• Journal of the Korean Institute of Telematics and Electronics A
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• v.31A no.1
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• pp.9-16
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• 1994

In this paper, we propose a frequency assignment algorithm to minimize intermodulation effect which is caused by nonlinear amplipification of the satellite transponder. Allmost all of the published algorithms up to now are applicable to one-level SCPC systems, the application range of those algorithms is very restricted from the viewpoint of actual practice. In this paper, we develope and propose a new frequency assignment algorithm which utilize the basic concept of Okinaka's DELINS-INSDEL algorithm to extend its applicabilty from one-level SCPC systems to multi-level systems. The proposed TDTI algorithm provides considerable generality in reducing intermodulation effect in practical satellite communication systems because of its alpplicability to multi-level and multi-bandwidth systems as well as one-level systems. Besides the TDTI algorithm which shows excellent characteristics in performance but requires somewhat long excution time. the WTDI-SDELINS algorithm is proposed in this paper to compensate TDTI's demerits in excution time. Considering the fact that there are very little published sterategies for multi-level and muti-bandwidth systems. the algorithm proposed in this paper is quite meaningful.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.34D no.12
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• pp.22-30
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• 1997

The design procedure for direct coupled combline filter with tapped line in/out was summarized on Ku-band satellite frequency downconverter for stellite application. We calculated the resonator dimensions, spacing between successive resonators, ground plane spacing and tapping position of in/output lines in accordance with the given procedure. Partitions wer eemployed between adjacent resonators by inserting irises to improve filter response characteristis. The designed filter was manufactued with aluminum alloy package to reduce mass, and resonators wer machined from the filter body and in/output lines wer fixed on resonators with epoxy to survive in vibration conditon during launch.

• Journal of the Korea Society of Computer and Information
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• v.21 no.6
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• pp.47-53
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• 2016

This paper deals with the capacity constrained time slot assignment problem(CTSAP) that a satellite switches to traffic between $m{\times}n$ ground stations using on-board $k{\leq}_{min}\{m,n\}$ k-transponders switching modes in SS/TDMA time-division technology. There was no polynomial time algorithm to solve the optimal solution thus this problem classified by NP-hard. This paper suggests a heuristic algorithm with O(mn) time complexity to solve the optimal solution for this problem. Firstly, the proposed algorithm selects maximum packet lengths of $\({mn \atop c}\)$ combination and transmits the cut of minimum packet length in each switching mode(MSMC). In the case of last switching mode with inefficient transmission, we applies a compensation strategy to obtain the minimum number of switching modes and the minimum makespan. The proposed algorithm finds optimal solution in polynomial time for all of the experimental data.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.13 no.1
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• pp.7-11
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• 2002

A novel microstrip type law-pass filter using thin or thick film resistors is proposed to efficiently eliminate harmonic spurious response in stop-band. The proposed low-pass filter shows the spurious suppression enhancement of 20 dB over a conventional one. The designed low-pass filter could be used as a harmonic rejection filter of a local oscillator for Ku-band satellite payload system.

• Proceedings of the Korea Information Processing Society Conference
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• 2008.11a
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• pp.1344-1347
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• 2008

VSAT시스템은 중심지구국, 무궁화위성 그리고 다수의 단말지구국을 포함하는 성형망으로 구성되고, 광범위한 데이터서비스를 제공할 수 있으며 사용자의 사용목적과 용도에 따라서 여러 가지 형태의 위성전송망 구성이 가능하다. 홍수경보망을 구성 시 최적의 전송품질을 구현하기 위한 위성링크설계는 한국의 환경특성, 무궁화위성의 특성 그리고 VSAT 시스템의 특성을 고려하여 설계한다. VSAT 시스템은 디지털 데이터 전송용으로 인바운드(Inbound)는 TDMA, 아웃바운드(Outbound)는 TDM 전송방식을 이용하였으며 중심국과 단말국의 크기는 3.7m, 1.2m로 설계되었다. VSAT망에서 링크설계는 VSAT망에 할당된 위성 중계기(Satellite Transponder)의 출력전력 및 대역폭 범위 내에서 중심지구국(Hub Station)과 단말지구국(Remote Station)이 주어진 전송규격에 따라 정보를 효율적으로 전송할 수 있도록 설계하여. VSAT망으로 홍수관리의 효율적 운영을 제안한다.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.14 no.5
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• pp.506-512
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• 2003

An output multiplexer of manifold type is widely used in a recent satellite transponder f3r its mass and volume reduction. For correct operation, the filter of such a multiplexer must be singly terminated. In this paper, a simple synthesis method of a 6-pole dual-mode singly terminated filter is described. From the transfer function of the filter, network parameters such as in/output terminations and coupling matrix are obtained with the aid of orthogonal projection and plane rotation. The rotation order, pivot, and rotation angle of the plane rotation process are given for easy filter synthesis. Two different-structure filters are taken into consideration and the network parameters of each filter have been obtained from the same transfer function. The method described in this paper can be applied to the other degree singly terminated filter.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.2A
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• pp.166-173
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• 2004

Satellite communication system uses a high non-linear HPA(high power amplifiers) in the earth station and satellite transponder. Therefore, it is important to consider the nonlinear effect of HPA on the communication system. In this paper, we find the variation of power spectrum density by nonlinearity HPA and the change of harmonic component according to IBO (input back-off). When the BPSK is used for satellite communication system, we analyze BER performance including the external co-channel interference (CCI) and the adjacent channel interference (ACI) resulting from the HPA nonlinearity. BER degrades as ACI magnitude grows up when the uplink SNR, uplink SIR (signal to co-channel interference power ratio) and downlink SIR are constant at some level. In case there is only non-linear HPA in the satellite, it is shown that BER considerably depends on the ACI magnitude ACI. When there are two non-linear HPAs in the both earth station and satellite, much BER degradation results from the CCI and ACI.

• Journal of Satellite, Information and Communications
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• v.1 no.2
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• pp.63-70
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• 2006

This paper presents the results of Ka band qualification model multiplexers for COMS Payload to be launched in 2008. These are the input and output multiplexers of the satellite transponder to use available frequency resources effectively and the diplexer of the satellite antenna to use the same reflector for both transmitting and receiving frequency bands, respectively. The input multiplexer with four frequency channels has four(4) independent channel filters which consist of an 8-pole elliptic band-pass filter for high frequency selectivity and a 2-pole equalizer for group delay equalization. For low insertion loss, mass and volume reduction, manifold type os employed for output multiplexer. E-plane T-junction is used for either splitting or combining a frequency band into two sub-bands. Asymmetric inductive irises are used to tune the receiving filter easily. The electrical performance and environmental test such as vibration test, mechanical shock test, thermal vacuum test and EMC test are performed and the results of all qualification model multiplexers are compliant to the requirement of each multiplexer. Followed by this qualification, the flight model equipment will be developed.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.2A
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• pp.159-166
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• 2008

In this paper, we proposed an algorithm to solve the problem that can't maintain hop synchronization using only early-late gate tracking loop due to the drift of geo-stationary satellite in frequency hopping satellite communication system. When the signal is transferred to downlink through DRT(Dehop-Rebop Transponder), the problem with synchronization loss is occurred periodically when using only early-late gate tracking loop, because of energy loss in each side portion of hop due to orbital variation of the satellite. To solve this problem, we have developed Anti-Shrink synchronization tracking algorithm which uses the prediction value of transmission timing and the structure of inner-outer gate instead of early-late gate with the ranging information. Through simulations, we showed that the performance of the Anti-Shrink algorithm is better than that of simple inner-outer energy ratio algorithm and similar to that of conventional early-late tracking loop algorithm with ranging information. No synchronization failure in the proposed algorithm was occurred because of less energy loss and robustness without the ranging information.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39C no.1
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• pp.36-44
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• 2014

Broad band and wide area satellite communication has advantage that can be always communicate with anyone regardless of time and space. In the other hands, its communication quality is easy to be affected by interference signals. Due to the fact that interference signal can be transmitted from everywhere, it's hard to find the illegal source of signal and it has huge influence. In this paper, with this influence of interference signal, we introduce the interference rejection method, implementation and test result in the digital satellite communication processing the signal using variety of digital method. It will be useful information to improve the interference rejection function and also be helpful on the field of satellite communication.