Efficiency data transmission technique
US4720839A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Dec 2, 1986 |
| Grant date | Jan 19, 1988 |
| Priority date | — |
| Expiry date | Dec 2, 2006 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04L25/497
- WIPO fieldDigital communication
- WIPO sectorElectrical engineering
Abstract
Partial response and quadrature partial response data transmission system characterized by increased transmission rate, lower signal-to-noise ratio, low cost and simpler hardware implementation than prior art systems. A steep filter (almost rectangular) is connected to the output of a cosine filter, forming a composite filter, wherein the cut-off frequency of the rectangular filter is less than the Nyquist frequency by a predetermined amount which is inversely proportional to the amount in percentage by which the data transmission rate exceeds the Nyquist rate. The system is thus capable of signalling at the Nyquist rate and greater, without requiring that channel filter parameters or the basic clock rate be adjusted. A smaller number of signal levels can be selected (as compared to previously existing methods) for spectrally efficient applications, and the resulting more robust system can also be used to transmit PAM, QAM, and other baseband or modulated signals.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.