• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.12 no.4
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• pp.31-36
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• 2012

In this paper, we proposed spectrum sensing using cooperative relay to solve problem of sensing performance degradation due to CPE (Customer-Premises equipments) which causes low SNR (signal-to-noise ratio) problem. In cooperative communication system, AF (amplify-and-forward) and DF (decoded-and-forward) is widely used for relay mechanism. Also, it is expected that cooperative relay scheme guarantees the high sensing performance by its diversity gain. Based on these backgrounds, in this paper, we apply to cooperative relay scheme to the CR (Cognitive Radio) system, and simulation results show comparison of the sensing performance.

• Journal of Electrical Engineering and Technology
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• v.10 no.4
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• pp.1780-1785
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• 2015

In this paper, the adaptive particle swarm optimization (APSO) algorithm is employed to design a gain-enhanced antenna with a reflector for energy harvesting. We placed the reflector below the main radiating element. Its back-radiated field is reflected and added to the forward radiated field, which could increase the antenna gain. We adopt the adaptive particle swarm optimization (APSO) algorithm, which improves the speed of convergence with a high frequency solver. The result shows that performance of the optimized design successfully satisfied the design goal of the frequency band, gain and axial ratio.

• 제어로봇시스템학회:학술대회논문집
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• 1996.10b
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• pp.660-663
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• 1996

There has been many activity to increase accuracy in machining center by reducing tracking error. The tracking error can cause bad effect in high speed rigid tapping in which syncronization servo motor with spindle is relatively important. To reduce tracking error, feed forward control has been used, but no method is provided knowing motor dynamics, force variation, etc. In this paper, we observe that, despite of tracking error of relevant axis, high speed tapping could be possible by reducing contour error of axis to be syncronized. We present the method to increase accuracy in high speed tapping to minimize contour error by automatically fitting gains of servo and spindle.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.46 no.6
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• pp.94-102
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• 2009

In [1], the authors have proposed a novel scheme to achieve full diversity and to combat the time delays from each relay node, but decode-and-forward (DF) model operation mode puts more processing burden on the relay. In this paper, we not only extend their model into amplify and forward (AF) model proposed in [2],[3], but also propose an efficient decoding algorithm, which is able to order the joint channel coefficients of overall channel consisting of source-relay link and relay-destination link and cancels the previous decoded symbols at the next decoding procedure. The simulation results show that this algorithm efficiently improves its performance achieving 2-3dB gain compared to [1] in high SNR region and also useful to DF achieving more than 3dB gain compared to an original algorithm.

• Journal of Broadcast Engineering
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• v.17 no.1
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• pp.95-107
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• 2012

Network coding was proposed to increase the achievable throughput of multicast in a network. Recently, combining network coding into user cooperation has attracted research attention. For cooperative transmission schemes with network coding, users combine their own and their partners messages by network coding. In previous works, it was shown that adaptive DF with network coding can achieve diversity gain and additional throughput gain. In this paper, to improve performance of conventional protocols and maximize advantage of using network coding, we propose a new network coding based user cooperation scheme which uses adaptively amplify-and-forward and decode-and-forward according to interuser channel status. We derive outage probability bound of proposed scheme and prove that it has full diversity order in the high SNR regime. Moreover, based on the outage bound, we compute optimal power allocation for the proposed scheme.

• Proceedings of the KIPE Conference
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• 2002.07a
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• pp.360-363
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• 2002

In the resonant converters which can provide high efficiency and high power density, the resonant voltage stress is about $4\~5$ times the input voltage. It needs the power switch with high ratings. This is a reason why the conduction loss is increased. In this paper, it proposes the alternately zero voltage switched forward, flyback multi resonant converter topology for reducing the voltage stress using alternately zero voltage switching technique. And the proposed AT forward MRC Is experimentally considered about the loop gain with HP4194A network analyzer

• Proceedings of the KIPE Conference
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• 2001.07a
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• pp.260-263
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• 2001

In this paper, we experimentally considered the stability of AT forward MRC with the characteristics of high efficiency and high power density. The converter ratings are input 48V, output 5V/50W, The maximum voltage stress is measured to about 170V of 2 times the input voltage when the input is 58V. The $81.66\%$ of maximum efficiency could be obtained. For the stability of the converter, it is compensated through the error op amp in MC34067. A phase margin and a gain margin for relative stability are measured using HP4194A network analyzer.

• Journal of the Korean Society of Industry Convergence
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• v.18 no.1
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• pp.1-9
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• 2015

This research dealt with a two-degree-of-freedom controller which was used for 2-dimensional force generator based on an linear motor. The gain margin of the controller may be reduced when the time constant is near to the sampling time of a discrete controller. In case of low gain controller, it cannot satisfy the control performance. A two-degree-of-freedom controller based on PI-control was proposed. It can manage performance and stability respectively. It also had a kind of a feed-forward control. This scheme can not only lessen gain of conventional PI controller in order to stability but also obtain high tracking performance.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.7
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• pp.140-148
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• 2013

This paper presents a iterative Bose-Chaudhuri-hocquenghem (i-BCH) code and its high-speed decoder architecture for 100 Gb/s optical communications. The proposed architecture features a very high data processing rate as well as excellent error correction capability. The proposed 6-iteration i-BCH code structure with interleaving method allows the decoder to achieve 9.34 dB net coding gain performance at $10^{-15}$ decoder output bit error rate to compensate for serious transmission quality degradation. The proposed high-speed i-BCH decoder architecture is synthesized using a 90-nm CMOS technology. It can operate at a clock frequency of 430 MHz and achieve a data processing rate of 100 Gb/s. Thus, it has potential applications in next generation forward error correction (FEC) schemes for 100 Gb/s optical communications.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.39 no.7
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• pp.618-626
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• 2011

In order to complete missions in a complicated terrain or highly dangerous area, an unmanned aerial vehicle(UAV) needs a fine controller to precisely follow the desired path. A PID controller used for the path following feeds forward path curvature information to the control input to improve the path following performance. High gain for PID controller is necessary to follow path tightly. However the high gain could cause instability or performance degradation when the vehicle has slow dynamics. We present PID controller design method which considers response delay of vehicle as well as path curvature. In order to obtain path curvature the desired path is described as a 3rd order polynomial by applying cubic spline interpolation. We apply the proposed controller to the path following of a UAV which is operated in high altitude and has very slow lateral dynamics. The lateral dynamics are modelled as a first order delayed system in the controller design. Nonlinear simulation shows the UAV with proposed controller follows an arbitrary path very tightly.