• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.11 no.2
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• pp.268-277
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• 2000

Nowadays, the interference between neighbor basestations is getting higher as mobile communication services expand, then the increase of the interference causes IMD(Intermolulation Distortion) problems for not only active devices but also passive devices. In this paper, we have designed and assembled several adapters having variable plating thickness and materials to analyze PIMD(Passive Intermodulation Distortion) mechanisms for coaxial cables which is one of the representative passive RF devices. The measurement results of the assembled adapters show that IM level depends on conductivity of plating materials, plating thickness, device structure, aging effect and so on. Furthermore, we have obtained PIMD mechanisms and some control methods of PIMD from the results.

• Proceedings of the KIEE Conference
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• 2000.07d
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• pp.2513-2515
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• 2000

The Hot Strip Mill(HSM) process consists of reheating furnace, roughing mill, finishing mill and coiler. Reheating furnace heats slab and roughing mill, finishing mill produces strip from this slab. The quality of this production mainly depends on finishing mill, which consists of 6 or 7 stands. Between stands a looper is installed for the better material flow. Automatic gage control(AGC), speed control system and looper system, which are connected with each other, are the main control systems for HSM. The low strip tension can make a loop between stands, which can be caused cobble. On the other hand, high strip tension causes thickness and width reduction, which affects the product quality, and can lead to tear the strip, if it is too high. Because of it, a proper strip tension is needed for better material flow: e.g. A good looper control system is substantial for the better production quality. What is handled in this paper is, the looper controller, which is developed to minimize the fluctuation of width of strip by maintaining an appropriate strip tension between stands and to achieve the stability of the looper control system. And its performance compared with a conventional PID controller is also discussed. The difficulties associated with the maintenance of the constant tension are described.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2015.11a
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• pp.39-40
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• 2015

방송망의 효율적인 관리 및 운영을 위해 다양한 측정 및 모니터링 방법이 제안되고 있다. 특히 디지털 방송신호의 특징상 송신 장비의 열화가 진행되더라도 수신 장비의 채널 복호 및 오류정정, 다양한 형태의 페이딩(fading) 간섭으로 인해 이를 정확히 파악하기 어렵다. 또한 운영 인력의 축소, 관리 대상 매체의 증가 등 방송사의 인력관리의 문제등도 감안할 때, 다양한 매체의 종합적인 품질 관리를 위해서는 집약적이고 시간 지속적인 측정방법의 도입이 필요하다. 본 논문은 이러한 다매체 다채널 방송 환경에서 효율적인 측정 및 모니터링을 위해 집적화된 형태의 방송 모니터링 시스템의 구현 방법을 제안한다. 제안하는 시스템은 다양한 매체의 튜너를 하나의 제어기에 연결하고 이를 스케줄링 기법에 의해 순차적으로 측정한 후 방송 품질의 핵심 파라미터 측정결과를 네트워크를 통해 원격 서버로 전송한다. 이를 통해 단기 및 장기모니터링을 실시할 수 있으며, 일간, 월간, 연간 신호의 변화를 종합적으로 측정 및 모니터링 할 수 있어 시간 및 계절에 따른 신호 품질의 변화 및 순간적인 방송 신호의 변화 등을 감지할 수 있는 새로운 형태의 방송 품질 모니터링 시스템이다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.7 no.7
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• pp.1399-1405
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• 2003

This paper proposes an MAC protocol for fair packet data services in stoned CDMA system. In slotted CDMA system, the packets transmitted in the same slot act as multiple access interference, so that unsuccessful packet transmissions are entirely caused by multiple access interference. Therefore, in order to get the optimal system throughput, the number of simultaneously transmitted Packets should be kept at a proper level. In the proposed protocol, the base station calculates the new and retransmitted packet transmission probability of mobile stations according to the offered load and then broadcasts these probabilities. Mobile stations, which have a packet, attempt to transmit packet with the received probabilities. Simulation results show that the proposed scheme can offer better system throughput than the conventional scheme, and guarantee a good fairness among all mobile stations regardless of the offered load.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.2 no.1
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• pp.71-77
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• 1998

In this Paper, the training principles and the control method of adaptive array antennas using the LMS and CMA algorithms for the $\pi$/4 QPSK signal is showed and the convergence characteristics, the adaptivity of directional pattern SINR and the replication of desired signal of adaptive arrays are compared and discussed each other. Computer simulation results showed that the SINR of LMS adaptive array was 13.8［dB］, and that of CMA was 12.8［dB］, and also the convergence characteristics of LMS was fast a little than that of CMA. The LMS adaptive array was also performed null point well for the interference signal direction than that of the CMA adaptive array.

• Journal of KIISE:Information Networking
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• v.30 no.1
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• pp.65-74
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• 2003

In this Paper, we propose a downlink service admission strategy that considers users QoS requirements by using a novel service quality prediction index for multi-service WCDMA mobile systems. The Proposed downlink service admission strategy is obtained by computing average received Power of each service, assuming a relative other-cell interference factor. With the proposed method we obtain a downlink service admission region where users of different services properly can be admitted. And adding the fairness at the proposed downiinh service admission strategy, we Propose another downlink service admission strategy. In the numerical examples, the downlink service admission region with fairness and the downlink service admission region without fairness of voice service and data services are obtained by proposed downlink service admission strategies, respectively.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.26 no.11B
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• pp.1595-1599
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• 2001

In this paper, we have desired and implemented of ASK modulator MMIC operating at 5.8 GHz for OBE used in AGPS(Automatic Gate Passing System). The proposed ASK modulator MMIC was implemented to apply a single supply voltage of 3 V to the drain in order to decrease ACP(Adjacent Channel Power). As a result, it is exhibits a broad linear modulation range from 0.7 V to 3 V and an On/off characteristic over 40 dB. The layouts of ASK modulator MMICs was designed and fabricated by using ETRI 0.57m MESFET library The chip size was 1.0mm $\times$x1.0mm.

• Journal of KIISE:Computing Practices and Letters
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• v.16 no.5
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• pp.591-595
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• 2010

In this paper, a method that dynamically adapts the traffic flow of automated guided vehicles (AGVs) used in automated container terminals to the changing operational condition is presented. In a container terminal, the AGVs are vulnerable to traffic congestion because a large number of AGVs operate in a limited area. In addition, dynamically changing operational condition requires the traffic flow of AGVs to be continuously adjusted to keep up with the change. The proposed method utilizes a genetic algorithm to optimize the traffic flow. Exploiting the dynamic nature of the problem an approach that reuses the results of the previous search is tried to speed up the convergence of the genetic algorithm. The results of simulation experiments show the efficiency of the proposed method.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.6 no.5
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• pp.724-730
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• 2002

Digital communication systems are required to cause the minimum interference to adjacent channels, they must therefore employ the linear power amplifiers. In respect to linear power amplifiers, there are many linearization techniques. Feedforward power amplifier represent very wide bandwidth and high linearization capability. In the feedforward systems, overall efficiency is reduced due to the loss of delay line. In this paper, delay filter instead of transmission delay line adapted to get more high efficiency. Experimental results showed that ACLR (Adjacent Channel Leakage Ratio) has improved 17.43(dB), which is added 3.44(dB) by using the delay filter.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.3
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• pp.1083-1095
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• 1996

Shock wave/boundary layer interaction frequently causes the shock wave to oscillate violently and thus the global flow field to unstabilize. In order to stabilize the shock wave system in the diffuser of a supersonic wind tunnel, the present study attempted to control the shock oscillations by using a passive control. A porous wall with the porosity of 19.6% was mounted on a shallow cavity. Experiment was made by means of schlieren optical observation and wall pressure measurements. The flow Mach number just upstream the shock system and Reynolds number based on the turbulent boundary layer thickness were 2.1 and 1.8 * 10$\^$6/, respectively. The results show that the present passive control method on the shock wave/boundary layer interaction in the supersonic diffuser can significantly suppress the oscillations of shock system, especially when the shock system locates at the porous wall.