문에서는 1) 넓은 잠금 범위를 위한 이중 루프 동작과 2) 차세대 패키지 스큐 개선에 대한 전압 발생기와 안티퓨즈 회로를 사용한 프로그래머블 레프리카 딜레이, 두 가지 이점을 갖는 Delay Lock Loop(DLL)을 기술하였다. 이중 루프 동작은 차동 내부 루프 중 하나를 선택하기 위해 외부 클럭과 내부 클럭 사이의 초기 시간차에 대한 정보를 사용한다. 이를 이용하여 더 낮은 주파수로 DLL의 잠금 범위를 증가시킨다. 덧붙여서, 전압발생기와 안티퓨즈 회로를 사용한 프로그래머블 레프리카 딜레이의 결합은 패키지 공정 후에 온-오프 칩 변화로부터 발생하는 외부 클럭과 내부 클럭 사이에 스큐 제거를 해준다. 제안된 DLL은 0.16um 공정으로 제조되었고, 2.3v의 전원 공급과 42㎒ - 400㎒의 넓은 범위에서 동작한다. 측정된 결과는 43psec p-p 지터와 400㎒에서 52㎽를 소비하는 4.71psec 실효치(rms)지터를 보여준다.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• 제5B권2호
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• pp.181-188
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• 2005

In this paper, a DC smoothing filterless soft switching pulse modulated high frequency AC power conversion circuit connected to utility. frequency AC power source is proposed for consumer induction heating hot water producer, steamer and super heated steamer. The operating principle of DC link filterless utility frequency AC-high frequency AC (HF AC) power conversion circuit defined as high frequency cycloinverter is described, which can operate under a principle of ZVS/AVT and power regulation based on alternate asymmetrical PWM in synchronization with the utility frequency single phase AC positive or negative half wave voltage. The dual mode modulation control scheme based on high frequency PWM and commercial frequency AC voltage PDM for the proposed high frequency cycloinverter are discussed to enlarge its soft switching commutation operating range for wide HF AC power regulation. This high frequency cycloinverter is developed for high frequency IH Dual Packs Heater (DPH) type boiler used in consumer and industrial fluid pipeline systems. Based on the experiment and simulation results, this high frequency cycloinverter is proved to be suitable for the consumer use IH-DPH boiler and hot water producers. The cycloinverter power regulation and power conversion efficiency characteristics are evaluated and discussed.

• 대한금속재료학회지
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• 제49권4호
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• pp.329-333
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• 2011

To develop wide-band noise absorbers with a special design for low-frequency performance, this study proposes a tin oxide (Sn-O) thin films as the noise absorbing materials in a microstrip line. Sn-O thin films were deposited on polyimide film substrates by reactive sputtering of the Sn target under flowing $O_{2}$ gas, exhibiting a wide variation of surface resistance (in the range of $10^{0}-10^{5}{\Omega}$) depending on the oxygen partial pressure during deposition. The microstrip line with characteristic impedance of $50\Omega$ was used for the measurement of noise absorption by the Sn-O films. The reflection parameter $(S_{11})$ increased with a decrease of surface resistance due to an impedance mismatch at the boundary between the film and the microstrip line. Meanwhile, the transmission parameter $(S_{21})$ diminished with a decrease of surface resistance resulting from an Ohmic loss of the Sn-O films. The maximum noise absorption predicted at an optimum surface resistance of the Sn-O films was about $150{\Omega}$. For this film, greater power absorption is predicted in the lower frequency region (about 70% at 1 GHz) than in conventional magnetic sheets of high magnetic loss, indicating that Ohmic loss is the predominant loss parameter for the conduction noise absorption in the low frequency band.