| 摘要 |
PROBLEM TO BE SOLVED: To provide an automatic gain control unit for stably controlling the gain with respect to rapid variations in an input signal level by executing different gain control according to the input signal level, and to provide a method for automatically controlling the gain. SOLUTION: There are provided a level detector 11 for detecting the absolute value L1 of an output signal (y) in an AGC circuit 1, an averaging section 12 for obtaining the average level L2 of the absolute value L1, a gain control unit 13, and a multiplier 14. A gain coefficient G, outputted from the gain control unit 13 is multiplied by an input signal (x) by the multiplier 14, is outputted as the output signal (y) and is supplied to the level detector 11. The gain control unit 13 increases or decreases the gain coefficient by a threshold TH1, so that the output signal (y) becomes a fixed level, when the average level of the input signal is a threshold TH2 or higher. When the average level of the input signal is less than the threshold TH2, control is performed so that the gain coefficient is made to asymptotically approach a prescribed value. COPYRIGHT: (C)2007,JPO&INPIT
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