Data modem receiver
US4849989A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Aug 29, 1988 |
| Grant date | Jul 18, 1989 |
| Priority date | — |
| Expiry date | Aug 29, 2008 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04L27/00
- WIPO fieldDigital communication
- WIPO sectorElectrical engineering
Abstract
In a data modem receiver (80) the received signal is digitized in an A/D-converter (84), the output of which is applied to notch filter means (88, 96) which eliminates secondary channel signals, and which applies an output signal to a pair of IIR filters (112, 116), responsive to the frequency components present in a training signal. The values of the IIR filter output sigals are determined and compared with a pair of threshold levels provided by a threshold setter circuit (152) responsive to the peak received signal level to detect the receipt of a training signal. In response to the detection of a training signal, DFT calculations are initiated for timing recovery and modem address identification, using samples stored in a buffer shift register (206). A gain control circuit (220) is located subsequent to a band-pass filter (212) coupled to the buffer shift register (206).
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.