DIGITAL PHASE MODULATION/DEMODULATION CIRCUIT

摘要

PURPOSE: To provide a digital phase modulation/demodulation circuit capable of being constituted on an IC and preventing the deterioration of a code error rate and a modulation distortion rate. CONSTITUTION: A 90 deg. phase shift circuit 6 generates a carrier signal having the phase difference of 90 deg. against a carrier signal by a digital processing based on the carrier signal with a step waveform whose absolute value of a peak value inputted from a step waveform generation circuit to a carrier signal input terminal 3 is two stages and whose ratio of the peak value is 1:√2. A first mixer circuit 4 and a second mixer circuit 5 multiply the respective carrier signals by base band signals inputted from base band signal input terminals 1 and 2, and they output multiplication signals where mix modulation distortion at the time of the multiplication operation is sufficiently reduced. An addition circuit 7 outputs an addition signal where a higher harmonic component is sufficiently suppressed from an output terminal 8.