| 摘要 |
PURPOSE:To shorten control response time and to prevent the deterioration of an error rate characteristic by deciding the attenuation amount of a variable attenuator according to the average value of the attenuation amount under signal reception in a no signal state and switching control to automatic gain control while receiving signals. CONSTITUTION:When a burst signal transmitted from each ground station is set on standby, the loop of automatic gain control is opened. and a gain control circuit 10 sets a control gain from the output of an average value circuit 9 to a variable attenuator 11. When a carrier detection circuit 5 detects the burst signal, the reception is transmitted to a signal reception judgement circuit 8, the input to the gain control circuit 10 is switched to the output of a filter circuit 4, and the loop is closed. Then, in the case of no signal waiting for the burst signal, the average value of the attenuation amount under burst signal reception is set at the variable attenuator 11. Thus, even when the burst signal is transmitted, the amount to be controlled is reduced, and a prescribed demodulator input level can speedily be set. |
