Waveform generator operable in accordance with a plurality of band limitation characteristics

A waveform generator for quadrature modulation operable in accordance with a plurality of band limitation characteristics, comprising:

• serial-to-parallel conversion means for converting serial transmission data to parallel data;
• mapping means for converting parallel data from said serial-to-parallel conversion means to amplitude-phase information and outputting the information as I-channel symbol data and Q-channel symbol data;
• first waveform generating means for generating a waveform signal band-limited using a first band limitation characteristic in accordance with said I-channel symbol data from said mapping means;
• first memory means for storing in advance a difference signal between a waveform signal band-limited using the first band limitation characteristic for said I-channel symbol data and a waveform signal band-limited using a second band limitation characteristic for said I-channel symbol data and outputting said difference signal in accordance with said I-channel symbol data;
• first adding means for adding the waveform signal from said first waveform generating means to the difference signal from said first memory means and outputting the waveform signal band-limited using the second band limitation characteristic for said I-channel symbol data;
• first selector switch means for selectively outputting either the waveform signal from said first waveform generating means or the waveform signal from said first adding means;
• second waveform generating means for generating a waveform signal band-limited using a first band limitation characteristic in accordance with Q-channel symbol data from said mapping means;
• second memory means for storing in advance a difference signal between a waveform signal band-limited using the first band limitation characteristic for said Q-channel symbol data and a waveform signal band-limited using a second band limitation characteristic for said Q-channel symbol data and outputting said difference signal in accordance with said symbol data;
• second adding means for adding the waveform signal from said second waveform generating means to said difference signal from said second memory means and outputting the waveform signal band-limited using the second band limitation characteristic for said Q-channel symbol data;
• and
• second selector switch means for selectively outputting either the waveform signal from said second waveform generating means or the waveform signal from said second adding means.