| 摘要 |
PROBLEM TO BE SOLVED: To provide a modulator provided with a nonlinear distortion compensation function capable of obtaining a sufficient compensation effect with a simple configuration only by a receiver side. SOLUTION: The demodulator is provided with a distortion compensation circuit for applying distortion compensating by an adaptive operation according to distortion of a demodulation signal to an orthogonal demodulator 11 conventionally used by a receiver side and conducting demodulation of the base band type quasi- synchronization system. When amplitude compensation units 12a, 12b of this compensation circuit multiplies an amplitude compensation rate from a compensation rate arithmetic circuit 14 with Ich, Qch digital signals, a compensation polarity detection circuit 13 outputs a control signal in response to the result of discriminating degree of correctness of the amplifier distortion compensation on the basis of an error signal obtained by a discrimination circuit 24 and a compensation polarity discrimination region obtained by a vector of a data signal to the compensation rate arithmetic circuit 14, and the compensation rate arithmetic circuit 14 calculates the amplitude compensation rate on the basis of a relation between an average operating point estimate value generated depending on the control signal by the compensation rate arithmetic circuit 14 and a signal amplitude of the digital signals. |
