| 摘要 |
PROBLEM TO BE SOLVED: To suppress expansion of a spectrum attended with phase modulation. SOLUTION: This modulator is constituted of a phase shifter 11 that converts a digital signal into 2-series of orthogonal signals and outputs the signals so that a period when a self phase change of a multilevel digital signal displayed on orthogonal axes isπ/2 (rad) is in existence without fail in the case of a state transition of the received digital signal, a band limit filter 12 applying band limit to an output of the phase shifter 11 and a phase modulator 13 applying phase modulation to the output of the filter 12. Since the state transition is caused atπ/2 (rad), expansion of a spectrum in the nonlinear amplifier 3 is suppressed and conversion distortions of AM/AM and AM/PM are relaxed.
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