• 대한전자공학회논문지SD
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• 제46권2호
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• pp.1-8
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• 2009

본 논문에서는 일반적인 Folding 구조를 이용한 R-String Folding Block과 Second Folding Block을 제안하여 최대 500Msample/s로 동작하는 ADC를 설계하였다. 제안된 Folding ADC의 R-String Folding Block에서는 상위 4bit를 병렬로 처리하여 디지털 출력을 얻어내며, Second Folding Block에서는 하위 4bit를 새로운 pipeline 방식을 통해 디지털 출력을 얻어낸다. HSPICE 시뮬레이션 과정을 통해 ADC 동작을 확인하였으며 최대 샘플링 주파수인 500Msample/s로 동작할 경우의 평균 전력소모는 1.34mW로 매우 작음을 확인하였다. 램프입력을 인가하면서 디지털 출력이 변할 때의 입력전압을 측정하여 DNL과 INL을 구한 결과 DNL은 $-0.56LSB{\sim}0.49LSB$, INL은 $-0.94LSB{\sim}0.72LSB$의 특성을 나타내었다. 사용된 MOSFET 파라미터는 MOSIS에서 제공하는 $0.35{\mu}m$ 공정 파라미터이다.

• 한국의학물리학회:학술대회논문집
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• 한국의학물리학회 2002년도 Proceedings
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• pp.373-375
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• 2002

4D CT is a dynamic volume imaging system of moving organs with an image quality comparable to conventional CT, and is realized with continuous and high-speed cone-beam CT. In order to realize 4D CT, we have developed a novel 2D detector on the basis of the present CT technology, and mounted it on the gantry frame of the state-of-the-art CT-scanner. In the present report we describe the design of the first model of 4D CT-scanner as well as the early results of performance test. The x-ray detector for the 4D CT-scanner is a discrete pixel detector in which pixel data are measured by an independent detector element. The numbers of elements are 912 (channels) ${\times}$ 256 (segments) and the element size is approximately 1mm ${\times}$ 1mm. Data sampling rate is 900views(frames)/sec, and dynamic range of A/D converter is 16bits. The rotation speed of the gantry is l.0sec/rotation. Data transfer system between rotating and stationary parts in the gantry consists of laser diode and photodiode pairs, and achieves net transfer speed of 5Gbps. Volume data of 512${\times}$512${\times}$256 voxels are reconstructed with FDK algorithm by parallel use of 128 microprocessors. Normal volunteers and several phantoms were scanned with the scanner to demonstrate high image quality.

• 전기전자학회논문지
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• 제24권2호
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• pp.392-402
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• 2020

본 논문은 광센서 없는 태양광 추적 시스템을 제안한다. 태양광 추적, MPPT, ESS, 모니터링의 4가지 기능을 모듈화하여 시스템을 구현하였다. 9개의 태양광 패널을 기본단위로, 바람의 영향을 저감하고, 광센서 없이 태양광 추적이 가능하도록 상하좌우 패널의 높낮이를 다르게 한 격자형 구조를 채택하였다. 저가형 MCU를 이용한 부스트 컨버터 PWM 스위칭을 위해 기존 MPPT의 연산 방법을 개선하였다. ESS 모듈은 리튬 이온 배터리 12개(직렬 3셀과 병렬 4셀)를 기본 단위로 구성하여 온도 및 전기 특성의 이상 유무 감시가 가능하게 하였다. 각 모듈의 MCU는 Atmega128 또는 Raspberry PI로 구성하였으며 운전 정보를 상호 교환하고, IoT 기술을 응용하여 실시간 원격 모니터링과 클라우드에 데이터베이스를 구축하여 유지보수가 가능하게 하였다. 실험을 위해 제작된 태양광 발전 시스템의 운전 데이터는 각 모듈의 분산 및 원격 모니터링의 가능성, 유지보수의 편의성 및 광추적 성능을 증명한다.

• 대한의용생체공학회:학술대회논문집
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• 대한의용생체공학회 1997년도 추계학술대회
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• pp.365-368
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• 1997

We are developing a small gamma camera or imaging malignant breast tumors. The small scintillation camera system consists of NaI(Tl) crystal ($60\;{\times}\;60\;{\times}\;6\;mm^3$) coupled to position sensitive photomultiplier tube (PSPMT), nuclear instrument module (NIM), analog to digital converter (ADC), and personal computer. High quality flood source image and hole mask image were obtained using the gamma camera developed in this study. Breast phantom containing $2{\sim}7\;mm$ diameter spheres was successfully imaged with parallel hole collimator. The obtained image displayed accurate activity distribution over the imaging field of view. Linearity and uniformity correction algorithms are being developed. It is believed that the developed small gamma camera could be useful or detection of malignant breast cancer.

• Journal of Power Electronics
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• 제16권3호
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• pp.1110-1121
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• 2016

The mathematical model of a three phase PWM converter under the stationary αβ reference frame is deduced and constructed based on a Proportional-Resonant (PR) regulator, which can replace trigonometric function calculation, Park transformation, real-time detection of a Phase Locked Loop and feed-forward decoupling with the proposed accurate calculation of the inductance voltage vector. To avoid the parallel resonance of the LCL topology, the active damping method of the proportional capacitor-current feedback is employed. As to current vector error elimination, an optimized PR controller of the inner current loop is proposed with the zero-pole matching (ZPM) and cancellation method to configure the regulator. The impacts on system's characteristics and stability margin caused by the PR controller and control parameter variations in the inner-current loop are analyzed, and the correlations among active damping feedback coefficient, sampling and transport delay, and system robustness have been established. An equivalent model of the inner current loop is studied via the pole-zero locus along with the pole placement method and frequency response characteristics. Then, the parameter values of the control system are chosen according to their decisive roles and performance indicators. Finally, simulation and experimental results obtained while adopting the proposed method illustrated its feasibility and effectiveness, and the inner current loop achieved zero static error tracking with a good dynamic response and steady-state performance.

• 조명전기설비학회논문지
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• 제16권3호
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• pp.20-28
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• 2002

본 논문은 고주파 유도가열용 전원에 사용되는 VVVF기능을 내장한 시분할 방식 고주파 공진 인버터 회로를 제시하였다. 제안한 인버터는 종래의 전압형 하프 브릿지 직렬 공진 인버터를 단위 인버터로 하여 이 단위 인버터 3개를 입력전원에 병렬로 접속하여 스위칭 주파수의 3배의 출력 주파수를 얻을 수 있으며, 또, 인버터 내부에 VVVW 기능을 부여하여 출력전압.주파수를 제어 할 수 있고 ZVS 기능도 가지고 있다는 특징을 가지고 있다. 회로의 해석은 정규화 파라메타를 도입하여 범용성 있게 기술하였고, 인버터 특성을 스위칭 주파수, Phase-Shift의 위상차각($\phi$) 변화와 제 파라메타에 따라 특성평가를 행하였다. 실험을 통해 이론해석의 타당성을 검증하였으며, 향후 유도가열 웅용, DC-DC 컨버터 등의 전원 시스템에 웅용 가능성을 보여주고 있다.

• 조명전기설비학회논문지
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• 제28권1호
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• pp.16-28
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• 2014

This paper presents a novel high-power-factor circuit topology of AC to AC current-fed type high frequency resonant inverter which includes the function of power factor correction(PFC) in the proposed inverter to operate the AC input block with high power factor. The proposed circuit topology of AC to AC current fed type high resonant inverter removes DC link electrolytic capacitor and has also the one of power factor correction(PFC) in the inverter circuit without an additional PFC circuit since the input current by constituting it in parallel as an unit inverter, which assumes the class-E high frequency resonant inverter of conventional current-fed type, flows in the form of the resultant current flowing through each constant current reactor($L_{d1}$, $L_{d2}$). The circuit analysis of proposed inverter is generally described by adopting the normalized parameters and the evaluation of its operating characteristics are conducted by using the parameters such as the ratio of switching and resonant frequency(${\mu}$), coupling coefficient(k) and so on. An example of procedure for circuit design based on the characteristic values obtained from the theoretical analysis is presented. To confirm the validity of the theoretical analysis, the experimental results are also presented. In the future, the proposed inverter shows it can be practically used as power supply system for induction heating application, DC-DC converter etc.

• 대한의용생체공학회:의공학회지
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• 제19권2호
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• pp.143-152
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• 1998

In this paper, we present the performances of a Doppler system using single channel RF(Radio Frequency) sampling. This technique consists of undersampling the ultrasonic blood backscattered RF signal on a single channel. Conventional undersampling method in Doppler imaging system have to use a minimum of two identical parallel demodulation channels to reconstruct the multigate analytic Doppler signal. However, this system suffers from hardware complexity and problem of unbalance(gain and phase) between the channels. In order to reduce these problems, we have realized a multigate pulsed Doppler system using undersampling on a single channel, It requires sampling frequency at $4f_o$(where $f_o$ is the center frequency of the transducer) and 12bits A/D converter. The proposed " single-Channel RF Sampling" method aims to decrease the required sampling frequency proportionally to $4f_o$/(2k+1). To show the influence of the factor k on the measurements, we have compared the velocity profiles obtained in vitro and in vivo for different intersequence delays time (k=0 to 10). We have used a 4MHz center frequency transducer and a Phantom Doppler system with a laminar stationary flow. The axial and volumetric velocity profiles in the vessel have been computed according to factor k and have been compared. The influence of the angle between the ultrasonic beam and the flow axis direction, and the fluid viscosity on the velocity profiles obtained for different values of k factor is presented. For experiment in vivo on the carotid, we have used a data acquisition system with a sampling frequency of 20MHz and a dynamic range of 12bits. We have compared the axial velocity profiles in systole and diastole phase obtained for single channel RF sampling factor.ng factor.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2006년도 International Symposium on GPS/GNSS Vol.2
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• pp.385-390
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• 2006

This paper examines the sampling and jitter specifications and considerations for Global Navigation Satellite Systems (GNSS) software receivers. Software radio (SWR) technologies are being used in the implementation of communication receivers in general and GNSS receivers in particular. With the advent of new GPS signals, and a range of new Galileo and GLONASS signals soon becoming available, GNSS is an application where SWR and software-defined radio (SDR) are likely to have an impact. The sampling process is critical for SWR receivers, where it occurs as close to the antenna as possible. One way to achieve this is by BandPass Sampling (BPS), which is an undersampling technique that exploits aliasing to perform downconversion. BPS enables removal of the IF stage in the radio receiver. The sampling frequency is a very important factor since it influences both receiver performance and implementation efficiency. However, the design of BPS can result in degradation of Signal-to-Noise Ratio (SNR) due to the out-of-band noise being aliased. Important to the specification of both the ADC and its clocking Phase- Locked Loop (PLL) is jitter. Contributing to the system jitter are the aperture jitter of the sample-and-hold switch at the input of ADC and the sampling-clock jitter. Aperture jitter effects have usually been modeled as additive noise, based on a sinusoidal input signal, and limits the achievable Signal-to-Noise Ratio (SNR). Jitter in the sampled signal has several sources: phase noise in the Voltage-Controlled Oscillator (VCO) within the sampling PLL, jitter introduced by variations in the period of the frequency divider used in the sampling PLL and cross-talk from the lock line running parallel to signal lines. Jitter in the sampling process directly acts to degrade the noise floor and selectivity of receiver. Choosing an appropriate VCO for a SWR system is not as simple as finding one with right oscillator frequency. Similarly, it is important to specify the right jitter performance for the ADC. In this paper, the allowable sampling frequencies are calculated and analyzed for the multiple frequency BPS software radio GNSS receivers. The SNR degradation due to jitter in a BPSK system is calculated and required jitter standard deviation allowable for each GNSS band of interest is evaluated. Furthermore, in this paper we have investigated the sources of jitter and a basic jitter budget is calculated that could assist in the design of multiple frequency SWR GNSS receivers. We examine different ADCs and PLLs available in the market and compare known performance with the calculated budget. The results obtained are therefore directly applicable to SWR GNSS receiver design.

• 한국산학기술학회논문지
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• 제20권3호
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• pp.491-499
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• 2019

최근에, 전원 공급 장치에 있어서 파워의 품질에 대한 요구가 높아지고 있다. IEC 61000-3-2 규격은 조명을 위한 AC/DC 전원 공급 장치에 대하여 역률(PF)과 전체 파형 왜곡률(THD)에 대한 규격을 만족하도록 요구하고 있다. 또 출력단의 전류 변화에 의해 발광체 광량이 바뀜에 따라 발생되는 플리커 현상에 대해 유럽권 선진국가는 ripple rate의 기준을 15~30%로 설정해 규제하고 있다. 따라서 국내에서도 기준을 마련하고 규제를 추진 중에 있다. 그래서 본 논문은 PFC 규격을 만족하고, 회로 1차, 2차 간 절연 기능을 가지기 위해 Flyback 컨버터를 적용하며, LED 전류의 저주파 리플을 저감하기 위해 Flyback, Coupled Inductor, LC 병렬 공진 필터, LLC 공진 필터, Cuk을 이용한 각각의 LED 구동회로를 PSIM을 통해 시뮬레이션 함으로써 각각의 방식들을 비교하였으며, 출력측 리플 저감을 위해 1차측에 Coupled Inductor와 2차측에 LC 공진을 적용한 Coupled LC 공진 회로를 제안하였으며, Coupled LC 공진 방식은 출력 커패시터가 78uF으로 작으며, 출력 리플은 전압 2.38V, 전류 0.05A로 기존의 방식보다 22%의 출력 리플 저감을 확인 하였다.