Automode signal detection in full duplex modems
US5309476A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Sep 26, 1991 |
| Grant date | May 3, 1994 |
| Priority date | — |
| Expiry date | Sep 26, 2011 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04L27/0012
- WIPO fieldDigital communication
- WIPO sectorElectrical engineering
Abstract
Method and apparatus for determining occurrence of an S1 modem identification sequence is disclosed. An S1 sequence is found to exist when the sum of conjugate complex multiplication of signal sample amplitudes taken at an interval T/2 result in a negative scalar value for an arbitrary number of sequential occurrences. Complex samples taken from incoming baseband waveform at twice the modulation rate are interleaved in pairs of two with two even numbered samples and two odd numbered samples being considered separately by first performing complex multiplication followed by scalar multiplication of an output of the complex multiplication and an output of the previous complex multiplication delayed by one modulation interval T. The separate results from the sets of pairs of signal samples are summed to form a scalar whose value when consistently less than 0 indicates the presence of an S1 modem identification sequence in accordance with the CCITT S1 recommendation.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.