Satellite communication bands

RHCP gain values over the 3D sphere are comprised in the interval [—2.5, 7.5] dBic, with maximum boresight values of 5 dBic for the GPS band and 6 dBic for the Iridium band, in unbent simation. The measured axial ratio, at both frequency bands, is lower than 5 dB over a wide angular region around the zenith. In conclusion, such an antenna represents a suitable candidate for simultaneous use in GPS and Iridium satellite communication, with satisfactory performance. However, the use of a probe feed inherently puts a limitation on the achievable bandwidth, which can surely be enlarged by making use of more sophisticated feeding techniques. 

Communication. Microwaves are commonly used by communication systems on the Earth s surface, in satellite communications, and in deepi-space radio communications. Microwaves are commonly used by television news media to transmit audio and video from a specially equipped van to a television station. Mobile telephone networks operate in the lower end of the microwave band, while others operate at frequencies just beneath the microwave band. Networks of microwave relay links have largely been replaced by fiber-optic networks. Wireless transmission employing local area network (LAN) protocols such as Bluetooth operate in the 2.4 GHz microwave band. Other LAN protocols operate at higher microwave frequencies. Wireless Internet services operate in the 3.5-4.0 GHz range. 

Satellite Communications and GPS. Satellite communications developed in both the United States and Russia shortly after the launch of Sputnik in 1957. Most satelhte transmissions are in the micro-wave bands, but some use other electromagnetic wavelengths as well. There are a variety of devices for satellite transmissions, but many of them use an enhanced vacuum tube technology with names such as magnetron and gyrotron. Elarly satellite antennae were very large but have been greatly reduced in size. 

Table 16.22 contains a partial list of frequency allocations for satellite communications. The World Administrative Radio Conference, WARC-92 allocated L-band frequencies for LEO personal communications services and for LEO small sateUite data relay. The World Radiocommunication Conference, WRC-95,... 

Sources Final Acts of the World Administrative Radio Conference (WARC-92), Malaga-Torremolinos, 1992 1995 World Radiocommunication Conference (WRC-95). Also, see Gagliardi, R.M. 1991. Satellite Communications, van Nostrand Reinhold, New York. Note that allocations are not always global and may differ from region to region in all or subsets of the allocated bands. 

The Material can be used in the frequency range from 1427 to 1535 MHz, the 1.5 GHz Band. Currently it is used in a number of radio communication services, including point to point fixed services, point to multipoint fixed services in rural and remote areas for the operation of Digital Radio Concentrator Systems. (DRCS) used for the delivery of public telecommunications services, mobile-satellite services and aeronautical mobile telemetry services. The investigated materials can be exploited for effective EMI-Shielding against radiation of this extensively used communication band. 

Detection of buried objects Communication with submarines, electrical power Telephone audio range Navigation, sonar Navigation, radio beacon AM, maritime radio Shortwave radio, citizen s band Television, FM, police, mobile Radar, television, navigation Radar, satellite Radar, space exploration... 

The rapid growth of satellite and mobile radio communications has led to a requirement for narrow band, frequency-stable filters and oscillators. Selectivity and stability are necessary to ensure that signals are confined to closely defined allotted frequency bands and to prevent the intrusion of unwanted signals which would interfere with the satisfactory performance of the system. Antennae are also critical components of any wireless communications system. The need for compactness in satellite and hand-held mobile systems is self-evident. 

Mobile satellite services operating at L-band around 1.6 GHz have revolutionized communications with ships and aircraft, which would normally be out of reliable communications range of terrestrial radio signals. The International Maritime Satellite Organization (INMARSAT) operates the dominant system of this type. 

Frequency-division multiple access has been the most prevalent access for satellite systems untQ recently. Individual users being assigned a particular frequency band may communicate at any time. SateUite filters subdivide a broad frequencyband into a number of transponder channels, for example, the 500-MHz upHnk ESS band from 5.925 to 6.425 GHz maybe divided into 12 transponder channels of 36-MHz bandwidth plus guard bands. This Emits the interference among adjacent channels in the corresponding downhnk band of 3.7. 2 GHz. 

Ku- or C-band satellite is a costly but effective way to link critical communications elements. C band has an added advantage over Ku during heavy rain or snow storms. Liquid or frozen water can disrupt Ku-band satellite transmission. A signihcant liability of satellite transmission for ultrareliable facilities is the possibility that a storm could cause a deep fade, even for C-band links. Another liability is short but deep semiannual periods of sun outage when a link is lost while the sun is focused directly into a receive dish. Although these periods are predictable and last for only a minute or two, there is nothing that can prevent their effect unless you have alternate service on another satellite with a different sun outage time, or terrestrial backup. 

Communications System Battery Power (W) Mass of Satellite Band of Operation... 

The United States launched an advanced communications satellite known as the INTESAT-IV system in the 1990s, which represented a fourth-generation commercial communications satellite, incorporating the latest radiofrequency and digital components with minimum weight, size, and power consumption. This system offers specified communications service requirements and can be used in support of future manned space flight missions. Frequency operating bands and secondary battery power requirements for this particular communications satellite are summarized in Table 2.15. 

During the visibility periods, the communications with the spacecraft will be carried out by means of a dual radio link in the VHF 400 MHz band, with a raw transfer rate of 9600 bit/s. For the rest of the orbit, the satellite will maintain a periodic downlink stream in an amateur band also in the range of the 400 MHz. 

---