Earth station transmission power control system for keeping an eirp of

Abstract

In an earth station (11), an amplifier (15) amplifies a pilot information signal with a variable gain. An up link pilot is thereby transmitted with a controllable transmission power. A beacon receiver (28) detects a level or C/N with which a beacon signal emitted by a satellite reaches the station. A pilot receiver (33) detects a level or C/N for a down link pilot radiated by the satellite in response to the up link pilot. A controller (37) controls the gain to keep a ratio between the levels or C/N's constant. For keeping a similar ratio constant, another station may transmit a transmission signal with a likewise controllable transmission power and receive the down link pilot together with a return signal radiated by the satellite in response to the transmission signal. Still another station may control a similarly controllable transmission power in consideration of an up link attenuation which is estimated from the level or C/N of the down link pilot. One of up link signals may be substituted for the up link pilot with that one of down link signals used for the down link pilot which is radiated by the satellite in response to that one up link signal. Up link signals transmitted with the power so controlled, are radiated by the satellite as down link signals with a substantially constant EIRP despite an attenuation which might be caused to the up link signals by rain or mist.