| 摘要 |
PROBLEM TO BE SOLVED: To stably operate a Cartesian feedback even when an amplifier having the characteristic whose phase characteristic is remarkably changed by an amplitude value is used and to improve a distortion improvement factor. SOLUTION: A modulation input - phase/conversion table 6 converts the common-mode modulation signal and the orthogonal modulation signal which are outputted from a distortion compensation circuit 1 into the converted amount of the phase characteristic of an amplifier 3 according to the amplifier-phase characteristic of the amplifier. A subtracter 8 subtracts the output of the modulation input - phase/conversion table 6 from phase adjustment amount adjusting phase rotational amount which does not depend on the modulation signal, the adjustment amount is inputted in an infinite phase converter 7 and the phase of the carrier wave of an quadrature modulator 2 is controlled. Because the phase characteristic of a feedback signal is compensated by changing the phase of the carrier wave of the quadrature modulator 2 according to the amplitude value of a modulation burst band signal, the phase margin of the feedback signal can be maintained even when the phase characteristic of the amplifier 3 is changed by an inputted amplitude value. |
