AFC circuit, carrier recovery circuit and receiver device capable of regenerating a carrier reliably even at the time of low C/N ratio
US6490010B1 · kind B1 · utility
Inventors
Key dates
| Filing date | May 14, 1999 |
| Grant date | Dec 3, 2002 |
| Priority date | — |
| Expiry date | May 14, 2019 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04N5/50
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
Stabilized carrier recovery is achieved even at the time of a low C/N ratio by measuring the phase of a signal and controlling VCO or NCO (Numerical Controlled Oscillator) using only a period having few constellation points. At this time, false lock phenomenon is avoided as follows. That is, relatively short SYNC modulated by an already-known pattern is entered into a modulation wave, VCO or NCO oscillation frequency is swept in a wide range and sweep is stopped at a frequency in which the SYNC can be received, thereby carrying out coarse control AFC. Further, a period having long to some extent, having few constellation points is provided in the modulation wave and then, a difference between the frequency of a received modulated signal and a local oscillation signal of VCO or NCO is obtained in this period. This frequency difference is analyzed according to the phase differential function method, self-correlation function method or count method, and the VCO or NCO is controlled based on this result of analysis.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.