PURPOSE: To generate an average power of non-modulation signal of a multi-value QAM system independently of a multi-number by providing a means generating the average power of (2n×2m)-set of non-modulation signals to a transmitter.

CONSTITUTION: Four sets of binary digital signals S0∼S3 and one set of clock signal CLK are inputted to a transmission logical circuit 1 in figure, where the logical operation such as waveform shaping, code conversion and additive operation is conducted and the signals are inputted to D-A converters 2 and 3 as two rows of parallel axis (for PCH) and two rows of vertical axis (for QCH) digital signals P, Q. The D-A converters 2, 3 input the digital signals P, Q and convert then respectively into 4(22=4)-value of signals Sp, Sq. The four-value 2-row (4-value × 4-value) signals Sp, Sq are inputted to an orthogonal linear modulator 6, where the multi-value QAM modulation in a carrier frequency (f) is applied, the result is amplified to a prescribed level by an amplifier 7 and a desired 16QAM modulation signal Sm is obtained.