High-speed modem synchronized to a remote CODEC
US5394437A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Oct 20, 1992 |
| Grant date | Feb 28, 1995 |
| Priority date | — |
| Expiry date | Oct 20, 2012 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04L25/4927
- WIPO fieldDigital communication
- WIPO sectorElectrical engineering
Abstract
A modem that operates reliably at a symbol rate that corresponds to twice its bandwidth even when it is coupled to a receiving A/D converter that operates under control of a clock is realized by synchronizing the modem's operation to the A/D's clock. The superior operation of this modem advantageously extends to A/D clock frequencies beyond the frequency of twice the modem's bandwidth. To minimize quantization noise, the modem's output is conditioned to minimize intersymbol interference by adjusting the modem's output to the A/D converter's sampling times and slicing levels. When the A/D's clock is higher than twice the bandwidth of the modem's output signal, some intersymbol interference cannot be avoided. In accordance with this invention, the position and value of this interference is computed at the receiver and subtracted from the received signal.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.