• The Journal of Korean Institute of Communications and Information Sciences
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• v.37C no.11
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• pp.1138-1147
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• 2012

In this paper, an efficient power control based MF-TDMA resource allocation scheme is proposed for next generation military satellite communication systems. The proposed scheme has the flexibility is used to support heterogeneous terminals with differ in transmission capabilities. The method can be divided into two parts : burst size calculation and burst structure determination. At first, we estimate the link budget taken into account a dynamic satellite link state variation. Then, applicable ACM level and burst size is chosen. In burst structure determination phase, we reorganize the burst structure in time-frequency domain by controlling limited power, bandwidth, time resources. In particular, we compensate the power spectral density among different terminals to integrate them in same transponder, Furthermore, we increase the packing efficiency by controlling the ACM level of the burst in applicable power spectral density range. Simulation results show that the method increase the spectral efficiency and burst packing efficiency. In addition, slot allocation rejection ratio is successfully reduced.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.16 no.4 s.95
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• pp.366-372
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• 2005

This paper presents analysis of a slot array antenna having a low side lobe level and high front-to-back ratio for a repeater system of a satellite DMB(Digital Multimedia Broadcasting) service. Antennas for this repeater system require a high gain and enough isolation to reduce interferences between signals in system. Therefore, it is necessary to suppress a side lobe level and to increase front-to-back ratio. Unlike a structure 134 by lossy microstrip lines, in this work a single cavity-backed slot antenna array using a single waveguide feed is proposed to obtain the reliability for high power handling and high radiation efficiency. The side lobe level and front-to-back ratio are enhanced with tapered array technique and an optimized vertical reflector. The measured side lobe levels in H- and E-plane are under $-33.24\;\cal{dB}$ and $-35.78\;\cal{dB}$, respectively. The front-to-back ratio over $37.84\;\cal{dB}$, and the peak gain of over $17\;\cal{dBi}$ are measured.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.29A no.11
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• pp.49-56
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• 1992

In this paper a band-pass filter using dielectric resonators with tuning screw and spacer at Ku-band is designed and constructed. For the filter design and construction, the coupling coefficient K between two resonators is numberically evaluated. The external quality factor Q$_{ex}$ is also calculated with a microstrip line which is necessary for the field excitation of dielectric resonator. The coupling between dielectric resonator and microstrip line depends mainly upon the magnetic field and is principal parameter in band-pass filter. The Q$_{ex}$ and K data which are evaluated by numberical analysis are practically applied to the filter construction. The theoretical Band-pass filter responses are given by Chebyshev approximation and they are nearly similar to the experimental results.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2005.11a
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• pp.107-110
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• 2005

This paper describes the design and fabrication of synchronous clock recovery module for S-DMB Gap Filler. Using the 2.304MHz TTL signal from gap filler tuner, clock recovery module with 10MHz output frequency including holdover function is designed. The measured performance of the clock recovery module shows a stability of less than 0.01ppm, 29 sec stability time, 10 sec holdover time, and maximum -113dBc/Hz@100Hz phase noise.

• Proceedings of the Korean Institute of Communication Sciences Conference
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• 2006.07a
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• pp.234-234
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• 2006

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.05a
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• pp.374-379
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• 2001

The satellite electronic equipment is exposed to high level random vibration environment during the launch of spacecraft. The random vibration can cause damage of electronic equipment. Thus very careful consideration on the launch environment, especially for high level random vibration, is required in the design stage of transponder equipments of communication satellite. For the structural integrity of the communication satellite transponder equipment under qualification level random vibration, Finite Element analysis was carried out using the commercial code, MSC/Nastran and ANSYS and stress levels are presented. In order to validate the femodel, modal test was also performed and compared with numerical results.

• 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.

• Proceedings of the IEEK Conference
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• 2002.06a
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• pp.235-238
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• 2002

In this paper we describe the design and implementation of Electrical Ground Support Equipment(EGSE) for the CBS transponder testing. The main task of EGSE is to check out satellite systems, at system or subsystem level, during integration and validation phases of their life-cycle. Through a combination of hardware and software elements, EGSE supports manual, semi-automatic and fully automated testing. Automation is achieved by offering users simple, yet powerful means to write their own test application programs (test sequences) in high-level, test-oriented language and to run them in a strict real-time environment. The core of this environment is a user-configurable real-time database, containing all the information needed to calibrate acquired data, check them against predefined thresholds, automatically react to out-of-range conditions, display data using animated graphics or synoptic windows, and so on.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.31 no.2
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• pp.96-102
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• 2003

The thermal design of MGSE(Mechanical Ground Support Equipment) panel is performed for thermal vacum thest of Ka-band EQM(Engineering Qualification Model) payload of communications and broadcasting satellite. The thermal environments are predicted to evaluate the performance of transponder equipments in the thermal vacum chamber. SINDA is used to verify the thermal design of the heat pipe layout. Embedded 16 heat pipes in the EQM payload developed for Ka-band trasponder equipments are designded properly. The heat fluz loaded on the external facesheet is 265W/㎡ for the hot platear function test of the traspinder equipments, and the zero heat flux for the cold plateau case. The maxium predicted heat transport capability is 2723 W-cm.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.18 no.4
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• pp.572-584
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• 1993

In this paper, we propose an efficient method to allocate carrier frequencies so as to minimize intermodulation products in two-level SCPC systems in which Hub station and many Remote stations communicate each other through the satellite transponder. Also we present a very efficient method to evaluate intermodulation products with highly reduced CPU time in two-level SCPC systems. We study and analyze the performance of some possible methods to extend the Deletion and Insertion operation, which is proposed by Okinaka and applied to only one-level SCPC systems, to two-level SCPC systems. The proposed algorithm is carefully selected out of these methods and is optimized, which shows superior performance to any other published strategies, especially in that it has very excellent characteristics in terms of generality for practical application. Considering the fact that most published strategies are seldom applicable to actual two-level SCPC systems, we can say that the proposed algorithm in this paper is quite meaningful.