Digital filters and demodulators
US4794341A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Nov 4, 1986 |
| Grant date | Dec 27, 1988 |
| Priority date | — |
| Expiry date | Nov 4, 2006 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04L7/0029
- WIPO fieldDigital communication
- WIPO sectorElectrical engineering
Abstract
A filter, in which digital representations of a signal are stored as samples in a store (8) preferably in the order of their occurrence. Multipliers (9) multiply the samples by coefficients (C1 to C36) representing a function with which the samples are to be convolved. To compensate for the variable time delays in the signal, sets of coefficients representing the function with different time delays are stored. The set to be convolved with the signal is chosen in dependence upon the time delay of the signal. A signal indicative of the time delay is derived from an input to the shift register and fed-forward. The filter is preferably used in a digital demodulator of phase and/or amplitude modulated signals. The function is then an impulse function defining (at least in part) a desired frequency response of the filter, and the filter corrects the timing of symbols represented by the signal. In the digital demodulator, the symbol timing recovery and correction (4) takes place before carrier phase recovery (5) and demodulation.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.