Telecommunications – Carrier wave repeater or relay system – Monitoring
Patent
1989-04-06
1990-07-10
Griffin, Robert L.
Telecommunications
Carrier wave repeater or relay system
Monitoring
455 52, H04B 160
Patent
active
049411993
ABSTRACT:
Compensation for rain fades in a VSAT communications network is obtained by a uplink power control mechanism incorporated in a master station, which maintains the power output level of the satellite transponder constant without incorporating excessive static margins into the link power budget. A variable attenuator, which controls the output power of the master station's high power amplifier is initially set at a prescribed level which will produce the intended satellite amplifier EIRP for a `clear sky` condition. The master station monitors the output of the satellite amplifier and derives a measure of the signal-to-noise ratio of downlinked signals. Knowing the variable attenuator setting and the signal-to-noise ratio of the downlinked signals, the magnitude of attenuation of outlink carrier frequency signals transmitted from the master station to the satellite is determined. In the event of a rain fade, the setting of the variable attenuator is adjusted by an amount that compensates for the fade and thereby causes outlink carrier frequency signals conveyed by the satellite amplifier device to remain effectively constant. An estimate of the error in the attenuator setting is preferably derived in accordance with the ratio of the difference between the squared (I) and (Q) channel values ((S+N).sup.2 -N.sup.2) to the square of the quadrature channel-derived noise value N.sup.2 of a Costas loop in the master station's receiver.
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patent: 4731866 (1988-03-01), Muratani et al.
patent: 4752967 (1988-06-01), Bustamante et al.
patent: 4776035 (1988-10-01), Duggan
"Closed-Loop Transmitting Power Control System for K-Band Satellite Communications," EGAMI, 1983, IEEE, vol. AES-19, No. 4.
"Prediction of Attenuation by Rain," Crane, 1980 IEEE, vol. COM-28, No. 9.
"Communications Satellite Systems," Martin, 1978.
Griffin Robert L.
Kuntz Curtis
Scientific Atlanta
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