• Journal of Satellite, Information and Communications
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• v.5 no.1
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• pp.22-26
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• 2010

In this paper, we propose an effective method for detecting signals among multi-user in cooperative communication system. Spread sequence is inserted to NULL space of synchronization channel to synchronize between each user among frame formats of the cooperative communication and then transmitted. In the receiver, the wanted signal is detected by using correlation among the inserted spread sequences. As simulation results, correlations among the signals using Kasami/Walsh sequence in AWGN, Rician, and Rayleigh channel are shown. Using the simulation results in this paper, we expect a reliable cooperative communication.

• Journal of Satellite, Information and Communications
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• v.7 no.2
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• pp.25-29
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• 2012

In this paper, we implemented LED beam forming communication system controlled by stepping motor. ATMega1284 was used as a MCU of main control board which has two main external IO, one is RS232 for connection with PC, the other is PORT for connection with motor driving board. Stepping motor rotated 360 degree when provided 160 clock and its rotation radius was increased by Archimedian Spiral. So LED can provide its light anywhere in the space and its beam forming was controlled by PC connected with RS232 of main control board. The action of beam forming was verified via actual HW/SW implementation.

• Journal of Satellite, Information and Communications
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• v.10 no.1
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• pp.88-91
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• 2015

Wireless power transmission (WPT) is a technology using free space as a conductor for transmitting electric power, which aims to transfer not just the transmission signal but also the electrical energy itself. This paper takes issue with the microwave wireless transmission technology utilizing in long-distance transmission. To construct the WPT system, several components are needed, such as RF Oscillator which converts AC power to RF through DC status, high gain antenna and RF rectifier that converts RF back to DC. The array topology is good a candidate for wide use. The objective of this research is to study the efect of the WPT systmem on electric power system.

• Journal of Satellite, Information and Communications
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• v.12 no.2
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• pp.11-14
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• 2017

In this paper, we introduce a method of light focusing effect using prism structure to solve optical discontinuity of conventional external signage LED panels. The prims structures were patterned on a transparent polycarbonate substrate with MEMS and femto-second laser process. We have confirmed that the patterned prism structures on the substrate made artificial LED lights on empty space between the panels by light guide effect of the structure. The artificial light's lateral positions were controlled by thickness of polycarbonate substrate. This cost effective prim patterned transparent film can be utilized on digital signage LED panels to achieve good optical communication.

• Journal of Satellite, Information and Communications
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• v.1 no.2
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• pp.45-50
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• 2006

A satellite and ground stations which are developed in a program are tested whether the interface between the satellite and ground is well established before satellite operations. These compatibility tests are performed when the satellite is connected with the ground stations after all satellite and ground stations requirements are verified. The content of the RF compatibility test is to check whether the interface requirements which are described on the Interface Control Document are well developed. During the early operation phase and tentative contingency operations of the satellite, KARI ground station uses other oversea ground stations which are located worldwide according to contract between the KARI and the contractor. Since oversea ground stations were not developed for the designated space program, system integrator should check whether the oversea ground stations are satisfied with interface requirements. Using the RF suitcase, RF interface and the content of RF communication can directly be verified during RF compatibility test on oversea ground station without KARI ground station's support. The RF compatibility test using RF suitcase was performed oversea ground stations as well as KARI ground station located on Korea. The content of RF compatibility test was standardized in order to be used at any oversea ground stations, especially fitted for the operations concept of launch and early operations phase. The test content would be RF characteristics, protocol, command loop test, telemetry loop test, and ground station interface test.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.45 no.4
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• pp.318-327
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• 2017

Synthetic Aperture Radars (SARs) that can be performed regardless of weather and day-and-night conditions have been developed for Earth remote sensing in recent decades. Korea Aerospace Research Institute (KARI) has developed and launched successfully the KOrea Multi-Purpose SATellit-5 (KOMPSAT-5) which is the first Korean SAR satellite in 2013, and is currently developing the KOMPSAT-6 which is the next generation series of the SAR satellite. This paper describes the development of the system performance analysis simulator which is necessary for spaceborne SAR payload design and analysis. The system performance analysis simulator consists of the antenna pattern generation simulator, the SAR performance analysis simulator, and the image quality analysis simulator. The simulation results of this research show that this simulator can be applicable as the design and analysis tool for the spaceborne SAR payload system during the design phase.

• Journal of Satellite, Information and Communications
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• v.12 no.4
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• pp.110-114
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• 2017

Using a small mobile wireless network as a supplement to the disaster safety network can be useful for eliminating small radio shadowing areas, reducing traffic overloads in disaster areas, and quickly building a disaster communication network in difficult access areas. Potable base station is needed to build a small mobile wireless network, and the portable base station using TVWS(TV White Space) is effective in terms of utilization of radio frequency resources and construction cost of wireless networks. In this paper, we design and implement a power amplifier for portable base station operating in TVWS. The implemented power amplifier operates at 470 ~ 698MHz. The gain of the implemented amplifier is more than 20.1dB, the input/output return loss is more than 11.4dB, and the isolation is more than 39.9dB when the output is off. The IMD characteristic of the power amplifier has characteristics of 61.0dBc with 18.8dBm output at 470MHz, 59.3dBc wih 18.6dBm output at 550MHz and 56.5dBc with 19.0dBm output at 690MHz. The power amplifier implemented in this paper can be used as a power amplifier for portable base station.

• Journal of Satellite, Information and Communications
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• v.7 no.3
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• pp.1-7
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• 2012

In this paper, we was performed the interference analysis to determine an optimal coexisting criteria for the european digital video broadcasting service (DVB-T2) and the IMT-advanced LTE based TV Band Device (TVBD). The TVBD was equipped with the spectrum cognition method. To this end, we set the various transmission parameters, that includes the emission and blocking mask, antenna height and gain, transmission power and bandwidth, channel model etc. Based on this parameters, we were calculated the allowable transmit power, the number of TVBD and the change in probability of interference for the TVBD user operating in the adjacent channels of the DVB-T2 user. Also this paper presents how many TVBD users can sharing with DVB-T2 for spectral cognition performance.

• Journal of Satellite, Information and Communications
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• v.7 no.2
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• pp.67-71
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• 2012

This paper represents the impact analysis results of antenna reflector for the UHF-band antenna of Space Launch Vehicle. Three types of UHF-band antenna reflector model have been proposed and simulated to compare their characteristics such as resonance frequency, reflection loss and radiation pattern etc. Simulation results showed that resonance frequency and return loss of each reflector models were rarely affected even if reflector sizes are changed. The antenna gain and 3dB bandwidth were slightly changed to the worse directions as the reflector sizes are smaller.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.26 no.9
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• pp.821-827
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• 2015

Electromagnetic waves which are emitted from the Sun due to solar flare explosion can cause failures in HF radio communications in the day-side area of the Earth, that is so-call as Radio Blackouts. The international scale representing the severity of the Radio Blackouts is determined by the solar X-ray flux which is measured by United States Geostationary Operational Environmental Satellite. However, the scale is not always applicable to HF communication users in the different area on the Earth, because the HF communication effects depend not only on the X-ray strength but also on the subsolar point location. To solve this problem, we developed a HF radio spectrum monitoring system utilizing a spectrum analyzer. This system conducts a real-time measure of the HF spectrum, and automatically calculates signal to noise ratios and the occurrences of the HF blackouts as comparing with the interference level which is described from the ITU recommendation.