发明授权
- 专利标题: Digital tone generator
- 专利标题(中): 数字音源
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申请号: US09086628申请日: 1998-05-29
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公开(公告)号: US06400821B1公开(公告)日: 2002-06-04
- 发明人: John M. Burgan , James H. Carlquist , John R. Oakley
- 申请人: John M. Burgan , James H. Carlquist , John R. Oakley
- 主分类号: H04M100
- IPC分类号: H04M100
摘要:
A digital tone generator (1110) includes a digital signal generator (1138) which generates a digital waveform data sequence which is representative of a tone having a predetermined waveform, and a pulse-width modulator (1132) which provides an adaptive duty cycle period (622, 630) which is responsive to the digital data waveform data sequence for selecting clock pulses of a number sufficient to generate a pulse-width modulated digital tone signal. The digital tone generator (110) can also include a low pass filter (36) which processes the pulse-width modulated digital tone signal to generate an analog tone signal. The digital waveform sequences generated by two digital tone generators (38, 40) can be digitally added by a digital adder (28) to provide a composite tone data signal, which can be processed by the adaptive pulse-width modulator (700) to produce a pulse-width modulated tone signal representative of a DTMF tone.