Code converters
US4209773A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Nov 28, 1977 |
| Grant date | Jun 24, 1980 |
| Priority date | — |
| Expiry date | Nov 28, 1997 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH03M7/3031
- WIPO fieldBasic communication processes
- WIPO sectorElectrical engineering
Abstract
A digital-to-analogue converter which uses a technique of two-level quantization in order to generate a pulse density code signal which yields the analogue signal when filtered. Standard digital logic adders and registers are used in the conversion of PCM signals to the pulse density code. The adders and registers are arranged as a feedback loop in which an approximation signal capable of either a "high" or a "low" level is compared repetitively with a PCM signal and the difference is accumulated, but at the end of each operation the accumulated total is tested and the value of the approximation signal for the next cycle is chosen so as to reduce the accumulated total. The cycle period is set by a clock, and the approximation signal is the pulse density code signal. The noise spectrum of the pulse density code signal may be adjusted by the addition of an offset signal to the incoming PCM signal. The digital-to-analogue converter is suitable for use in converting linear PCM telephone speech signals into analogue signals.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.