| 摘要 |
PURPOSE:To prevent the divergence of loop control by subtracting a DC offset component added to a loop excessively in the control loop of pre-compensation with respect to the input signal of a transmitter imparted with distortion, etc., then executing compensation only to the variation portion of the amplitude of the output signal of the transmitter imparted with the distortion, etc. CONSTITUTION:A zero detector 1 monitors an input signal Din, and detects the point of time when its amplitude becomes zero, and drives a switch 2 by this detection signal (d) to close a path to supply the output of a difference device 80 to a holding circuit 3. At this time, the holding circuit 3 inputs and holds an excessive DC component to be zero originally of difference between a converted output D2 obtained by converting the output of a demodulator 40 of the output of the transmitter 30 imparted with the distortion, etc., and the input signal Din because the switch 2 is closed. Then, the difference device 81 subtracts the DC portion held by the holding circuit 3 from the converted output D2 of the A/D converter 50 at next zero detection time, and feeds back only the variation portion of the amplitude of the transmitter 30 imparted with the distortion, etc., to a compensation circuit 10 through the difference device 80. Thus, the loop control can be converged. |
