• 대한전자공학회논문지TC
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• 제39권9호
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• pp.28-34
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• 2002

본 논문에서 제시한 새로운 형태의 전치왜곡 회로는 Harmonic Generator에서 발생되는 저주파 혼변조 신호 성분만을 추출하여, 이것을 Vector Modulator에서 원 신호와 진폭 변조시키는 것이다. 이러한 회로를 이용하여 3차, 5차 혼변조 신호를 발생시켜 전력 증폭기의 혼변조 신호를 감쇠시키는 선형화기를 구현하였다. 구현된 전치왜곡 선형화기는 국내 개인 휴대 통신(PCS) 기지국 송신 대역인 1840MHz~1870MHz주파수에서 동작되도록 제작, 측정을 하였다. 그 결과 반송파 2-tone 신호를 인가할 때 3차 혼변조 왜곡 특성은20dB 이상, 5차 혼변조 왜곡 특성은 10dB 이상의 개선효과를 얻었고, IS-95 CDMA 신호를 인가하였을 때 인접채널 전력 비를 10dB이상 개선시켰다.

• 한국항행학회논문지
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• 제13권3호
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• pp.399-405
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• 2009

본 논문은 메타 재질 구조를 바탕으로 한 가변 감쇠기와 그 응용에 대하여 기술 하였다. 손실이 존재하는 전송선로를 이용한 감쇠기 단위 셀은 CRLH(Composite Right/Left Handed) 전송선로와 다이오드 바이어스 전압에 따라서 내부 저항값의 변화에 따라서 손실을 제어할 수 있는 PIN다이오드로 구성되어 있다. 또한, 내부의 초기 삽입 손실을 줄이기 위해서 두 개의 PIN 다이오드를 병렬로 연결하였다. 이 감쇠기는 감쇠기 단위 셀 숫자를 증가시킴으로서 감쇠량을 증가시킬 수 있는 주기적 구조로 설계되었다. 단위 셀의 전기적 특성은 주파수 1.5 GHz ~ 2.5 GHz에서 10dB의 감쇠량과 최대 15o의 위상변화를 확인하였다. 이러한 특성의 감쇠기를 직렬로 연결하여 벡터 변조기에 응용하였다.

• 한국광학회:학술대회논문집
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• 한국광학회 1990년도 제5회 파동 및 레이저 학술발표회 5th Conference on Waves and lasers 논문집 - 한국광학회
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• pp.102-111
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• 1990

In this thesis, an optical bidirectional inner-product associative memory model using liquid crystal television is proposed and analyzed theoretically and realized experimentally. The LCTV is used as a SLM(spatial light modulator), which is more practical than conventional SLMs, to produce image vector in terms of computer and CCD camera. Memory and input vectors are recorded into each LCTV through the video input connectors of it by using the image board. Two multi-focus hololenses are constructed in order to perform optical inner-product process. In forward process, the analog values of inner-products are measured by photodetectors and are converted to digital values which are enable to control the weighting values of the stored vectors by changing the gray levels of the pixels of the LCTV. In backward process, changed stored vectors are used to produce output image vector which is used again for input vector after thresholding. After some iterations, one of the stored vectors is retrieved which is most similar to input vector in other words, has the nearest hamming distance. The experimental results show that the proposed inner-product associative memory model can be realized optically and coincide well with the computer simulation.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2004년도 전력전자학술대회 논문집(2)
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• pp.625-629
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• 2004

This paper presents a systematical approach to study carrier based PWM techniques (CPWM) in diode-clamped and cascade multilevel inverters by using a proposed named multi-modulating pattern method. This method is based on the vector correlation between CPWM and the space vector PWM (SVPWM) and applicable to both multilevel inverter topologies. A CPWM technique can be described in a general mathematical equation, and obtain the same outputs similarly as of the corresponding SVPWM. Control of the fundamental voltage, vector redundancies and phase redundancies in multilevel inverter can be formulated separately in the CPWM equation. The deduced CPWM can obtain the full vector redundancy control, and fully utilize phase redundancy in a cascade inverter In this continued part, it will be deduced correlation between CPWM equations in multi-carrier system and single carrier system, present the mathematical model of voltage source inverter related to the common mode voltage and propose a general algorithm for multi-modulating modulator. The obtained theory will be demonstrated by simulation results.

• 한국전자파학회논문지
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• 제12권1호
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• pp.37-43
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• 2001

본 논문에서는 전력증폭기의 선형성을 광대역으로 개선시키기 위하여 delay 특성의영향에 대하여 고려하였다. 사용된 전력 증폭기의 이득은 37dB이고, 3단의 1W급으로 설계되었다. Error 증폭기는 4단으로 설계되었으며 이득은 55dB이다. 그리고 방향성 결합기 및 전력 분배기를 설계하였으며, 또한 크기와 위상을 조절하기 위한 장치로 vector modulator를 사용하였다. 각 모듈을 통합하여 주파수 2.11GHz에서 2.2GHz까지 delay 특성을 고려한 광대역 선형 전력 증폭기를 설계하였으며, 30MHz의 대역폭에 걸쳐 C/I$_3$비가 25dB 이상의 개선 효과를 얻었다.

• ETRI Journal
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• 제36권6호
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• pp.924-930
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• 2014

This paper presents a $0.13{\mu}m$ CMOS 3-level envelope delta-sigma modulation (EDSM) RF signal generator, which synthesizes a 2.6 GHz-centered fully symmetrical 3-level EDSM signal for high-efficiency power amplifier architectures. It consists of an I-Q phase modulator, a Class B wideband buffer, an up-conversion mixer, a D2S, and a Class AB wideband drive amplifier. To preserve fast phase transition in the 3-state envelope level, the wideband buffer has an RLC load and the driver amplifier uses a second-order BPF as its load to provide enough bandwidth. To achieve an accurate 3-state envelope level in the up-mixer output, the LO bias level is optimized. The I-Q phase modulator adopts a modified quadrature passive mixer topology and mitigates the I-Q crosstalk problem using a 50% duty cycle in LO clocks. The fabricated chip provides an average output power of -1.5 dBm and an error vector magnitude (EVM) of 3.89% for 3GPP LTE 64 QAM input signals with a channel bandwidth of 10/20 MHz, as well as consuming 60 mW for both channels from a 1.2 V/2.5 V supply voltage.

• Journal of Power Electronics
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• 제14권1호
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• pp.115-124
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• 2014

This paper presents the implementation of two-arm modulation (TAM) technique for the independent control of a two-induction motor drive fed by a five-leg inverter (FLI). A carrier-based space vector pulse width modulation technique for TAM is proposed to generate switching signals for FLI. Two independent three-phase space vector modulators are utilized to control two motors. The motor drive system applies two separate indirect field-oriented control methods. The stationary voltage outputs from the vector control are synthesized in the three-phase space vector modulator to generate switching signals for FLI. The performance of the independent control of the motors and the voltage utilization factor are likewise analyzed. Simulation and experimental results verify the effectiveness of the proposed method for the independent control of the two-motor drive system. The proposed technique is successfully validated by dSPACE DS1103 experimental work.

• Journal of Power Electronics
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• 제13권5호
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• pp.787-797
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• 2013

Despite the advantages offered by multilevel inverters, one of the main drawbacks that prevents their widespread use is their circuit complexity as the number of power switches employed is usually high. This paper presents a new multilevel inverter topology with a considerable reduction in the number of power switches used through the switch-sharing approach. The fact that the proposed inverter applies two bidirectional power switches for sharing among the three phases does not prevent it from producing seven levels in the line-to-line output voltage waveforms. A modified scheme of space vector modulation via the application of virtual voltage vectors is developed to generate the PWM signals of the power switches. The performance of the proposed inverter is investigated through MATLAB/SIMULINK simulations and is practically tested using a laboratory prototype with a DSP-based modulator. The results demonstrate the satisfactory performance of the inverter and verify the effectiveness of the modulation method.

• Journal of Advanced Marine Engineering and Technology
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• 제21권5호
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• pp.591-597
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• 1997

Instantaneous velocity distribution within coaxial circular pipe for measurement velocity of high speed is acquired simultaneously by applying the 2-dimensional PTV system consisting of a pulse generator(AOM:Acousto-Optical Modulator), a continuous-output laser and a PC image grabber together with experimental apparatus. The basic mechanism of AOM and vector identification method and performance-related image processing techniques are discussed. Representative measuring regions $90{\times}90$mm are selected and instantaneous vectors are represented and fully developed turbulent flow of maximum velocity up to about 1.0 m/sec is obtained.

• 한국전자파학회논문지
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• 제28권10호
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• pp.769-778
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• 2017

본 논문은 동일대역 전이중 통신(In-band Full-Duplex: IFD) 방식에 필요한 RF/아날로그 영역에서의 자기간섭 신호의 제거회로를 설계하고, 이를 이용하여 FM 변조 신호를 송신하면서, 동시에 수신 신호의 FM 복조가 가능하도록 설계했다. 서큘레이터(circulator)를 이용하여 단일 안테나 방식으로 송수신을 동시에 가능하게 했다. 수신 회로에는 송신으로 인한 자기간섭 신호 제거를 위해, 송신 신호를 탭핑하여 벡터 변조기(vector modulator)로 위상과 크기를 제어한 후, 수신 신호에 포함된 자기간섭 신호를 제거하였다. 자기간섭 신호의 제거를 위하여 채널변화에 따른 최적의 위상과 크기를 능동적으로 제어해야 한다. 이를 위해 동위상과 직교위상 아날로그 상관기를 이용하여 송신 신호와 수신측 자기간섭 신호의 상관 계수를 구하여 상관 계수가 최소가 되도록 제어회로를 구현하였다. 무전기 모덴 칩은 SA58646을 사용하였고, 반송파는 465 MHz 주파수에 12.5 kHz 대역폭을 가지는 FM 변조신호를 사용하였다. 안테나 포트 출력 파워가 17.2 dBm일때, 모뎀 입력단에 수신되는 자기간섭 신호가 -49.2 dBm으로 측정되어 SIC(Self Interference Cancellation) 레벨은 66.4 dB로 측정되었다.