Digital-to-analog converted (DAC) and method that set waveform rise and fall times to produce an analog waveform that approximates a piecewise linear waveform to reduce spectral distortion
US5663728A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | May 18, 1995 |
| Grant date | Sep 2, 1997 |
| Priority date | — |
| Expiry date | May 18, 2015 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH03M1/785
- WIPO fieldBasic communication processes
- WIPO sectorElectrical engineering
Abstract
A DAC converts a sequence of digital codewords into an approximately piecewise linear analog waveform that follows rising and falling edges between plateau levels. The DAC processes, in parallel, each bit of the codewords to produce component waveforms that are weighted according to their bits significance and summed together to produce the piecewise linear analog waveform. Waveform shaping circuits control the rise and fall times of each component waveform so that the analog waveform's rising and falling edges settle to within a desired error bound of a linear output ramp whose slope is a function of the difference between successive codewords and the rise or fall times. The rise and fall times are preferably approximately the same. Limiting switches control the plateau levels of the component waveforms so that the analog waveform's plateaus settle to within the desired error bound of the ideal values represented by the codewords. The linear region of the limiting switches are expanded to maintain the linearity of the rising and falling edges established by the waveform shaping circuits.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.