• JSTS:Journal of Semiconductor Technology and Science
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• 제15권5호
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• pp.504-510
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• 2015

This paper presents a power and area efficient SAR ADC for multi-channel near threshold-voltage (NTV) applications such as neural recording systems. This work proposes a split dual-capacitive-array (S-DCA) structure with shifted input range for ultra low-switching energy and architecture of multi-channel single-ended SAR ADC which employs only one comparator. In addition, the proposed ADC has the same amount of equivalent capacitance at two comparator inputs, which minimizes the kickback noise. Compared with conventional SAR ADC, this work reduces the total capacitance and switching energy by 84.8% and 91.3%, respectively.

• 한국전자파학회논문지
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• 제8권2호
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• pp.107-115
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• 1997

본 논문에서는 23 GHz 국간(Point-to-point) 통신용 Push-Push발진기를 Split Ring 공진기(Split Ring Resonator)를 사용하여 설계, 제작하였다. Split Ring 공진기(SRR)는 둥가회로를 이용한 이론적인 해석 및 MPIE(Mixed Potential Integral Equation)수칙해석 툴을 이용 해석하였다. 이 해석된 결과를 사용하여 전송 모드로 마이크로 스트립 라인과 결합된 SRR를 분석하였다. 제작된 발진기은 23 GHz에서 출력 전력은 4dBm, 기본 주파수 및 3차 고조파 억제는 - 20 dBc, - 34 dBc의 특성과 발진주파수에서 1 MHz offset에서 -109 d dEc/Hz의 SSB위상잡음 및 1.4%의 변환 효율을 나타내었다. 이 실험결과는 이론 및 시뮬레이션 결과와 일치함을 알 수 있다.

• 제어로봇시스템학회논문지
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• 제4권1호
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• pp.45-55
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• 1998

In this paper, a robust path tracker and depth controller of Autonomous Underwater Vehicle based on sliding mode control is presented. We have also designed augmented equivalent control inputs by analyzing the sliding mode with the reaching mode. This can enhance the reaching rate, and improve chattering problems, that is, noise caused by the control plane actuator of the vehicle, which is one of the problems that occur when sliding mode control is used. Also to resolve the steady state error generated in the path tracker under current effect, a modified sliding plane is constructed. Also a redesigned sliding plane and control input using transformation matrix is proposed to do easy design of MIMO depth controller. For state variables that cannot be measured directly, reduced order sliding mode control is used to design an observer. The performance of designed path tracker and depth controller is investigated by computer simulation. The results show that the proposed control system has robust performance to parameter variation, modelling error and disturbance.

• 소음진동
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• 제9권5호
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• pp.1019-1028
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• 1999

Free vibration characteristics of cantilevered laminated composite beams with a transverse non0propagating open carck are investigated. In the present analysis a special ply-angle distribution referred to as asymmetric stiffness configuration inducing the elastic coupling between chord-wise bending and extension is considered. The open crack is modelled as an equivalent rotational spring whose spring constant is calculated on the basis of fracture mechanics of composite material structures. Governing equations of a composite beam with a open crack are derived via Hamilton's Principle and Timoshenko beam theory encompassing transverse shear and rotary inertia effect. the effects of various parameters such as the ply angle, fiber volume fraction, crack depth, crack position and transverse shear on the free vibration characteristics of the beam with a crack is highlighted. The numerical results show that the natural frequencies obtained from Timoshenko beam theory are always lower than those from Euler beam theory. The presence of intrinsic cracks in anisotropic composite beams modifies the flexibility and in turn free vibration characteristics of the structures. It is revealed that non-destructive crack detection is possible by analyzing the free vibration responses of a cracked beam.

• 소음진동
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• 제5권1호
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• pp.107-115
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• 1995

드릴스트링의 종진동 해설을 위한 이론적 모델을 제시하였다. 드릴스트링은 균일봉들로 모델링하였으며, 비트와 바닥 암석과의 경계조건은 스프링과 댐퍼로 모델링하였다. 연결부(tool joint)의 영향, 드릴스트링 주위의 진흙물(mud)과 주변 암석의 영향등은 이론적으로 산정하였다. 비트에서의 경계조건을 산정하기 위하여, 드릴스트링의 종진동에 대한 강제진동 시험기법을 개발하여 실제의 드릴스트링에 대한 실험을 비트에 걸리는 힘(WOB)을 변화시키면서 수행하였다. 그 결과는 이론치 와 잘 일치함을 확인하였다. 본 연구결과 가장 중요한 결론은 드릴스티링의 종진동 해석에 있어서, 바닥 암석의 강성이 고려되어야 하며, 이 강성은 비트에 걸리는 힘의 크기에 따라 다르다는 것이다.

• 치과방사선
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• 제29권1호
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• pp.241-254
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• 1999

The purpose of this study was to investigate whether a radiometric analysis of radicular cysts and periapical granulomas is useful in the differential diagnosis. In this experiment, twenty-nine periapical radiographs of the radicular cyst and those periapical granuloma were used. The periapical radiography was taken by intraoral paralleling device. The X-ray film was digitized and digitally filtered to reduce film-grain noise. We estimated density difference of the inner/outer area, roundness or circularity, bone profile or scan line of the margin and cumulative percentage frequency curve of radicular cyst & periapical granuloma. The obtained results were as follows; 1. The differences in density between ROIs of inner and outer area of radicular cysts were smaller than those of periapical granulomas. 2. The equivalent circular diameter was over 6.3mm, there was significant difference between periapical cyst and periapical granuloma. 3. In differential diagnosis of radicular cyst and periapical granuloma using bone profile. sensitivity. specificity and accuracy were considerably high(0.83. 0.86. 0.86) respectively. 4. Cumulative percentage frequency curve of the radicular cyst was closer to the pseudo-pixel value of 50 than average curve, whereas periapical granuloma was closer to that of 0. Hence we conclude that digital radiometric features might be useful in the differential diagnosis between radicular cyst and periapical granuloma.

• 한국통신학회논문지
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• 제24권7A호
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• pp.1005-1015
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• 1999

본 논문에서는 BPSK (binary shift keying) 방식을 사용하고 IFFT (inverse fast Fourier transform)와 FFT를 이용하여 기저 대역 변조기 및 복조기를 디지털로 구현한 MC-CDMA (multi carrier-code division multiple access) 시스템과 동일한 비트오율 (bit error rate) 성능을 갖고, 계산량과 대역폭을 줄이는 IFFT/FFT 기반의 새로운 디지털 구현 알고리즘 및 제안된 알고리즘에 적용되는 등화기 구조를 제안한다. 제안된 방법은 2개의 N/2-point 실수신호를 N/2-point IFFT와 FFT를 이용하여 동시에 변환하고 다시 복원할 수 있는 변형된 FFT 알고리즘에 기반을 두고 있다. 제안된 방법의 성능은 부가성 백색 가우시안 잡음 채널과 주파수 선택적 페이딩 채널 하에서 equal gain combiner와 maximal ratio combiner 등화기에 의한 다이버시티를 이용하여 수신했을 경우에 대한 모의실험을 통해 확인하였다.

• 전기학회논문지
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• 제65권5호
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• pp.831-835
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• 2016

In this paper, a dual-channel feed-forward transimpedance(TIA) array is realized in a standard $0.18-{\mu}m$ CMOS technology which exploits automatic gain control function to provide 40-dB input dynamic range for either detecting targets nearby or sensing imminent danger situations. Compared to the previously reported conventional feed-forward TIA, the proposed automatic-gain-control feed-forward TIA(AFF-TIA) extends the input dynamic range 25 dB wider by employing a 4-level automatic gain control circuit. Measured results demonstrate the linearly varying transimpedance gain of 47 to $72dB{\Omega}$, input dynamic range of 1:100, the bandwidth of $${\geq_-}670MHz$$, the equivalent input referred noise current spectral density of 6.9 pA/${\surd}$HZ, the maximum sensitivity of -26.8 dBm for $10^{-12}BER$, and the power consumption of 27.6 mW from a single 1.8-V supply. The dual-channel chip occupies the area of $1.0{\times}0.73mm^2$ including I/O pads.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 하계학술대회 논문집 B
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• pp.1260-1263
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• 2000

Vector control of a single phase induction machine(SPIM) is usually employed by mechanical methods than electrical ones. The disadvantage of a SPIM has large noise at the starting. Using auxiliary winding which is only utilized for starting, the SPIM can be controlled with the vector control method. Regarding a auxiliary winding one phase, the SPIM is analyzed by the unsymmetrical two phase motor and phase transformation is unnecessary such as three phase IM. Including a auxiliary winding, SPIM is modeled by mathematical getting by component of turns ratio with main to auxiliary winding. It will be take with complicated resultant formula, by comparison to symmetrical three phase TM. For using the vector control theory, it must be decoupled of rotor flux and torque component. stator current is controlled and decoupled. This paper presents a variable-speed control system of SPIM, which to decoupled with flux and torque component and to use machine equivalent circuit referred to rotor, conventionally three phase IM by similar method.

• 한국통신학회논문지
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• 제15권12호
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• pp.1044-1052
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• 1990

비트 동기화(bit synchronization)를 기저 대역의 PAM 신호에 대하여 weighted least square 추정 기법과 등가인 Gauss Markov 추정을 이용하여 연구하였다. 백색 가우시안 확률 분포를 갖는 잡음하에서, 천이 위상과 데이터 레벨의 추정을 2차원적으로 동시에 수행하여 수신단에서 완전한 신호를 복원하는, 검파기 포함형의 비트 동기화기(synchronizer) 실현에 관한 연구를 수행하였다. 컴퓨터 시뮬레이션으로 실현성을 확인하였으며, 기존의 대표적 동기화 방식인 maximum likehood 추정 이론에 근거한 DTTL(digital data transition tracking loop)와 그리고 minimum likehood 추정 기법에 근거한 방식과의 추정 오차 성능을 비교 평가하였다.