• The Journal of Korean Institute of Communications and Information Sciences
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• v.37B no.11
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• pp.1072-1081
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• 2012

For Ka-band satellite communication system, a new flexible payload technologies which can compensate rain attenuation have to be developed. The Ka-band satellite output power control technology enables to adjust downlink output power of satellite payload in Ka-band (19.8 ~ 22.2 GHz). In this paper, we introduce multi-beam antenna with multi-port amplifiers for Ka-band flexible output power allocation system. We have designed multi-beam antenna with array-fed reflector to form 8 beams on the Korean Peninsula. The target EIRP per beam is more than 59 dBW. The system is designed to present 6 dB boost beams for rainfall areas. Individual beams were optimized by the excited amplitude and phase of feed elements of the feed cluster. The multi-port amplifier(MPA) is one of effective approaches for flexible power allocation in combination with multi-beam antenna. In case of using MPA in multi-beam system, the inter-port isolation characteristic of MPA is important parameter to avoid interference among the output ports. In this paper, we propose a new MPA structure that consists of two $4{\times}4$ Buttler matrixes and phase/amplitude controllable power amplifier modules.

• Journal of the Institute of Electronics and Information Engineers
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• v.49 no.9
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• pp.43-48
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• 2012

This paper presents an iterative single-frequency continuous-wave signal-based I/Q regeneration method for improving image-rejection performance of multi-port junction-based direct receivers (MPDRs). This paper analyzes I/Q regeneration in MPDRs as I/Q mismatch compensation for direct conversion receivers. Based on the analysis, this paper evaluates the accuracy of I/Q regeneration in terms of the image-rejection ratio (IRR). The proposed method improves the IRR performance more than 20 dB compared to existing I/Q regeneration methods. Simulation results show that MPDRs using the proposed method can achieve an IRR of more than 70 dB, and that the bit error rate performances are almost the same as those of conventional coherent demodulators, even in fading channels.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.23 no.4
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• pp.449-456
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• 2012

Herein, we design a wideband $8{\times}8$ waveguide Butler matrix in order to use in a multi-port amplifiers(MPAs) at Ka-band. To achieve the broadband characteristic, we design a binomial 6-slot 3 dB directional coupler which is used to configure the $8{\times}8$ Butler matrix. The measured results of the fabricated $8{\times}8$ Butler matrix have low insertion loss of less than 0.3 dB, good return loss of over 26 dB and high isolation of over 35 dB within the design bandwidth of 3 GHz.

• Proceedings of the Korean Society of Coastal and Ocean Engineers Conference
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• 2006.09a
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• pp.129-132
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• 2006

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2012.10a
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• pp.411-413
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• 2012

다기능 경량 등부표는 바다와 강에 설치되어 선박 항로표시 및 수산, 양식 산업 시설물 경계표시 등 선박충돌사고 및 인명사고를 미연에 방지하기 위한 용도이며, 또한 수심이 낮은 해안과 암초지역은 물론 어떤 장소에서도 설치 및 운용이 용이하여 다양한 용도로 활용할 수 있도록 개발되었다.

• Journal of Korea Port Economic Association
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• v.19 no.1
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• pp.207-221
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• 2003

Now we are faced on the national policy to aim at the nationwide logistics center in North-East Asia. To come true, Korean ports developments policies are better off going towards integrated governmental supportive system build-up, activated infra-structures, back-yard developments, legal and institutional system, international co-ordination networks system, customer-oriented port management system like one-stop services, and multi-variate financing resources. Above all, Related governmental institutions strongly have self-confidences and devotional efforts to make them all implemented not losing own way.

• Proceedings of the Korea Port Economic Association Conference
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• 2003.07a
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• pp.343-357
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• 2003

Now we are faced on the national policy to aim at the nationwide logistics center in North-East Asia. To come true, Korean ports developments policies are better off going towards integrated governmental supportive system build-up, activated infra-structures, back-yard developments, legal and institutional system, international co-ordination networks system, customer-oriented port management system like one-stop services, and multi-variate financing resources. Above all, Related governmental institutions strongly have self-confidences and devotional efforts to make them all implemented not losing own way.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.6
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• pp.651-659
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• 2010

In this paper, a new six-port direct conversion receiver for high-speed multi-band multi-mode wireless communication system such as software defined radio(SDR) is proposed. The designed receiver is composed of two CMOS four-port BPSK receivers and a dual-band one-stage polyphase filter for quadrature LO signal generation. The four-port BPSK receiver, implemented in 0.18 ${\mu}m$ CMOS technology for the first time in microwave-band, is composed of two active combiners, an active balun, two power detector, and an analog decoder. The proposed polyphase filter adopt type-I architecture, one-stage for reduction of the local oscillator power loss, and LC resonance structure instead of using capacitor for dual-band operation. In order to extent the operation RF bandwidth of the proposed six-port receiver, we include I/Q phase and amplitude calibration scheme in the six-port junction and the power detector. The calibration range of the phase and amplitude mismatch in the proposed calibration scheme is 8 degree and 14 dB, respectively. The validity of the designed six-port receiver is successfully demonstrated by modulating M-QAM, and M-PSK signal with 40 Msps in the two-band of 900 MHz and 2.4 GHz.

• Journal of Korean Port Research
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• v.13 no.1
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• pp.175-182
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• 1999

The ocean wave is hydrodynamically investigated to get more reliable solution. To improve the computational accuracy more fine grids are used with relatively less computer storage on the free surface. One element of the free surface is discretized into more fine grids because the free-surface waves are much affected by the grid size in the finite difference scheme. Here the multi-grid method is applied to confirm the efficiency for the S103 ship model by solving the Navier-Stokes equation for the turbulent flows. According to the computational result approximately 30% can be improved in the free surface generation, Finally the limiting streamlines show numerical result is similar to the experiment by twin tuft.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2011.06a
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• pp.216-217
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• 2011

The problem of automated stacking cranes (ASC) dispatching in container terminals is addressed in this paper. We propose a heuristic-based ASC dispatching approach which adopts multi-criteria decision strategy. By aggregating different criteria the proposed strategy can consider multiple aspects of the dispatching situation and make robust decision in various situations. A multi-objective evolutionary algorithm (MOEA) is adopted to tune the weights associated to each criteria to minimize both the quay crane delay and external truck delay. The proposed approach is validated by comparison with different dispatching heuristics and simulation results obtained confirms its effectiveness.