• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.20 no.4
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• pp.396-405
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• 2009

This paper describes playback downlink and telecommand uplink channel design performed for a transportable small-sized KOMPSAT(Korea Multi-Purpose Satellite) ground station. As a result of downlink channel design, required receiving performance was calculated from the threshold signal-to-noise ratio of playback signal and it was revealed that this performance can be guaranteed in 1.5 m ground station with 6.5 dB/K of G/T. For the uplink channel design, 40 dBW of EIRP was derived from the threshold signal-to-noise ratio of telecommand signal received at on-board receiver. The implemented small-sized ground station based on design was evaluated to be fully acceptable for KOMPSAT TT&C(Telemetry, Tracking and Command) system and playback downlink design without taking account of additional 3 dB system link margin was shown to be effective because it had provided constantly initial channel performance without any remarkable degradation over several years of tests with KOMPSAT and KOMPSAT-2, for both uplink and playback downlink in the elevation angle above $10^{\circ}$.

• Journal of Astronomy and Space Sciences
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• v.37 no.1
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• pp.11-18
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• 2020

Satellite optical communication has gained significant attention owing to its many quality features (e.g., a larger bandwidth, license free spectrum, higher data rate, and better security) compared to satellite microwave communication. Various experiments have been performed during many space missions to demonstrate and characterize inter-satellite links, downlinks, and uplinks. Korea has also planned to establish an experimental communication system using a geostationary earth orbit (GEO) satellite and the Geochang station as an optical ground station for low Earth orbit (LEO)-to-ground optical relay links. In this study, the performance of inter-satellite communication links and downlinks was investigated for the new Korean experimental communication system in terms of link margin, bit error rate (BER), and channel capacity. In particular, the performance of the inter-satellite links was analyzed based on the receiving apertures and the transmitting power, while that of the downlink was analyzed in terms of atmospheric turbulence conditions and transmitting power. Finally, we discussed two system parameters of receiving aperture and transmitting power to meet the three criteria of link margin, BER, and channel capacity.

• Journal of Space Technology and Applications
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• v.4 no.1
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• pp.48-61
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• 2024

In this paper, we introduce the concept of the cube satellite Chungnam National University Laser Unity Bus (CLUB), which can provide an integrated infrastructure for various ground-space laser applications. With the advent of the new space era, the rapid expansion of space utilization has begun to reveal the limitations of conventional radio frequencies. As space missions diversify, lasers are garnering attention as a viable alternative. Between ground and space, lasers are applied in various fields including satellite laser ranging (SLR), laser weapons, and laser communication. However, laser used between the ground and space are significantly influenced by the Earth's atmosphere. Consequently, understanding the atmospheric effects on laser propagation is crucial. In particular, atmospheric turbulence, which refracts and distorts laser beams, intensifies closer to the Earth's surface, exerting a greater impact on the uplink than on the downlink. While downlink verification is facilitated by ground detection, verifying the uplink poses challenges due to the necessity of space-based detection. In response to these challenges, we propose the idea of cube satellite as a means to enhance understanding and verification of laser propagation in the uplink. Additionally, we present the results of conceptual design by analyzing requirements, focusing on mission design of the CLUB cube satellite, following the stages of systems engineering for systematic cube satellite development.

• Proceedings of the KSRS Conference
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• 2005.10a
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• pp.98-100
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• 2005

This paper describes link analysis on the processed data, HRIT (High Rate Information Transmission) and LRIT (Low Rate Information Transmission), for the preliminary design of interface between COMS (Communication, Ocean and Meteorological Satellite) and ground station. At the MODAC (MeteorologicaVOcean Data Application Center), the processed data are transmitted to user station via COMS with normalization and calibration by pre-processing of MI (Meteorological Imager) data. Due to consider satellite as radio relay, overall analysis containing uplink and downlink is needed. Specific link parameters can be obtained with using the outcomes of SRR (System Requirement Review) which was held on 13-14 June 2005, in Toulouse. From the relation between overall link margin and output power of HPA (High Power Amplifier) of MODAC, it is shown that even though the minimum power related with COMS receiving power range is transmitted at MODAC, the obtained link margin of HRIT could be above 3 dB at user station which antenna elevation angle is 10 degree.

• Proceedings of the Korea Information Processing Society Conference
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• 2004.05a
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• pp.1533-1536
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• 2004

위성의 비행소프트웨어는 위성이 주어진 임무를 수행할 수 있도록 위성을 제어하는 것으로 지상으로부터의 원격 명령을 받아 처리하고 원격측정 데이터를 지상으로 송신하는 기능과 자세 결정 및 제어, 전력 제어, 열 제어, 탑재체 관리 등의 기능을 수행한다. 본 논문은 다목적실용위성 2호의 비행소프트웨어에서 원격측정 데이터를 저장하고 지상으로 전송하는 기능을 수행하는 MMD (Mass Memory and Downlink Management) 소프트웨어의 설계 및 구현 내용과 시험절차, 방법, 시험결과 등에 대해서 서술하였다.

• Journal of The Institute of Information and Telecommunication Facilities Engineering
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• v.2 no.3
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• pp.36-47
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• 2003

Wideband Code Division Multiple Access (WCDMA) is one of the air interface techniques proposed for the third generation (3G) mobile communication system. WCDMA was selected because it fulfills the IMT-2000 requirements for higher data rate trans mission, support of multimedia capabilities and other flexible services due to its variable bit rates and larger bandwidth, improved capacity and coverage, efficient power control and support for advanced and improved detector structures. Performance evaluation of 3G wireless network through simulation plays an important role in the design and implementation of the actual system, aiding the wireless system designer by providing them the necessary performance conformance statistics prior to implementation. In accordance with this goal, a simulator engine was developed entirely on a MATLAB platform to emulate the behaviour of the WCDMA air interface for both the uplink and downlink in a real world fading mobile environment. This paper discuss the development of the simulator along with a brief description of its functionalities and user interface. The WCDMA air interface mode focused in this paper is in accordance to the 3GPPs frequency division duplex (FDD) mode and restricted to the physical layer description. Performance results for the selected cases for the downlink, uplink, varying mobile velocity and sampling rates are also provided.

• Proceedings of the KSRS Conference
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• 2004.10a
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• pp.467-470
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• 2004

In early 2004, KARI developed 5ft S-Band TT&C antenna for especially KOMPSAT-2 operation in LEOP phase. This paper shows system features of 5ft S-Band antenna and its test result with KOMPSAT-l. Tracking test, command uplink test and telemetry downlink test were performed. Through tests, 5ft antenna was verified to be operational in uplink and downlink with KOMPSAT series. Due to its inherent wide 3dB beam-width of about 7deg at S-Band, this antenna system can be used very effectively even though orbital information is less accurate like LEOP and spacecraft safe mode.

• Bulletin of the Korean Space Science Society
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• 2004.10b
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• pp.344-346
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• 2004

KOMPSAT-2 (Korea Multi Purpose Satellite 2) which is scheduled to launch in 2005 year will communicate with KARI TTC (Tracking, Telemetry, and Command) station flying along sun synchronous orbits (685 km). The command from KARI TTC passes S-band omni-antenna, RF assembly, and transponder and finally reachs OBC (On Board Computer). The telemetry from KOMPSAT-2 arrives at KARI TTC through inverse procedure. In this paper, RF compatibility test between KOMPSAT-2 and KARI TTC station is demonstrated. RF interface for this test was established through real space and uplink signal test and downlink signal test and uplink & downlink signal test were performed.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.3 no.4
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• pp.839-847
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• 1999

This paper presents the performance evaluation of direct broadcasting satellite by monte-carlo(MC) and quasi-analytic(QA) simulation method in the existence of uplink/downlink adjacent channel interference(ACI), co-channel interference(CCI), and gaussian noise. Korea's satellite system parameters and link design are used at the simulation. MC and QA simulation methods are a valuable adjunct to analytical performance.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.31A no.5
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• pp.58-67
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• 1994

In this paper, It was designed the 2.8GHz local oscillator which convert 14.5 14.8GHz uplink frequency to 11.7 12.0GHz downlink frequency by the receiving mixer on the communication satellite transponder according to the rating of domestic satellite. Mukunghwa 1. To prevent the variation of the communication channel bandwidth, it needs a high stability and low phase noise characteristics. So we designed to get the target frequencey by multipling the output signal from the crystal oscillator. We got the simplicity of the circuit by manufacturing the X4 multiplier with transistor which is ordinarily used as a device of a below X3 multiplier for the efficiency.