• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1996년도 한국자동제어학술회의논문집(국내학술편); 포항공과대학교, 포항; 24-26 Oct. 1996
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• pp.1265-1268
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• 1996

This paper describes a new pulse width modulation (PWM) scheme suitable for microprocessor-based PWM inverters. Optimal switching patterns minimizing the performance index corresponding to the distortion factor are decided in real time by numerical calculation using the microprocessor-implemented control system. This PWM method is compared with conventional methods, such as the natural PWM and the direct PWM. Harmonic analysis using digital simulations shows that the proposed PWM scheme has much less low-order harmonics than the other methods. The validity of this method is verified in experiments using a microprocessor-based control system, where a 16-bit single-chip microcontroller, Intel 80c196kc is used.

• 제어로봇시스템학회논문지
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• 제5권7호
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• pp.862-867
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• 1999

In general, the realization of high performance brushless permanent magnet motors which are widely used in servo drive is focused on the linear control for ripple-free torque. This is also the main problem that should be solved in all AC motors including induction motor to achieve high performance control, and recent papers deal with this problem. In this paper, the novel optimal excitation scheme of brushless permanent magnet motor producing loss-minimized ripple-free torque based on the d-q-0 reference frame is presented including 3 phase unbalanced condition. The optimized phase current waveforms that are obtained by the proposed method can be a reference values and the motor winding currents are forced to track it by delta modulation technique. As a results, it can be shown that the proposed work can minimize the torque ripple by the optimal excitation current for brushless permanent magnet motor with any arbitrary phase back EMF waveform. Simulation and experimental results prove the validity and practical applications of the proposed control scheme.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1994년도 추계학술대회 논문집
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• pp.175-178
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• 1994

In this study, the design program for optimal wire batch around service line is made to improve the dielectric strength at the primary winding using Finite Element Method. The automatic convergence algorithm for finding of limit object value using loop circulation method is developed to make the optimal design simulator The modulation method is suggested to make division time faster which is very important for full program efficiency. As a result, the program execution time is reduced about 32% and the optimal wire batch design is obtained.

• Journal of Information Processing Systems
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• 제10권2호
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• pp.163-175
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• 2014

This paper will focus on improving the performance of orthogonal frequency division multiplexing (OFDM) in Rayleigh fading environments. The proposed technique will use a previously published method that has been shown to improve OFDM performance in independent fading, based on ordered sub-carrier selection. Then, a simple non-iterative method for finding the optimal bit-loading allocation was proposed. It was also based on ordered sub-carrier selection. We compared both of these algorithms to an optimal bit-loading solution to determine their effectiveness in a correlated fading environment. The correlated fading was simulated using the JTC channel models. Our intent was not to create an optimal solution, but to create a low complexity solution that can be used in a wireless environment in which the channel conditions change rapidly and that require a simple algorithm for fast bit loading.

• 전기전자학회논문지
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• 제22권4호
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• pp.1019-1024
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• 2018

In this paper, we suggest a combined cost function to find out the optimal operation of an envelope tracking system, and evaluated its performance with Quadrature Amplitude Modulation (QAM) waveform, with which envelope tracking coefficients for the peak drain efficiency and the bandwidth of power amplifiers are determined. Based on the classical envelope tracking theory, the operation of the supply modulator, which is a key part of the envelope tracking process, is modeled and analyzed mathematically. Then characteristics of the modulator by setting envelope shaping function as a cubic polynomial and sweeping the coefficients of this function was analyzed. By sweeping the coefficients, efficiency and bandwidth at each condition with 64-QAM signal was used to obtain optimal point of the supply modulator. Compared to the conventional shaping functions, the optimized function showed the bandwidth reduction by 12.7 percent point while the efficiency was maintained.

• 방송공학회논문지
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• 제4권2호
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• pp.164-175
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• 1999

본 논문에서는 QPSK 디지틀 전송 기술을 사용하는 위성방송 전송 시스템에 대한 위성 채널 특성과 전송 신호 특성에 대한 영향을 분석하여 전송 시스템의 설계 기준점을 결정할 수 있도록 하였다. 전송 채널 특성에 의한 열화도는 약 2.0dB, 전송 신호 스펙트럼 특성에 의한 열화는 0.4dB, 그리고 수신기 특성에 대해 약 0.2dB의 열화 특성을 갖는 위성 및 전송 시스템에 대한 가용 설계 파라미터 값들을 제안하였다. 열화 특성을 만족하는 설계 파라미터 값들은 ${\pm}\;0.5dB$ 이내의 진폭 응답 특성 그리고 0.1nsec/MHz, $0.2sec/MHz^2$ 이내의 전파 지연 특성을 나타내었다. 또한, 최대 서비스 가용도를 갖는 위성 전송 시스템의 TWTA 동작은 0dB OBO가 적당하며, 위상 잡음 영향을 최소화하기 위해서는 0.707 damping 계수 및 40kHz 대역폭을 갖는 PLL 회로가 최적의 동작 특성을 나타내었다. 본 논문의 시스템 성능 분석 및 설계 파라미터 값들은 위성을 통한 고속 데이터 전송 시스템에 대한 설계 기준점으로 활용될 수 있다.

• 한국통신학회논문지
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• 제34권1C호
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• pp.90-97
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• 2009

OFDM (Orthogonal Frequency Division Multiplexing) 전송방식의 장점은 높은 주파수 효율, RF간섭에 대한 강인성, 낮은 다중 경로 왜곡 등을 들 수 있다. 다중 사용자 OFDM의 채널용량을 확대하기 위해서는 사용자간의 부채널과 비트 할당의 효율적인 알고리즘을 개발하여야 한다. 본 연구에서는 다중 사용자의 전송요구량을 만족하는 최적 부채널 및 비트 할당 문제를 0-1 정수계획법 모형으로 형성하고, 원래 문제의 선형계획법 완화 (linear programming relaxation)문제를 dual-decomposition과 subgradient 알고리즘을 사용하여 해를 구하는 효과적인 알고리즘을 제시한다. 또한 dual-decomposition으로 구한 목적함수값은 원래 문제의 선형계획법 완화문제의 최적목적함수 간과 동일함을 증명하였다 모의실험을 통하여 다수의 문제에 대하여 원래 문제의 최적 목적항수값에 대한 dual-decomposition으로 구한 하한의 성능을 제시하였다. MQAM (M-ary Quadrature Amplitude Modulation)을 사용하고 3개의 독립적인 Rayleigh 다중 경로로 구성된 주파수 선택적 채널을 가정한 경우 MATLAB을 사용한 모의실험에서 0-1 정수계획 법으로 구한 최적해의 성능을 실험하였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1995년도 하계학술대회 논문집 C
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• pp.1281-1283
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• 1995

In this paper, we develop a prototype of the Optical SCM transmission module. This module is possible to application to electric facilities for control and measurements. Transmission channel number is two channels, namely, image and digital signal. In the image transmission, modulation method is AM, baseband signal is NTSC video signal and demodulation use PLL. Modulation of digital signal is QPSK, 1.544Mbps and demodulation use PLL. First, we calculate theoretical analysis about RF and Optical link in the transmission. This calculation is well correspond with practical system and transmission experiment is excellent, but this is only two channel model. And now, we plan to multichannel transmission to measure intermodulation, frequency assignments and optimal channel numbers et al.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2002년도 ITC-CSCC -1
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• pp.421-424
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• 2002

In this paper, we introduce an encoder design technique of multiple symbol trellis coded modulation for noncoherent continuous phase frequency shift keying (MTCM/NCPFSK) on the interleaved Rician fading channel. To find dominant factors which affects the error probability of MTCM/NCPFSK, we derive the pairwise error probability (PEP) of MTCM/NCPFSK and find that the error probability mainly depends on the effective length of error event and the corresponding squared product distance (SPD) for the small value of Rician parameter K. Using this performance criteria, we search for the optimal encoder of MTCM/NCPFSK for the interleaved Rician fading channel. We also compare that encoder with the encoder designed for additive white Gaussian noise channel.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1993년도 한국자동제어학술회의논문집(국제학술편); Seoul National University, Seoul; 20-22 Oct. 1993
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• pp.554-557
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• 1993

The error analysis for the Time-in-Flight Laser Range Finder with Multiple Tone Amplitude Modulation relevant to the phase detection error is made. The distance can be estimated to solve the formulate which express the relationship between the absolute distance from the range finder to the object and the wavenumbers and the phases of the modulated waves by the optimization technique. The main cause of the estimation error can be considered as the phase detection error induced from the amplitude modulator and the phase detector. To clarify the phase detection error and the optimal amplitude frequency set, the numerical analysis are made.