• Journal of electromagnetic engineering and science
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• v.4 no.1
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• pp.8-12
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• 2004

In this paper, a triple-band printed dipole antenna using parasitic elements is proposed for the multiple wireless services. The proposed antenna is designed and experimentally analyzed at the bands of PCS, IMT-2000, and ISM services. To achieve triple frequency operation, the proposed antenna contains two parasitic elements, which act as additional resonators by coupling from the driving dipole antenna. From the measured results, the resonant frequencies of this antenna are 1.79 ㎓, 2.03 ㎓, and 2.41 ㎓ and the measured impedance bandwidths are 90 MHz(1760∼1850 MHz), 210 MHz(1,930∼2,130 MHz), and 30 MHz(2,400∼2,430 MHz) for VSWR<2. The measured antenna gains are 2.14 ㏈i, 0.9 ㏈i, and 0.5 ㏈i, respectively. Antenna parameters for trifle-band operation are investigated and several antenna characteristics are discussed.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.26 no.12B
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• pp.1754-1757
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• 2001

In this paper, a R-band hybrid amplifier with the coplanar waveguide(CPW) and the photonic bandgap(PBG) structure is designed and fabricated. The PBG and the CPW techniques are simultaneously employed in amplifier to improve the power added efficiency(PAE) and the IMD(Intermodulation Distortion) in R-band. In this paper, the PBG structures are optimized to obtain matching network. The output impedance of amplifier and the input impedance of PBG are matched to minimize the return loss. The PAE and the IMD were improved 15% and 4.5dB compared with the conventional amplifier, respectively.

• Electronics and Telecommunications Trends
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• v.16 no.3 s.69
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• pp.39-51
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• 2001

최근 전기ㆍ전자 분야의 급속한 발전과 더불어 PCS 및 IMT-2000 등과 같은 무선 이동통신 서비스 사용이 증가함에 따라 전자파(Electromagnetic Wave)를 이용한 기술들이 하루가 다르게 개발되고 상용화되고 있다. 이러한 전자파 이용에 따른 역기능(inverse effect)으로 전자파 환경 오염에 대한 심각성과 국내ㆍ외 규제 기준의 폭이 점점 더 강화되고 있는 실정이다. 특히 전자파장해(EMC)에 대한 국제 규제 환경이 날로 강화되고 있어, 관련 분야의 제반 규제에 대한 기술적인 파악 및 대책 기술의 개발이 요구되고 있다. 본 고에서는 전자파장해 관련 국제 표준화 기구와 역할, 그리고 그러한 기구에서 논의중인 규제규격에 대해 알아보고, 이러한 기술기준에 대응하기 위한 노력의 일환으로 추진되어 온 국내ㆍ외 연구기관에서 수행된 전자파장해 관련 연구에 대해 기술하고자 한다.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.54 no.3
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• pp.180-185
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• 2005

Microstrip antennas generally have a lot of advantages that are thin profile, lightweight, low cost, and conformability to a shaped surface application with integrated circuitry. In addition to military applications, they have become attractive candidates in a variety of commercial applications such as mobile satellite communications, the direct broadcast system (DBS), global positioning system (GPS), and remote sensing. Recently, many of the researches have been achieved for improving the impedance bandwidth of microstrip antennas. The basic form of the microstrip antenna, consisting of a conducting patch printed on a grounded substrate, has an impedance bandwidth of $1\~2\%$. For improvement of narrow bandwidth of microstrip patch, we were designed U-slot microstrip patch antenna in this paper. This antenna had wide bandwidth for all personal communication services (PCS) and IMT-2000. For the design of U-slot microstrip patch antenna using a finite difference time domain(FDTD) method. This numerical method could get the frequency property of U-slot patch antenna and the electromagnetic fields of slots.

• Proceedings of the Korean Information Science Society Conference
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• 2001.10c
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• pp.589-591
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• 2001

90년대 이후 계속해서 이동통신 기술은 발전에 발전을 거듭해왔다 1세대 아날로그 이동통신에서 2세대 디지털 이동통신 그리고 2.5세대라고 하는 PCS(Personal Communication Service)에 이어 3세대 이동통신의 혁명이라는 IMT2000 서비스가 눈앞으로 다가왔다. 1,2 세대 이동통신이 음성통학 위주의 서비스를 제공하였다면, 2.5세대에서는 소비자의 욕구가 음성통화를 벗어나 데이터서비스를 요구함에 따라 점차적으로 데이터 서비스에 대한 비중이 증가하게 되었다. 3세대 이동통신에서는 보다 빠르고, 보다 많은 데이터를 전송하기 위한 방안이 고려되었다. 본 논문에서는 2.5세대 이동통신에서 제공되는 데이터 서비스를 이용하여 GPS 모듈과 연동하여 물류단말기에 응용할 수 있는 소프트웨어 모듈을 구현하였다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.8C
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• pp.819-827
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• 2002

Personal mobile communication has been developed up to IMT-2000 which is called the third generation mobile communication. The first generation of personal mobile communication was analog cellular, the second was digital cellular, and the 2.5 generation was PCS. Before the third generation had been developed, the personal mobile communication service was focused mainly on the voice-oriented service. But, we can expect that multimedia service after the third generation system will be the core of the subject. T In this thesis, we propose a dynamic resource allocation algorithm in the UTRA TDD systems which can support the asymmetric traffic propensity and multimedia traffic. The proposed algorithm consists two sub-algorithms. One is the dynamic channel allocation method that determines the amount of bandwidth assigned between uplink and downlink according to resource allocation status list through asymmetric traffic propensity. The other is the channel access mechanism that assigns RU to bearer service generated in a cell. By simulation, the proposed dynamic resource allocation algorithm is proved to support asymmetric propensity of traffic and shows a better throughput for multimedia traffic.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.23 no.9A
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• pp.2221-2229
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• 1998

Handoff is an important parameter for system performance and capacity analysis in CDMA cell planning. In this paper, simulation tool for analyzing the effects of soft handoff on cell planning of CDMA network is developed by studying propagation model in 1.9GHz frequency specrum, soft hadnoff algorithm given by IS-95, and several parameters for CDMA cell planning. By using the tool, soft handoff gain and effects of soft handoff on cDMA system performance and capacity are analyzed. Research results and simulation tool developed in this paper can be used for optimal CDMA cell planning for PCS and IMT-2000 in 1.9GHz frequency spectrum such as locating base station and parameter optimization.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.39 no.5
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• pp.225-231
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• 2002

This paper proposes a discriminative collision resolution scheme for the wireless Medium Access Control (MAC) protocols to support the Quality of Service (QoS) requirements of real-time applications. Our scheme deals with access requests in different ways depending on their delay requirements. In our scheme, a Collision Resolution Period (CRP) is used to quickly resolve collisions for the delay sensitive traffic in order to support their delay requirements. Performance analysis and simulation results show that our algorithm may successfully meet the delay requirements of real time applications by reducing access delays and collisions.

• Proceedings of the IEEK Conference
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• 2002.07a
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• pp.690-693
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• 2002

According to the growth of communication biz, embedded market rapidly developing in domestic and overseas. Embedded system can be used in various way such as wire and wireless communication equipment or information products. There are lots of developing performance applying speech recognition to embedded system, for instance, PDA, PCS, CDMA-2000 or IMT-2000. This study implement minimum memory of speech recognition engine and DB for apply real time embedded system. The implement measure of speech recognition equipment to fit on embedded system is like following. At first, DC element is removed from Input voice and then a compensation of high frequency was achieved by pre-emphasis with coefficients value, 0.97 and constitute division data as same size as 256 sample by lapped shift method. Through by Levinson - Durbin Algorithm, these data can get linear predictive coefficient and again, using Cepstrum - Transformer attain feature vectors. During HMM training, We used Baum-Welch reestimation Algorithm for each words training and can get the recognition result from executed likelihood method on each words. The used speech data is using 40 speech command data and 10 digits extracted form each 15 of male and female speaker spoken menu control command of Embedded system. Since, in many times, ARM CPU is adopted in embedded system, it's peformed porting the speech recognition engine on ARM core evaluation board. And do the recognition test with select set 1 and set 3 parameter that has good recognition rate on commander and no digit after the several tests using by 5 proposal recognition parameter sets. The recognition engine of recognition rate shows 95%, speech commander recognizer shows 96% and digits recognizer shows 94%.

• Journal of KIISE:Software and Applications
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• v.33 no.6
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• pp.580-587
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• 2006

As PDA, IMT-2000, and e-Book are developed and popular in these days, the number of users who use these products has been increasing. However, available memory size of these machines is still smaller than that of desktop PCs. In these products, TrueType fonts have been increased in demand because the number of users who want to use good quality fonts has increased, and TrueType fonts are of great use in Windows CE products. However, TrueType fonts take a large portion of available device memory, considering the small memory sizes of mobile devices. Therefore, it is required to reduce the size of TrueType fonts. In this paper, two-phase compression techniques are presented for the purpose of reducing the sire of hangul bitmap data embedded in TrueType fonts. In the first step, each character in bitmap is divided into initial consonant, medial vowel, and final consonant, respectively, then the character is recomposed into the composite bitmap. In the second phase, if any two consonants or vowels are determined to be the same, one of them is removed. The TrueType embedded bitmaps in Hangeul Wanseong (pre-composed) and Hangul Johab (pre-combined) are used in compression. By using our compression techniques, the compression rates of embedded bitmap data for TrueType fonts can be reduced around 35% in Wanseong font, and 7% in Johab font. Consequently, the compression rate of total TrueType Wanseong font is about 9.26%.