Automatic modulation and RF carrier level control of sync suppressed television signals
US6940561B1 · kind B1 · utility
Assignee
Inventors
Key dates
| Filing date | Nov 3, 2000 |
| Grant date | Sep 6, 2005 |
| Priority date | — |
| Expiry date | Sep 19, 2023 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04N5/40
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
The depth of modulation and the absolute RF carrier level of an amplitude-modulated video signal are automatically adjusted. For adjustment of the depth of modulation, a sync tip of the video signal is sampled, corrected and normalized to a reference level, e.g., a 50% video level. A reference pulse is inserted into the video signal, e.g., in a sync pulse or in lines 22 and/or 23 of the vertical blanking interval. The reference pulse is sampled and compared to the normalized sync tip pulse to determine an error. The error is converted to an adjustment signal for a charge pump which increases or decreases the depth of modulation accordingly. For adjustment of the absolute carrier level, the insertion of a reference pulse is not required. Instead, a reference value is stored in a memory and retrieved for comparison with the corrected sync tip pulse. An error term is computed and converted to an adjustment signal for a charge pump which increases or decreases the absolute carrier level accordingly. Several modulation circuits can share a common microprocessor controller.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.