• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.10 no.5
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• pp.237-244
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• 2010

In this paper, the dual parabolic cylindrical reflector systems are analyzed as the reflector system for the CATR(Compact Antenna Test Range) facility. The near-field at the test zone of the CATR is calculated by using the PO(Physical Optics) approximation. The CATR has to provide an uniform plane wave with the minimum amplitude and phase ripple and the low cross polarization. Therefore, in this paper, the near-field pattern are calculated, and the ripple and taper of the field and the cross polarization are investigated with the position of the subreflector and the test region. It is confirmed that the analysis results can be used for the design of the CATR with the dual parabolic cylindrical reflector.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.4
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• pp.371-380
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• 2010

The CATR(Compact Antenna Test Range) is a testing facility which is to provide the uniform plane wave by using the reflector. As the ripple of the uniform plane wave caused by the diffraction rays at the edge of the reflector, serrations are attached at the edge of the reflector to minimize the ripple of the uniform plane wave in the CATR. The diffraction field of the serration is normally analyzed by the Fresnel diffraction formula which is expressed as the double integration, and the structure of the serration is expressed as Fourier series to apply the double integration of the Fresnel diffraction formula. In this paper, the novel shark-fin shaped serrations which have the height modulation of the adjacent serrations are proposed. And the triangular serrations and the novel shark-fin shaped serrations are compared to confirm that the performance of the quiet zone by the shark-fin shaped serrations is better than by the triangular serrations. It is also confirmed that the novel shark-fin shaped serrations which have the height modulation of the adjacent serrations are lower ripple than which have the same height of the adjacent serrations. Accordingly, the novel shark-fin shaped serrations with the height modulation can be used at the edge of the reflector to provide the uniform plane wave in CATR.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.4
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• pp.451-460
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• 2008

Gregorian offset dual-shaped reflector antennas have been widely used in the satellite communication systems for their high gain and low sidelobe characteristics. However, in this paper, it is designed as the CATR(Compact Antenna Test Range) reflector system, and its near-field characteristics are investigated. The CATR facility needs to provide an uniform plane wave with the minimum amplitude and phase ripple and the low cross polarization to the test region. Therefore, the reflector near-field patterns are calculated and presented with the variations of the aperture power distribution, the feed horn pattern, and the distance from the aperture to the test zone. Also, the offset dual-shaped reflector is fabricated at 30 GHz, and its near-field patterns are measured. The measured results are in good agreement with the calculated results. From theses results, we confirm that the designed offset dual-shaped reflector can be used as the reflector system for the compact antenna test range.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.10 no.2
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• pp.113-122
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• 2010

The ripple within the quiet zone in the CATR(Compact Antenna Test Range) would be increased due to the diffraction at the edge of the reflector. Therefore, the reflector equipped with the serrations is generally used to reduce the ripple within the quiet zone. In this paper, the modified asymmetric triangular serrations are proposed, and the diffraction of the proposed serrations is analyzed using the Fresnel diffraction formula. The ripple of amplitude and phase between the conventional triangular and the proposed serrations are compared to confirm the ripple of the proposed serrations. As the result of the modulated the reflector size, height of the serrations and numbers of serrations, it is confirmed that the ripple of the proposed serrations is less than the conventional triangular serrations. Accordingly, proposed serrations are expected to reduce the ripple within quiet zone.

• Journal of Satellite, Information and Communications
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• v.7 no.1
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• pp.86-91
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• 2012

This paper described validation results of COMS Ka band antennas beam coverages which were developed by ETRI. After satellite launch, In Orbit Test(IOT) activities are stat to check spacecraft and payloads are still in healthy condition after launch. During IOT phase, ETRI measured radiation patterns of COMS Ka band antennas and compare with ground test(CATR) results. The antenna patterns similarity between IOT results and CATR results show that COMS Ka band antenna withstand launch vibration and in the good healthy condition. After IOT, ETRI performed field test for beam coverage measurements with vehicle to check if Ka band beam coverage are formed well as designed. For the beam coverage measurement, 17 points were selected over the Korean peninsula. The field measurement data were very similar with CATR data and this confirms that beam coverage are formed well over the Korean peninsula as expected.

• Review of KIISC
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• v.21 no.2
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• pp.53-60
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• 2011

국제표준화기구 ITU-T에서는 연구그룹(Study Group)17이 정보통신 응용보안에 관한 표준화를 리드하는 연구그룹으로, 산하 4개의 연구과제(Question)를 구성하여 정보보호 국제표준을 개발하고 있다. 이 연구과제들 중 Q.7(의장, 나재훈, ETRI)에서는 안전한 응용 서비스라는 범주로 안전한 응용 프로토콜, 웹서비스 보안, P2P(Peer-to-Peer) 보안 등 정보통신환경의 응용서비스 보호에 적용될 수 있는 국제표준들의 개발을 담당하고 있다. Q.8(의장, Liang Wei, CATR)에서는 서비스 지향 구조라는 범주로 SOA(Service Oriented Architecture) 기술 및 통신 보안에 관련된 국제표준들의 개발을 담당하고있다. 현재 Q.7에서는 총 7건의 국제표준을 제정하였으며, 총 6건의 표준초안들이 개발중에 있다. Q.8의 경우는 현재 총3건의 표준초안들이 개발중에 있다. 본 논문에서는 해당 연구과제들의 표준화 현황과 향후 추진 방향을 제시한다.

• Journal of Communications and Networks
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• v.13 no.4
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• pp.377-384
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• 2011

Cooperative beamforming has previously been proven to be an efficient way to improve the cooperative diversity. This method generally requires all relay nodes to participate in beamforming, which can be seen as "all participate" cooperative beamforming. However, not all relay nodes have constructive impacts on the end-to-end bit error rate (BER) performance. Based on this observation, we propose a new cooperative scheme which only selects those "appropriate" relay nodes to perform cooperative beamforming. Such relay nodes can be simply determined with mean channel gains. Therefore, the selection complexity is significantly reduced as global instantaneous channel state information is not required. This scheme guarantees that energy is only allocated to the "appropriate" relay nodes, and hence provides superior diversity. We also prove that power allocation among source and selected relay nodes is a convex problem, and can be resolved with lower computational complexity. Simulation results demonstrate that our scheme achieves an essential improvement in terms of BER performance for both optimal and limited feedback scenarios, as well as high energy-efficiency for the energy-constrained networks.