| Extremely High Frequency |
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Radio Signal s in this band are extremely prone to Atmospheric Attenuation , making them of very little use over long Distance s. Even over relatively short distances, Rain Fade is a serious problem, caused when Absorption by Rain reduces Signal Strength . APPLICATIONS This band is commonly used in Radio Astronomy . In the United States, the band 38.6 - 40.0 GHz is used for licensed high-speed microwave data links, and the 60 GHz band can be used for unlicensed short range (1.7 km) data links with data throughputs up to 2.5 Gbit/s (gigabits per second). This is a Civil Air Patrol frequency, as well. It is used commonly in flat terrain. The 71-76, 81-86 and 92-95GHz bands are also used for point-to-point high-bandwidth communication links. These frequencies, as opposed to the 60GHz frequency, require a transmitting license in the US from the FCC , though do not suffer from the effects of oxygen absorption as the 60GHz does. There are plans for 10 GBit/s links using these frequencies as well. In the case of the 92-95GHz band, a 100MHz band has been reserved for space-borne radios, making this upper band limited to a transmission rate of only a few gigabits. Applications include Radar systems with high resolution. A recent development has been imagers for security applications as clothing and other organic materials are translucent in some mm-wave atmospheric windows. SEE ALSO EXTERNAL LINKS Academic
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