• 전자공학회논문지S
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• 제34S권6호
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• pp.94-103
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• 1997

This paper presents motor speed and revolution angle detection method using a sinusoidal AC tacho-generator. The 2-phase or 3-phase output tacho-generator can be adopted, and its' output voltages must have sinusoidal waveforms. Because the detection algorithm is simple, the proosed method can be implemented with analog devices or microprocessor conveniently. And the proposed method has a very short detection delay time. Especially in the analog implementation, there is no delay time without the settling time of analog devices. With the experimental results, it is verified that the proposed method can acculately detect the instantaneous motor speed and revolution angle over the wide ranges.

• 전자공학회논문지A
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• 제32A권5호
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• pp.31-41
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• 1995

In this paper, the relationship between k consecutive outputs of the conventional differential detector and output of differential detector with k-symbol periods delay for differential MSK and GMSK systems is investigated. It is hown that there exists periodity in modulo-2 sum and product of k successive outputs of the conventional differential detector with the output of a detector with k-symbol periods delay circuit. This relationships are used to achieve performance gains over conventional differential detection. The error rate performance of the method is carried out by computer simulation and performance improvement is achieved for differential MSK and GMSK systems.

• Journal of the Optical Society of Korea
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• 제18권5호
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• pp.466-471
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• 2014

An asynchronous optical packet-switching (AOPS) node with load-balancing capability can achieve better performance in reducing the high packet-loss ratio (PLR) and time delay caused by unbalanced traffic. This paper proposes a novel dynamic load-balancing algorithm for an AOPS node with limited buffer and without wavelength converters, and considering the data flow distribution and service levels. By calculating the occupancy state of the output ports, load state of the input ports, and priorities for data flow, the traffic is balanced accordingly. Simulations demonstrate that asynchronous variant data packets and output traffic can be automatically balanced according to service levels and the data flow distribution. A PLR of less than 0.01% can be achieved, as well as an average time delay of less than 0.46 ns.

• Journal of Communications and Networks
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• 제9권2호
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• pp.141-149
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• 2007

Multiple-input multiple-output (MIMO) transmit pre-coding/beamforming can significantly improve system spectral efficiency. However, several obstacles prevent precoding from wide deployment in early wireless networks: The significant feedback overhead, performance degradation due to feedback delay, and the large storage requirement at the mobile devices. In this paper, we propose a precoding method that addresses these issues. In this approach, only 3 or 6 bits feedback is needed to select a precoding matrix from a codebook. There are fifteen codebooks, each corresponding to a unique combination of antenna configuration (up to 4 antennas) and codebook size. Small codebooks are prestored and large codebooks are efficiently computed from the prestored codebook, modified Hochwald method and Householder reflection. Finally, the feedback delay is compensated by channel prediction. The scheme is validated by simulations and we have observed significant gains comparing to space-time coding and antenna selection. This solution was adopted as a part of the IEEE 802.16e specification in 2005.

• 한국통신학회논문지
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• 제18권4호
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• pp.591-601
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• 1993

본 논문에서는 기존 차동 복조기의 k개의 연속적인 출력과 k비트 지연된 차동 복조기 출력간의 관계를 MSK 및 GMSK 시스팀에 대하여 고찰하였다. MSK 및 GMSK 의 신호에 대한 k비트 지연 회로를 사용한, k차 복조기의 출력은 기존 차동 복조기의 k개의 연속적인 출력의 곱이다. 이를 수학적인 과정을 통하여 증명하였으며 이러한 관계를 이용하여 Makrakis가 제시한 2비트 지연기를 사용하여 성능을 개선시킬 수 있는 수신기구조를 임의의 비트 지연기를 사용할 수 있는 수신기 구조를 일반화시켰다. 제안된 방식의 오율 성능을 컴퓨터 시뮬레이션을 행하였으며 성능 개선이 됨을 알 수 있었다.

• International Journal of Internet, Broadcasting and Communication
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• 제12권3호
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• pp.1-8
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• 2020

This paper studied a method of estimating target information using a radar in wireless communication. Position information on the target can be estimated angle, distance and velocity. The velocity information can be estimated since the Doppler frequency is changed in the moving target. The signal incident on the receiving array antenna is multiplied by the delay time and the reference signal to represent the output signal. This output signal is estimated by applying FFT (Fast Fourier Transform) after calculating signal correlation through correlation integrator. Since the output signal must be calculated within the correlator, it should be processed with the Dwell time. The correlation signal of the correlation integrator outside this Dwell time is indicated by the velocity measurement error. The FFT is applied to the signal that has passed through the correlated integrator in order to estimate the distance of the signal. The Doppler resolution must be improved because the FFT estimates target information using the Doppler information. The Doppler resolution decreases with increasing the integration time. The velocity information estimation should have no spread of the velocity. As a result of the simulation, there was no spread of the target velocity in this study.

• 대한전자공학회논문지
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• 제18권4호
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• pp.34-42
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• 1981

PMOS집적기술을 이용하여 512-Bit mask programmable ROM을 설계하고 제작하였다. ROM의 내용은 제작공정에서 gate pattern으로 기억시켰으며 chip의 출력을 512(32×16)개의 점의 행렬로써 오실로스코프에 나타내어 확인하였다. 제작된 chip은 -6V와 - l2V의 범위에서 정상적으로 동작하였다 소모전력과 전달지연시간은 -6V에서 각각 3mW와 13μsec였다. -12V에서는 소모전력이 27mW로 증가하였으며 전달지연시간은 3μsec로 감소하였다. Chip의 출력은 TTL gate의 인력을 직접 구동시킬 수 있었으며 chip select에 의하여 출력을 disable 시켰을 때는 높은 임피던스 상태를 유지하였다.

• 한국지능시스템학회논문지
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• 제19권4호
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• pp.464-469
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• 2009

본 논문은 네트워크 상에서 구현되는 불확실 Takagi-Sugeno (T-S) 퍼지 시스템의 관측기 기반 강인 안정화를 논의한다. 네트워크 기반 시스템에서 입력 지연은 필연적으로 발생하며 마코프 (Markov) 확률 과정으로 표현함을 가정한다. 강인 퍼지 관측기 기반 샘플치 제어기를 설계하기 위하여 입출력 단에 영차의 샘플/홀드를 가정하여 T-S 퍼지 시스템을 이산화하고 확률적 과정에 따라 변화하는 도약 시스템으로 표현한다. 확률적 강인 안정 가능성 조건은 선형 행렬 부등식으로 표현된다.

• Current Optics and Photonics
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• 제7권3호
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• pp.297-303
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• 2023

In this paper, we demonstrated a high-energy (285 mJ) mid-infrared flashlamp-pumped electro-optically 𝚀-switched Er:YAG master oscillator power amplifier (MOPA) system and comprehensively investigated its temporal, spectral, and spatial characteristics. To increase the output energy, we optimized the delay between the timings at which the flashlamps of the master oscillator and power amplifier were triggered. In addition, the output energy was improved while minimizing thermal effects by cooling the MOPA system to a temperature slightly above the dew point. Consequently, the MOPA structure boosted the output energy without damaging the lithium niobate Pockels cell, which is a crucial element in 𝚀-switching. This design realized pulses with energies up to 0.285 J and pulse durations of approximately 140 ns at a wavelength of 2,936.7 nm. This high-energy mid-IR Er:YAG MOPA system can be used for various scientific, engineering, and military underwater applications.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2004년도 ICCAS
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• pp.1162-1167
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• 2004

This paper presents the design methodology of digital fuzzy controller(DFC) for the systems with time-delay. We propose the fuzzy feedback controller whose output is delayed with unit sampling period and predicted. The analysis and the design problem considering time-delay become easy because the proposed controller is syncronized with the sampling time. The stabilization problem of the digital fuzzy system with time-delay is solved by linear matrix inequality(LMI) theory. Convex optimization techniques are utilized to solve the stable feedback gains and a common Lyapunov function for designed fuzzy control system. To show the effectiveness the proposed control scheme, the network control example is presented.