17_29 - J. Astron. Space Sci. 17(2), 257266 (2000) A SYSTEM...

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J. Astron. Space Sci. 17(2), 257–266 (2000) A SYSTEM DESIGN AND ANALYSIS FOR SATELLITE COMMUNICATION LINK Tae Jin Chung and Jong Won Eun Satellite Communications System Department 161 Kajong-Dong, Yusong-Gu, Taejon, 305-350,Korea email: tjchung@etri.re.kr, jweun@etri.re.kr (Received October 15, 2000; Accepted November 22, 2000) ABSTRACT A satellite RF communication link is analyzed based on a simple fundamental equa- tions by systematic approach in this paper. The number of variables related to a design and analysis of satellite RF link is often a dozen or more, thus it is a tedious and time- consuming task. With the given input data, the important parameters are calculated step by step and three communication characteristics such as communication channel capacity, carrier-to-noise ratio (CNR) at the satellite and ground station are analyzed. It gives very useful information to the system engineers for designing and analyzing the overall satellite communication system in the conceptual design phase. Key words : satellite, RF, link margin 1. INTRODUCTION During the last 30 years, spacecraft placed in Geostationary Earth Orbit (GEO) have been used to support all forms of communication via satellite-voice, data, and broadcasting. The major advan- tages of these systems is their unchanging position with respect to the earth surface, thus no control overhead is required to track the satellites. However, more recently a number of projects involv- ing the employment of constellations of Low Earth Orbit (LEO) and Medium Earth Orbit (MEO) satellites which are in the process of being implemented, are challenging the supremacy of GEO systems. Satellites in roughly circular orbit probably will be in operation at different altitudes; satellites in elliptic orbit may have widely differing altitudes at perigee and apogee. Power output of the transponders in differing communication satellite may vary by an order of magnitude or more. With the advent or greater booster launch capability, communication satellites may greatly increase in weight, permitting an increased number of transponders per satellite or improved antenna gains or both. The ground stations that will transmit to and receive messages from communication satellites in these days are equally diverse in character. Movable parabolic dish antennas range from a few meters corresponding author 257 Korean Space Science Society Provided by KAO Korean Astronomical Data Center
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258 Figure 1. Satellite communication link geometry. in diameter to an about 26m. The effective overall receiver noise temperatures available today range from as little as about 30 K to thousands of degrees Kelvin. And the required signal-to-noise-ratios at one ground receiver may differ considerably, depending on the type of modulation employed. Even for rather simple problems resulting in overall system design or analysis, the number of
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17_29 - J. Astron. Space Sci. 17(2), 257266 (2000) A SYSTEM...

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