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Overview of Satellite Systems

An introduction to satellite communication systems, including frequency allocation, Intelsat, U.S. Domsats, polar orbiting satellites, and satellite services.

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Overview of Satellite Systems

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  1. Chapter 1. Overview of Satellite Systems 第一章 衛星通訊系統概述 亞洲大學 資訊工程學系碩士班 呂克明教授 二○○六年九月十八日

  2. Chapter 1. Overview of Satellite Systems(第一章 衛星通訊系統概述) • Introduction (緒言) • Frequency Allocation for Satellite Service (衛星通訊頻率分配) • Intelsat (國際通訊衛星) • U. S. Domsats (美國國內通訊衛星) • Polar Orbiting Satellite (低軌繞極衛星) • Homework problems (習題)

  3. Introduction(緒言) • The use of satellites in communication systems (衛星在通訊系統的應用) is very much a fact of everyday life, as is evidenced by the many homes which are equipped with antennas, or dish, used for reception of satellite television(衛星電視). • An essential part of telecommunications systems (電信系統) worldwide, carry large amounts of data and telephone traffic. • Satellites offer a number of features not readily available with other means of communications. (衛星提供許多功能是其他通訊手段所無法做到的.) • Linking simultaneously (同時鏈結): Star point of a communications net linking together many users simultaneously, users who may be widely separated geographically. • Landing right (落地權): Due to ignore political boundaries, satellite signals may not be a desirable feature.

  4. Introduction(緒言) (continued) • Distance insensitive (和距離無關): Any satellite system costs about the same to provide a satellite communications link. • Can be economical (經濟實惠): if it is in continuous use and can be spread over a large number of users. • Remote sensing (遙感, 遙測): detection water pollution (水質污染), monitoring and reporting weather conditions (監測和氣象報導), agriculture (農業), and mining distribution (礦產分布), and in search and rescue operations for downed aircrafts (尋找與救助掉落的飛機).

  5. Frequency Allocations for Satellite Services(衛星通訊頻率分配) • International Telecommunication Union (ITU, 國際電信聯盟) • Established in 1985 or earlier • Three (3) regions: • Region 1: Europe, Africa, formerly Soviet Union, and Mongolia • Region 2: North and South America and Greenland • Region 3: Asia (excluding Region 1 areas), Australia, and the south-west Pacific

  6. Frequency Allocations for Satellite Services(衛星通訊頻率分配)(continued) • Satellite services (衛星通訊服務的種類): • Fixed satellite service (FSS) (固定衛星通訊) • Broadcasting satellite service (BSS) (廣播衛星通訊) • Mobile satellite services (移動衛星通訊) • Navigational satellite services (衛星導航通訊) • Meteorological satellite services (氣象衛星通訊)

  7. Frequency Allocations for Satellite Services(衛星通訊頻率分配)(continued) • Frequency Band (GHZ) Designations (頻寬的名稱): • VHF: 01-0.3 (電視) • UHF: 0.3-1.0 (電視, 手機800兆, 900兆) • L-band: 1.0-2.0 (短程雷達, 機場雷達) • S-band: 2.0-4.0 (長程雷達, 軍用雷達, 氣象雷達, ISM) • C-band: 4.0-8.0 (通訊衛星) • X-band: 8.0-12.0 (飛機雷達) • Ku-band: 12.0-18.0 (通訊衛星) • Ka-band: 18.0-27.0 (通訊衛星) • V-band: 40.0-75.0 (研究頻道) • W-band: 75-110 (研究頻道) • Mm-band: 110-300 (研究頻道) • μm-band: 300-3000 (研究頻道)

  8. INTELSAT (國際通訊衛星) • International Telecommunication Satellite: • Created in 1964 • Over 140 member countries • More than 40 investing entities • Early Bird satellite (晨鳥衛星) in 1965 • Six (6) evolutions of INTELSAT satellites between 1965-87 • Geostationary (同步衛星) orbit • Covers 3 regions: • Atlantic Ocean Region (AOR), • Indian Ocean Region (IOR), and • Pacific Ocean Region (POR)

  9. U. S. Domsats (美國國內通訊衛星) • Domestic Satellite: • In geostationary orbit (同步衛星軌道) • Over 140 member countries (多國的衛星組織) • Direct-to-home TV service (直接到戶電視衛星) • Three (3) categories of U. S. DBS system: high power, medium, and low power. • Measure in equivalent isotropic radiated power (EIRP, 等效全向輻射功率). • The upper limit of EIRP: • High power (60 dBW), • Medium (48 dBW), and • Low power (37 dBW).

  10. Polar Orbiting Satellites (低軌繞極衛星) • An infinite number of polar orbits cover north and south polar regions • Weather (ultraviolet sensor also measure ozone level, 紫外線遙測極地臭氧層) satellites between 800 and 900 km • National Oceanic and Atmospheric Administration (NOAA,美國海洋暨大氣總署) operate a weather satellite system (氣象衛星) • Satellite period is 102 minutes and earth rotated 25 degree. • Estimate the sub-satellite point at the following times after the equator 90 degree E North-South crossing: • a) 10 minutes, 87.5 degree E and 36 degree S; • b) 102 minutes, 65 degree E and equator; • c) 120 minutes, 60 degree E and 72 degree S.

  11. Polar Orbiting Satellites (低軌繞極衛星)(continued) • The system uses both geostationary operational environment satellite (GOES) and polar operational environment satellite (POES) • Sun synchronous: they across the equator at the same local time each day • The morning orbit, at an altitude of 830 km, crosses the equator from south to north at 7:30 AM, and the afternoon orbit, at an altitude of 870 km, at 1:40 PM. • Search and rescue (SAR) satellite: Cospas-Sarsat

  12. Homework Problems-I (習題一) • 1.1- Describe briefly the main advantages offered by satellite communications. Explain what is meant by a distance insensitive communications system. • 1.2- Comparisons are sometimes made between satellite and optical fiber communications systems. State briefly the areas of application for which you feel each system is best suited. • 1.3- Describe briefly the development of INTELSAT starting from the 1960s through to the present. Information can be found at Web site: http://www.intelsat.com/ • 1.4- From the Web page given above, find the positions of the INTELSAT 7 and INTELSAT 8 series of satellites, as well as the number of C-band and Ku-Band transponders on each.

  13. Homework Problems-II (習題二) • 1.8- Give reasons why Ku-band is used for the DBS service? • 1.10- Given that the earth’s equatorial radius is 6,378 km and the height of the generationary orbit is 36,000 km, determine the intersatellite distance between the GE American Communications, Inc. satellite and Hughes Communication Galaxy, Inc. satellite, operating in Ka band. • 1.11- Explain what is meant by a polar orbiting satellite. A NOAA polar orbiting satellite completes one revolution around the earth in 102 min. The satellite makes a north to south equatorial crossing at longitude 90 degree W. Assuming that the orbit is circular and cross exactly over the poles, estimate the position of the sub-satellite point at the following times after the equatorial crossing: (a) 0h, 10 min; (b) 1h, 42 min; (c) 2h, 0 min. A spherical earth of uniform mass may be assumed.

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