| 摘要 |
PURPOSE:To eliminate the separate transmission of the gain control signal to the receiver side, by performing both the compression and expansion of level based on the estimate signal. CONSTITUTION:The output estimate signal of a signal estimating circuit 15 of the transmitter side is supplied to a comparator to receive a level comparison with the reference level given from a variable reference level generator 16 in terms of the analog conversion value. In case digital signal is higher than the reference level, the gain G1 of a variable gain unit 13 is reduced by the comparator 17. At the same time, the reference level of the generator 16 is changed to a level that is reduced by the same value as the reduction of the gain G. And a reverse effect is obtained in case the digital signal is lower than the reference level. On the other hand, a gain control part 19 of the receiver side increases the gain G2 through a comparator in case the analog conversion level of the estimate signal obtained from a digital modulated wave is higher than the reference level. At the same time, the reference level is changed to a higher level by an extent equivalent to the increase of G2. And a reverse effect is obtained when the reference level is higher than the analog conversion level. Accordingly the digital modulated wave received the level compression at the transmitter side receives a level expansion at the receiver side by an extent equivalent to the compression of level. |
