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Downlink CNR
Downlink CNR (''Carrier to noise ratio'' in satellite reception) is an important figure in system TVRO design. Below are certain parameters used in CNR computation. Figure of merit Figure of merit is given as :f=\frac Where t is the temperature and g is the gain of the receiver antenna. For lossless case :t=t_a+(n-1)\cdot t_0 and :f=\frac where n is the noise factor, ta is the noise temperature of the antenna and t0 is the temperature of the environment (taken as 2900K). F in db is simply :F= 10 \ \log_ (f) Path loss Path loss is defined as : l= (\frac)^2 Where \lambda is the wavelength of the carrier and the d is the distance in meters between the satellite and the receiver . For Geosynchronous satellites this distance is at the projection on the earth (at the mean sea level). In actual cases the distance is slightly more than this figure depending on the geographic location. (But for geosynchronous satellites the variation is less than 1%). The Path loss in dB is :L = ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Communications Satellite
A communications satellite is an artificial satellite that relays and amplifies radio telecommunication signals via a transponder; it creates a communication channel between a source transmitter and a receiver at different locations on Earth. Communications satellites are used for television, telephone, radio, internet, and military applications. Many communications satellites are in geostationary orbit above the equator, so that the satellite appears stationary at the same point in the sky; therefore the satellite dish antennas of ground stations can be aimed permanently at that spot and do not have to move to track the satellite. Others form satellite constellations in low Earth orbit, where antennas on the ground have to follow the position of the satellites and switch between satellites frequently. The high frequency radio waves used for telecommunications links travel by line of sight and so are obstructed by the curve of the Earth. The purpose of communications sate ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
