Modem communication system having main and secondary channels
US4860308A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Mar 30, 1988 |
| Grant date | Aug 22, 1989 |
| Priority date | — |
| Expiry date | Mar 30, 2008 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04M11/06
- WIPO fieldTelecommunications
- WIPO sectorElectrical engineering
Abstract
A data modem communication system includes a data modem transmitter adapted to transmit data on a main channel at a relatively high bit rate and to transmit data at a relatively low bit rate on a secondary channel. At the receiver, a single analog-to-digital converter (54) supplies digital signals via a notch filter (58) to the main channel receiver (60) and to the secondary channel receiver (62) wherein a single IIR low-pass digital filter (110) is utilized for processing at three different sample rates to eliminate the main channel signal with frequency conversion taking place between processing at the first and second sample rates. The invention enables the provision of a reliable secondary channel while using a minimum amount of circuitry for complex-valued digital signal processing.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.