• The Bulletin of The Korean Astronomical Society
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• v.37 no.2
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• pp.192.1-192.1
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• 2012

영상레이더 (SAR: Synthetic Aperture Radar) 혹은 통신 안테나/탑재체를 장착한 위성은 원하는 주파수 대역의 운용을 위해 대형 안테나 구조물 장착이 필수적이다. 이러한 대형 구조물은 일체형으로 제작되어 위성체에 접속되었을 때, 요구 무게 및 점유하는 부피가 매우 큰 특징을 지닌다. 따라서, 대형 안테나 구조물의 중량으로 인해 발사비 증가가 불가피하며, 페어링 내부의 허용된 공간에 안테나 크기는 큰 제약적 요인이 된다. 그리고, 전개식이어도, 전개후 질량 관성이 큰 구조물이 된다. 위성체의 발사 비용과 직결되는 안테나의 경량화를 위한 많은 기술이 연구되고 있다. 특히, 접이식 팽창형 안테나는 반사체의 유연한 메쉬 구조 및 경량 지지구조물로 안테나의 무게를 줄이고 수납 효율을 향상시킨다. 또한, 전개 후 안테나의 목적한 기능을 충분히 보장함과 동시에 질량 관성이 작은 구조물에 의한 위성의 기동성을 극대화할 수 있다. 국내에서도 전천후 지상관측감시 및 통신 안테나의 필요성 증대에 따라 초경량 전개형 안테나 개발의 필요성이 크게 대두되고 있으나, 현재까지는 관련 기술개발 사례가 전무한 실정으로 국내 독자적 기술 확보가 시급한 실정이다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.42 no.6
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• pp.522-528
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• 2014

A UHF/VHF full-duplex communication using monopole and dipole antenna has been widely used for cube satellite applications. This kind of communication system requires a dedicated structure panel for antenna integration, which is the one of the disadvantages of the conventional communication system from the accommodation point of view considering the extremely limited volume of the cube satellite. In this study, to maximize the accommodation efficiency of the cube satellite, the commercial UHF half-duplex antenna combined with buck converter for communication modes transition has been considered in the communication system design. Its effectiveness has been verified through link budget analysis based on the antenna specifications and satellite's operation conditions. In addition, the antenna deployment mechanism for the synchronous release of multi-antennas has also been introduced.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.39 no.3
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• pp.279-288
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• 2011

This paper will discuss the alignment techniques and measurement results of geostationary satellite communication antennas for correct antenna pointing and also the fixtures. To get the best performance in terms of antenna pointing and fixtures, zero G condition have been simulated and laser tracker and theodolite system have been applied. As a result, alignment stability was verified within the tolerance, ${\pm}\;0.25mm$ and ${\pm}\;0.013^{\circ}$ and finally Ka-band deployable antenna alignment has been accomplished within the tolerance, ${\pm}\;0.5mm$ and ${\pm}\;0.015^{\circ}$.

• Journal of Space Technology and Applications
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• v.1 no.3
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• pp.364-374
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• 2021

This research discusses the change in radio frequency (RF) characteristics according to the number of Gores on the deployable mesh antennas for potential micro-satellite applications. The deployable type of lightweight mesh antenna can be used for various space missions such as communication/SAR/ SIGINT. In order to implement an ideal curvature of antenna surface, sufficient number of antenna rib structures are required. However, the increase in antenna ribs affects various design factors of the antenna system, especially total system mass, complexity of deployable mechanism and reliability. In this paper, the proper number of ribs for the mesh antenna were derived by comparison of electro-magnetic (EM) simulation results of example of antenna model in accordance with the various number of ribs.

• Journal of Aerospace System Engineering
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• v.17 no.4
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• pp.1-9
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• 2023

Recently, as Synthetic Aperture Radar (SAR), communication, and signal surveillance missions of spacecraft have become more advanced, research has been actively conducted on the deployable large mesh antenna system with excellent storage efficiency compared to the deployment area, and light weight. Deployable Mesh antennae are characterized by an increase in the number of Openings Per Inch (OPI), which is a measure of mesh weaving density as the mission frequency band increases, and this OPI change directly affects the thermal optical properties of the mesh antenna, so research on this is required. In this paper, to verify the thermal relationship between the optical properties of the mesh and antenna reflector, thermal sensitivity analysis between the mesh and the antenna reflector is performed by in-orbit thermal analysis with various optical characteristics of the mesh based on existing overseas research cases. In addition, the temperature gradient effect of the mesh reflector is analyzed.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.40 no.5
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• pp.439-445
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• 2012

The COMS(Communication, Ocean, and Meteorological Satellite) is subjected to shock loads when the stage or fairing of a launch vehicle is separated and the satellite is separated from the launch vehicle during the launch vehicle flight. And, after the satellite is separated from the launcher, the COMS is subjected to shock loads when the solar array is deployed, Ka-Band communication antenna is deployed, and meteorological imager radiator cover is released. In order to validate the satellite safety against these shock loads on ground, shock tests were performed. In this paper, the shock tests performed in the course of the COMS development are described, and the method to assess the test result is presented with an example of Geostationary Ocean Color Imager(GOCI). In Ariane-5 launch vehicle, the clampband release shock for satellite separation is lower than the fairing or stage separation. In this paper, the extrapolation method to take into account the maximum shock load from the launch vehicle by using the satellite separation shock test result is also introduced.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.18 no.1
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• pp.39-46
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• 1993

In this paper, an offset paraboloidal reflector antenna satisfied efficiency of over 60% and sidelobe envelope line of 29-25$log\theta$ was designed and manufactured for Ku-band VSAT(Very Small Aperture Terminal) antenna. The radiation patterns of experimental antenna were computed by applying the series expansion method using the Zernike polynomials. The measured patterns are in good agreement with the computed results. The Gain, efficiency, and sidelobe envelop line fairly well satisfy the design specifications except first sidelobe level.

• Journal of Satellite, Information and Communications
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• v.5 no.2
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• pp.34-39
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• 2010

Due to big demand for satellite and communication service using personal handheld terminals, demand for satellites with huge antennas is increasing correspondingly. While such large antennas are realized by various types of deployable antennas, the reflecting surface is made by many facets irrespective of deploying mechanisms. In order to analyze the faceted-reflector more accurately, an existing ray-tracing method is improved. The algorithm allows the rays to cross each other, which is the main characteristic of the faceted-reflector, and takes unevenness of amplitude and phase over the aperture plane into consideration. For the study of the effect of facet configuration, facet generating algorithm is devised. From the analysis algorithm and the facet-generating algorithm, it has been found that the number of facets in a radial direction affects both directivity and sidelobe level. On the other hand, the number of facets in a circumferential direction affects sidelobe level only.

• Journal of Convergence for Information Technology
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• v.11 no.11
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• pp.51-56
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• 2021

In this paper, performance degradation in the cross-eye jamming due to amplitude mismatch of two jamming antennas is considered. The mismatch of the amplitude ratio is modeled as a random variable with a normal distribution of the difference between the actual amplitude ratio and the nominal amplitude ratio due to mechanical defects. In the proposed analytic performance analysis, the first-order Taylor series expansion and the second-order Taylor series expansion is adopted. Performance measure of the cross-eye jamming is the mean square difference (MSD). The analytically derived MSD is validated by comparing the analytically derived MSD with the first-order Taylor series-based simulation-based MSD and the second-order Taylor series-based simulation-based MSD. It shows that the analysis-based MSD is superior to the Monte-Carlo-based MSD, which has a high calculation cost.

• Journal of Navigation and Port Research
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• v.29 no.5 s.101
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• pp.403-408
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• 2005

The techniques of estimating angle of arrival(AOA) have played a key role for enhancement of wireless communications using array antennas. Among those techniques, the superresolution algorithms, such as MUSIC and ESPRIT, calculate the covariance matrix of the array output vectors which are observed at the array antennas, and then by using eigen-decomposition of the covariance matrix, they estimate AOAs of the received signals with high accuracy. However, superresolution algorithms based eigenvalue decomposition fails to estimate AOAs under multipath environments. Under multipath environments, it is difficult to estimate AOAs of the received signals due to coherency and high-correlation. To resolve coherent signals, the covariance matrix is calculated by using the conventional spatial smoothing technique, and then the techniques based on eigen-descomposition is applied. The result of the conventional spatial smoothing technique, however, is obtained at the cost of losing effective spatial aperture. Moreover, the conventional technique ignores any information in the cross-correlations of the array outputs the subarrays. As the result, the performance for AOA estimation is degraded. In this paper, we propose a new spatial smoothing technique, which consider the cross-correlation for subarrays. By computer simulation, the AOA estimation performance of the proposed method is compared with the conventional method and evaluated.