Echo cancellation in two-wire transmission path repeaters
US4782525A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Nov 27, 1985 |
| Grant date | Nov 1, 1988 |
| Priority date | — |
| Expiry date | Nov 27, 2005 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04B3/238
- WIPO fieldTelecommunications
- WIPO sectorElectrical engineering
Abstract
A two-wire transmission path repeater includes, between two hybrid circuits coupled to the path, an echo canceller and an amplifier for each direction of transmission, each echo canceller including a transversal filter and a subtracting circuit. The power ratio between signals before and after the subtracting circuit of each echo canceller is used to distinguish between simplex and duplex signals. If the power ratio exceeds a given value, which is dependent upon the input signal power, for only one transmission direction then a simplex signal in the opposite direction is determined, the gain of the amplifier for the one transmission direction is reduced, and adaptation of the transversal filter coefficients for the opposite direction is prevented. If the power ratio for both directions falls below the given value then a duplex signal is determined, the gain of both amplifiers is increased and adaptation of the coefficients of both transfer filters is continued for a short period, then the gain of both amplifiers is reduced and adaptation prevented, thereby facilitating stable operation of the repeater.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.