C-Band Band 5925 6.425 7,075 11.7 band 2,2 132514 FIGURE 102.6 Ku- and C-band frequency allocation chart. rotection for the two operating TWTAs(3-for-2 redundancy) For the remaining transponder channels, 5 spare 20-W TWTAs provide protection for 14 operating TWTAs(19-for-14 redundancy). Redundant communica tions receivers are provided on a 4-for-2 basis. The power radiated from a satellite is described as its effective radiated isotopic power(EIRP)and is the radiated power of the satellite in decibels referenced to one watt of power. The units are in dBw. The strength of the signal received on the ground is a function of the spacecraft location and that of the ground station and will vary depending upon location. A map of the signal strength contours is called the satellite's" footprint. Geosynchronous Satellites There are over 500 Ku-band and C-band satellites in geosynchronous orbit. These satellites are typically spaced anywhere between 1 to 3 degrees apart. Older satellites no longer in active service may be spaced less than one degree in an inclined orbit. The frequency plan for C-and Ku-band satellite services is shown in Fig. 102.6. The typical transmit frequency band used for fixed satellite services in the Ku-band is 14.0-14.5 GHz Receive frequency is 11.7-12.2 GHz Some satellites also use the extended band. For C-band satellites, the typical operating transmit frequency is 5.925-6.425 GHz and the receive frequency is 3.7-4.2 GHz. The operating band was extended at WARC 79 to 7.075 GHz to be assigned to individual countries for domestic satellite systems. Ka-band satellites have down links in the frequency range 17-23 GHz and uplinks in the range 27-31 GHz. Some European and Japanese satellites operate in this range[ Long, 1991]. The satellite performance data indicate a wide range of variation in the specifications among the various satellites. Most satellites have a design lifetime of 10 years. The newer GEO satellites tend to have an extended very few ars. Most domestic U.S. satellites have 24 transponders. The older generation of Asian satellites life of 12-15 transponders per satellite. Some planned satellites will have a large number of transponders. Nominal transponder bandwidths include 36, 54, and 72 MHz. ellite power is increasing in the newer generation of satellites. Lower-power satellites have an EIRP in the 20-35 dBW range. There are a significantly large number of medium-power satellites in the 35-45 dBW range Newer high-power satellites tend to have power in the 50-60 dBW range. Direct broadcast satellites are planned for transponder power in the 60-120 w range. The power generally varies with polarization, frequency, and beam. Table 102.2 is a profile of typical satellite performance characteristics. Mobile Satellite Systems Mobile satellite systems encompass communications on land, in the air, or over the oceans ideally allowing a person to communicate with anyone anywhere Long, 1991]. The Inmarsat system is a mobile communications system providing global coverage through a variety of communication paths. In the United States, the FCC has authorized American Mobile Satellite Corporation(AMSC)to provide domestic mobile satellite services. AMSC makes use of geostationary satellites to provide a domestic offering similar to the international offering of Inmarsat e 2000 by CRC Press LLC© 2000 by CRC Press LLC protection for the two operating TWTAs (3-for-2 redundancy). For the remaining transponder channels, 5 spare 20-W TWTAs provide protection for 14 operating TWTAs (19-for-14 redundancy). Redundant communica￾tions receivers are provided on a 4-for-2 basis. The power radiated from a satellite is described as its effective radiated isotopic power (EIRP) and is the radiated power of the satellite in decibels referenced to one watt of power. The units are in dBW. The strength of the signal received on the ground is a function of the spacecraft location and that of the ground station and will vary depending upon location. A map of the signal strength contours is called the satellite’s “footprint.” Geosynchronous Satellites There are over 500 Ku-band and C-band satellites in geosynchronous orbit. These satellites are typically spaced anywhere between 1 to 3 degrees apart. Older satellites no longer in active service may be spaced less than one degree in an inclined orbit. The frequency plan for C- and Ku-band satellite services is shown in Fig. 102.6. The typical transmit frequency band used for fixed satellite services in the Ku-band is 14.0–14.5 GHz. Receive frequency is 11.7–12.2 GHz. Some satellites also use the extended band. For C-band satellites, the typical operating transmit frequency is 5.925–6.425 GHz and the receive frequency is 3.7–4.2 GHz. The operating band was extended at WARC ’79 to 7.075 GHz to be assigned to individual countries for domestic satellite systems. Ka-band satellites have down￾links in the frequency range 17–23 GHz and uplinks in the range 27–31 GHz. Some European and Japanese satellites operate in this range [Long, 1991]. The satellite performance data indicate a wide range of variation in the specifications among the various satellites. Most satellites have a design lifetime of 10 years. The newer GEO satellites tend to have an extended life of 12–15 years. Most domestic U.S. satellites have 24 transponders. The older generation of Asian satellites have very few transponders per satellite. Some planned satellites will have a large number of transponders. Nominal transponder bandwidths include 36, 54, and 72 MHz. Satellite power is increasing in the newer generation of satellites. Lower-power satellites have an EIRP in the 20–35 dBW range. There are a significantly large number of medium-power satellites in the 35–45 dBW range. Newer high-power satellites tend to have power in the 50–60 dBW range. Direct broadcast satellites are planned for transponder power in the 60–120 W range. The power generally varies with polarization, frequency, and beam. Table 102.2 is a profile of typical satellite performance characteristics. Mobile Satellite Systems Mobile satellite systems encompass communications on land, in the air, or over the oceans ideally allowing a person to communicate with anyone anywhere [Long, 1991]. The Inmarsat system is a mobile communications system providing global coverage through a variety of communication paths. In the United States, the FCC has authorized American Mobile Satellite Corporation (AMSC) to provide domestic mobile satellite services. AMSC makes use of geostationary satellites to provide a domestic offering similar to the international offering of Inmarsat. FIGURE 102.6 Ku- and C-band frequency allocation chart