• Journal of Broadcast Engineering
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• v.1 no.1
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• pp.1-6
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• 1996

Digital DBS service using Korea Sat starts at Korea Telecom's Yong-in transmission site. Total 6 transmitting stations are needed. At each transmitting station, 4 TV programs are compressed and multiplexed using MPEG-2, modulated into IF, RF signals, then finally transmitted through antenna. At DBS transponder, received signal is down converted, amplified and re-transmitted to earth. At receiver, signal is received by 45cm dish antenna, then wanted program is selected, demultiplexed and decoded. Transmission performance of BER lOE-ll is implemented by using FEe coding and QPSK modulation. For pay TV management, conditional access system, smart card and modem are used.

• Proceedings of the Korea Information Processing Society Conference
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• 2000.10b
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• pp.1267-1270
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• 2000

위성통신 시스템은 기존의 지상망이나 광 케이블 기술에 비해 통신 대역폭의 유연성과 다중 접속능력, 이동통신, 광역성, 멀티포인트 및 브로드캐스팅 등의 본래의 특징으로 인해 초고속정보통신망 구축에 중요한 역할을 하게 된다. 특히 OBP (On-Board Processing) 기술을 적용하면 기존 위성통신 탑재장치의 수동적인 중계 기능 이외에 복조/재변조, 부호/복호화 및 오류정정, 중계기 및 빔간의 상호 연결/절체 등의 새로운 기능이 추가되어 능동적인 중계를 가능하게 함으로써 통신 품질의 향상, 통신 링크의 전송 효율 개선, 전송 용량 증대 등의 장점을 갖고있다. OBP 탑재 위성 B-IDSN 중계망은 하나의 거대한 가상 ATM 교환기로 간주되고, 여러중계 지구국들중 목적 중계 지구국으로 패킷들을 직접 라우팅 할 수 있는 장점이 있다. 본 논문은 OBP 탑재 위성 B-ISDN 연동 프로토콜 연구를 수행하는 것으로서, 위성 B-ISDN 구조와 각 지구국별 신호 기능 및 B-IDSN 신호 시스템인 DSS2 계층 3 신호 프로토콜, B-ISUP 프로토콜, S-BISUP 프로토콜의 구조를 분석하였다. 또한 점-대-다지점을 위한 B-ISDN의 연결과 소유권 및 각각의 프로토콜에 대한 메시지와 프리미티브를 정의하여, 이를 토대로 OBP 탑재 위성 B-IDSN 연동 프로토콜의 기본 호 처리 절차를 설계 및 구현하고, 이를 테스트하였다.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.2
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• pp.231.1-231.1
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• 2012

한국해양과학기술원 해양위성센터에서 주관운영을 수행하고 있는 천리안 위성의 해양탑재체인 천리안 해양관측위성(이하 GOCI)은 정지궤도위성용 해색센서로서, 태양을 광원으로 지구상의 해수 표면 부근에서 반사되어 대기를 통과한 가시광 및 근적외 대역을 8개 밴드로 분광하여 관측하는 센서이다. 해색센서의 경우, 일반적으로 센서에 입사되는 광신호의 약 90%가 대기에 의한 신호이며, 약 10%에 해당되는 신호만 원래 관측목적인 해수에 의한 신호이기 때문에, 5% 이내의 높은 복사보정 정확도가 요구된다. 이러한 높은 복사보정 정확도를 만족시키기 위해서는, 지상에서의 현장관측을 통한 위성자료 검보정 뿐만 아니라, 발사 후 위성 궤도상에서 센서의 복사보정을 수행하는 궤도상 복사보정이 체계적으로 수행되어야 한다. GOCI는 태양을 기준광원으로 하는 태양광 복사보정을 채택하여, 센서의 셔터부에 태양광 복사보정을 위한 2개의 태양광확산기(Solar Diffuser)를 장비하고 있다. 본 발표에서는 궤도상 시험 후 약 16개월에 걸친 궤도상 복사보정 운영결과와 관련하여, 발사 후 일별, 월별, 계절별 등 각 기간별 센서의 이득변화를 관찰하였으며, 그 결과 1년을 기준으로 약 3% 범위로 주기적인 이득 변화가 있음을 확인하였다. 지상시험결과와의 비교에 의해, 태양광확산기에 대한 태양입사각이 이러한 주기적인 이득 변화의 주 원인임을 궤도상 복사보정 운영결과를 통해 밝히고자 한다.

• Aerospace Engineering and Technology
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• v.8 no.1
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• pp.49-57
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• 2009

The camera electronics in the KOMPSAT-3 payload provides the several control clocks in order to move the charges, which are converted from the light in the pixel, in the vertical and horizontal direction. Generally, the control clocks depend on the CCD internal design in the system. The KOMPSAT-3 payload uses the CCD controlled by 3-phase vertical clocks and 4-phase timing. The camera generates the various clocks such as the vertical clocks, the horizontal clocks, the summing clocks, the reset clocks and so on. The vertical clocks are deeply related to the camera performance and synchronized with satellite scan-rate even though they are relatively slow. Also, it gives the horizontal clocks without distortion under the very fast pixel-rate. This paper shows the design and simulation of the CCD clocks driver for the KOMPSAT-3 payload.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.47 no.11
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• pp.812-820
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• 2019

The GNSS receiver for KSLV(Korea Space Launch Vehicle)-II provides real-time navigation data as well as precise time and time interval. The precise time signals provided by the GNSS receiver that can be used for the time synchronization between onboard systems, and between the onboard systems and ground stations have the forms of the 1PPS(One Pulse Per Second) and IRIG-B(Inter-Range Instrumentation Group Time Code B) which are synchronized with UTC(Coordinated Universal Time). A signal for timing faults also informs whether the time synchronization signals are available or not. This paper describes the time synchronization signals of the GNSS receiver for KSLV-II and their performance assessment.

• Journal of Satellite, Information and Communications
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• v.8 no.2
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• pp.88-93
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• 2013

The wideband chirp signal generator to enhance the resolution of synthetic aperture radar of obtaining the earth observation image is needed. This paper deals with designing, manufacturing and testing the wideband digital chirp signal generator having high resolution for LEO earth observation satellite. The wideband digital chirp signal generator is implemented with the memory-map based structure which is mostly applied in the satellite, and consists of the digital module to generate the digital chirp signal and the RF module to perform the quadrature modulation. The I/Q signals stored in the memory of the digital module are D/A converted and delivered to be quadrature modulated with the reference signal of 1275 MHz in the RF module. Furthermore, the test bench and GUI to validate the signal generator function are also developed. It is found that the requirement of 144 MHz bandwidth for the digital chirp signal generator is well met. Finally it is noteworthy that the distortion occurred in the chirp signal generator was compensated by the pre-distortion compensation.

• Journal of Advanced Navigation Technology
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• v.26 no.1
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• pp.9-14
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• 2022

In this paper we investigate the advantages when the GPS Antenna is installed on the rear missile body. In conventional design the GPS antenna locates on the front part of missile. However it causes degraded GPS positioning performance since the missile body blocks the GPS signals. This paper proposes the GPS array antenna design which locates on the rear part of missile body and has the tilted antenna patches to achieve the maximum area of receiving GPS signals. We simulate LOS region of receiving signals and conducted anechoic chamber test to define the effective signal receiving region. And we conduct field test and flight test to check out the enhancement of signal receiving area.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.6B
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• pp.616-624
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• 2002

In satellite communication, which use the satellite, the protection of TT&C channel which controls the position, performance, and operation is required. In this thesis, we analyzed the weakness of authentication algorithm which is used for protection of TT&C generation and operation. Also, we proposed the authentication algorithm which complements key recovery attack structurely without increasing additional computational amount and verified its performance. The proposed authentication algorithm can satisfy Rivest's recommendation by increasing the computational complexity from $2^{55}$ operations to $2^{111}$ operations. In addition, it can be applied to the existing satellite system because the length of TT&C data and message authentication codes used for the input of authentication algorithm are unchanged.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.38 no.1
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• pp.58-63
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• 2010

In this paper, we propose a simple technique for the detection of a frequency jump in the GPS clock behavior. GPS satellite atomic clocks have characteristics of a second order polynomial in the long term and a non-periodic frequency drift in the short term, showing a sudden frequency jump occasionally. As satellite clock anomalies influence on GPS measurements, it requires to develop a real time technique for the detection of the clock anomaly on the real-time GPS precise point positioning. The proposed technique is based on Teager energy which is mainly used in the field of various signal processing for the detection of a specific signal or symptom. Therefore, we employed the Teager energy for the detection of the jump phenomenon of GPS satellite atomic clocks, and it showed that the proposed clock anomaly detection strategy outperforms a conventional detection methodology.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.11 no.4
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• pp.15-31
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• 2001

In this paper we classify security threat elements of satellite communication into four parts; Level-0(satellite propagation signal), Level-1(satellite control data), Level-2(satellite application data) and ground network security level according to the personality and data of the satellite communication network. And we analyze each security levels. Using analyzed security threat elements, we divide security requirements into signal security level and information security level separately. And then above the existent signal security level countermeasure, we establish the countermeasure on the basis of information security policy such as satellite network security policy, satellite system security policy and satellite data security policy in information security level. In this paper we propose secure satellite communication network through the countermeasure based on information security policy.