• The Journal of the Korea Contents Association
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• v.3 no.2
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• pp.78-86
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• 2003

The Minisoy of Information and Communication(MIC) requires telecompanys to share base stations in order to prevent the duplicated investment and environmental destruction which would be caused by the indiscreet construction of basestations for enlarging their own service area among telecompanys. This paper discusses' the problems of mobile communication services that have been generated in common-repeater at the Metropolitan subway. These problem include factors of power obstacles, communication equipment and establishment obstacles. The content of this paper is helpful in organizing the basestation sharing of IMT-2000 and the 4th generation mobile system, and provides the basics of a higher quality service for common-service communication.

• Information and Communications Magazine
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• v.15 no.4
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• pp.77-88
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• 1998

주파수 경매 정책의 필요성은 이동통신 분야의 수요 급증 (98년 4월말 현재 CDMA 이동전화 가입자가 570만, 무선호출 1500만, PCS 가입자 300만)과 더불어 IMT-2000과 같은 무선 이동 멀티미디어 서비스 개발과 2000년부터 실시되는 디지털 방송 서비스 등을 위해 효율적 전파 자원인 주파수 관리가 필요하며, 전파사업의 국내 관련 기술의 조기 정착이 요구되고 있다. 따라서 전파 자원 관리도 이용자 편의 증진과 새로운 통신 서비스 측면에서도 적극적으로 검토되어야 한다.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.12 no.6
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• pp.882-889
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• 2001

In this paper, the characteristics of u-slot antennas are computed by changing the feed structure, and compared with the measured results. The impedance bandwidths of 13 %(255.1 MHz) and 30.7 %(602.1 MHz) are obtained for probe feed and L-strip feed, respectively. It is known that the designed L-strip feed can be used for increasing the bandwidth of u-slot antennas. In addition, it is shown that the designed L-strip feed u-slot antenna can be used for domestic PCS and IMT-2000 dual band applications.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.11 no.7
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• pp.1139-1146
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• 2000

In this paper, circular-polarized dipole antenna with a novel structure is designed, simulated and fabricated for PCS or IMT-2000 base station at an arbitrary test frequency(1.575 GHz). Its radiation pattern is analyzed by means of physical optics(PO). The designed antenna is made up of a horizontal and a vertical dipole elements at a height of λ/4 above an reflector. One of λ/4 length vertical dipole element is located at a height of λ/8 above an reflector. In this case, circularly polarized radiation pattern is obtained by making impedance difference due to adjusting the length of each element. The characteristic of antenna measured from this study is that return loss is 18.4 dB, -10 dB bandwidth is 360 MHz(22.8%), 2 dB axial ratio bandwidth is 30 MHz, -3 dB beamwidth is 76$^{\circ}$, 2 dB axial ratio beamwidth is 58$^{\circ}$, axial ratio is 1.7 dB at 1.575 GHz. Radiation pattern is in well agreement with the result of PO.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.5 no.4
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• pp.668-675
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• 2001

Recently, the performance of the commercial PCS(Personal Communication Service) system has been improved to the uppermost limit and ultimately the next generation mobile communication is to be realized by IMT-2000 (International Mobile Communication-2000) to provide multimedia services. Therefore, the new type receiving system is researched actively and one of the most important part in a receiver is direct conversion method. The direct conversion method is suitable for low power consumption, small size, MMIC, and low price, which is to be adopted to the next generation mobile communication systems. In this case, however, several problems occur due to DC-offset. The DC-offset suppresses amplification of the required signal because of the leakage signal of frequency synthesizer in the system. In this thesis, the removing method of DC-offset was considered. There are four removing techniques of DC-offset, which are AC-coupling, large capacitor, DC-feedback loop, and DC-free coding. Among these, the AC-coupling method is the most simplest method and the DC-feedback loop method has the best performance. Then, the performance of the AC-coupling method and DC-feedback loop method are evaluated by HP's ADS simulation tool. As a result, the AC-coupling method cannot be used to the digital communication systems due to data loss. On the other hand, it was confirmed that the DC-feedback loop method is suitable for the direct conversion receiver.

• Journal of electromagnetic engineering and science
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• v.7 no.2
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• pp.69-73
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• 2007

A new wideband cylindrical monopole antenna is presented for multiple band applications. Multiple band property of the proposed antenna is achieved by adjusting the coupling structure with steps between the antenna base and the ground plane. The measured -10 dB impedance bandwidths are $1.74{\sim}3.06GHz\;and\;5.59{\sim}10.62GHz$, which can cover various kinds of wireless services, such as $PCS(1.75{\sim}1.87GHz),\;IMT-2000(1.92{\sim}2.17GHz),\;WiBro(2.3{\sim}2.39GHz),\;WLAN(2.412{\sim}2.483GHz,\;5.725{\sim}5.825GHz),\;DMB(2.63{\sim}2.655GHz)$, High-band $UWB(7.2{\sim}1.02GHz)$.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.43 no.11 s.353
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• pp.216-220
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• 2006

One of the approaches for reducing the size of the quarter wavelength monopole antenna is the helix and the stacked structure. This paper presents a formula for the relationship between the geometrical parameter and the operating frequency of a slacked helix chip antenna. The stacked helix chip antenna was designed for PCS/IMT-2000 dual-bands operation. The fabricated antenna uses an FR-4 substrate with relative permittivity of 4.2, and its dimensions are $15{\times}7.5{\times}0.4mm^3$. The measured impedance bandwidth (VSWR<2) is 400MHz at the operating frequency.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.26 no.3
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• pp.257-267
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• 2015

This paper presents a ultra-wideband sinuous antenna that operates in a whole frequency range (0.824~5.85 GHz) of Cellular/GSM-800, GSM900, ISM, GPS, DCS/GSM1800, PCS/GSM1900, WCDMA/UMTS/IMT2000, WiBro, WLAN and WiMax. The proposed antenna, which is composed of two sinuous arms, is designed as a self-complementary structure in order to have frequency-independent characteristics. It also uses a wideband balun of Klopfenstein taper structure to match to $50{\Omega}$. Experimental results show that the -10 dB return loss bandwidth of the proposed antenna is 5.24 GHz that ranges from 0.76 to 6 GHz, which covers all the frequency bands of the various wireless services. Within the entire operating frequency range, the measured radiation patterns in both E-plane and H-plane show nearly constant bidirectional broadside beams and the maximum antenna gain is measured to fall between 2.32~6.01 dBi.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.15 no.12 s.91
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• pp.1190-1198
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• 2004

In this paper, meander-line planar monopole antenna mounted on PCS/IMT-2000/WLAN handset for SAR reduction is designed. Frequency characteristics and SAR value optimized with various design parameters are analyzed and designed. Designed internal monopole antenna mounted on the handset is simulated. The 1 g and 10 g peak average SARs of internal monopole antenna are 0.656 and 0.387 W/kg respectively. And internal monopole antenna and external monopole antenna attached on the handset are tested. As a result, internal monopole antenna 1 g and 10 g peak average SARs are 0.686 and 0.356 W/kg. And external monopole antenna's results are 1.33 and 0.812 W/kg, respectively. So internal monopole antenna has a about $50\%$ SAR reduction in comparison with external monopole antenna.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.13 no.6
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• pp.546-551
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• 2002

In this paper, a triple controlled type DDFS-driven PLL frequency synthesizer with reduced complexity is used to show its applications for broadband wireless communication systems by frequency synthesis control. Since the proposed DDFS-driven PLL synthesizer is very simplified to use only phase accumulator in DDFS, it improves the switching speed and power consumption than the conventional DDFS-driven PLL frequency synthesizer. It is appropriate for applications with requirements of broadband, low-power consumption and high switching speed, since the proposed synthesizer can cover a wide range of frequency bands by the triple frequency control parameters. Method and results of frequency control parameters assignment are shown for the several frequency bands applications such as GSM, IMT-2000, Bluetooth and PCS system.