Jamming signal scrambling and descrambling systems for CATV
US4748667A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Nov 4, 1986 |
| Grant date | May 31, 1988 |
| Priority date | — |
| Expiry date | Nov 4, 2006 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04K2203/14
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
Scrambling and descrambling systems utilizing jamming signals provide improved pictures with minimal distortion due to ghosts and artifacts. The television signal is combined with a jamming signal or signals located preferably in the vestigial sideband (VSB) of the modulated picture carrier and at about a null in the spectrum of the modulation of the picture carrier by the horizontal sync. The jamming signal or signals also preferably are placed between the harmonic components of the horizontal sync which define the horizontal sync spectrum and at frequencies which comply with governmental regulations respecting frequency locations of strong signals of CATV purposes. The jamming signals are generated by phase locking to the horizontal sync signals of the television signals or to a submultiple of the horizontal sync frequency. Artifacts are further reduced by preemphasis of the transmitted television signal in the sideband opposite to that in which the jamming signal or signals are located and spaced by an equal frequency increment from the location of the jamming signal energy. In order to extract the jamming signal, so as to descramble the television signal for reproduction in the…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.