System for encoding and decoding amplitude modulated signals
US4002825A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Jul 25, 1973 |
| Grant date | Jan 11, 1977 |
| Priority date | — |
| Expiry date | Jul 25, 1993 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04K1/00
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
A system for encoding or scrambling an amplitude modulated signal, such as the video component of a standard television signal, and for subsequently decoding or unscrambling the signal so as to restore the original message content. Encoding is achieved by shifting the phase of the carrier component relative to the phase of the side-bands by an amount sufficient to significantly distort the modulation envelope. Decoding is achieved by summing the received signal with a corrective signal having a frequency, amplitude, and phase which effectively cancels the phase-shifted carrier component and substitutes therefor a carrier component of phase and amplitude which will render intelligible the modulation envelope.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.