| 摘要 |
PURPOSE:To secure the steady and high-speed draw-in of the automatic gain control device, by holding the control voltage of the voltage control amplifier at a certain level even in case no input signal exists. CONSTITUTION:Oscillator 6 and adder 7 are provided. Oscillator 6 generates the signal lower than the prescribed level, such as the initialized signal, and then operates in response to the detection signal of carrier detector 5. In other words, the initialized signal is sent to adder 7 in case when the voltage of the detection signal is at a low level. On the contrary, oscillator 6 sends no initialized signal when the detection signal is at a high level. Accordingly, the input signal of voltage control amplifier 1 does not become to the zero level, and thus the control voltage can rise rapidly up to the stabilized voltage. Thus the control voltage rises up at the level higher than the zero level. As a result, the steady and high-speed draw-in is possible for the automatic gain control device. |
