| 摘要 |
PURPOSE:To realize accurate gain compensation even to level fluctuation of a short time of sample period by utilizing the advantages of a feedback AGC(F. BAGG) circuit and a feedforward AGC(F.FAGC) while following to considerably timewise slow fluctuation of a signal level. CONSTITUTION:An AM-PM-VSB signal inputted with a wide dynamic range is compensated for the gain against a long slow fluctuation by the F.BAC circuit 11 in the circuit section 10, its output level fluctuation is suppressed, and a signal normalized to the unit amoung [1] is outputted. After two orthogonal normalized carrier signals Cc and Cs are multiplied and subject to synchronous detection, the output is regenerated as complex base band signals xr, xi through LPF14, 15. A level detection/decision circuit 13 calculates a signal vector absolute value, it is compared with a prescribed threshold value and when the absolute value is close to the unit among [1], the F.FAGC circuit 12 of the post stage is set, and when the absolute value is close to [0], the circuit 12 is deenergized so as to obtain the normalized complex base band signal on a unit circle. |
