• Proceedings of the KIEE Conference
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• 2004.07d
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• pp.2170-2172
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• 2004

UAV(Unmanned Aerial Vehicle)에 위치 추적 및 비행 데이터에 의한 항로추정기법에 대한 연구 중 비행영상과 데이터를 무지향성안테나와 지향성안테나 두 가지로 수신을 받았다. 그러나 국내 전파법상 제한된 출력 때문에 송수신 거리의 영향을 받아 지향성안테나를 사용할 수밖에 없었다. 지향성안테나의 단점은 전 범위가 아니라 일정범위에서만 송수신이 가능하다. 본 논문은 지향성안테나의 단점인 일정범위가 아닌 안테나를 움직임으로써 전범위에서 송수신이 가능하도록 하는 안테나 방향 제어를 연구한 내용과 움직이는 물체로부터 좌표데이타, 고도, 삼축가속도 센서를 수신하여, 이 데이터로 적용하여 자세 및 이동경로를 산출하여 안테나가 최적의 움직임을 가질 수 있도록 연구한 내용을 기술하였다.

• Proceedings of the IEEK Conference
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• 2003.07a
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• pp.609-612
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• 2003

For combating multipath fading in wireless radio environment, diversity schemes is useful. In this paper, for performance improvement of polarization diversity system, we analyzed a two-branch polarization diversity at the receiving end of a mobile link when the transmitter emits a circularly polarized wave. And In order to calculate the correlation coefficient considering the XPD(cross polarization discrimination) between the received signals for the two diversity branches, a simple theoretical model of circular polarization diversity is adopted and calculate correlation coefficient. From the analysis results, it is seen that the correlation coefficient of circular polarization diversity evaluated by the XPD is less than that of vertical polarization diversity. And also, we designed and fabricated circular polarization diversity system with microstrip antenna. we analyzed data measured in indoor NLOS environment using fabricated circular polarization diversity system. From the measurement results, it is clearly seen that the diversity effect of circular polarization diversity system is higher 3dB than vertical polarization diversity system.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.1
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• pp.317-321
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• 2012

In this paper, properties of directional coupler with high directivity was investigated. The directional couler is used to check and verify the power, frequency, and antenna reflection of signal at transmission station for mobile communications. To get the high directivity in the directional coupler, directional coupler was simulated and fabricated. we obtained the directional coupler having more than 31dB directivity.

• Proceedings of the KAIS Fall Conference
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• 2008.11a
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• pp.294-296
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• 2008

본 논문에서는 변형된 Monopole 안테나에 의한 GSM 900, 1800, 1900 3중 대역 BAR TYPE 형 휴대폰내장형 안테나를 설계 및 제작 하였다. 본 논문은 실제 상용화된 휴대 단말기의 내장형 안테나를 Monopole 타입으로 설계하여 현재 상용 중인 안테나에 부합하는 특징을 가지도록 하였다. 설계된 안테나를 제작 측정한 결과 기존의 안테나 보다 약 5.51% 1.39dB 특성이 개선되었다.

• Proceedings of the KAIS Fall Conference
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• 2005.05a
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• pp.163-165
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• 2005

본 논문에서는 GSM/DCS/USPCS 대역에서 사용할 수 있는 PIFA 형태의 내장형 안테나를 설계하고 이를 제작하였다. 이 안테나는 제한된 공간에서 기본 PIFA에 적절한 슬릿을 구성하여 트리플 밴드를 형성 시켰으며, GSM 대역에서 Maximum Gain -3.25dB$\~$6.37dB, DCS 대역에서 Maximum Gain -0.46dB$\~$2.95dB의 결과를 얻었다. 방사패턴 또한 전 방향성에 가까운 특성을 가지고 있으며 현재 GPRS용 휴대폰에 적용시키고 있다.

• Journal of Korea Society of Digital Industry and Information Management
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• v.4 no.2
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• pp.49-55
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• 2008

Combining OFDMA with MIMO is the key technology for the 4G mobile communication. OFDMA can relieve inherent difficulties of high-speed transmission. MIMO technology can be largely categorized into two techniques: one is STC for diversity gain and the other is SM for high frequency efficiency. In this paper, we depict various MIMO techniques of two transmit antenna and compare the computational complexity of decoding process for the techniques. Then, we analysis the performance of the techniques in the WiBro downlink environment based on OFDMA. We perfer ML algorithm which is the optimum performance and ZF algorithm of least computational complexity for SM detection.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.3
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• pp.301-303
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• 2016

This paper proposes a method providing diversity gain using small base stations in a cell coverage in order to improve diversity gain. The small base stations and the conventional base station consist a virtual MIMO array by using the cooperative communication scheme. Also, transmission diversity scheme is applied. A mobile user can receive the signals having the improved reliability by the applied transmission diversity scheme and the cooperative communication scheme.

• Journal of the Korea Society for Simulation
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• v.13 no.2
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• pp.1-12
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• 2004

This paper estimated the arrival angle and electric wave delay time using the space method law and the directions of arrival (DOA) estimation algorithm in case of signal correlation. Space method law is the method used to repress cross correlation before applying the weight value to the receiving signal. The values of the diagonal elements in the correlation matrix were averaged to replace as the diagonal elements value. In the area of wireless communication or mobile communication, there are high correlations in case of low delay time difference in multiple waves. This causes the quality of the communication to drop due to interference with the desired signal elements. This paper estimated the arrival angle and electric wave delay time using the space method law and the MUSIC algorithm. With the arrival angle algorithm, the arrival angle cannot be estimated below 5 in case of signal correlations because the angle resolution capacity decreases accordingly. The super resolution capacity was estimated to determine the arrival angle below 5 in this paper. In addition, the proposed algorithm estimated the short delay time difference to be below 20ns.

• ETRI Journal
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• v.27 no.6
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• pp.768-776
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• 2005

We compare the achievable throughput of time division multiple access (TDMA) multiple-input multiple-output (MIMO) schemes illustrated in the 3rd Generation Partnership Project (3GPP) MIMO technical report, versus the sum-rate capacity of space-time multiple access (STMA). These schemes have been proposed to improve the 3GPP high speed downlink packet access (HSDPA) channel by employing multiple antennas at both the base station and mobile stations. Our comparisons are performed in multi-user environments and are conducted using TDMA such as Qualcomm's High Data Rate and HSDPA, which is a simpler technique than STMA. Furthermore, we present the unified optimal power allocation strategy for HSDPA MIMO schemes by exploiting the similarity of multiple antenna systems and multi-user channel problems.

• Journal of electromagnetic engineering and science
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• v.10 no.4
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• pp.303-308
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• 2010

This paper proposes a method for improving the isolation characteristic of multi-input multi-output (MIMO) antennas using a split ring resonator (SRR) array structure between the two radiating elements. The fabricated antenna satisfies the 10 dB return loss requirement in the Mobile-WiMAX frequency band from 3.4 GHz to 3.6 GHz. The isolation between the two radiating elements is improved by approximately 20 dB at the center frequency by inserting a SRR array structure. The measured peak gains of the two elements are 2.3 dBi and 2.4 dBi, respectively.